Cell and tissue kinetics最新文献

Concentration of extracellular Ca++ optimum for growth of cell types of mesodermal origin have been reported to be up to 100-fold higher than concentrations optimal for epidermal or other epithelial lining cells. In order to examine Ca++ requirements of epithelial v. fibroblastic cells derived from a common tissue source, prior to prolonged culture, freshly isolated mouse epidermal keratinocytes, hair follicle cells and dermal fibroblasts were plated at high density or at clonal density in medium ranging from 0.014 to 1.4 mM Ca++. Epithelial skin cells grew best at Ca++ levels below 0.1 mM while dermal fibroblasts grew best at a Ca++ concentration of 1.4 mM. The epithelial cell types exhibited marked morphologic changes in response to Ca++, while the fibroblasts did not. These results suggest that the variations in Ca++ response between lining epithelium and mesenchymal cells resulted from inherent differences in these cell types, but a mechanism for such differential effects has not yet been defined.

This study has explored the possibility of applying the metaphase-arrest method with colchicine to two models of induced liver growth in the rat, regenerative growth and phenobarbital-induced growth. At a dosage of 0.5 mg/kg body weight (BW), colchicine caused a linear accumulation of mitoses for up to 90 min when administered at 3 days after the start of phenobarbital treatment; however these mitoses included a number of anaphases and telophases. No anaphase escape was seen when this dose of colchicine was given at various times after partial hepatectomy, though the arrested mitoses were invariably more fragmented and some may have even degenerated beyond recognition as early as 90 min after injection. It is concluded that the optimal dose of stathmokinetic agent is heavily dependent on the relative liver weight, and thus would change continuously during compensatory hyperplasia.

In cell kinetic experiments, as in many other branches of biological science, we often sample at various stages of an experiment: we may for example take a sample of animals, then from each study a sample of sites, and from each site take replicate observations. This sampling process can be optimized to give maximum precision to an estimated quantity, but care must be taken in analysing data so gathered because the analysis depends on the precise sampling strategy.

In order to study cell proliferation in intact human cervical epithelium, a technique involving metaphase arrest has been utilized. Metaphase accumulation is observed following intraepithelial administration of vincristine sulphate, at a predetermined optimum dose of 50 micrograms/ml. A significant delay before the onset of stathmokinetic activity is demonstrated; thereafter linearity of accumulation is apparent over a 4-hr period following injection. The technique appears applicable to the estimation and comparison of cell production rates in vivo of normal cervical epithelium, cervical intraepithelial neoplasia, wart-affected cervical epithelium and early invasive carcinoma. However, individual values are likely to be imprecise in isolation, indicating the need to study relatively large numbers of subjects in each group. Some practical difficulties are discussed.

The adaptive liver growth response was investigated in intact and adrenalectomized rats. When adult male rats were given a single oral dose of mirex (100 mg/kg body weight) there was a 72% increase in relative liver weight (RLW) in 72 hr. Based on [3H]-thymidine [( 3H]TdR) incorporation into hepatic DNA, there was also a wave of DNA synthesis which peaked at 48 hr and decreased to essentially control values by 96 hr post mirex dose. In mirex-dosed adrenalectomised (Adx) animals, the RLW was increased by only 38% and there was sustained DNA synthesis. When mirex-dosed Adx rats were given corticosterone supplements, the RLW response was similar to the RLW response in intact mirex-dosed rats. However, the 48-hr DNA synthesis peak seen in intact mirex-dosed rats was eliminated. From these data it is suggested that mirex-induced adaptive liver growth has two components: a hypertrophic component which is mediated by corticosterone, and a hyperplastic component which is independent of corticosterone.

Centrifugal elutriation was used to separate 9L rat brain tumour cells into fractions enriched in the G1, S, or G2/M phases of the cell cycle. Cells enriched in early G1 phase were recultured, grown in synchrony, and harvested periodically for analysis of their DNA distribution and polyamine content. Mathematical analysis of the DNA distributions indicated that excellent synchrony was obtained with low dispersion throughout the cell cycle. Polyamine accumulation began at the time of seeding, and intracellular levels of putrescine, spermidine, and spermine increased continuously during the cell cycle. In cells in the G2/M phase of the cell cycle, putrescine and spermidine levels were twice as high as in cells in the G1 phase. DNA distribution and polyamine levels were also analysed in cells taken directly from the various elutriation fractions enriched in G1, S, or G2/M. Because we did not obtain pure S or G2/M populations by elutriation or by harvesting synchronized cells, a mathematical procedure--which assumed that the measured polyamine levels for any population were linearly related to the fraction of cells in the G1, S, and G2/M phases times the polyamine levels in these phases and that polyamine levels did not vary within these phases--was used to estimate 'true' phase-specific polyamine levels (levels to be expected if perfect synchrony were achieved). Estimated 'true' phase-specific polyamine levels calculated from the data obtained from cells either sorted by elutriation or obtained from synchronously growing cultures were very similar.

This study looked at the changes in the interfollicular DNA labelling index (LI) with time after strontium-90/yttrium-90 beta irradiation of approximately 100 mm2 of mouse flank skin, after a dose of 100 Gy which produces transitory moist desquamation. Within 24 hr of such a dose the LI of the irradiated area was essentially zero (0.07 +/- 0.03%), whilst those of the side area and of the control area were 15.0 +/- 2.6% and 21.4 +/- 2.7%, respectively. The LI of the side and the control areas then fell within 3-5 days to approximately 4% and approximately 2% respectively, whilst that of the irradiated area rose rapidly to a peak value of 30.2 +/- 1.7% at 10 days post-irradiation. There was a 20% reduction in the diameter of the area with detectable radiation damage within 5 days, and this is primarily due to cell proliferation and migration from the unirradiated margins of the field. In contrast, between days 10 and 20 the major source of repopulation is probably derived from local migration and proliferation of surviving hair follicle basal cells within the irradiated field.

Nocodazole, a temporary inhibitor of microtubule formation, has been used to partly synchronize Ehrlich ascites tumour cells growing in suspension. The gradual entry of cells into mitosis and into the next cell cycle without division during drug treatment has been studied by flow cytometric determination of mitotic cells, analysing red and green fluorescence after low pH treatment and acridine orange staining. Determination of the mitotic index (MI) by this method has been combined with DNA distribution analysis to measure cell-cycle phase durations in asynchronous populations growing in the presence of the drug. With synchronized cells, it was shown that in the concentration range 0.4-4.0 micrograms/l, cells could only be arrested in mitosis for about 7 hr and at 0.04 microgram/ml, for about 5 hr. After these time intervals, the DNA content in nocodazole-blocked cells was found to be increased, and, in parallel, the ratio of red and green fluorescence was found to have changed, showing entry of cells into a next cell cycle without division (polyploidization). It was therefore only possible to partially synchronize an asynchronous population by nocodazole. However, a presynchronized population, e.g. selected G1 cells or metabolically blocked G1/S cells, were readily and without harmful effect resynchronized in M phase by a short treatment (0.4 microgram/ml, 3-4 hr) with nocodazole; after removal of the drug, cells divided and progressed in a highly synchronized fashion through the next cell cycle.

The in-vitro proliferation kinetics of young rabbit articular chondrocytes were compared in primary culture and at the first passage. The growth curves labelling and mitotic indices, percentage labelled mitosis (PLM) curves and DNA content distributions by flow-microfluorometric analysis during a 7-day growth period were determined in both cases. The length of the cell cycle and the doubling time calculated from the exponential part of the growth curve were quite similar: Tc = 19 hr and Td = 20 hr for the primary culture, Tc = 17 X 3 hr and Td = 20 hr for the first passage. However, the growth curve and the DNA distribution during the 7-day period showed some differences. The duration of the lag period studied by the growth curve was longer in the primary culture than at the first passage. This phenomenon was also observed using the FCM analysis. The growth fraction determination on the second day of culture was in accordance with the lower proliferation capacity of the cells in primary culture. These data suggest that it would be better to study growth kinetics and drug modifications in articular chondrocytes at the first passage than in primary culture.

Loss of cells from vital and necrotic areas of the syngeneic mammary adenocarcinoma EO 771 in male C57 BL/6J mice may be measured by use of 125I-labelled 5-iodo-2'-deoxyuridine (125I-UdR). Later than 50 hr after an intraperitoneal injection of 20 muCi 125I-UdR the incorporated activity of the entire tumour was externally measured and found to decrease with time after injection. The injected amount was neither chemo- nor radiotoxic. By injecting the vital dye 'light green', unstained necrotic and stained viable regions were separately excised and measured for loss of activity throughout the natural development of the labelled tumour. With the appearance of necrotic regions, labelled viable cells became necrotic, and activity was slowly eliminated. With increasing proportions of necrosis during tumour growth, the rate of loss of activity of the whole tumour decreased. Loss of activity from viable tumour regions reflected cell death and exceeded the loss rates of the whole tumour by a factor of 2 to 3. The data show that loss of activity from the whole tumour results from a superposition of different elimination rates of viable and necrotic tumour regions and is not an immediate consequence of cell death in the course of undisturbed tumour development.