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Biomedical subjects

M C Snella

Publications and source records attributed to M C Snella.

At least 19 recordsLinked to original sources
PubMed1989

Cell recruitment into lung wall and airways of conventional and pathogen-free guinea pigs after inhalation of endotoxin.

The cell kinetics of the acute inflammatory response to inhaled endotoxin (lipopolysaccharide, LPS) was studied in the lungs of conventional (CV) and pathogen-free (SPF) guinea pigs. Airway cells were obtained by bronchoalveolar lavage (BAL). Lung wall cells were prepared via collagenase digestion of lung tissue slices. Acute exposure to LPS triggered the influx within 4 to 12 h of equivalent numbers (approximately 70 x 10(6)) of neutrophils into the lung walls of both CV and SPF guinea pigs. The recruited neutrophils then proceeded into the airways of CV animals, and by 48 h all recruited neutrophils were recoverable by BAL. In contrast, only one third of recruited neutrophils in the lungs of SPF animals moved from the lung wall into the airways. Analysis of neutrophil chemotactic factor (NCF) production identified lung wall cells as the major source of LPS-induced NCF activity in both groups and as virtually the sole source in SPF animals. The results emphasize the importance of studies on the precise lung tissue distribution of both recruited neutrophils, and endogenous NCF-producing cells, in elucidating the acute inflammatory response in the lungs.

Animals↗
PubMed1987

[Demonstration of gram-negative bacteria and endotoxins in the air surrounding a sewage treatment plant: effect of contaminated aerosols on the health status of the staff].

Data on airborne gram-negative bacteria and endotoxin contamination in a sewage treatment plant are reported and compared with data from similar plants in Scandinavia. Respiratory, digestive, and cutaneous symptoms were investigated on the basis of medical files. The contamination levels which can be considered safe are discussed in the light of the actual exposure of workers.

Adult↗
PubMed1987

Interstitial and free lung cells in acute inflammation in the guinea-pig.

Different cell types were studied in bronchoalveolar lavage fluid (BAL) and solid lung tissue of guinea-pigs. Whereas alveolar macrophages (AM) and eosinophils predominated in BAL, the proportion of AM and lymphocytes was highest in the lung tissue. After an inhalation exposure to LPS, the number of neutrophils increased rapidly in the lung tissue reaching a maximum after 4 hours, and more slowly in the airways reaching a maximum after 24 hours. This suggests that other mechanisms than secretion of chemotactic factors from AM, shown to be active up to 4 hours after exposure, are responsible for the later phase of the neutrophil invasion into the airways. Passive migration or other mediators may be involved.

Animals↗
PubMed1986

[A data bank of international studies on pollution. Possibilities for its use by Switzerland].

GRID (Global Resource Information Data Base) is part of GEMS (Global Environment Monitoring System), which is controlled by the United Nations in its programme on the protection of the environment. Recently, GRID-processor premices have been provided by the University of Geneva. The main preoccupation of GRID is to capture, analyse and distribute data concerning environment: soil types, water resources, vegetation, animal population, human settlements, socio-economical data and, what is more important to us, data on air pollution. GRID facilities are at the disposal of international organisations which are concerned by the environment, as well as all research workers involved in this field of research. In our article, the organisational as well as modelling possibilities of GRID are presented and illustrated. A proposal is made to use GRID's facilities for Swiss epidemiological studies, on the effects of air pollution on human health.

Air Pollution↗
PubMed1986

Production of a neutrophil chemotactic factor by endotoxin stimulated alveolar macrophages in vitro.

Alveolar macrophages (AM) isolated from normal guinea-pigs and from those chronically exposed to endotoxin (LPS) were cultured in the presence of various concentrations of LPS (from 0.5 ng to 5 micrograms/ml). The presence of a neutrophil chemotactic factor (NCF) in culture supernatants was tested in migrations chambers. Contamination of all reagents has been tested using LAL test (Limulus Amoebocyte Lysate). The results indicate a production of NCF with low LPS concentrations (0.5 and 5 ng/ml) within the first 6 h of incubation: when larger doses are used the response decreases and a significant inhibition is observed with 5 micrograms LPS/ml (P less than or equal to 0.05). When contaminated medium was used, all responses observed were three times higher than with LPS-free medium (P less than or equal to 0.01). However, the response pattern was the same. AM from chronically exposed animals exhibit the same response patterns: the magnitude of NCF production was higher than with normal AM but not significantly. The data suggests that initial conditions of AM in vitro or in vivo with reference to LPS contamination have to be determined as they are of importance when AM NCF production has to be tested.

Animals↗
PubMed1985

Endotoxin inhalation induces neutrophil chemotaxis by alveolar macrophages.

Guinea-pigs were exposed to an aerosol of bacterial endotoxin (lipopolysaccharide, LPS). The free lung cell response and alveolar macrophage (AM) chemotaxis were studied. Neutrophils from guinea-pig blood gave larger migration responses than those obtained by intraperitoneal glycogen stimulation or human neutrophils. An increase in the number of neutrophils in the airways was found with a peak at 12-24 hours after exposure. In animals pre-treated with LPS inhalation for 4 months, the reaction was of shorter duration and smaller magnitude. AM showed in vitro chemotactic activity up to 4 hours after exposure; no difference was found in pre-treated animals. The results suggest that the neutrophil invasion in the airways after LPS is dependent on two mechanisms, the initial being AM chemotaxis, which is not modified by pre-exposure to LPS, and another unknown factor, which is modified by pre-exposure to LPS.

Aerosols↗
PubMed1985

[Teaching social and preventive medicine to pharmacy students].

The new Swiss reglementation for the final examination of students in pharmaceutics make social and preventive medicine a mandatory part of the curriculum. The number of hours attributed to the new subject differ markedly between the various schools of pharmacy. They are influenced by the attitude of the institutes and faculties (schools), professional societies but also by the students involved. The experiences of the first year are briefly discussed. Most important is to use the opportunity to improve the collaboration between the different partners in health care.

Curriculum↗
PubMed1985

Manganese dioxide induces alveolar macrophage chemotaxis for neutrophils in vitro.

Workers exposed to airborne manganese dioxide (MnO2) may develop pneumonia resistant to chemotherapy. Previous animal experiments have demonstrated that exposure to airborne MnO2 induces an invasion of neutrophils into the airways 4-12 h after exposure. Experiments were undertaken to further study the role of alveolar macrophage (AM) in the development of this response. Guinea pig lung lavage fluid was centrifuged and washed, and cell suspension incubated on one side of a leukocyte migration chamber. MnO2 (2.5 mg/ml) was incubated with the cells for different time periods. Peritoneal neutrophils from guinea pigs were isolated and incubated on the other side of the chamber. Observations of the free lung cells demonstrated that phagocytosis of the MnO2 particles commenced immediately and was virtually completed within 30 min. Cells from control animals caused small directional migration across the filter. Cells which had phagocytosed MnO2 particles showed a significantly higher degree of neutrophil migration. The data suggest that pneumonia, in terms of neutrophil invasion into the lungs after MnO2 exposure, is associated with an activation of AM with subsequent release of neutrophil recruiting factor.

Animals↗
PubMed1982

Lung cell reactions after inhalation of bacterial lipopolysaccharides.

Cells in airway lavage fluid were studied in guinea pigs exposed to an aerosol of bacterial lipopolysaccharide (LPS). The major response after a single exposure was a large increase in the number of macrophages and neutrophils. The neutrophil response decreased markedly after repeated exposure. De-complementation of the animals did not affect the response to a single exposure, nor did exposure to zymosan produce a neutrophil increase. It is suggested that other factors than serum complement activation initiate the neutrophil increase after LPS inhalation. One conceivable mechanism is the activation of pulmonary macrophages.

Aerosols↗
PubMed1981

Effects of bacterial endotoxin inhalation.

Airborne Gram-negative bacteria contamination has been demonstrated in several environments like cotton or flax factories, rooms with humidifiers and sewage treatment plants. Inhalation of LPS by animals provokes a bronchial invasion by neutrophils, a platelet aggregation in pulmonary capillaries, a local immune response and fever. Inhalation by human is related with clinical symptoms like fever, chills, malaise, muscle and joint aches and chest thightness. It appears from data in the literature that LPS airborne contamination is sufficient to provoke such symptoms. It seems important to study more precisely the contamination of suspected air in presence of these symptoms.

Air Microbiology↗
PubMed1980

[CO-pollution, a health risk in Geneva?].

The results from CO measurements at different locations in Geneva show that the highest levels are found in streets in the center of the city. An evaluation of the medical risks is performed against the most sensitive criteria--effects on the central nervous system, the cardiac muscle and the fetus. It is concluded that symptoms of anoxia may develop among persons with existing cardiovascular diseases.

Air Pollution↗
PubMed1977

[Cellular reactions in the lungs after inhalation of cotton dust and of endotoxin].

The free lung cell count has been studied in guinea pigs after exposure to extracts of various cotton dusts. A good correlation was found between the increase in leukocyte count in the airways and the number of gram-negative bacteria in the different dusts. The importance of endotoxin in the acute effects following exposure to cotton dust is discussed.

Aerosols↗
PubMed1976

Acute inhalation toxicity of cotton plant dusts.

The number of free lung-cells was studied in guinea-pigs after acute exposure to extracts of various cotton dusts. A good correlation was found between the increase in number of leucocytes in the airways and the number of Gram-negative bacteria in the different dusts. Experiments using the Shwartzmann reaction and the Limulus titration test demonstrated a relationship between the content of different endotoxins in the dusts and the pulmonary reaction. A model for the acute exposure effects after exposure to cotton dust is proposed.

Animals↗