Biomedical subjects

R Bjerknes

Publications and source records attributed to R Bjerknes.

At least 91 records · Page 5Linked to original sources

PubMed1984

Exocytosis of zymosan particles by human phagocytes.

The kinetics of human leucocyte phagocytosis and exocytosis of fluorescein-isothiocyanate (FITC)-labelled zymosan particles were studied by flow cytometry (FCM). The leucocytes rapidly associated with zymosan particles, and internalization was confirmed by a fluorescence quenching technique. For incubation periods longer than about 60 min, exocytosis of ingested particles was observed. All human phagocytes ejected zymosan particles. The rate of exocytosis was about 1 particle per phagocyte per h, and was independent of the number of internalized particles. Exocytosis was dependent on temperature and glucose, but did not require Ca++ and Mg++ ions. Phagocytosis and exocytosis occurred concurrently, and phagocytosis accelerated ejection of previously internalized particles. The exocytosed particles were partially degraded by the phagocytes, and rephagocytosis of ejected zymosan particles was slower than the uptake of control particles. Phagocytes undergoing exocytosis remained intact during the 210 min examined. The findings indicate a heretofore neglected vector in the interaction of prey and phagocytosing cells.

Exocytosis↗

PubMed1984

The effect of serum opsonins on the phagocytosis of Staphylococcus aureus and zymosan particles, measured by flow cytometry.

Human leukocyte phagocytosis of S. aureus and zymosan particles was measured by flow cytometry (FCM). Killing of bacteria was measured by a standard microbiological method. When pooled human serum was heated to 56 degrees C for 30 min, the percentage of phagocytosing polymorphonuclear neutrophilic leukocytes (PMNLs), the rate of phagocytosis and killing of S. aureus by the whole leukocyte population were reduced to about 50% of the control values. The results indicate that the impaired phagocytosis and killing were due to the lack of attachment of bacteria opsonized with heat-stabile serum opsonins, mainly IgG, to 50% of the PMNLs. A prey-predator model was used to compare phagocytosis of S. aureus in heated and control serum. The rate of phagocytosis by those PMNLs that were active in heated serum was the same as that of all the leukocytes in control serum, suggesting that heat-labile serum opsonins did not affect the rate of phagocytosis by these PMNLs. PMNLs and monocytes phagocytosed zymosan particles in control serum, but in heated serum only a fraction of the leukocytes, corresponding to the fraction of monocytes phagocytosed. Thus, all PMNLs seem to be capable of phagocytosis by heat-labile serum opsonins. The combined use of S.aureus and zymosan particles may be of advantage in rapid screening of serum opsonin activities and phagocyte function in infectious and haematological disorders.

Adhesiveness↗

PubMed1984

Inhibition of phagocytosis by monoclonal antibodies to human myeloid differentiation antigens.

The influence of eight antimyeloid monoclonal antibodies on human leukocyte phagocytosis was investigated using flow cytometry. A granulocyte-specific monoclonal antibody, VIM-D5, inhibited the phagocytosis of both zymosan particles and Staphylococcus aureus in a dose-dependent fashion. In the presence of 5 micrograms/ml, the numbers of phagocyte-associated zymosan particles and bacteria were reduced by about 35% and 40%, respectively. Another monoclonal antibody, VIM-12, reacting with granulocytes, monocytes, and null lymphocytes, inhibited both granulocyte and monocyte phagocytosis of S. aureus. The inhibition was dose dependent, and in the presence of 10 micrograms/ml, the number of phagocyte-associated bacteria was reduced by about 40%. VIM-12 did not influence the phagocytosis of zymosan particles. Both VIM-D5 and VIM-12 inhibited the internalization phase of phagocytosis, whereas the attachment to the phagocyte surface was unaltered. The combined effect of VIM-D5 and VIM-12 was additive, amounting to about 70% reduction of phagocytosis of bacteria. The remaining six antimyeloid antibodies had no effect on leukocyte phagocytosis. The combined use of antimyeloid monoclonal antibodies and flow cytometry appears to be a promising tool for the study of phagocyte functions.

Antibodies, Monoclonal↗

PubMed1983

Human leukocyte phagocytosis of zymosan particles measured by flow cytometry.

Human leukocyte phagocytosis of fluorescein-isothiocyanate (FITC)-labelled zymosan particles was studied by a flow cytometric (FCM) assay allowing discrimination of adhered and ingested zymosan particles. Free zymosan particles, non-phagocytes and phagocytes could be discriminated and quantified by simultaneous registration of fluorescence and light scatter. All leukocytes capable of phagocytosis were phagocytosing, and within 15 min 80% of the zymosan particles were adhered or ingested. Compared to the FITC-fluorescence of free zymosan particles, the mean fluorescence of phagocyte-associated zymosan particles was reduced by about 35%, indicating ingestion and processing of zymosan particles. Abolishing the FITC-fluorescence of extracellular zymosan particles by crystal violet, the number of zymosan particles adhered and ingested could be calculated from FCM measurements of phagocyte fluorescence. This showed that in 15 min 83% of the phagocyte-associated zymosan particles were actually ingested.

Flow Cytometry↗

PubMed1980

The stathmokinetic method in vivo. Time-response with special reference to circadian variations in epidermal cell proliferation in the hairless mouse.

Groups of hairless mice were injected i.p. with a stathmokinetic dose of 0.15 mg colcemid at seven different times of the day and animals killed 0, 15 and 30 min, 1, 2, 3 and 4 hr after the injection. The proportion of cells in metaphase and ana/telophase was determined in histological sections. The results showed a transient accumulation of metaphases about 30 min after the injection, followed by an increase in metaphases from 1 to 4 hr. Therefore, no value before 1 hr after the colcemid injection should be used in calculations of the mitotic rate. The presence of circadian rhythms with high mitotic activity in the morning and low activity in the evening was confirmed. It is shown by regression analyses that the accumulation period of 4 hr is sufficiently short to reflect circadian variations in epidermal cell proliferation and that the 4-hr accumulation value alone is sufficient to estimate the mitotic rate.

Animals↗

PubMed1979

Circadian rhythms in mouse epidermal basal cell proliferation. Variations in compartment size, flux and phase duration.

Several kinetic parameters of basal cell proliferation in hairless mouse epidermis were studied, and all parameters clearly showed circadian fluctuations during two successive 24 hr periods. Mitotic indices and the mitotic rate were studied in histological sections; the proportions of cells with S and G2 phase DNA content were measured by flow cytometry of isolated basal cells, and the [3H]TdR labelling indices and grain densities were determined by autoradiography in smears from basal cell suspensions. The influx and efflux of cells from each cell cycle phase were calculated from sinusoidal curves adapted to the cell kinetic findings and the phase durations were determined. A peak of cells in S phase was observed around midnight, and a cohort of partially synchronized cells passed from the S phase to the G2 phase and traversed the G2 phase and mitosis in the early morning. The fluctuations in the influx of cells into the S phase were small compared with the variations in efflux from the S phase and the flux through the subsequent cell cycle phases. The resulting delay in cell cycle traverse through S phase before midnight could well account for the accumulation of cells in S phase and, therefore, also the subsequent partial synchrony of cell cycle traverse through the G2 phase and mitosis. Circadian variations in the duration of the S phase, the G2 phase and mitosis were clearly demonstrated.

Animals↗

PubMed1977

Growth kinetics of Kaposi's sacroma.

This is a study of cell kinetics in nodular and florid (fungating) Kaposi's sarcomas. One or more tumours from 9 patients were examined at the Uganda Cancer Institute. The very variable clinical doubling time was assessed by direct measurements of tumour diameters, and an average obtained. The mitotic count, rate of entry of cells into mitosis and cell cycle time were measured in biopsy material, and use to estimate the potential doubling time. From the difference between the potential and the actual doubling times, the rate of cell loss and the cell loss factor were calculated. The average actual clinical doubling time was slightly, but not significantly, higher for growing nodular tumours than for florid tumours. Some nodular tumours were similar to those reported in the literature for other human malignacies. Kinetic studies of static and regressing human tumours have not been reported previously. The rate of cell production found in this tumour is lower than the values reported in the literature for other malignancies. The calculated mitotic duration is long, but similar to previously reported values. The cell loss factor is high: in the static tumours it is 1.0, and in the regressing tumours greater than 1.0. In regressing tumours, the rate of cell loss was 30% higher than the rate of cell production. These tumours did not differ histologically from nearly florid tumours which were increasing in size. It is postulated that regression is determined by local vascular or mechanical factors, supplemented possibly by delayed hypersensitivity responses in some patients.

Cell Count↗

PubMed1974