bluuebunny/crossref_metadata_2025 huggingface dataset:
THE PROLIFERATION OF LYMPHOID CELLS IN GUINEA‐PIG BONE MARROW
Authors: Miller S. C. , Osmond D. G.
Published: May 2008

A double isotope DNA labelling method has been used to determine the duration of DNA synthesis (S) in bone marrow lymphoid cells classified by their nuclear diameters in smears. Incorporation of 3H‐thymidine was confined almost entirely to marrow lymphoid cells of 8·0‐15·0 μm nuclear diameter (large lymphoid cells). After exposure to 3H‐thymidine in vivo and 14C‐thymidine 40‐104 min later in vitro, the proportion of cells labelled with 3H alone to those labelled with 14C(±3H) in radioautographic smears, plotted against time indicated the efflux from S per hour. Collectively, 28·3 ± 1·1% of all large lymphoid cells were in S and the efflux from S was 15·1% per hour. With decreasing cell size (nuclear diameter) the efflux fell progressively from 28·3% per hour (11·0 μm) to 9·2% per hour (8·0‐8·9 μm) and the proportion of cells in S declined from 54·9 ± 2·3% to 14·8 ± 1·6%. Influx into S, measured in vitro by reversing the sequence of isotopes, closely resembled the corresponding efflux values in vivo relative to cell size. Most DNA synthesizing marrow large lymphoid cells belonged to a subgroup with deeply basophilic cytoplasm. The results demonstrate that basophilic large lymphoid cells in the marrow are actively proliferating and have a mean S phase duration of 6·6 hr. The largest marrow lymphoid cells (11·0 μm) proliferate most rapidly (S phase, 3·5 hr; maximum cell cycle time, 6·4 hr) while S duration is prolonged progressively to 10·9 hr for the smaller cells (8·0‐8·9 μm).
INCREASE OF DNA POLYMERASE ACTIVITY FIRMLY BOUND TO NUCLEI DURING THE DNA SYNTHETIC PHASE OF THE CELL CYCLE
Authors: Furlong N. B. , Novak W. B. , Stubblefield T. E.
Published: May 2008

DNA polymerase activities were measured on nuclear and supernatant fractions obtained from hamster fibroblast cells (the Don‐C clone) grown in tissue culture and mitotically synchronized by selective removal of cells arrested in metaphase following a brief exposure to colcemid. A reproducible fraction (5–10%) of the polymerase activity was found to remain bound in the nuclear pellet after repeated cycles of freezing and thawing. The specific activity of this firmly‐bound nuclear DNA polymerase was found to increase during S‐phase in proportion to DNA synthesis. The bulk of this activity, after extraction in 1 m salt, exhibited an S value of 8·7 on neutral high salt sucrose gradients and was 24 times more active with poly dA. dT10 as template than with heat denatured DNA. The rest of the cellular DNA polymerase activity showed no significant variation correlated with the cell cycle. This activity also had an S value from 8 to 9 but it was only 2·8 times more active with the homopolymer template than with heat denatured DNA. DNA polymerase activity similar to the firmly‐bound activity was found in extracts prepared from metaphase chromosomes.
CYTOKINETIC ANALYSIS OF THE JB‐1 ASCITES TUMOUR AT DIFFERENT STAGES OF GROWTH
Authors: Dombernowsky P. , Bichel P. , Hartmann N. R.
Published: May 2008

The cell kinetics of the murine JB‐1 ascites tumour have been investigated on days 4, 7 and 10 after transplantation of 2·5 × 106 cells. The experimental data, growth curve, percentage of labelled mitoses curves, continuous labelling curves and cytophotometric determination of single‐cell DNA content have been analysed by means of a mathematical model for the cell kinetics. The important result was the existence of 8% non‐cycling cells with G2 DNA content in the 10‐day tumour, while only 0·2 and 0% were observed in the 7‐ and 4‐day tumours, respectively. The doubling times determined from the growth curve were 22·8, 70 and 240 hr, respectively, in the 4‐, 7‐ and 10‐day tumours. Growth fractions of 76, 67 and 44% were calculated for the same tumour ages. The mean cell cycle time increased from 14 to 44 hr from day 4 to 7 due to a proportional increase in the mean transit time of all phases in the cell cycle. In the 10‐day tumour, the mean cell cycle changed to 41 hr and TG1 decreased to 0·5 hr. The cell production rate was 4·3%/hr in the 4‐day tumour, 1·2%/hr in the 7‐day tumour and 1·0%/hr in the 10‐day tumour. The cell loss rates in the same tumours were 1·3, 0·2 and 0·7%/hr, respectively. The analysis made it probable that the mode of cell loss was an age‐specific elimination of non‐cycling cells with postmitotic DNA content.
CHANGES OF LYMPHOCYTE KINETICS IN THE NORMAL RAT, INDUCED BY THE LYMPHOCYTE MOBILIZING AGENT POLYMETHACRYLIC ACID
Authors: Ormai S. , Hagenbeek A. , Palkovits M. , van Bekkum D. W.
Published: May 2008

The changes in lymphocyte kinetics induced by the lymphocyte mobilizing agent polymethacrylic acid (PMAA) were studied in the normal rat. Quantitative data are presented concerning the degree of lymphocyte mobilization in the spleen and in various lymph nodes at different times after PMAA administration. Data were also obtained regarding the exact site of lymphocyte mobilization in the spleen. Evidence is given that PMAA mobilizes both T and B lymphocytes.

Furthermore, results are presented on the different routes along which mobilized lymphocytes reach the blood. It is concluded that lymphocytes mobilized from the various lymph nodes are transported to the peripheral blood mainly by way of the efferent lymphatics (‘indirect’ route) while lymphocytes mobilized from the spleen will enter the blood chiefly via the so‐called ‘direct’ route.

The relevance of these data to lymphocyte kinetics is discussed in relation to the planning of effective irradiation schedules for extra‐corporeal irradiation of the blood during induced lymphocyte mobilization.
KINETICS OF GROWTH OF HAEMOPOIETIC COLONY CELLS IN AGAR
Authors: Testa N. G. , Lord B. I.
Published: May 2008

Cell kinetic parameters of mouse granulocytic and mononuclear cells growing in colonies in agar cultures have been measured. Analysis of flash and continuous labelling studies with 3H‐thymidine together with determinations of colony size, growth fraction and mitotic indices, gave the following values for the phases of the cell cycle: G1= 6·3 1·6 hr, S = 5·8 ± 1·4 hr, G2= 1·7 ± 0·1 hr and M = 0·7 ± 0·1 hr (42 ± 8 min). No difference in the cell cycle parameters of granulocytic and mononuclear cells were found in this study.

Colonies of different size from cultures of the same age group had similar labelling indices, indicating that the size of a colony is not a function of the rate of proliferation of cells in the colony. Rather, variation in colony size is probably representative of an initial delay in the onset of colony development.
CELL KINETICS IN MOUSE THYMUS STUDIED BY SIMULTANEOUS USE OF 3H‐THYMIDINE AND COLCHICINE
Authors: Borum Kirstine
Published: May 2008

Following an injection of 3H‐thymidine to mice there is no initial incorporation in small thymocytes, only in larger ones. In the course of time small thymocytes aquire the label. Whether the delayed uptake in small thymocytes is due to a direct cell to cell transfer of labelled nuclear material from inititally labelled larger cells to small thymocytes, or whether it is due to small thymocytes being formed from larger cells by mitotic division was investigated by the administration of Colcemid® immediately after one injection of 3H‐thymidine. In the absence of cell division no labelled small thymocytes appeared with time. This finding does not support the idea of a cell to cell transfer of DNA; it rather lends support to the view that small thymocytes arise by mitotic division of larger cells in the thymus. During the treatment with Colcemid® the migration of cells took place from peripheral to central cortex just like under normal conditions.
DIFFERENCES IN REUTILIZATION OF THYMIDINE IN HEMOPOIETIC AND LYMPHOPOIETIC TISSUES OF THE NORMAL MOUSE
Authors: Feinendegen L. E. , Heiniger H. J. , Friedrich G. , Cronkite E. P.
Published: May 2008

Swiss Albino mice received a single i.v. injection of 3H‐thymidine (TdR) or of 125I‐deoxyuridine (IUdR). Bone marrow, thymus, spleen and mesenteric lymph node were examined for the efficiency of precursor incorporation into DNA, and for DNA renewal from day 1 to day 8.

TdR is 5–8 times more efficiently incorporated by the different organs in vivo and in vitro than is IUdR. This indicates that the discrimination against IUdR occurs at the level of DNA synthesizing cells.

A diminished DNA turnover rate measured with 3H‐TdR in comparison with 125I‐UdR is interpreted to indicate reutilization of TdR.

TdR reutilization was observed in bone marrow and spleen from at least day 1 on, and in the thymus from day 3 on, following pulse labeling of DNA synthesizing cells. The degree of TdR reutilization appears higher in the thymus (67%) than the bone marrow (43%) and spleen (38%). The mesenteric lymph node indicates either no, or a very low efficiency of TdR reutilization. The data are also consistent with a reutilization equally efficient for TdR and IUdR.

It is suggested that the TdR salvage pathway in hemopoietic tissues is largely localized to single organs which have immediate access to TdR made available by catabolism of DNA. The contribution of TdR from systemic reutilization to the organs studied falls within the limits of error of measurements. Moreover, the TdR salvage pathway especially in the lymph node may involve other DNA breakdown products than nucleosides.
HEMOPOIETIC CELL LINE‐SPECIFIC EFFECTS OF RENAL GRANULOPOIETIC FACTOR (GPF) ON TRANSPLANTABLE MOUSE MARROW STEM CELLS: COMPARISON WITH ERYTHROCYTE STIMULATING FACTOR (ESF) AND ENDOTOXIN
Authors: Delmonte L.
Published: May 2008

The Till‐McCulloch spleen colony system was used to differentiate the time‐ and dose‐dependent effects of GPF (calf renal granulopoietic factor), ESF (erythrocyte stimulating factor) and Pyrexal (endotoxin from S. abortus equi) on the total and differential exocolonizing potential of treated donor mouse marrow cells. A single optimal dose of either hemopoietin given to the donor was found to activate transplantable colony forming units (CFU) of the hemopoietin‐specific cell line. There followed a series of time‐dependent oscillatory waves of specific CFU activation, the magnitude of which gradually dampened over a period approximating the stimulated cells’generation time. Flooding doses of GPF and ESF abrogated this phenomenon. Combination treatment with GPF and ESF cancelled out the cell line‐specificity of CFU stimulation, presumably due to the two hemopoietins’competition for a common stem cell. Multiple doses of GPF were found to potentiate the granulopoietic effects of a single dose of GPF, the response apparently being limited both by the magnitude of the stimulation and by the size of the available CFU pool(s). A single dose of Pyrexal failed to evoke a GPF‐like or ESF‐like CFU increase and shifted the marrow's differential exocolonizing potential in the direction of the erythrocytic cell line. The CFU response to GPF is thus qualitatively and quantitatively distinct from those evoked by ESF and endotoxin. The possibility is proposed that GPF may be specific for the granulocytic line at the level of the CFU compartment(s).
EFFECTS OF ISOGENIC BONE MARROW CELL DOSE ON ERYTHROKINETICS OF LETHALLY X‐IRRADIATED MICE
Authors: Smith L. H. , Goodman Joan W. , Hodgson George S.
Published: May 2008

The effect of isogenic bone marrow cell dose on several parameters of hemopoietic regeneration in lethally X‐irradiated mice was studied. The appearance of 59Fe in red blood cells (RBC) and spleen, the hematocrits, and the spleen weights were measured at various times after irradiation and the injection of 105, 106, 107 or 108 marrow cells. Results show that with increasing cell dose, regeneration of erythropoiesis was detectable earlier, proceeded at a faster rate, reached a peak more quickly, and subsided to normal levels sooner. The initial spleen‐weight growth rate was independent of cell dose, although the onset of growth was earlier the higher the dose. The maximum rate of RBC production was attained earlier the larger the cell dose and was a decreasing function of the hematocrit at that time, which in itself was an increasing function of cell dose. These data support the concept of a proportional model for control of erythropoiesis as described by Hodgson (1970).

The present data are interpretable in terms of an A‐ and B‐cell model for erythropoiesis as suggested by Lajtha, Gilbert & Guzman (1971). This model postulates a compartment of undifferentiated multipotent A cells and a compartment of differentiating erythropoietic B cells capable of amplification according to the need for RBC. Application of the present data to the A‐B cell model generates a tentative description of the changes in kinetics of amplification in the B‐cell compartment as the size of the A‐cell base is changed.
CYTOKINETIC STUDIES OF THE REGENERATIVE PHASE IN THE JB‐1 ASCITES TUMOUR
Authors: Dombernowsky P. , Bichel P. , Hartmann N. R.
Published: May 2008

The cell kinetics of recurrent growth of the murine JB‐1 ascites tumour have been investigated 0 hr and 24 hr after aspiration of the main part of the tumour in the plateau phase of growth.

The experimental data: growth curve, percentage of labelled mitoses curve and continuous labelling curves combined with cytophotometric determination of single‐cell DNA content were analysed using two alternative mathematical models for the cell kinetics.

Investigations 24 hr after aspiration showed that the doubling time had decreased to 70 hr as compared with 240 hr in the plateau tumour. This was due to a release of non‐proliferating cells into the cell cycle, resulting in an increase in the growth fraction from 44% to 72%. The decrease in the doubling time was also due to a shortening of the mean cell cycle time from 41 to 20.5 hr.

The analysis rendered it likely that the aspiration caused a shift in the mode of cell loss from an age‐specific elimination of old non‐cycling cells with post‐mitotic DNA content in the plateau tumour to an elimination of younger cells immediately after mitosis.

Investigations from 0 to 10 hr after aspiration verified the release of non‐proliferating cells with both G1 and G2 DNA content into the cell cycle. The release was initiated from 3 to 6 hr after aspiration. 24 hr after aspiration the experimental data did not indicate any further transition.
COMPARATIVE PROLIFERATIVE KINETICS OF CELLS FROM NORMAL HUMAN EPIDERMIS AND BENIGN EPIDERMAL HYPERPLASIA (PSORIASIS) IN VITRO
Authors: Chopra D. P. , Flaxman B. A.
Published: May 2008

Proliferation kinetics of epidermal cells from normal human skin and lesions of psoriasis (benign epidermal hyperplasia) were studied in vitro. Epithelial out‐growths were obtained from skin explants and the cell cycle studied using the conventional method of following two successive curves of labeled mitoses after an initial pulse with 3H thymidine. The length of Tc was 59 hr and 53.5 hr respectively for normal and psoriatic cells. The shorter Tc for psoriasis was due to a shorter duration of S. The growth fraction was 66% and 74% for normal and psoriatic cells respectively as determined by continuous labeling with 3H thymidine. Under the conditions of the present experiments, therefore, normal and psoriatic epidermal cells showed no significant difference in proliferative capacity.
EXISTENCE OF A SPERMATOGONIAL CHALONE IN THE RAT TESTIS
Authors: Clermont Yves , Mauger Annick
Published: May 2008

Adult rats with normal or X‐irradiated testes were used in an experiment to test the possible existence of a chalone in the testis. On the 11th day following irradiation, i.e. as the type A spermatogonia proliferated actively to restore the partially destroyed spermatogonial population, the animals with irradiated testes were subdivided into three groups. Rats of the first group were injected intraperitoneally with a saline extract of normal adult rat testes. Animals of the second group were injected with an equal amount of physiological saline while the rats of the third group received equivalent injections of a saline liver extract. Two additional groups of rats with non‐irradiated testes, injected with the testicular extract or saline solution, served as controls. Following the last injection all animals were injected with 3H‐thymidine and sacrificed. From each animal one testis was used to determine the specific radioactivity of its DNA, the other testis was processed for radioautography. The testicular extract produced a significant decrease in uptake of radioactivity by the irradiated testes. There was no difference in the radioactivity uptake by the testes of non‐irradiated rats. Correspondingly the labeling index of type A spermatogonia was significantly lower in animals of the first group than in the other two groups of animals with irradiated testes. However, there was no difference in the labeling indices of Intermediate and type B spermatogonia or of preleptotene spermatocytes in the animals receiving the extracts or the saline solution. In animals with non‐irradiated testes there was no difference in the labeling indices of type A or other types of spermatogonia or of spermatocytes. These data were taken to indicate that a saline extract of normal adult testes contains a substance that can inhibit specifically the proliferation of type A spermatogonia during the repair phase of the spermatogonial population following irradiation. This substance was tentatively considered as a spermatogonial chalone.
NON‐STEADY‐STATE ANALYSIS OF CELLULAR DEVELOPMENT
Authors: Wheldon T. E. , Kirk J. , Orr J. S.
Published: May 2008

A discrete, compartmental, representation is proposed for cellular development. Equations describing the kinetics of cellular development (with or without cell proliferation) are derived in both differential and integral form.

Using an integral formulation, a method is proposed for the computation of compartment transit times (maturation times) which does not require the use of radioactive or other tracers. Although some restrictive conditions are imposed, the applicability of the method does not depend on strictly steady‐state conditions, nor on purely exponential growth or decay. The method permits analysis of cellular development in certain non‐steady cases for which existing analytical methods are inadequate.

It is possible that patterns of cellular development during embryogenesis, recovery from insults, or growth in culture (e.g. of normal and leukaemic human granulocytes) could be examined using this method of analysis.
CORRELATION BETWEEN TISSULAR AND DIVISION FUNCTIONS IN THE LIVER OF YOUNG RATS
Authors: Barbason H. , Cantfort J. Van , Houbrechts N.
Published: May 2008

The division and tissue specific functions are studied in the liver of young rats during the first post‐natal weeks. The division function is tested by the mitotic and the 3H‐thymidine labelling index, the specific tissular function by the cholesterol‐7 alpha‐hydroxylase activity. The nycthemeral rhythm is triggered simultaneously for the two functions at the 20th day of life. From this time, spontaneous or induced mitoses occur during the day (rest period) and the cholesterol‐7‐alpha‐hydroxylase during the evening (period of activity). The results are explained by the influence of the hypothalamoadrenal axis, which presents a circadian activity with a maximum in the evening.
ON THE MECHANISM OF THYROID MEDIATED MITOGENESIS IN ADULT ANURA. I. PRELIMINARY ANALYSIS OF GROWTH KINETICS AND MACRO‐MOLECULAR SYNTHESES, IN LENS EPITHELIUM, UNDER THE INFLUENCE OF EXOGENOUS TRIIODOTHYRONINE
Authors: Worgul B. V. , Rothstein H.
Published: May 2008

Injection of triiodothyronine into adult frogs leads to an increase in the mitotic index of a number of tissues. The work reported here shows that in one such tissue, lens epithelium, the mitogenic effect is chiefly due to an increase in growth fraction. Practically all of the cells in the population enter DNA synthesis (although not simultaneously) as a consequence of treatment.

The administration of hormone also leads to an increase in intranuclear 3H actinomycin D binding. In addition 3H uridine and 3H amino acid incorporation rates rise as does microphotometrically detectable RNA and protein content.
PROLIFERATIVE RESPONSE IN THE RAT KIDNEY INDUCED BY A SINGLE, CARCINOGENIC DOSE OF DIMETHYLNITROSAMINE
Authors: Hard G. C. , Shaw D. M.
Published: May 2008

With the application of autoradiography, the pattern of DNA synthetic activity in the rat kidney following a carcinogenic dose of DMN was traced during the 3 weeks following treatment. Depending on cell class and location, DNA synthesis was constantly depressed for the first 1 or 2 days throughout all zones of the kidney. Mesenchymal cells of the cortex and outer band of the outer medulla commenced a wave of stimulated activity at the third day with a peak of response at the sixth day. Epithelial cells of these same two zones were slower to respond, attaining a peak of DNA synthetic activity at the tenth day. By the start of the third week, activity had returned to normal or near‐normal levels. The observations are discussed in relation to the known morphological events which occur in the kidneys of DMN‐treated rats prior to the development of neoplasia.
SEPARATION OF PROLIFERATING CFU FROM G2 CELLS OF MURINE BONE MARROW
Authors: Monette Francis C. , Gilio Michael J. , Chalifoux Paul
Published: May 2008

The technique of velocity sedimentation was employed to fractionate mouse bone marrow CFU‐s relative to two different phases of the cell cycle. CFU‐s in DNA synthesis which are destroyed by hydroxyurea were separated from other smaller CFU‐s which were shown to be insensitive to the drug and are presumably those CFU‐s in the G2 phase of cell cycle.
CELL SPECIFICITY OF CHALONE‐TYPE INHIBITORS OF DNA SYNTHESIS RELEASED BY BLOOD LEUCOCYTES AND ERYTHROCYTES
Authors: Bateman Angela E.
Published: May 2008

Inhibitors of DNA synthesis released into balanced salt solution by rat erythrocytes and by rat leucocytes have been found to possess target‐cell‐specific properties which would be expected of chalones. When assayed in short‐term in vitro cultures the erythrocyte product reduced DNA synthesis (as measured autoradiographically) in erythroblasts present in populations of bone‐marrow cells but did not affect the DNA synthesis in myeloid or lymphoid cells. The leucocyte product, under the same culture conditions, reduced DNA synthesis in leucocyte precursor cells. The grain counts over nuclei of different cell types were recorded as well as the DNA labelling index. Results so far obtained cannot ascribe the erythrocyte‐chalone‐produced reduction in labelling index to a blockage of entry into S phase. This cell‐specific inhibitor may reduce continuing DNA synthesis in S phase cells to undetectable levels, compared with synthesis in control media. The leucocyte product, however, most probably prevents entry of leucocyte precursor cells into S phase.

Possible relevance of these inhibitors as components of physiological control mechanisms or as therapeutic agents is discussed.
EXPRESSION OF CONGENITAL DEFECTS IN THE HAEMOPOIETIC MICRO‐ENVIRONMENT: PRE‐NATAL ERYTHROPOIESIS IN ANAEMIC ‘STEEL’(SljSlj) MICE
Authors: Cole R. J. , Tarbutt R. G. , Cheek E. M. , White S. L.
Published: May 2008

The production of red cells by the livers of congenitally anaemic SljSlj foetal mice is reduced, so that the red cell concentration reaches only 0.4 × 109/ml, compared to 2.3 × 109/ml in normal littermates. The deficiency in haemoglobin concentration is not so severe (3 g/100 ml compared to 10 g/100 ml), because SljSlj red cells are macrocytic and normochromic. The number of erythroblasts in the livers of SljSlj foetuses is considerably less than in normal littermates, but the ratio of early erythroblasts to late erythroblasts is not altered. The cell cycles of SljSlj and normal early erythroblasts are similar, but the cycle time of SljSlj late erythroblasts is longer than that of the corresponding normal cells. SljSlj foetal liver cells have a restricted response to erythropoietin in vitro in terms of haem synthesis, whereas foetal liver cells of normal littermates are highly responsive until the 16th day of gestation. Mixtures of late 16 day SljSlj and normal foetal liver cells (both non‐responsive alone) respond to erythropoietin in vitro.
MEASUREMENT OF THE KINETIC STATUS OF BONE MARROW PRECURSOR CELLS: THREE CAUTIONARY TALES
Authors: Lord B. I. , Lajtha L. G. , Gidali Julia
Published: May 2008

Measurements to determine the kinetic status of the morphologically unrecognizable haemopoietic precursor cells in the bone marrow are frequently carried out using techniques which inhibit or destroy cells in the DNA‐synthetic (S) phase of the cell cycle. For example, tritiated thymidine (3H‐TdR) has for many years been recognized as a highly specific label for DNA synthesis and, as such, administration of large doses of 3H‐TdR has often been used, both in vitro and in vivo, to kill cells in S. Assay of the surviving cells has then given a measure of the proportion of the total cells which are in the S‐phase of the generation cycle. Other compounds which have been used for the same purpose are: 125Iodo‐deoxyuridine (125I‐UdR), another S‐phase specific label, or hydroxyurea (HU) which prevents entry of cells into S and inhibits or kills cells already in S (Sinclair, 1965). For a variety of reasons, different laboratories tend to make different choices of the agent to be used for this purpose. As a result, it has sometimes proved difficult to marry data obtained from different sources. In the course of using 3H‐TdR, tritiated uridine (3H‐Ur), 125I‐UdR and HU in attempts toevaluate the kinetic status of bone marrow stem cells, it has become clear that their use is not straightforward and this paper presents data which illustrate some of the pitfalls associated with their use.
ORIGIN AND DIVISION OF LIVER MACROPHAGES DURING STIMULATION OF THE MONONUCLEAR PHAGOCYTE SYSTEM
Authors: Warr G. W. , Šljivić V. S.
Published: May 2008

The ability of a range of mononuclear phagocyte system stimulants to induce proliferation of mononuclear cells in the liver, or to induce an influx of such cells from an extra‐hepatic source, was investigated in mice using techniques of whole or part‐body X‐irradiation and 3H‐thymidine incorporation. Results indicated that whereas stilboestrol, endotoxin, zymosan and Corynebacterium parvum all induced an influx of new, dividing, sinusoid‐lining cells into the liver, only zymosan and C. parvum were able, in addition, to induce proliferation of the pre‐existing cell population.
STEM CELL KINETICS IN THE L 5222 RAT LEUKAEMIA
Authors: Hoelzer D. , Harriss Ecleen B. , Jäger Christine
Published: May 2008

The behaviour of normal haemopoietic stem cells of the bone marrow during the development of the acute transferable rat leukaemia, L 5222, has been investigated. The granulopoietic committed stem cells, measured by the in vitro colony technique, showed a marked decrease to less than half normal levels. Pluripotent stem cells included in the small lymphocytes of the bone marrow, and labelled with 3H‐thymidine by the complete labelling method, showed only a modest decrease in number and an unchanged labelling intensity. The results suggest that in this leukaemia the pluripotent stem cells may be affected in such a way that they are unable to react by proliferation to the depletion of the succeeding cell compartments. This might be due to inhibition by leukaemic cells or to a disturbed feedback regulation between the committed and pluripotent stem cell compartments.
OSCILLATION OF BLOOD MONOCYTE COUNTS IN HEALTHY INDIVIDUALS
Authors: Meuret Gerhard , Bremer Christel , Bammert Joachim , Ewen Jörg
Published: May 2008

Daily examinations of monocyte blood counts in healthy individuals indicated the presence of a monocyte cycle. The cycle length was between 3 and 6 days. The predominant period was 5 days. A similar oscillation frequency resulted from a computer simulation of a feedback loop which linked the blood monocyte compartment (controlled variable) to the stem cell differentiation rate (controlling variable).
AUTOSYNCHRONIZATION OF RAT LIVER CELLS WITH ENDOGENOUS CORTICOSTERONE AFTER PARTIAL HEPATECTOMY
Authors: Desser‐Wiest L.
Published: May 2008

After adrenalectomy in adult male rats 3H‐TdR incorporation into the liver parenchymal cells is increased 4–8 times and the mitotic index rises from 0–31 % to 1–3%; this is inhibited by corticosterone. After hepatectomy the serum corticosterone level increases from 18 μg/100 ml to 57 μg/100 ml. The corticosterone binding capacity of the serum declines from 2–06 to 0–17. The activity of tyrosine transaminase doubles, whereas the incorporation of 3H‐TdR into the liver cells is decreased by a factor of 5–7. Thereafter the binding capacity increases again and reaches, 24 hr after operation, a value of 3–82. The tyrosine transaminase activity and the serum corticosterone content return to normal. 3H‐TdR incorporation, however, increases by a factor of 7‐7 of the initial value. We concluded that in the first few hours after partial hepatectomy corticosterone blocks the liver cells in G1 and an accumulation of the cells occurs at this cell cycle phase. Folio wing the binding of the corticosterone by serum proteins a little later the liver cells enter the S‐phase synchronously.
THE EFFECT OF CYTOSINE ARABINOSIDE IN VITRO ON AGAR COLONY FORMING CELLS AND SPLEEN COLONY FORMING CELLS OF C57BL MOUSE BONE MARROW
Authors: Millard R. E. , Okell S. F.
Published: May 2008

This study reports the effect of cytosine arabinoside in culture on two classes of bone marrow progenitor cells in C57BL mice, agar colony forming cells (ACU) and spleen colony forming cells (CFU). Both normal cells and rapidly proliferating cells were studied.

The results show that in normal mice, 23 % of ACU but only 7 % of CFU are killed following 1 hr incubation with the drug. With longer periods of incubation, the survival of ACU in the controls is poor, and the results for the drug‐treated cultures suggest that the cells are held up in cycle. In continuously irradiated mice, the proportion of ACU and CFU killed after 1 hr incubation with drug is increased to 43–54%, confirming previous results that these cells are proliferating more rapidly than in normal mice. In mice treated with myerlan, 54 % of ACU are killed by 1 hr in vitro exposure to cytosine arabinoside, again confirming that ACU are rapidly proliferating. However, the proportion of CFU killed is lower (23 %).

These results are compared with other studies of the effect of cytosine arabinoside in vivo and also with thymidine suicide in the same strain of mice. The results show that cytosine arabinoside has the same effect as tritiated thymidine, and also that the proportion of CFU killed by these agents in vitro is lower than when the agents are injected in vivo. It is suggested that the conditions in culture have an adverse effect on CFU, which cease DNA synthesis, and are protected from the killing effect of cytosine arabinoside and tritiated thymidine.

Since cytosine arabinoside in vitro has an effect similar to tritiated thymidine in vitro on bone marrow progenitor cells in C57BL mice, in vitro incubation with cytosine arabinoside could be an alternative method to thymidine suicide for measuring differences in cell proliferation rate.
CHANGES IN CELL PROLIFERATION KINETICS OCCURRING DURING THE LIFE HISTORY OF MONOLAYER CULTURES OF A MOUSE TUMOUR CELL LINE
Authors: TWENTYMAN P. R. , WATSON J. V. , BLEEHEN N. M. , ROWLES P. M.
Published: May 2008

Following inoculation of monolayer cultures of EMT6 mouse tumour cells at 105 cells, a short lag is followed by 3 days of exponential growth with a population doubling time of 12 hr. A plateau cell number is reached between days 4 and 5 and is maintained for at least 8 days. During exponential growth, the pulse 3H‐TdR labelling index is 55–60%, all cells are in cycle, and the median cycle time is 11–12 hr. For the first 3 days of plateau phase, the labelling index is about 25 % and there is considerable cell loss. The cell cycle is 32–40 hr, and S‐phase is very long. Later in plateau phase, the labelling index falls to <2 % and there is little cell loss.

The changes in kinetics occurring in EMT6 cultures are discussed with reference to reported changes occurring in other cell lines.
CIRCADIAN INFLUENCE ON THE WAVE FORM OF THE FREQUENCY OF LABELED MITOSES IN MOUSE CORNEAL EPITHELIUM
Authors: Burns E. Robert , Scheving Lawrence E.
Published: May 2008

The FLM was studied in mouse corneal epithelium at two different phases of the mouse circadian system. The following results were obtained: (1) a circadian rhythm was found in the corneal mitotic index of both experimental groups, with the peak near 09.00 hours, the trough near 21.00 hours and a 10‐fold difference in values between the peak and the trough; (2) when 3H‐TdR was injected at 09.00 hours, the first wave of labelled mitoses rose earlier, attained a broader peak and fell later when compared to the first wave of labeled mitoses obtained when 3H‐TdR was injected at 21.00 hours; and (3) in both experimental groups there was a suggestion of a second wave of labeled mitoses, especially in the group injected with 3H‐TdR at 21.00 hours, where a flat second wave appeared in the region of 60–90 hr. Transit times derived from FLM curves obtained from such synchronous populations of cells are of questionable validity. Circadian rhythmicity and other causes of synchronization must be ruled out before accepting a single FLM curve as a valid indication of transit times.
RELATIONSHIPS BETWEEN CELL CYCLE DURATION, S‐PERIOD AND NUCLEAR DNA CONTENT IN ERYTHROBLASTS OF FOUR VERTEBRATE SPECIES
Authors: Grosset Lise , Odartchenko Nicolas
Published: May 2008

Erythroblasts of four vertebrate species (Triturus cristatus, Rana esculenta, Lacerta viridis and Gallus domesticus) differing markedly in their nuclear diploid DNA content, are used to study a possible relationship between cell cycle duration and DNA content. DNA is determined cytophotometrically and fluorometrically. The cell cycle is analysed by evaluating labelled mitoses after an injection of tritiated thymidine and also by double labelling with 14C‐ and 3H‐thymidine. A direct but non‐linear relationship is demonstrated between DNA content of erythroblast nuclei and the duration of DNA‐synthesis.
A COMPARISON OF COMPUTER METHODS FOR THE ANALYSIS OF FRACTION LABELLED MITOSES CURVES
Authors: Hartmann N. R. , Gilbert C. W. , Jansson B. , Macdonald P. D. M. , Steel G. G. , Valleron A.‐J.
Published: May 2008

Computer methods developed by the authors for analysis of fraction labelled mitoses curves (FLM curves) have been compared. Four test examples were used in the study; the first example was the synthesis of a FLM curve with fixed parameters and the others involved fitting actual data. Experimental FLM curves showing various degrees of damping were used in the curve fitting tests. In each test example the comparison was based on the assumptions of exponential growth, a growth fraction of unity and no cell loss. In three of the test examples good agreement between the methods was observed but in one example some important discrepancies arose in the analysis of a heavily damped FLM curve.
INHIBITORY EFFECTS OF MITOGENS ON ADENOIDAL LYMPHOCYTES IN VITRO
Authors: Nitschke Ruprecht , Karon Myron
Published: May 2008

Cultures of human adenoidal lymphocytes exposed briefly to either phytohemagglutinin (PHA), Staphylococcus filtrate (Staph‐F), concanavalin‐A(Con‐A), or pokeweed mitogen (PWM) incorporate increased amounts of thymidine earlier than replicate cultures exposed continuously to the mitogens. These effects can begin in the first 24 hr of culture and are seen maximally between 36 and 72 hr. Once a blastogenic response is established, PHA or PWM can diminish that response. Inhibition with PWM requires that the initial stimulation was with this mitogen, while PHA can inhibit blastogenesis to both PHA and PWM‐stimulated cells. Because these mitogens can have a paradoxical effect on adenoidal lymphocytes, being capable of both initiating and inhibiting DNA synthesis, this phenomena should be kept in mind when such systems are utilized for the evaluation of antigens and drug effects.
RATE AND TIME OF DNA SYNTHESIS OF INDIVIDUAL CHINESE HAMSTER CELLS
Authors: Dörmer P. , Brinkmann W. , Born R. , Steel G. G.
Published: May 2008

The duration of DNA synthesis of a diploid cell line of Chinese hamster fibroblasts was determined in a comparative study by the FLM technique, and also by a new technique for measuring the rate of DNA synthesis of individual cells. These methods produced comparable results when applied during exponential growth of the cells. The rate of DNA synthesis was measured by means of quantitative autoradiography following a short‐term incubation of the cells with 5 × 10‐6 M FUdR and 10‐5 M 14C‐TdR. The choice of the medium for this purpose did not seem to be critical. The autoradiographic silver grains over cells and 14C‐standard sources are counted by microphotometry using incident light bright‐field. The direct measurements of DNA synthesis rate are ‘compartment’ statistics which have been converted into ‘flux’ parameters for comparison with the FLM method and applicability in cell‐kinetic calculations.

Frequency distributions of the rate of DNA synthesis of individual cells thus obtained may resemble normal distributions quite closely. They result from several factors: differences in the rate of synthesis in different parts of the S‐phase, the density distribution of cells within the S‐phase, the variation in the time of DNA synthesis among individual cells, and the experimental error. In the case of a pronounced partial synchronization as probably has been present in one experiment performed in the lag phase, an incorrect time of DNA synthesis may result from the rate values. Due to the variation in DNA synthesis rate in different parts of the S‐phase it is not possible to determine the duration of DNA synthesis of an individual cell. However, the mean values of DNA synthesis time are reliable.

The new method will be preferentially applied for determining the duration of DNA synthesis of human cells in as far as difficulties are encountered with the classical methods. In addition, it may be used to advantage for studying cells which make up low percentages in mixed populations. It finally permits a safer morphological classification of the cells under study than is possible with the classical methods.
THE PHOSPHORYLATION OF NUCLEAR PROTEINS IN THE REGENERATING AND PREMALIGNANT RAT LIVER AND ITS SIGNIFICANCE FOR CELL PROLIFERATION
Authors: Letnansky Karl
Published: May 2008

In liver regeneration or neoplastic transformation, phosphorylation of nuclear proteins is stimulated. In the regenerating liver all main histone fractions are involved in this process. The type of histone phosphorylated seems to be dependent on the position of the partially synchronized cells within the generation cycle. At a time when most cells are exhibiting maximum HnRNA‐synthesis, histone F2a2 belongs to those fractions with highly stimulated phosphate incorporation. Phosphorylation of this fraction alone is stimulated by cyclic AMP in parallel to a stimulation of HnRNA‐synthesis.

The preneoplastic liver is characterized by oscillating phosphorylation and dephosphorylation reactions of nearly all histone fractions during the first days of N‐nitroso‐diethylamine administration. After 2 months of carcinogen feeding a 50–150% stimulation of the phosphorylation of Fl subfractions is observed. The phosphate content of the other histones, however, has returned to the original level.

A series of further proteins, isolated together with the histones, show very similar phosphorylation characteristics. These proteins are mostly of non‐histone origin. It is suggested that some of them are responsible for the transport of RNA with messenger properties within the cell.
ERYTHROID AND GRANULOCYTE‐MACROPHAGE PROGENITOR CELLS IN PRE‐NATAL ‘STEEL’ (SlJ/SlJ) ANAEMIC MICE
Authors: Cole R. J. , Regan T. , White S. L. , Cheek E. M.
Published: May 2008

The erythropietin sensitivities of dissociated cell cultures and explanted fragments of fetal livers of congenitally anaemic SlJ/SlJ mice, and their normal littermates, have been compared. The erythropoietin responsiveness of SlJ/SlJ foetal liver cells is deficient in both types of culture.

The maximum liver complement of erythroid colony forming cells (CFUe) occurs on the 16th day of development when ‘normal’ livers contain approximately 6 × 105 erythroid colony forming cells/liver. In SlJ/SlJ fetuses the maximum reached is only 1 × 105. Granulocyte‐macrophage colony forming cells (CFUC) in SlJ/SlJ fetal livers are also reduced to approximately 60% of normal numbers. Erythroid colony forming cells are also reduced in the spleen and femoral bone marrow of SlJ/SlJ mice in the 2–3 days preceding birth. Granulocyte‐macrophage colony forming cells are rare in the femoral marrow of pre‐natal SlJ/SlJ mice, but their production in the SlJ/SlJ pre‐natal spleen appears unaffected.
ANALYSIS OF TIME DEPENDENT CHANGES OF LYMPHOPOIETIC ACTIVITY IN ORGAN CULTURES OF EMBRYONIC CHICKEN THYMUS
Authors: JUhlin Roger , Alm Gunnar V.
Published: May 2008

The time dependent development of lymphocytes in organ cultures of the thymus obtained from 10‐day‐old chick embryos was characterized by an initial phase of exponential increase of the number of lymphocytes per thymus followed by a plateau phase with no further increase in cell number. The proportion of cells in DNA synthesis dropped rapidly during the first 10 days of culture. Simultaneously the lymphocytes turned progressively smaller, as evidenced by both cell diameter and dry mass and constituted a homogeneous population of small cells at the end of the culture period.

Thymic anlagen partially depleted of lymphoid precursor cells by a short hot pulse with 3H‐TdR showed a prolonged exponential phase and reached normal plateau cell numbers 2–4 days later than usual.

Furthermore, at least in the first part of the plateau phase, a reduction in the number of lymphoid cells per thymus resulted in a recovery in terms of the cell number which was associated with increased DNA synthesis.

These results are compatible with the regulation of thymic lymphopoiesis in organ culture through a mechanism operating via cell density.
MATRIX SIMULATION OF DUODENAL CRYPT CELL KINETICS
Authors: Roti Joseph L. Roti , Dethlefsen Lyle A.
Published: May 2008

Steady state crypt cell kinetics have been simulated using matrix algebra. The model crypt cell population is distributed through two proliferation compartments (P1 and P2) and a quiescent state (Q). Under steady state conditions half the daughter cells produced on completion of P1 enter G1 of P2 and half enter G1 of P1. Both P2 daughter cells enter Q. Cells in Q are non‐dividing but retain the potential to divide. On completion of Q, cells lose the potential to divide and move up onto the villi. The model has been developed by simultaneously simulating the following biological data: (1) the per cent labeled mitosis (PML) curve, (2) the number of labeled cells per crypt as a function of time following an injection of 3H‐thymidine, and (3) the total number of cells per crypt.
AGE DEPENDENCE OF THE NUMBER OF THE STEM CELLS IN HAEMOPOIETIC TISSUES OF RATS
Authors: VACEK ANTONÍN , BARTONÍĈKOVÁ ALENA , TKADLEĈEK LUDVÍK
Published: May 2008

The number and concentration of haemopoietic stem cells in the femoral bone marrow and spleen of Wistar rats of different ages were investigated. Stem cells were assayed by the spleen colony technique in irradiated rat recipients. The ability of the recipient spleen to harvest transplanted tissue as a macroscopic colony was found to be dependent on the recipient's age. Changes with senescence were observed also in the concentration and the size of the stem cell compartment both in the marrow and spleen. No differences were demonstrated in the seeding of transplanted colony‐forming units into the spleen of recipients of 1 and 4 months of age. A rats‐mice strain difference in the effect of senescence on the haemopoietic stem cells is discussed.
KINETICS OF HAEMOPOIETIC RECOVERY IN ENDOTOXIN‐TREATED MICE
Authors: Lahiri S. K.
Published: May 2008

Kinetics of mouse spleen colony forming units were studied after intra‐peritoneal injection of 1 μ/g body weight bacterial endotoxin S. typhosa. When these mice were used as unirradiated and sublethally irradiated donors, it was possible to study the effect of the endotoxin injection upon the cells. Use of the treated mice as irradiated recipients of normal cells gave information about the host effect.

In treated unirradiated mice, the total nucleated cell and the CFU counts were disturbed, and 2 days later a large fraction of the CFU were found in the DNA synthesis (S) phase. This meant that injection of endotoxin generated factors affecting the kinetics of the CFU and triggering the resting CFU into the proliferative cycle. If then the mice were given supralethal irradiation and used as recipients of normal bone marrow cells, more CFU seeded to the spleen as compared to normal recipients; but the dip and the growth rate of the CFU were not changed. Hence the endotoxin‐generated factors had been eliminated in 2 days.

A total body sublethal irradiation by 400 rad X‐ray 2 days after endotoxin injection reduced the post‐irradiation dip in the recovery curve of the CFU, indicating that though the factors affecting the cell kinetics had been eliminated, the cycling CFU behaved like a growing population. During the first week, the growth rate of the CFU remained the same as in control irradiated mice. The growth rate of the spleen CFU of the endotoxin‐treated mice slowed down during the second week, and their self‐replicating ability was low. Fluctuations in the DNA synthesizing fraction of the spleen CFU suggested a variability in the ratio of the length of the S phase and the cell generation time.
A SERUM FACTOR INDUCING MONOCYTOSIS DURING AN ACUTE INFLAMMATORY REACTION CAUSED BY NEWBORN CALF SERUM
Authors: van Waarde Dick , Hulsing‐Hesselink Elizabeth , van Furth Ralph
Published: May 2008

An intraperitoneal injection of newborn calf serum (NBCS) into CRF Swiss mice causes an inflammatory reaction characterized by an increase in the number of macrophages in the peritoneal cavity and a concomitant monocytosis. The serum of such mice contains a monocytosis‐inducing factor, as demonstrated by the intravenous injection of serum collected 18 (CalS 18) and 24 hr (CalS24) after the intraperitoneal injection of NBCS. Serum from normal untreated mice, from mice given an intraperitoneal injection of sterile pyrogen‐free saline, which does not cause an inflammatory reaction, or from mice 72 hr after an intraperitoneal injection of NBCS, when the inflammatory reaction has subsided, does not cause a monocytosis in test mice.

Intravenous injection of CalS 18 causes not only a monocytosis but also an increase in the number of promonocytes and bone marrow monocytes, suggesting an increased production of monocytes.

The effect of CalS 18, CalS24 and CalS 18 filtrate is specific for the mononuclear phagocytes, since only non‐significant increases in the numbers of lymphocytes and granulocytes were observed. The active factor in CalS 18 was shown to be different from the monocytosis‐inducing factor present in NBCS.

The monocytosis‐inducing factor in CalS 18 passes through an ultrafiltration membrane with an exclusion limit of 50,000 Daltons, so that the molecular weight must be below this value.