1,720,974 research outputs found
The clinical significance of phospholipids in lung pathology
No full textThe original publication is available at http://www.samj.org.zaCITATION: Van Papendorp, D. H. & Engelbrecht, F. M. 1981. Die kliniese belang van fosfolipiede longpatologie. South African Medical Journal, 60:176-180.The phospholipid composition of 35 human lungs with pathological lesions was analysed by means of thin-layer chromatography and densitometric scanning. The pathological conditions studied were: bronchopneumonia, myocardial infarction, chronic heart failure, chronic obstructive airway disease and tuberculosis. The phospholipid composition was compared with that of a control group consisting of sudden death cases (due to unnatural causes), i.e. relatively normal lungs. The phospholipid composition of the lungs in a specific pathological group showed the same pattern. However, significant differences were observed between corresponding phospholipid fractions from lungs in the various pathological groups. Compared with the lipid fractions from relatively normal lungs, these differences were even more marked. From the results it would appear that the abnormal composition of the phosholipid fractions might possibly be a cause of lung pathology. The increase and/or decrease in individual fractions and abnormal ratios between fractions might indicate abnormalities in the biosynthesis and catabolism of the lung phospholipids. Further research is necessary to elucidate the association of phospholipids with lung pathology. Phospholipid analysis of lung lavages and lung biopsies could be helpful in the diagnosis of lung diseases. Phospholipids in aerosol form could perhaps be used in treating certain lung disorders.Publisher’s versio
The effect of paraquat on the aerobic metabolism of rabbit alveolar macrophages and lung fibroblasts
Full text linkCITATION: Rossouw, D. J. & Engelbrecht, F. M. 1979. The effect of paraquat on the aerobic metabolism of rabbit alveolar macrophages and lung fibroblasts. South African Medical Journal, 55:20-23.The original publication is available at http://www.samj.org.zaIn this study the effects of paraquat on the aerobic metabolism and viability of isolated rabbit alveolar macrophages and lung fibroblasts were investigated, and compared with the effects of other known metabolic inhibitors, i.e. sodium fluoride (NaF) and potassium cyanide (KCN). The manometrically and polarographically determined endogenous oxygen consumption of lavaged alveolar macrophages compared very well (180,9 ± 35,8 and 169,3 ± 26,8 nmol per 106 viable cells per hour respectively). Exogenous glucose (10 mM) and autologous serum (1:3 v/v) added to the medium had no significant effect on the basal respiration rate. The mean cell protein content, determined by the micro-Kjeldahl and Lowry techniques, amounted to 242,6 ± 37,6 μg/106 macrophages. Paraquat (2 mM), like NaF (20 mM) and KCN (5 mM), decreased the viability of the macrophages far less than it did the oxygen utilization of the viable cells, and resulted in an 80% inhibitin of oxygen uptake. In contrast, paraquat (1 mM) induced a marked stimulation (230%) of the cyanide-insensitive respiration of alveolar macrophages. The concentrations of paraquat (nmol/103 cells) which reduce macrophage metabolism to almost zero were virtually non-toxic to fibroblasts, as measured by their oxygen consumption.Publisher’s versio
Morfologiese veranderinge tydens eksperimentele hipercholesterolemie
Full text linkCITATION: Rossouw, D. J. & Engelbrecht, F. M. 1973. Morfologiese veranderinge tydens eksperimentele hipercholesterolemie. South African Medical Journal, 47(32):1460-1466.The original publication is available at http://www.samj.org.zaThe morphological changes in various organs and tissues from rabbits with experimentally induced hypercholesterolemia were investigated. The outstanding histopathologic feature was the presence of atheromatous lesions in the aorta, pulmonary and intramural coronary vessels. In spite of the pronounced involvement of the subendocardial vessels, manifestations of ischemia and myocardial infarction could be demonstrated in only a limited number of animals. The presence of foam cells in the lung parenchyma imply that the lung has a more important role in handling abnormal cholesterol loads than has hitherto been anticipated. Hypercholesterolemia was also associated with marked adrenal hypertrophy. The infiltration of mononuclear cells, which was observed, could have had an effect on atherogenesis through its influence on the function of this gland. The zonal delimitation of the foam cells and lipoid infiltration in the peritubular spaces at the corticomedullary junction in the kidney, raise some interesting questions about the nature and function of the interstitial cells of the renomedullary region. Foam cells were also found to accumulate in the spleen and lymph glands. This may affect the function of these structures to such an extent that it could possibly enhance the histopathologic, biochemical and hematologic changes during hypercholesterolemia.Publisher’s versio
The influence of paraquat on the in vitro oxygen consumption of rabbit lung
Full text linkCITATION: Rossouw, D. J. & Engelbrecht, F. M. 1978. The influence of paraquat on the in vitro oxygen consumption of rabbit lung. South African medical Journal, 54(5):199-201.The original publication is available at http://www.samj.org.zaThe effects of paraquat on the aerobic metabolism of rabbit lung slices were investigated. The oxygen consumption of lung slices was examined at different oxygen tensions and in the presence or absence of glucose as substrate in a Krebs-Ringer phosphate medium. In an air phase, the oxygen consumption of control lung tissue with glucose in the medium was practically the same as the oxygen consumption without glucose over a 3-hr period. In a 100% oxygen phase, glucose induced a marked increase in oxygen uptake, which persisted for about 2 hours. Thereafter, a decrease occurred in oxygen consumption which was notably faster than of lung tissue without added glucose. With 10 mM glucose in the medium, paraquat (10-5 M and 10-3 M) immediately stimulated the oxygen consumption of lung slices. Although the initial increase in aerobic metabolism seemed to be glucose-dependent, the secondary inhibitory effect of paraquat appeared to be of the same magnitude in the presence or absence of glucose. Both the initial stimulation as well as the secondary inhibition were much more pronounced in a 100% oxygen atmosphere than in an air phase. These results indicate that the rabbit lung is sensitive to paraquat toxicity in vitro, and confirm that oxygen and paraquat supplement each other's toxicity in the lung.Publisher’s versio
Metabolic changes in the lungs after ischaemia
Full text linkCITATION: Engelbrecht, F. M., Edwards, I. J. & De Beer, D. P. 1980. Metabolic changes in the lungs after ischaemia. South African Medical Journal, 58:409-413.The original publication is available at http://www.samj.org.zaThe effects of variable periods of ischaemia on the isolated lungs of rats and rabbits, stored for up to 6 hours at 4°C, 21°C and 37°C under standardized conditions, were investigated in vitro in terms of oxygen consumption, the rate of 1-14C-leucine incorporation into soluble proteins, and 1-14C-palmitate incorporation into total phospholipids and lipid fractions. The endogenous oxygen uptake of rat lung slices in an air phase, from tissues stored at 4°C and 21°C under ischaemic conditions for 6 hours and at 37°C for 4 hours, was significantly different from the control values. The oxygen uptake of lungs from animals anaesthetized with pentobarbitone prior to exsanguination and stored for only 2 hours at 37°C differed significantly from control values. Judged by the rate of incorporation of radiolabelled leucine into soluble proteins and that of palmitate into total lipids and phospholipids of lungs after storage for increasing periods at 4°C and 37°C, significant differences were already found after 1 1/2 hours. From this observation it would appear that these parameters are very sensitive indicators for assessing irreversible lung damage due to ischaemia.Publisher’s versio
The effect of oxygen and paraquat on the 14C-glucose oxidation of rabbit alveolar macrophages and lung slices
Full text linkCITATION: Rossouw, D. J. & Engelbrecht, F. M. 1979. The effect of oxygen and paraquat on the 14C-glucose oxidation of rabbit alveolar macrophages and lung slices. South African Medical Journal, 55:558-560.The original publication is available at http://www.samj.org.zaIn this study, we measured the effects of different concentrations of paraquat (0.01 mM and 1.0 mM) on the 1-14CO2 and 6-14CO2 production of rabbit lung slices and isolated alveolar macrophages, in 20% and 95% oxygen phases respectively. A 95% oxygen phase induced an increase in the 6-14C-glucose oxidation of control lung slices over a 3-hour period, while the increased activity of the pentose pathway over the first 2 hours started to decline during the third hour of incubation. Paraquat (1.0mM) in 20% oxygen caused a consistent increase in the 6-14CO2 production by lung slices, but in a 95% oxygen phase gradually inhibited the 6-14C-glucose oxidation over a period of 3 hours. The pentose phosphate pathway was highly significantly stimulated by 1.0 mM paraquat in 20% and 95% oxygen over 3 hours. When isolated alveolar macrophages (viability 95%) were incubated in a 20% and a 95% oxygen phase respectively, both the 6-14C-glucose oxidation rates were significantly inhibited by 1.0 mM paraquat after 1 hour. Our results confirmed the initial increase in glycolytic metabolism induced by paraquat, but also indicated that the 6-14CO2 production was significantly inhibited by paraquat when lung slices were incubated in a 95% oxygen phase. The fact that the glucose metabolism in alveolar macrophages is more sensitive to paraquat exposure than that of cells in lung slices may be related to the genesis of the intra-alveolar pulmonary lesions described in the literature.Publisher’s versio
Experimental paraquat poisoning : histological, electron microscopic and autoradiographic changes in the lung
No full textCITATION: Rossouw, D. J., Chase, C. C. & Engelbrecht, F. M. 1984. Experimental paraquat poisoning : histological, electron microscopic and autoradiographic changes in the lung. South African Medical Journal, 66:485-489.The original publication is available at http://www.samj.org.zaParaquat is a potent and widely used herbicide which acts as a specific pulmonary toxin and causes lung fibrosis in man and animals. Some controversy still exists concerning the details of the morphogenesis of the pulmonary lesions. The lungs of rats exposed to intravenous injections of paraquat and sacrificed 6 - 24 days later were examined by light and electron microscopy. Autoradiography was used to detect possible paraquat accumulation in the lung 5 hours after a single intravenous injection. The findings on microscopy suggested an acute phase of damage to alveolar lining epithelium followed by epithelial regeneration. The most pronounced light and electron microscopic findings were: (1) signs of disruption of the alveolar wall; (ii) type II alveolar epithelial hyperplasia; (iii) mobilization of mononuclear cells, and (iv) migration and accumulation of fibroblast-like cells in the intra-alveolar and interstitial spaces. After three equally spaced intravenous injections of paraquat signs of interstitial connective tissue proliferation could be seen. Autoradiography showed low-grade radioactivity over the alveolar wall, indicating possible active uptake of paraquat by alveolar epithelium; this coincides with in vitro evidence of an active transport mechanism for paraquat by alveolar epithelial cells.Publisher’s versio
Shock lung : experimental studies on a haemorrhagic hypovolaemic rabbit model
Full text linkCITATION: Engelbrecht, F. M., Mouton, W. L. & Van Schalkwyk, L. J. 1983. Shock lung : experimental studies on a haemorrhagic hypovolaemic rabbit model. South African Medical Journal, 64:400-404.The original publication is available at http://www.samj.org.zaAn experimental model of haemorrhagic hypotension was standardized using rabbits to investigate the shock lung syndrome over a period of 120 minutes. Acute hypovolaemia was induced by withdrawal of blood under anaesthesia to a mean arterial pressure of 30 ± 5 mmHg within 10 minutes. The mean leucocyte counts and the release of lysosomal enzymes (acid phosphatase and β-glucuronidase) in the blood and in lung tissue, as well as the metabolic capacities of lung tissue in terms of protein and lipid biosynthesis, were investigated at set intervals after 30, 60, 90 and 120 minutes. The results indicate a progressive decline in leucocyte numbers over 120 minutes to about 40% of the original. An immediate granulocytopenia was observed with a relative lymphocytosis within 30 minutes. The β-glucuronidase and acid phosphatase contents of the plasma increased with time; β-glucuronidase activity increased progressively as leucocytes disappeared from the circulation. Concomitantly, the capacity of the lung tissue to synthesize protein and lipids was retarded with time, becoming significantly lower than baseline values after 60 minutes of hypovolaemia. The decline in leucocyte numbers in the circulation correlated well with the increase in β-glucuronidase activity and the retarded metabolic capacity of the lung tissue.Publisher’s versio
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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