bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetic Differences Between Fed and Starved Chinese Hamster Ovary Cells
Authors: Nelson John M. , Todd Paul , Metting Noelle F.
Published: May 2008

When Chinese hamster (CHO‐K1) cells are grown as monolayer cultures, they eventually reach a population‐density plateau after which no net increase in cell numbers occurs. the kinetics of aged cells in nutritionally deprived (starved) or density‐inhibited (fed) late plateau‐phase cultures were studied by four methods: (i) Reproductive integrity and cell viability were monitored daily by clonogenic‐cell assay and erythrosin‐b dye‐exclusion techniques. (ii) Mitotic frequencies of cells from 18 day old cultures were determined during regrowth by analysing time‐lapse video microscope records of dividing cells. (iii) Tritiated‐thymidine ([3H]TdR) auto‐radiography was used to determine the fractions of DNA‐synthesizing cells in cultures entering plateau phase and during regrowth after harvest. (iv) the rate of labelled nucleoside uptake and incorporation into DNA was measured using liquid scintillation or sodium iodide crystal counters after labelling with [3H]TdR or [125]UdR.

Non‐cycling cells in starved cultures accumulate primarily as G1, phase cells. Most cells not in G1 phase had stopped in G2, phase. Very few cells (< 2%) were found in S phase. In contrast, about half of the cells in periodically fed cultures were found to be in DNA‐synthetic phase, and the percentage of these S phase cells fluctuated in a manner reflecting the frequency of medium replacement. Populations of both types of plateau‐phase cultures demonstrate extremely coherent cyclic patterns of DNA synthesis upon harvest and reculturing. They retain this high degree of synchrony for more than three generations after the resumption of growth. From these data it is concluded that nutritionally deprived (starved) late plateau‐phase cells generally stop in either G1, or G2, phase, whereas periodically fed late plateau‐phase cultures contain a very large fraction of cycling cells. Populations of cells from these two types of non‐expanding cultures are kinetically dissimilar, and should not be expected to respond to extracellular stimuli in the same manner.
Different Epidermal Cell Kinetic Effects of Hydroxyurea When Injected At Two Different Times of the Day
Authors: Thorud E. , Clausen O. P. F. , Kauffman S. L.
Published: May 2008

Circadian rhythms in epidermal basal cell‐cycle progression in hairless mouse skin have been repeatedly demonstrated. A dose of 10 mg/animal hydroxyurea (HU), given to inhibit DNA synthesis was injected intraperitoneally to two groups of hairless mice. One group was injected at 10.00 hours MET, when the cell‐cycle progression and cell division rate are relatively high, and another group was injected at 20.00 hours, when the same variables are at minimum values. Various cell kinetic methods—[3H]TdR autoradiography, DNA flow cytometry and the stathmokinetic method (Colcemid)—were used to study HU‐induced alterations in cell kinetics.

Hydroxyurea (HU) immediately reduced the labelling index (LI) to less than 10% of controls when injected at both times of the day, and higher then normal values were observed 8 hr later. A subsequent decrease towards normal values was steeper in the 20.00 hours injected group. the proportion of cells with S‐phase DNA content was transiently reduced in both series, but the reduction was less pronounced and control values were reached earlier in the series injected at 10.00 hours. the observed alterations in LI and fraction of cells in S phase were followed by comparable alterations in the fraction of cells in G2 and in the mitotic rate. Hence the changes in G2 and mitotic rate are easily explained as consequences of the previous perturbations in the S phase.

The time‐dependent differences in the cell kinetic perturbations caused by HU in the S phase may be explained by a circadian‐phase‐dependent action of HU on the influx and efflux of cells to and from the S phase, respectively. At 10.00 hours the efflux of cells from S is most heavily inhibited; at 20.00 hours the influx is predominantly blocked. Hence, when physiological flux is high HU mainly blocks the efflux from S, but when flux normally is low, HU mainly blocks the entrance to S.

Within 20 hours after the HU injection, the cell kinetic variables had approached the unperturbed circadian pattern.
Alkalinization Stimulates Ca2+‐Dependent Spreading During the Activation of Resting Lens Epithelial Cells In Primary Culture
Authors: Glaesser Dietmar , Iwig Martin , Ngoli Dominique , Udelnow Christa
Published: May 2008

Lens epithelium, when attached to its natural substratum, the lens capsule, can be maintained in culture for more than 2 weeks in a simple HEPES‐ and EDTA‐buffered salt solution (HBS). In HBS, the epithelium shows the same characteristic phenomena of locomotion, initial retraction and respreading which in MEM plus serum precedes the inception of DNA synthesis. These phenomena have been shown to be dependent on extracellular Ca2+. 0·05 mM Ca2+ is necessary for maintaining cell‐to‐cell contacts of the in vivo epithelium. Higher concentrations of Ca2+ cause the epithelium to retract initially. In contrast, Mg2+ greatly favours cell‐substratum interactions leading to the formation of lamellopodia and an initial spreading of the epithelium. After some hours in culture the epithelium changes markedly in response to extracellular Ca2+ and Mg2+; it respreads and flattens in the presence of Ca2+, while Mg2+ becomes less effective in maintaining cell‐to‐substratum contacts. Mg2+‐dependent initial spreading is promoted at pH values near 7·0 but the Ca2+‐dependent respreading requires an alkalinization of the salt solution.
Two‐Step Cell‐Death Kinetics In Vitro During Cis‐Platinum, Hydroxyurea and Mitomycin Incubation
Authors: Böhmer Ralph‐M.
Published: May 2008

A human leukaemic cell line (REH) growing in suspension was incubated with cis‐platinum, hydroxyurea and mitomycin C at various concentrations causing complete cell‐cycle arrest. At different times the cell suspensions were harvested, diluted 1:1 with a buffer solution, stained without further treatment with a mixture of acridine orange (AO) and ethidium bromide (EB) and analysed with a biparametrical flow cytometer. Fluorescent plastic beads were introduced into the suspensions to provide an internal numerical reference for the control of cell loss.

The fluorescence distributions showed three groups of cells: vital cells (V) which were only stained with AO; dead cells in which EB stained cytoplasmic components but not the nuclear DNA (D1), and dead cells which allowed EB to stain both cytoplasm and nuclear DNA (D2). the kinetics of cells entering D1 depended on drug concentration and showed equal characteristics for cis‐platinum and mitomycin, but were different for hydroxyurea. the subsequent entry into D2 occurred about 15 hr later and showed no pronounced dependence on drug concentration. Parallel trypan‐blue (TB) exclusion tests revealed that TB only stained D2 cells and therefore is not useful for investigating cell‐death kinetics during exposure to cell‐killing agents.
Effects of [3H]Udr On the Cell‐Cycle Progression of L1210 Cells
Authors: Darzynkiewicz Z. , Carter Sally , Kimmel M.
Published: May 2008

Tritium‐labelled uridine ([3H]UdR) perturbs progression of L1210 cells through the mitotic cycle. the main effect manifests as a slowdown or arrest of a portion of cells in G2 and is already observed 2 hr after addition of 0.5–5.0 μCi/ml of [3H]UdR into cultures. At 2.5–5.0 μCi/ml of [3H]UdR a slowdown of cell progression through S is also apparent. Additionally, there is an increase in the number of cells with DNA values higher than 4C in cultures growing in the presence of [3H]UdR for 8–24 hr. A pulse of [3H]UdR of 2 hr duration labels predominantly (95%) cellular RNA. the first cell‐cycle effects (G2 slowdown) are observed when the amount of the incorporated [3H]UdR is such that, on average there are fewer than thirty‐six [3H] decays per cell which corresponds to approximately 12–19 rads of radiation. the S‐phase slowdown is seen at a dose of incorporated [3H]UdR twice as high as that inducing G2 effects. the specific localization of [3H]UdR in nucleoli, peripheral nucleoplasm and in cytoplasm, as well as differences in the kinetics of the incorporation in relation to phases of the cell cycle are discussed in the light of the differences between the effects of [3H]UdR and [3H]thymidine. Mathematical modelling of the cell‐cycle effects of [3H]UdR is provided.
Kinetic Analysis of Drug‐Induced G2 Block In Vitro
Authors: Kimmel Marek , Traganos Frank
Published: May 2008

The data on cell‐cycle effects of two prospective antitumour agents, (+)‐1,2,‐bis(3,5‐dioxopiperazine‐l‐yl)propane (soluble ICRF; NSC 169780) and 1,4‐bis(2′chloroethyl)‐1,4‐diazabicyclo [2.2.1] heptane diperchlorate (CBH; NSC 57198) were used to determine whether a modified stathmokinetic experiment could predict the effects of continuous, long‐term (0–48 hr) drug exposure in an in vitro L1210 murine leukaemia cell system. Generally, continuous drug exposure of exponentially growing cells does not provide sufficient quantitative information concerning cell‐cycle‐phase‐specific mechanisms of drug action. Alternatively, stathmokinetic experiments, which are usually limited to some fraction of one cell doubling time, provide little information about long‐term drug effects. By using mathematical models constructed for this purpose, however, stathmokinetic data can predict the overall proportion of cells affected by a drug though failing to discern between various kinds of drug action (e.g. reversible v. irreversible block, blocking v. killing action, etc.), especially when it occurs in G2 phase. In addition, it can be shown that for at least one of the drugs (soluble ICRF) the stathmokinetic experiment fails to predict ‘after‐effects’ of drug treatment which extend into the following cell cycle(s). It also becomes clear that the degradation of exponential growth characteristics of quickly dividing cells during long‐term, continuous drug exposure makes prediction of cell‐cycle kinetic perturbations uncertain when derived from short‐duration stathmokinetic experiments. However, with care, the joint application of ‘short term’ (e.g. stathmokinesis) and ‘long term’ (e.g. continuous exposure) techniques allow adequate quantitative insight into drug‐perturbed cell‐cycle kinetics. the applicability of modelling techniques is discussed: in the present instance it is limited to lower drug concentrations. For higher drug concentrations, effects like increased ploidy, ineffective division, etc., make it impossible in the present study to obtain a clear picture of the kinetics.
Determination of [3H]Tdr‐Labelling Indices of Cultured Cells Grown On Detachable Chamber Slides
Authors: Simpson William G. , Ballou Rick J. , Tseng Michael T.
Published: May 2008

The in vitro effects of xenobiotic agents on the incorporation of DNA precursors was determined using a detachable chamber slide assembly. the technique presented allows for the comparative assessment of several agents, even when a limited number of cells is available. the use of a glass slide also potentiates the use of higher magnifications with a greater resultant resolution than that achievable with past methods.
Haemopoietic modulation in tumour‐bearing animals: enhanced progenitor‐cell production in femoral marrow
Authors: Kovacs C. J. , Emma D. A. , Evans M. J. , Johnke R. M. , Scarantino C. W.
Published: May 2008

Altered haematopoiesis in the femoral marrow was observed in mice bearing the Lewis lung carcinoma (LLca). During tumour growth, a marked reduction was observed in the myeloperoxidase‐positive cells (granulocytes) of the marrow 7 days after inoculation of the LLca tumour reaching a nadir (17% of control) by day 28. Accompanying this suppression of mature white cells was a gradual expansion of the CFUc‐GM compartment followed by an increase in the number of femoral CFUs. Humoral‐stimulating activity (HSA) increased through day 14 in the serum of these animals; then returned to control levels by day 28. During this same interval, the more primitive erythroid progenitor (BFUe) compartment expanded to 168% of control, while the more differentiated (CFUe) compartment was reduced (45% of control at day 28). Reductions in both 59Fe‐incorporation and erythroblasts/femur confirmed the suppression of erythroid differentiation in marrow during tumour growth. Similar results were observed following the daily injection (188 mg equivalent dose; q 24 hr × 10) of the supernatant prepared from LLca tissue. Marked differences were observed between the response of the spleen and the marrow to the supernatant. the data suggest that the growth of the LLca tumour results in a dissociation of the normal continuity of haematopoietic steady‐state differentiation in the marrow of tumour‐bearing animals.
Crypt fission and crypt number in the small and large bowel of postnatal rats*
Authors: St. Clair W. H. , Osborne J. W.
Published: May 2008

The aim of this investigation was to study crypt fission, a process which may be instrumental in regulating crypt number in the intestine. Young Holtzman rats were killed at various times after parturition and samples of the small intestine and colon were removed and processed. A microdissection technique was used to separate crypts from other structures. Crypts were scored as normal or fissioning. the percentage of crypts in fission (PCF) reached peak values of 25% and 52% in the small bowel and colon, respectively, at 21 days post‐parturition. From this time onward, the PCF dropped until the adult value of approximately 7% was reached in each site. During this same period, the number of crypts increased from 1.9 × 106 to 3.3 × 106 in the small bowel and 2.2 × 105 to 6.5 × 105 in the colon. Thus an inverse relationship between the percentage of crypts in fission and crypt number was found. Distribution of fissure heights in fissioning crypts did not change as the animal aged. the majority of the fissures were found in the lower 1/4 of the fissioning crypts. This suggests that as soon as the fissure extends beyond the stem cell zone, division into two crypts soon occurs.
Quasi‐Exponential Generation Time Distributions From A Limit Cycle Oscillator
Authors: Klevecz R. R. , Shymko R. M.
Published: May 2008

In spite of the apparently random behaviour and the often exponential distribution of generation times expressed in cell populations, there is evidence for rather precise timekeeping in the cell cycle. In experiments using time‐lapse video‐tape microscopy, we have noted that cell generation times are often not distributed smoothly but in many cases seem to cluster at roughly 4 hr intervals. Phase shift responses following application of heat shock, ionizing radiation or serum pulses in each case show a pattern which is repeated twice in cells with an 8–9 hr modal generation time. We describe here a cell cycle model with an independent cellular clock controlling cell cycle events which accounts for the phase response data, while also reconciling the stochastic and periodic behaviour characteristic of animal cells.
Vindesine As A Stathmokinetic Agent In Human Rectal Tumours In Organ Culture
Authors: Pritchett C. J. , Senior P. V. , Sunter J. P. , Watson A. J. , Appleton D. R. , Wilson R. G.
Published: May 2008

Organ culture, using human colorectal mucosa and tumours, is a good system in which to test a new stathmokinetic agent such as vindesine. Using this system we have found that vindesine has similar metaphase‐arresting properties to vincristine, including at least a 6‐fold dose response difference in its ability to arrest mitosis in mucosa and tumour, mucosa being the more sensitive. Vindesine is a satisfactory stathmokinetic agent, but in view of its greater cost offers no particular advantages over vincristine.
Cyclic Amp Response to Various Haemopoietic Regulators
Authors: Wdzieczak‐Bakala J. , Pines M. , Guigon M. , Lenfant M.
Published: May 2008

Diffusible inhibitors and stimulators are involved in the regulation of bone marrow pluripotent stem cell (CFU‐S) proliferation. We have previously shown the existence of CFU‐S inhibitors in foetal calf marrow and liver and have started their purification. the lack of a simple and time‐saving test to determine the kinetic state of CFU‐S and the activity of the inhibitors led us to explore the possibility of a biochemical proliferation marker that could be used for screening purpose. Since it was shown that cyclic AMP was implicated in the regulation of CFU‐S proliferation, it was of interest to study the variations in cAMP levels after stimulation and inhibition of CFU‐S entry into cycle. the results of in vitro experiments showed that the increase in cAMP levels observed in bone marrow cells after incubation with different haemopoietic stimulators was specific neither for bone marrow cells nor for the various haematopoietic regulators. In the in vivo experiments, an increased cAMP level was observed 8 hr after one injection of Ara‐C at the time when CFU‐S are recruited into S phase. However, no modification of cAMP levels has been observed after injection of CFU‐S inhibitors in the Ara C‐treated mice. Although cAMP does not seem to be a suitable marker for testing the activity of inhibitory fractions during the purification process, this work has contributed to the study of CFU‐S stimulators.
Metaphase‐Arrest Technique Applied to Human Cervical Epithelium. Ii. Cell Production Rates In Normal and Pathological Cervical Epithelium
Authors: Ireland David
Published: May 2008

An application of the metaphase‐arrest technique to human cervical epithelium, in vivo, was utilized to obtain cell birth rate data for seventy‐six patients with normal and pathological cervical epithelium. Mean cell production rates for basal and parabasal layers of normal epithelium were 0.91 and 0.92 cells/1000 cells/hr respectively. Histologically normal epithelium adjacent to CIN (cervical intra‐epithelial neoplasia) had a significantly higher rate for the parabasal layer compared to the ‘normal’ group (P < 0.05). Values for the lower two‐thirds of CIN III were 8–10 times higher than for normal epithelium, with microinvasive carcinoma having the highest rates of all. Values for wart‐affected cervical epithelium (NCWVI) were intermediate between normal and CIN, but there was activity in the superficial layer, possibly reflecting activity of the papilloma virus. Large variation in birth rates between individuals in the same histological category was noted for each group, this being particularly the case in six patients with early invasive carcinoma.

The data is used to attempt to elucidate some of the uncertainties surrounding the aetiology and biological behaviour of cancer of the cervix and its precursors. Sources of inaccuracy are emphasized and practical difficulties discussed.
Effect of Erythropoietic Stimulation of the Chamber Host On the Growth of Haemopoietic Colonies In Plasma Clot Diffusion Chambers (PCDC)
Authors: Pojda Z. , Wiktor‐Jedrzejczak W.
Published: May 2008

Murine marrow cells were cultured in Millipore diffusion chambers implanted into the peritoneal cavity of variously conditioned murine hosts. Preirradiation (350 cGy), bleeding (0.5 ml) and phenylhydrazine injection (75 mg/kg i.v.) when performed together on the chamber host, induced better growth of erythropoietic and granulopoietic colonies inside the PCDCs than either of these manoeuvres alone. Small erythrocytic colonies (CFU‐E derived) and small granulocytic colonies were observed at day 3 of marrow culture. Erythropoietic bursts and large granulocytic colonies were observed at day 8 of chamber culture. Colonies of macrophage‐like cells, fibroblast‐like cells, mixed erythro‐granulopoietic colonies and megakaryoblasts were observed less regularly in chambers incubated in these conditions. the study provides a standardized, relatively reproducible PCDC culture system for studies of both erythro‐ and granulopoiesis, and does not require a hypoxic chamber.
Use of Growth‐Attachment Correlation Plots to Analyse Human Melanoma Cell Dependency On 2‐Oxocarboxylates and Serum
Authors: Kay G. F. , Ellem K. A. O.
Published: May 2008

Modulation of the population‐dependent growth of the human melanoma line MM96 by serum and a series of 2‐oxocarboxylates was analysed by a method offering several useful features. Initial cell attachment was measured by the use of cells prelabelled with [14C] thymidine (C) while the size of the replicating cell population on any particular day was monitored by [3H] thymidine (H) incorporation for that particular 24 hr. the 3H incorporation was normalized for the initial cell attachment as the 3H/14C ratio (H/C), which was found to be little affected by artifacts of precursor equilibration. the method allows large numbers of replicate samples so that quantitation of dose‐response relationships is simple and statistically robust, and simultaneous monitoring of cell attachment and growth within the same sample is routine.

Not only cell growth, but also attachment to the culture vessel surface was found to be increased by higher seeded population densities, by increasing serum concentration and by pyruvate supplementation. Further investigation of the pyruvate effect showed that all nine of the soluble 2‐oxocarboxylates tested were effective for both parameters, with little difference between them which was attributable to molecular structure.

Quantitative studies of the potentiation of growth and attachment by increasing cell density or a range of concentrations of 2‐oxocarboxylates led to the finding that increments in the growth parameter (H/C) were directly proportional to increments in attachment (C). Such a relationship would be unexpected in ordinary logarithmically‐growing cultures. the observation is consistent with the hypothesis that increases in initial cell attachment, whether induced by 2 oxocarboxylates or higher inoculation densities, lead to conditioning of the medium by cell factors which stimulate growth and are produced in amounts proportional to the attached cell numbers. Pyruvate, when present with higher serum concentrations, stimulated growth above the levels accounted for by concomitant increases in cell attachment. Serum also appears to have other potentiating factors in addition to those attributable to its content of 2‐oxocarboxylates. Differences in the response to 2‐oxocarboxylates of human melanoma cells and human diploid fibroblasts were noted, and suggest that the present observations may be due to unique properties of the melanoma cell.
Digestive Tract Cell Proliferation and Food Consumption Patterns of Ha/Icr Mice
Authors: Burholt D. R. , Etzel S. L. , Schenken L. L. , Kovacs C. J.
Published: May 2008

The relationship between the daily pattern of food consumption and the proliferation rate of the qesophagus, stomach, forestomach, small intestine and colon of Ha/ICR mice was examined. Proliferative activity was determined by [3H]TdR incorporation on a wet weight tissue basis, along with selective counting of labelled nuclei. Under conditions of ad libitum feeding with a 12 hr light cycle (lights on at 0600) mice eat most of their food during the dark period. A distinct circadian rhythm was observed in the oesophagus, stomach, forestomach and colon with the peak of [3H]TdR incorporation between 0400 and 0600 and the nadir between 1600 and 1800. Although a circadian fluctuation was observed in the small intestine, its amplitude was much less than in other areas. This rhythmic change in proliferation rate could be phase shifted by allowing the mice to feed only between 0800 and 1600 for 14 days. Under these conditions the peak in proliferative activity occurred between 1800 and 2000. Fasting reduced the daily level of proliferative activity in all of the digestive tract sites studied, and for all areas except the oesophagus greatly reduced or eliminated the circadian fluctuation. the forestomach and colon were the most influenced by fasting with 24 hr [3H]TdR incorporation reduced to 30–40% of the control value. Refeeding following a 48 hr fast produced a rapid increase in proliferative activity peaking at levels well above the control value at 16 hr after the onset of refeeding. the major exception to this was the small intestine which slowly returned to the control value during the first 24 hr. Partial refeeding produced a diminished refeeding response. Once the normal pattern of food consumption was re‐established following refeeding the normal proliferative fluctuations were again observed.
Separation By Velocity Sedimentation of Human Haemopoietic Precursors Forming Colonies in vivo and in vitro Cultures
Authors: Niskanen E. , Wells J. R. , Golde D. W. , Cline M. J.
Published: May 2008

Cells which give rise to granulocyte‐macrophage colonies under the influence of peripheral blood white cells (CFU‐c (WBC)) and Mo T cell conditioned medium (CFU‐c (Mo)) sedimented at a faster rate than the cells which form mixed erythroid‐granulocytic colonies in methylcellulose in vitro (CFU‐mix) and granulocytic (CFU‐dg) and megakaryocytic (CFU‐dm) colonies in diffusion chambers in mice. Despite identical peak sedimentation rate for the two CFU‐c populations, sedimentation profiles suggest that they are heterogeneous with respect to size. A proportion of CFU‐c (Mo) may be identical with CFU‐dg and CFU‐mix. Sedimentation profiles for cells which give rise to mixed colonies in vitro (CFU‐mix) and to granulocytic colonies in diffusion chambers in cyclophosphamide pretreated mice (CFU‐dg (CY)) and in Mo conditioned medium treated mice (CFU‐dg (Mo)) were similar. On the average CFU‐dm sedimented somewhat slower than CFU‐dg. These and other observations suggesting a close relationship between CFU‐dg and multipotential haemopoietic precursors are discussed.
Pig Epidermis: A Cell Kinetic Study
Authors: Morris G. M. , Hopewell J. W.
Published: May 2008

The basal cell density (BCD), labelling index (LI), duration of DNA synthesis (Ts) and cell cycle time (Tc) have been calculated for the epidermis of pigs in the age range 4–27 months. the BCD declined progressively from 143.4 ± 6.5 cells/mm at 4 months to 128.8 ± 8.3 cells/mm at 15 months, whereafter the values showed little change. There was a small decrease in LI with increasing age, from 7.9 ± 1.5% at 4 months to 5.9 ± 1.0% at 27 months. However, the change to housing animals outdoors as compared with indoors had a greater effect on the LI (∼10%). Severe weathering in the skin of animals housed outdoors resulted in a very high LI (∼20%). Neither Ts or Tc varied significantly with age. Ts was within the range 8.8–9.2 hr and Tc 127–161 hr. In animals housed outdoors Tc was reduced relative to animals housed indoors. the BCD and Ts were not affected by housing conditions. the kinetic parameters investigated in the pig were similar to those reported for man.
Analysis of Cell Flow and Cell Loss Following X‐Irradiation Using Sequential Investigation of the Total Number of Cells In the Various Parts of the Cell Cycle
Authors: Skog S. , Tribukait B.
Published: May 2008

The cell flow and cell loss of an in vivo growing Ehrlich ascites tumour were calculated by sequential estimation of changes in the total number of cells in the cell cycle compartments. Normal growth was compared with the grossly disturbed cell flow evident after a 5 Gy X‐irradiation.

The doubling time of normal, exponentially growing cells was 24 hr. the generation time was 21 hr based on double‐isotope labelling studies and the potential doubling time was 21 hr. Thus, the growth fraction was 1.0 and the cell loss rate about 0.5%/hr. Following irradiation, a transiently increased relative outflow rate from all cell cycle compartments was found at about 3 and 40 hr, and from S phase at 24 hr after irradiation. Minimum flow rates from all compartments were found up to 20 hr. Cell loss as calculated from the cell flow was compared with non‐viable cells determined by Percoll density separation. Increase in cell loss as well as non‐viable cells was observed at 24 hr after irradiation at the time of release of the irradiation‐induced G2 blockage. Up to 50 hr, about 70% of the initial total number of cells were lost. the experiments show the applicability and limitations of cell flow and cell loss calculations by sequential analysis of the total number of cells in the various parts of the cell cycle.
Dna Synthesis Rate Changes During the S Phase In Mouse Epidermis
Authors: Clausen O. P. F. , Kirkhus B. , Elgjo K. , Pedersen S. , Bolund L.
Published: May 2008

The in vivo DNA synthesis rate throughout the S phase of mouse epidermal cells was investigated. Epidermal basal cells were isolated at various times of the day from normal animals injected with [3H]TdR 30 min before sacrifice, and from pulse‐labelled animals with regenerating and growth‐inhibited epidermis. the cells were analysed by DNA flow cytometry combined with cell sorting. Cells from successive fractions of the S phase were sorted on glass slides and subjected to quantitative [3H]TdR autoradiography.

The results confirmed the presence of unlabelled (slowly replicating) cells in the S phase, the proportion of which was circadian stage‐dependent with minimum values at midnight and in the early morning. the DNA synthesis rate throughout the S phase showed a general trend with high values in the mid‐fractions, a pattern which was similar in normal and in growth perturbed epidermis. In the early morning the DNA synthesis rate pattern was bimodal with maxima both in the first and second half of the S phase, with a corresponding trough in mid‐S. At this time of day the cell progression rate through S is at its maximum, indicating a relationship between the overall DNA synthesis rate and the rate distribution pattern through S.
Mitotic Response to Wounding In Goitrous and Normal Rat Thyroid: Implications For Thyroid Growth Control
Authors: Wynford‐Thomas David , Michael Bradley , Stringer John , Harach Hector Ruben , Williams E. Dillwyn.
Published: May 2008

Abstract. Thyroid growth in the rat in response to a sustained elevation of serum thyrotropin (TSH) is limited by a progressive desensitization of the follicular cells to the mitogenic action of TSH which is not reversed by withdrawal of stimulation or by reduction of cell number. This study shows that, in thyroids which have reached a ‘plateau’ of growth, wounding induces a marked local follicular cell mitotic response which is equal in magnitude to that seen in control glands. This demonstrates that these cells, which are refractory to TSH, have not lost the capacity to divide. It is concluded that limitation of TSH‐induced thyroid growth is not due to a non‐specific loss of mitotic capacity resulting from severe hypothyroidism or goitrogen toxicity, or to an inherent limitation of the number of divisions which a follicular cell can undergo. the implications of these findings are discussed.
Effect of Trifluoperazine On Dna Synthesis During Liver Regeneration
Authors: Soriano Montserrat , Piñol Rosa , Enrich Carles , Bachs Oriol
Published: May 2008

Abstract. An intraperitoneal injection of the calcium‐calmodulin blocker trifluoperazine into rats at 4 hr after a partial hepatectomy produced a strong inhibition of DNA synthesis observed at 24 hr after surgery; but when injection was administered at 20 hr after hepatectomy, it did not produce any effect on DNA replication. These observations indicate that trifluoperazine acted by blocking one or more events involved in triggering DNA replication but it did not affect on‐going DNA synthesis. A more detailed study indicated that when trifluoperazine was injected at 4 hr after surgery, a 12 hr delay in the cytosolic calmodulin surge observed between 6 and 12 hr after partial hepatectomy (previous to initiation of DNA replication) and also in the starting of DNA synthesis was produced. These findings suggest that the pre‐replicative surge of cytosolic calmodulin could be involved in triggering DNA synthesis observed after partial hepatectomy.
Mesenteric Lymphoblast Localization Throughout the Murine Small Intestine: Temporal Analysis Relating Intestinal Length and Lymphoblast Division
Authors: McDermott M. R. , Horsley Beverley A. , Warner Alison A. , Bienenstock J.
Published: May 2008

Abstract. Mesenteric lymphoblasts (MLN) have a predilection to selectively localize in the lamina propria and epithelium of the small intestine. Using an adoptive transfer method, we examined the localization kinetics of these blasts in the intestinal wall with respect to their distribution from duodenum to terminal ileum and also assessed their mitotic activity by autoradiographic techniques. 3H‐thymidine‐labelled MLN cells were found throughout the small intestine by 6 hr post‐transfer and reached a maximum frequency in this organ by 24 hr post‐transfer.

Donor blasts were most frequent in the duodenum and terminal ileum regions of the gut. Subsequently, the frequency of labelled cells throughout the intestinal wall declined to near zero. the apparent accumulation of MLN blasts in the gut was not related to either a temporary retention and departure from the pulmonary vasculature or to mitotic division of labelled cells in the gut wall. A model describing the relationship between MLN blast localization kinetics in various segments of the intestine was formulated.
Graphical Method For Analysing Stathmokinetic Data
Authors: Roti Joseph L.
Published: May 2008

Abstract. The accumulation of cells in G2M measured flow cytometrically follows a straight line when plotted against time in colcemid with the transform ln (1 +fg2M), where fG2M, is the fraction of cells in the G2M peak. Extending this function to the value, In 2, will locate a point B. Drawing a line from point B to In 1 perpendicular to the abscissa, will locate point A at the initial value of In (1 +fG2M). A line from In 2 at t= O through point A will intersect the abscissa at the cell doubling time. Application of this method to the depletion of G1 cells is also possible.
Liver Dna Synthesis After Phenytoin Injection In Adult Nmri Mice
Authors: Lombard M.‐N. , Petter C. , Boucher‐Ehrensperger M.
Published: May 2008

Abstract. Stimulation of hepatocyte DNA synthesis was observed in adult mice, as measured by the number of parenchymal cells in S phase, at two different times after a single i.p. injection of diphenylhydantoin (DPH): 18 and 25 hr. No such stimulation was obtained for Kupffer or endothelial cells.
Rate of Non‐Adherent Cell Loss From Long‐Term Cultures of Murine Bone Marrow: Effect of Medium Conditioned By the Adherent Cell Population
Authors: Janssen W. E. , Snell F. M. , Anbar M.
Published: May 2008

Abstract. The rate of random spontaneous cell loss from the non‐adherent cell population of long‐term cultures of murine bone marrow was determined. the measured rate of non‐adherent cell loss is affected by previous conditioning of the medium in which the non‐adherent cells are suspended. Specifically, the measured rate of non‐adherent cell loss is significantly slowed when the non‐adherent cells are suspended in medium conditioned in long‐term haematopoietic cultures instead of fresh medium. It appears that a subset of the adherent cell population is the source of the factor or factors within the medium which result in this slower measured rate of non‐adherent cell loss. This effect may be due to the stimulation to division of haematopoietic progenitor cells, offsetting the lysis of other non‐adherent cells.
Stathmokinetic Analysis of Human Epidermal Cells in vitro
Authors: Kimmel Marek , Darzynkiewicz Zbigniew , Staiano‐Coico Lisa
Published: May 2008

Proliferation kinetics of cultured human epidermal cells is characterized in quantitative terms. Three distinct subpopulations of keratinocytes, two of which are cycling have been discriminated by two parameter DNA/RNA flow cytometry. Based on mathematical modelling, the cell cycle parameters of the cycling subpopulations have been assessed from stathmokinetic data collected at different time points after initiation of cultures (7–15 days). the first subpopulation is composed of low‐RNA cells which resemble basal keratinocytes of epidermis and which show some characteristics of stem cells; these cells have a mean generation time of approximately 100 hr. the second subpopulation consists of high‐RNA cells, resembling stratum spinosum cells of epidermis, which have an average generation time of approximately 40 hr. the third subpopulation consists of non‐cycling cells with Go/G1 DNA content, with cytochemical features similar to those of cells in granular layer of epidermis.

The results based on modelling can reproduce with acceptable accuracy the actual growth curve of the cultured cell population. Analysis of kinetics and differentiation of human keratinocytes is of interest in view of the recent application of cultured epidermal cell sheets for transplantation onto burn wounds. the results of this study also reveal the existence of regulatory mechanisms associated with proliferation and differentiation in the cultured epidermal cell population.
Growth Fraction of Myelocytes In Normal Human Granulopoiesis
Authors: Dresch C. , Troccoli G. , Mary J. Y.
Published: May 2008

Abstract. The labelling index (LI) of myelocytes (M) after flash labelling of normal human bone marrow cells with [3H]‐thymidine ([3H]TdR) is always lower that the LI obtained for myeloblasts (MB) and for promyelocytes (PM). This fact can be interpreted in two ways: it may mean that the duration of the G1 phase of the cell cycle is longer in M than in MB or PM, or it may mean that the proportion of cells in cycle, i.e., the growth fraction (GF), is lower in the M population than in MB or PM. the evolution of the LI and of the mean number of grains per cell was monitored in [3H]TdR‐labelled normal bone marrow during in vitro incubation for 50 hr. the generation time, measured by the halving time of the mean number of grains per cell after flash labelling, was similar for M to that for MB and PM. During continuous labelling, the LI of MB and PM reached 1 and the LI value for M never rose to more than 50% of the values recorded for MB and PM after 30 hr. These findings give support to the second hypothesis, i.e., a lower GF in the M population. Good correlation was found between the LI of M and the proportion of mature polymorphonuclear cells in the bone marrow of normal subjects and of patients with chronic benign neutropenia or hyperleucocytosis. Variations in the M growth fraction could be a medium‐term (2‐3 days) regulatory factor in granulocyte production.
Effects of Extremely Low Frequency (Elf) Electric Fields On Cell Growth and Dna Repair In Human Skin Fibroblasts
Authors: Whitson G. L. , Carrier W. L. , Francis Andrew A. , Shih C. C. , Georghiou S. , Regan James D.
Published: May 2008

Abstract. A number of physical and chemical agents in the environment have been studied for their ability to induce or alter DNA repair mechanisms in human cells. We have investigated the effects of 60 Hz, 1000 V/cm electric fields on DNA repair in normal human fibroblasts in vitro. an examination was done on the ability of electric fields suspected to cause damage which could be repaired by thymine dimer excision and measurable by the bromodeoxyuridine photolysis assay. the thymine dimer assay with enzyme‐sensitive site analysis was used to measure the cells' capacity for removing ultraviolet light (u.v.)‐induced pyrimidine dimers; (i) during exposure to electric field 24 hr before U.V. irradiation; (ii) 24 hr after U.V. irradiation; and (iii) up to 48 hr continuously after U.V. irradiation. Cell growth and cell survival following electric field exposure were also studied. Within the limits of these experiments, it was found that exposure to such electric fields did not alter cell growth or survival, and no DNA repair or alteration in DNA excision repair capacity was observed as compared with unexposed control cultures.
Cell Growth and Cell Division: Dissociated and Random Initiated?
Authors: Sennerstam R. , Stromberg J. O.
Published: May 2008

Abstract. The ‘random transition probability’ cekycle models have so far failed to convincingly link the transition events with phenomena describable by biochemical methods. the study presented was carried out on the F9 and PCC3 N/1 embryonal carcinoma (EC) cell lines. We now report an extended analysis of the two‐random transition probability (TP) model and preliminary results are presented showing that the deterministic L period in that model can be regarded as reflecting the ‘cell‐growth cycle’. Evidence is presented that suggests that the ‘cell‐growth cycle’ is a supramitotic deterministic phase—i.e. starting in one cell cycle and being completed in the next following G1 period and dissociated from the ‘DNA‐division cycle’. This phenomenon makes an interesting contribution to the old knowledge of a stepwise G1 prolongation during early embryogenesis in yielding a mechanism by which the cell can alter the ratio of nucleus to cytoplasm prior to the onset of gene expression.
Cell Kinetic Studies of the Effect of A Combined Therapy With 1‐βd‐Arabinofuranosylcytosine (Ara‐C) and X‐Irradiation On the L1210 Ascites Tumour
Authors: Fietkau R. , Maurer‐Schultze B.
Published: May 2008

Abstract. We studied the effect of combined therapy with X‐ray and 1‐β‐D‐arabinofuranosylcytosine (Ara‐C); firstly the effect of whole‐body X‐irradiation alone on the proliferation of the L1210 ascites tumour of the mouse was studied by autoradiographic and cytofluorometric (FCM) methods. the effect of X‐irradiation with 4 Gy was mainly a cytostatic one leading to an altered distribution of the cells throughout the cycle due to radiation induced mitotic delay. the cytocidal effect is negligible.

As is known from previous studies (Fietkau, Friede & Maurer‐Schultze, 1984) the effect of 200 mg/kg Ara‐C consists of an inhibition of DNA synthesis and of killing a considerable portion of the L 1210 cells, predominantly of S phase cells.

With respect to the importance for potential therapeutic regimens, the influence of the sequence and the time interval between the two therapeutic steps on the survival of tumour‐bearing mice was studied. Most combination therapies significantly increase the survival of tumour‐bearing mice compared to the single therapeutic steps; however, no significant differences between the various combined therapies were found. Whole‐body X‐irradiation with 4 Gy followed by the application of 200 mg/kg Ara‐C 10 hr later resulted in the greatest increase of the mean survival time of tumour‐bearing animals, from 13.2 to 17.4 days. It was shown that apart from the cytocidal effect on S‐phase cells, Ara‐C also kills cells sublethally damaged by a preceding X‐irradiation.
Influence of the Beta‐Adrenergic Antagonists Propranolol, Practolol and Oxprenolol On the Proliferation of Rat Jejunal Crypt Cells
Authors: Maurer‐Schultze B. , Brau N. , Theiss M. , Wachsmuth E. D.
Published: May 2008

Abstract. Beta‐adrenergic blockade by quite large doses of propranolol, practolol and oxprenolol, once or continuously applied, does not influence jejunal crypt‐cell proliferation in the rat. After a single i.p. injection of 20 mg/kg propranolol or practolol and even of 100 mg/kg practolol, the mitotic index, the labelling index and the duration of the S phase do not differ between treated and untreated control animals nor between animals treated with the different drugs. Continuous application of 30 mg/kg/d propranolol, practolol or oxprenolol for 7 or 14 days does not affect the mitotic and labelling indices either, nor does it change the duration of the cycle of the jejunal crypt cells and its phases as determined by the percent labelled mitoses method. These results are in contrast to those reported previously by Tutton & Helme (1974).
A Computer Model of Spermatogenesis In the Rat; Correlation With Flow Cytometric Data Based On Autoradiographic Cell‐Cycle Properties
Authors: van Kroonenburgh M. J. , van Gasteren H. J. , Beck J. L. , Herman C. J.
Published: May 2008

Abstract.A computer model of rat spermatogenesis was created, based on autoradiographic studies of durations of the phases of the cell cycle (G1, S, G2and mitotic phases) of each germ‐cell type. With this model it is possible to predict and to gain insight into the changes of the DNA content occurring during the normal process of spermatogenesis. the relative proportions of haploid, diploid, S phase and tetraploid germ cells with increasing age of the rats were calculated. Calculated and actual experimental flow cytometry data were compared to test the accuracy of the model, and these show good agreement. the present work demonstrates that single‐parameter DNA analysis of testicular cells is primarily a reflection of germ cells in the spermatocyte and spermatid stages of development, and of non‐germ cells. the FCM single‐parameter DNA analysis of testicular cells is relatively insensitive to changes in the stem cell and spermatogonial stages of germ‐cell development.
Use of Bromodeoxyuridine For Cell Kinetic Studies In Intact Animals
Authors: Wynford‐Thomas D. , Williams E. D.
Published: May 2008

Abstract. A method is described for the use of BUdR for tracing cell proliferation patterns in the intestinal mucosa of intact mice.

The method has several distinct advantages over existing methods.

Bromodeoxyuridine (BUdR) is a well‐established alternative to tritiated thymidine ([3H]TdR) as a tracer for studying DNA replication. However, its use in cytological as opposed to biochemical studies has been largely confined to examination of metaphase spreads, particularly analysis of sister chromatid exchange (Block, 1982). For this, BUdR incorporation into DNA has been demonstrated using the fluorescent dye Hoechst 33258, together with fluorescence microscopy (Latt, 1973), or Giemsa staining (Perry & Wolf, 1974). Recently, introduction of a monoclonal antibody which recognizes BUdR in single‐stranded DNA (Gratzner, 1982) has enabled BUdR to be used for studying cell cycle kinetics in a manner exactly analogous to the use of [3H]TdR. This has been reported for whole cells in suspension and in monolayer (Dolbeare et al., 1983; Dean et al., 1984; Raza et al., 1984). BUdR included in tissue culture medium is taken up and incorporated into newly synthesized DNA via the same pyrimidine salvage pathway as [3H]TdR (thymidine kinase). A concentration of as little as 10 μm—well below cytotoxic levels (Cerni, 1984)—is sufficient to give readily detectable labelling by immunocytochemistry with a pulse of less than 15 min. the validity of BUdR labelling for cell kinetic studies has been well established in comparisons with other methods by Dolbeare et al. (1983), Dean et al. (1984), and Raza et al. (1984).

We describe here the use of BUdR together with an immunocytochemical detection system applied to sections of wax‐embedded tissues, which provides a convenient method of cell cycle analysis in intact animals.