Effect of actinomycin-D on the staining of whole cells with acridine orange

Flow cytofluorometric techniques have been used to investigate the interference of actinomycin-D with the staining of acridine orange in whole cells. The results show that reduction in fluorescence intensity will only occur at actinomycin-D concentrations greater than 10(3) ng/ml in our system, providing the drug is washed out prior to staining.

A randomized study of misonidazole and radiotherapy for grade 3 and 4 cerebral astrocytoma

The results are reported of a small clinical trial carried out to assess the potential value of the hypoxic cell radiosensitizer misonidazole in the radiation treatment of Grade 3 and 4 supratentorial astrocytomas. A total of 55 patients were randomly allocated to one of 3 treatment groups. No significant differences were seen between the median survivals of patients in the 2 control radiation groups and that of the third group in which oral misonidazole at a dose of 3 g/m2 preceded each of 4 weekly radiation doses. Possible reasons why no improvement was seen are discussed in detail.

An examination of the relative resistances to aflatoxin B1 and susceptibilities to gamma-glutamyl p-phenylene diamine mustard of gamma-glutamyl transferase negative and positive cell lines

Two epithelial cell lines have been derived from rat liver. One, containing only low levels of gamma-glutamyl transferase (GGT) was obtained from normal liver and the other, containing high levels of the enzyme was isolated from an aflatoxin B1-induced hepatoma. The GGT levels present in the two cell lines have been examined by histochemical staining, by a fluorescence assay using disrupted cells, and also by intact fluorescence-labelled cells in a laser flow cytofluorimeter. The cells containing high levels of GGT have been found to be less sensitive to microsomally-activated aflatoxin B1 than are the GGT negative cells, a feature of the in vivo situation. Evidence for activation of the gamma-glutamyl derivative of an alkylating mustard analogue of p-phenylene diamine by the GGT positive cells is presented. This finding could be of relevance to the possible chemotherapy of GGT-rich lesions in vivo.

Inferences on RNA synthesis rates during mitosis from flow cytofluorimetric RNA histograms

Flow cytofluorimetric techniques with acridine orange staining have been used to study RNA levels of cells during and immediately after mitosis. It can be inferred from the histogram data that, of the mitotic cells, those in telophase have the highest RNA content, and that the rate of synthesis increases rapidly between anaphase and telophase. These inferences correlate with results obtained from parallel labeled precursor studies.

Nucleic acid profile of the EMT6 cell cycle in vitro

Simultaneous RNA and DNA estimations were carried out during the cell cycle of EMT6/M/CC cells growing in vitro following synchronization by mitotic selection. The determinations were performed with a flow cytofluorimeter on individual cells stained with acridine orange. It was found that the RNA content increased during G1 then remained virtually constant between early and mid S phase, but a second increase occurred during late S. The rate of uptake of tritiated uridine paralleled these changes in RNA levels, and it was also found that the rate of uptake in metaphase and anaphase was virtually zero, but a rapid increase occurred in telophase. The increase in DNA during S was approximately linear, and the intermitotic phase and cycle durations were very similar to previously reported results.

A linear transform of the multi-target survival curve

A completely linear transform of the multi-target survival curve is presented. This enables all data, including those on the shoulder region of the curve, to be analysed. The necessity to make a subjective assessment about which data points to exclude for conventional methods of analysis is, therefore, removed. The analysis has also been adapted to include a "Pike-Alper" method of assessing dose modification factors. For the data cited this predicts compatibility with the hypothesis of a true oxygen "dose-modification" whereas the conventional Pike-Alper analysis does not.

Different esterase activities of exponential and plateau phases of EMT6 cells monitored by flow cytofluorimetry

The reaction rates of enzymes hydrolysing fluorescein diacetate have been studied in populations of intact tissue-culture EMT6, cells using flow cytofluorimetric techniques. It was found that the activity of these enzymes increased in plateau phases and that this correlated inversely with plating efficiency. Highly abnormal substrate-dependent reaction velocity kinetics were found in 14-, 21-, 28- and 35-day cultures.

Fluorescence discrimination between diploid cells on their RNA content: a possible distinction between clonogenic and non-clonogenic cells

Flow cytofluorimetric techniques, using acridine orange fluorescence to measure RNA and DNA simultaneously in EMT6 cells, have been employed to discriminate between three diploid DNA populations in vivo on the basis of their RNA content. Cells with the lowest RNA levels seem to be in the process of disintegration. Cells with the highest RNA levels correspond to those with the highest plating efficiency, and those with intermediate RNA levels are those with the lowest plating efficiency. In vitro studies have shown that log-phase cells have higher RNA levels than cells in the late plateau phase of growth.

The application of age distribution theory in the analysis of cytofluorimetric DNA histogram data

Age distribution theory has been employed in a model to analyse a variety of histograms of the DNA content of single cells in samples from experimental tumours growing in tissue culture. The method has produced satisfactory correspondence with the experimental data in which there was a wide variation in the proportions of cells in the intermitotic phases, and generally good agreement between the 3H-thymidine labelling index and the computed proportion in S phase. The model has the capacity to analyse data from populations which contain a proportion of non-cycling cells. However, it is concluded that reliable results for the growth fraction and also for the relative durations of the intermitotic phase times cannot be obtained for the data reported here from the DNA histograms alone. To obtain reliable estimates of the growth fraction the relative durations of the phase time must be known, and conversely, reliable estimates of the relative phase durations can only be obtained if the growth fraction is known.

The perturbed cell proliferation kinetics of the EMT6/M/AC tumour in mice treated with anti-mouse lymphocyte serum

The cell proliferation kinetics of the EMT6/M/AC tumour were determined at two volumes, 6-3 mm3 and 180 mm3, in mice treated with anti-mouse lymphocyte serum, AMLS. Comparison of the growth curve with that obtained in non-AMLS treated animals showed a marked increase in the growth rate at all volumes in the treated group. In contrast, the cell cycle time and the intermitotic phase times were not significantly different in the treated and untreated groups at comparable volumes. The increase in the growth rate in AMLS treated mice was obtained in spite of decreases in both the rate constant for cell production and the growth fraction, and was due to a marked decrease in the rate constant for cell loss.

Effects of x-radiation on the spinal cord: an experimental study of the morphological changes in central nerve fibres

The morphological changes in central nerve fibres after irradiation have been studied in the spinal cord of young adult rats exposed to 100-6 000 rad doses of 250 kV x-rays using the technique of single fibre teasing as well as conventional light and electronmicroscopic examination of cord sections. Two groups of degenerative changes were found in myelinated fibres. The first consisted of breakdown of paranodal myelin and nodal widening. These changes were found as early as two weeks after exposure to 500-6 000 rad doses and increased in frequency with dose and time in the first two months after irradiation. Paranodal myelin breakdown was less frequent after two months but nodal widening was more prominent. Increasing numbers of thinly myelinated fibres were found after three months suggesting that paranodal demyelination was followed by remyelination. This early group of changes confined to the myelin sheath provides a possible pathological basis for the self-limited sensory syndrome which sometimes occurs within a few weeks or months of irradiation of the spinal cord in man. The second type of change which was also first detected as early as two weeks after irradiation and which appears to be unrelated to the first, consisted of random Wallerian-type degeneration of fibres of all calibres in the spinal white matter. The number of affected fibres was initially small but increased with time and there was no clear dose relationship. This random fibre degeneration is probably the forerunner of the later-occurring delayed radionecrosis of the spinal cord which other workers have found to occur with a latent period of up to twelve months after exposure to doses exceeding 1900 rads to the rat.

The cell proliferation kinetics of the EMT6/M/AC mouse tumour at four volumes during unperturbed growth in vivo

The cell proliferation kinetics of the EMT6/M/AC mouse tumour were determined at four different volumes between 1-5 mm3 and 175 mm3. The decrease in the growth rate between these volumes are mainly due to a decrease in the rate constant for cell production. A small increase in the rate constant for cell loss occurred, but this was thought to be insignificant. The cell loss factor increased from 40% at 1-5 mm3 to over 70% in the 175 mm3 tumours. An increase in the median cell cycle time, from 14-1 hr to 18-5 hr was also found between these same volumes. Results obtained for the NCTC fibrosarcoma and the R-1 rhabdo-myosarcoms indicate that there may be a threshold volume in these sarcomas below which little or no cell loss takes place. This was not found in the EMT6/M/AC tumour.