bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of RNA synthesis in DNA replication of synchronized populations of cultured mammalian cells
Authors: Fujiwara Yoshisada
Published: February 2005

Using the harvesting method of synchronizing L cells, the relationship of RNA synthesis of DNA replication was studied by the use of selective inhibitors of RNA synthesis such as actinomycin D and chromomycin succinate. The synthesis of the early replicating DNA fraction is a process sensitive to the inhibition of RNA synthesis during the G1 period.

The synthesis of early replicating DNA was inhibited by chromomycin succinate without affecting the initation of DNA synthesis. However, actinomycin D inhibited the synthesis of early replicating DNA and prevented the initiation of DNA synthesis in 50% of the synchronized cells. However, it was found that the continued synthesis of RNA during the S period is not essential for the synthesis of late replicating DNA.

In addition to this specific response of DNA synthesis to the inhibitors of RNA synthesis, another function of early and late replicating DNA was determined relative to the cell viability. Cells synthesizing early replicating DNA were killed more efficiently by chromomycin than at other stages of the cell cycle. This indicates that the early replicating DNA unit plays a more important role in cell reproduction than the late replicating DNA unit.
Factors influencing hematopoietic spleen colony formation in irradiated mice. IV. The effect of erythropoietic stimuli
Authors: Marsh John C. , Boggs Dane R. , Chervenick Paul A. , Cartwright George E. , Wintrobe Maxwell M.
Published: February 2005

A variety of erythropoietic stimuli influenced the number of endogenous spleen colonies in irradiated mice and the number of transplantable colony forming cells in the spleen and marrow of unirradiated mice.

Bleeding was the most effective stimulus. Bleeding before irradiation resulted in a 30‐fold increase in endogenous spleen colonies and in increases in spleen weight, spleen iron and iododeoxyuridine uptake and volume of packed red cells ten days after irradiation. Bleeding unirradiated mice produced a 10‐fold increase in the number of transplantable colony forming cells in the spleen and a slight decrease in the total number in the humerus. Bleeding before irradiation resulted in a significant reduction in 30‐day post irradiation deaths, an effect abolished by splenectomy. Plasma from bled mice induced an increase in endogenous colonies when injected before irradiation into normal mice.

Injection of erythropoietin, testosterone or testosterone plus cobalt induced effects which were, in general, qualitatively similar to those of bleeding, although they were less effective quantitatively. Except for a slight effect induced by ten injections of erythropoietin, post‐irradiation stimulation in normal mice proved ineffective. Erythropoietin increased colony numbers and spleen iron uptake when given after irradiation to hypertransfused mice.

The results of these studies do not support the concept that the colony forming cell and the erythropoietin sensitive cell are separate entities.
Properties of a hybrid between lines sensitive and insensitive to contact inhibition of cell division
Authors: Weiss Mary C. , Todaro George J. , Green Howard
Published: February 2005

Hybrid cell lines have been prepared between 3T3, a line highly sensitive to contact inhibition of division, and cl 1‐D, an L cell derivative which is not sensitive. A number of hybrid clones isolated were found to be quite sensitive, indicating that in this respect the 3T3 behavior is the more fully expressed in the hybrid. On serial subculture, the hybrid lines gave rise to variants less sensitive to contact inhibition.
Deficient Fe59 and I125 deoxyuridine uptake by lympho‐hemopoietic cell transplants engaged in homograft reactions
Authors: Davis William E. , Schofield Raymond , Cole Leonard J.
Published: February 2005

Erythropoietic activity of spleen cell grafts was measured (Fe59 uptake) in X‐irradiated recipient mice under conditions in which these grafts were engaged in homograft reactions against allogeneic target cells or in graft‐versus‐host reactions. Such Fe59 incorporation was greatly reduced at 7 to 10 days after graft implantation relative to that of control grafts. This reduced erythropoiesis did not occur when the spleen cell graft was immunologically incompetent. Transplantation of bone marrow‐lymph node cell mixtures also resulted in a relative decline in Fe59 uptake, but only when minimal numbers (105 to 106) of marrow cells were injected. The incorporation of I125 UdR in the spleen of irradiated recipients was used to assess cellular proliferation. Incorporation of this label was reduced when measured 7–10 days after implantation of the lympho‐hemopoietic cell graft, but reached a peak at five days—the latter indicating stimulated lymphopoiesis. These data are consistent with the concept of depletion of a pluripotent stem cell pool (limited in size under these experimental conditions) due to excessive and concurrent functional demands for erythropoiesis and lymphopoiesis. An alternative explanation would involve cytotoxic effects on hemopoietic elements present in the milieu of the immunologic reaction.
The rhythm of mating in Paramecium aurelia, syngen 3
Authors: Karakashian Marlene W.
Published: February 2005

The periodic mating behavior of some stocks of Paramecium aurelia, syngen 3, exhibits features typical of circadian rhythms. In the most extensively studied stock (37p), rhythmicity persists at least four days in continuous darkness, but disappears rapidly in continuous illumination (200 foot‐candles). The period of the free‐running rhythm is 22.2 hours, and relatively insensitive to ambient temperature. Cycles of illumination and temperature can regulate the mating rhythm. Changes in illumination at specified times in the circadian cycle will induce shifts in the phase of the rhythm. Stock differences with respect to the persistence of the rhythm and the environmental control of its phase have been observed.
Monocyte kinetics: Observations after pulse labeling
Authors: Whitelaw D. M. , Bell M. F. , Batho H. F.
Published: February 2005

Because monocytes and their precursors cannot be recognized with certainty in tissues, an approach to the study of monocyte kinetics was made through examination of the peripheral blood. Injection of a single pulse of tritiated thymidine into rats resulted in the appearance of labeled monocytes identified as circulating peroxidase‐positive mononuclear cells. The increase in the percent of labeled cells and in the mean grain count per cell followed a course described by a mathematical model with a generation time of 21 hours and a DNA synthesis time of 12.5 hours. The generation and synthesis times appear to be very uniform for the monocyte so that the phasing of cells represented by the uptake of label could be followed for more than two generations, a property not shared by neutrophils or lymphocytes. Monocytes appear in the circulation within eight hours of DNA synthesis.
Reversibility of ouabain induced inhibition of cell division and cation transport in Ehrlich ascites cells
Authors: Mayhew E. , Levinson C.
Published: February 2005

Ouabain induced inhibition of cation transport and cell division in Ehrlich mouse ascites tumor cells is reversible, suggesting that this agent does not bind irreversibly to its site of action.
Hemopoietic progenitor cells with limited potential for differentiation: Erythropoietic function of mouse marrow “lymphocytes”
Authors: Bennett Michael , Cudkowicz Gustavo
Published: February 2005

Filtration of mouse marrow cell suspensions over columns of glass wool increased the frequency of small and medium‐sized lymphocytes (SML) and of erythropoietic progenitor units (EPU) by about the same factor. Identical results were obtained when erythropoiesis was assayed by isotope uptake (59FeCl3 and 125IUdR) or by the spleen‐colony techniques.

Transfusion of prospective donor mice with erythrocytes virtually eliminated morphologically recognizable erythroid cells from marrow without affecting the frequency of EPU. Injection of prospective donors with cortisol decreased the frequency of SML in marrow but not that of EPU or erythropoietin‐sensitive cells. However, glass wool filtration of lymphocyte‐poor marrow taken from mice pretreated with cortisol resulted in a similar increase in frequency of residual SML and of EPU. Therefore, it appears that a subpopulation of marrow SML are EPU.

Whereas glass wool filtration increased the frequency of erythropoietic progenitor and colony‐forming units, the filtration failed to change the frequency of leukopoietic progenitor or colony‐forming units (assayed in mice hypertransfused with erythrocytes to suppress erythropoiesis). It follows that separate progenitor cells for erythropoiesis and leukopoiesis are present in bone marrow of adult mice, in addition to pluripotent stem cells.
Energy‐limitation of a sodium‐independent amino acid transport in ovarian oocytes of the frog
Authors: Merriam R. W. , Pollack Gerald
Published: February 2005

The frog, Rana pipiens, hibernates through the winter with ovaries containing oocytes which, in size and appearance, are ready for ovulation and maturation. From November through April, the normal time of egg laying, ovulation and maturation can be induced by interrupting hibernation and administering gonadotropic hormones. In the studies reported here, it has been found that oocytes taken from hibernating animals in early winter take up amino acids from a saline medium at a relatively rapid rate. Respiratory inhibition produced by such agents as dinitrophenol (DNP) and anaerobiosis, does not completely stop uptake but slows it down markedly.

In late winter, amino acid uptake tends to be slower in normal cells and when DNP or cyanide is added, a marked acceleration of the rate of uptake is observed. The uptake in poisoned cells is accumulative, producing internal concentrations higher than that of the medium. At this concentration of DNP, amino acid incorporation is almost completely stopped. Fluoride abolishes the DNP stimulation of amino acid uptake. Removal of sodium ion from the incubating medium has no effect on either uptake or incorporation.

These data are interpreted to mean that a capacity for oxidative phosphorylation in oocytes diminishes during winter hibernation. In the spring either an anaerobic capacity comes into being or becomes capable of being switched on. During this time the rate of amino acid uptake, even in the downhill phase, is limited by energy availability and is not dependent on a sodium gradient.
The effect of temperature on ATP levels in cells of an ascitic Hepatoma
Authors: Jones P. C. T.
Published: February 2005

The effect of temperature on intracellular ATP levels in cells of the ascitic Hepatoma 129 has been determined using an UV‐enzymic method. ATP levels are found to vary inversely with temperature over the range (4°–37°C) studied, and this variation is found to be reversible. An indication of a possible direct correlation of ADP level with temperature was also obtained.

A correlation is deduced between rise in intracellular ATP level and decrease in cytoplasmic viscosity, both from the present results, and from similar effects recently reported by Landau ('61) for increase in pressure.

The significance of these observations is discussed with reference to the model for cytoplasmic viscosity proposed by Marsland ('56) and the wider biological significance of this effect is explored.
Water diffusion and water permeation in eggs from three Anuran species
Authors: Haglund Birgit , Loeffler Clarence A.
Published: February 2005

Water exchange has been studied in ovarian and body cavity eggs of three Anuran species (Rana esculenta, R. pipiens and R. temporaria) with the isotope exchange method using the automatically recording diver balance. In order to estimate the rate of water diffusion in egg cytoplasm (D), a factor required to determine the rate of water permeation (= the exchange coefficient, E), three different chemical treatments (digitonin, ethanol and formaldehyde) have been used to remove the surface barrier to water flow. The obtained mean value of D, 5 × 10−6 cm2 sec−1, has been accepted as a close approximation of water diffusion in the egg cytoplasm. This value has been used to determine the exchange coefficients in the egg types of the above mentioned species. Comparisons have been made between the calculated values of E both within and between species, and some suggestions have been made concerning the influence of microvilli on the rate of water exchange. Although, on the average, water exchange proceeds at a greater rate in ovarian than in body cavity eggs, a measurable diffusion barrier at the surface can be demonstrated.
Impairment of deoxyribonucleic acid synthesis by dietary zinc deficiency in the rat
Authors: Sandstead Harold H. , Rinaldi Robert A.
Published: February 2005

Dietary zinc deficiency has been shown to decrease the in vivo incorporation of thymidine into the nuclear DNA of liver parenchymal cells in the rat. A single injection of 100 μg of zinc was sufficient to rapidly reverse the effect of zinc deficiency on the synthesis of DNA.
The dependence of DNA synthesis on protein synthesis in HeLa S3 cells
Authors: Weiss Barbara G.
Published: February 2005

The rate of DNA synthesis in HeLa S3 cells, as measured by incorporation of C14‐labeled thymidine, is strongly dependent on protein synthesis at all times during the S phase. The relation between the rate of DNA synthesis and the rate of protein synthesis is linear when measured two or three hours after reducing the rate of protein synthesis with either puromycin or cycloheximide. The effect is manifested rapidly, is found in both random and synchronized cultures, and is independent of the method of synchronization.
Transformation of chick fibroblast cultures with avian myeloblastosis virus
Authors: Moscovici C. , Moscovici M. G. , Zanetti M.
Published: February 2005

Cellular transformation was induced with avian myeloblastosis virus strain BAI‐A (standard AMV) and with a strain of AMV containing subgroup B only. Cultures of muscle tissues from either chick embryo or day old chicks were used for this study. Results were similar in C/O and C/A cells. Leukemogenic virus was continuously produced by these transformed cultures.
Lethal effects of fluorodeoxyuridine on cultured mammalian cells at various stages of the cell cycle
Authors: Lozzio Carmen B.
Published: February 2005

The lethal damage induced by the exposure of synchronized Chinese hamster cells to various concentrations of 5‐fluoro‐2′deoxyuridine (FUdR) was not selectively restricted to cells exposed during the period of DNA synthesis S. The colony survival fraction observed after treatment for one hour with 5 × 10−5 M FUdR was very low (0.0001–0.0003) whether the drug was administered during early G1, late G1, early S or in middle S. The survival of cells treated with the same concentration of FUdR during mitosis, however, was significantly higher (0.62) showing that mitotic cells were less sensitive to FUdR. Administration of 10−7M thymidine or “conditioned” medium for one hour reversed the lethal effect of FUdR or improved the survival, depending on the time after removal of the FUdR at which these substances were given.
Chemical modification of crayfish axons by protein crosslinking aldehydes
Authors: Shrager Peter G. , Strickholm Alfred , Macey Robert I.
Published: February 2005

A series of aldehydes of varying protein crosslinking strengths have been tested on intact and internally perfused crayfish axons. Non‐crosslinking aldehydes have no effect, or cause a gradual decline in resting potential and overshoot with no widening of the spike. Strong crosslinking compounds, such as acrolein, crotonaldehyde, and glutaraldehyde, widen the action potential significantly while reducing its amplitude. Differences in the shapes of the resulting action potentials and accompanying impedance changes suggest that each crosslinking aldehyde exerts different effects on the axon. Glutaraldehyde, the strongest crosslinking agent tested, slows both rising and falling phases of the spike, and also of the impedance change, suggesting a prolongation of the transient increase in sodium conductance. The ability of protein crosslinking agents to alter excitability, and particularly to slow the various phases of the action potential, provides support for the hypothesis that a conformational change in a protein or protein‐phospholipid complex is involved in excitation.
The relationship of protein synthesis to cell division and oral development in synchronized Tetrahymena pyriformis GL‐C: An analysis employing cycloheximide
Authors: Frankel Joseph
Published: February 2005

The effects of cycloheximide on synchronized Tetrahymena pyriformis strain GL‐C were investigated at concentrations ranging from 0.01 to 10 μg/ml. The initial inhibition of protein synthesis was nearly total (>85%) at 1 μg/ml and above, partial (50–80%) at 0.2 to 0.05 μg/ml, and slight (<30%) at 0.02 μg/ml. Eventual recovery of protein synthesis to a rate approaching that of the controls took place at concentrations of 1 μg/ml and less. When the drug was added before a “transition point” at 55 minutes after the end of the synchronizing treatment (EST), cell division was blocked by 10 μg/ml, and delayed at concentrations of 1 μg/ml or less. The duration of delay was related to the degree of initial inhibition, and to the time required for recovery of protein synthesis; it also depended on the time after EST at which the drug was added. At a given concentration, maximum division delay was observed just prior to the “transition point;” this maximum delay was correlated with resorption of differentiating oral primordia, followed by the appearance of new primordia. The lesser delays observed at earlier times were correlated with temporary blockage of development of primordia in the “stomatogenic field” stage. Resumption of oral primordium development was, in both cases, temporally correlated with a substantial recovery of protein synthesis. After the “transition point,” cell division, and completion of oral development, was delayed slightly at the lower concentrations, and more substantially at 1 and 10 μg/ml, with some division‐arrest at the latter concentration. Except for the recovery phenomenon, the developmental responses elicited by cycloheximide were similar to those observed earlier with puromycin.

The bearing of these findings on the mechanism of synchronization in Tetrahymena is considered in the Discussion.
The expression of differentiation by chick embryo thyroid in cell culture. I. Functional and fine structural stability in mass and clonal culture
Authors: Spooner Brian S.
Published: February 2005

The stability of glandular epithelial cells has been investigated utilizing the techniques of cell culture. Embryonic chick thyroid was chosen as a representative cell type and methods were developed for the successful clonal culture of thyroid follicular cells.

Thyroid cells were found to be morphologically and functionally stable while undergoing rapid division in both dense (monolayer) and dilute (clonal) cell culture. Differentiated features were retained for a minimum of 32 days of primary clonal culture (approximately 17 generations under clonal conditions). During the culture period, the cells retained their epithelial morphology, retained their cytoplasmic rough endoplasmic reticulum, and continued to produce chromatographically detectable thyroid hormones. Hormone production in culture was a specific thyroid characteristic since control cultures of embryonic heart and liver did not contain the hormones.
Recovery of proliferative capacity of agar colonyforming cells and spleen colony‐forming cells following ionizing radiation or vinblastine
Authors: Chen Michael G. , Schooley John C.
Published: February 2005

The effects of sublethal radiation and the mitotic inhibitor, vinblastine sulphate, on the number of cells in mouse bone marrow capable upon transplantation of forming macroscopic colonies on the surface of the spleens of irradiated recipient mice (CFU) and on the number of cells capable of forming colonies in soft agar after cell culture (ACFU) were studied as a function of time after injury. The results show that ACFU are radiosensitive and vinblastine‐sensitive cells, comparable in sensitivity to erythropoietin‐sensitive cells. The temporal pattern of recovery following radiation of ACFU, different from that for CFU, is compatible with the concept that these are two distinct but closely related stem cell populations. The relevance of these findings to models of hematopoiesis and to studies on the precursors of macrophages and monocytes in inflammatory exudates is discussed.
The possible mediation by cyclic AMP of parathyroid hormone‐induced stimulation of mitotic activity and deoxyribonucleic acid synthesis in rat thymic lymphocytes
Authors: Whitfield J. F. , MacManus J. P. , Rixon R. H.
Published: February 2005

Purified parathyroid hormone (PTH) strongly stimulates the initiation of deoxyribonucleic acid (DNA) synthesis and thereby raises the flow of cells into mitosis in rat thymic lymphocyte populations maintained in vitro. These actions of PTH are potentiated by caffeine and inhibited by imidazole which indicates that the hormonal action is mediated by cyclic adenosine 3′,5′,‐monophosphate (cyclic AMP). The feasibility of cyclic AMP being the mediator of PTH action is established by the observation that a low concentration (10−7 M) of dibutyryl cyclic AMP precisely mimics the stimulatory action of the hormone on DNA synthesis and cell proliferation.
Differential proliferation of erythroid and granuloid spleen colonies following sublethal irradiation of the bone marrow donor
Authors: Wolf Norman S. , Trentin John J.
Published: February 2005

Spleen colonies produced by sublethally irradiated mouse bone marrow cells were compared to those produced by unirradiated marrow cells in lethally irradiated mice. Sublethally irradiated marrow cells gave rise to many fewer spleen colonies. At seven days of colony age, the ratio of erythroid colonies to granuloid colonies was lower (< 1) than for colonies formed by unirradiated marrow (2 to 3 or more). Delay of harvest of colonies to day 10 or 12 resulted in 6 to 11 fold increase in the ratio of erythroid to granuloid colonies due largely to the belated appearance of erythroid colonies.
Fetal erythroid cell development: Density gradients and size distributions
Authors: Zucker Robert M.
Published: February 2005

Electronic size distributions of erythroid cells from fetal C57BL‐6J mice during the eleventh through twentieth days of gestation indicate that the erythropoietic cell populations are constantly changing. The mean volume of the liver derived non‐nucleated erythroid population decreases from four times the mean adult erythrocyte volume on the thirteenth gestation day to twice the adult erythrocyte volume at birth. The mean volume of the nucleated erythroid cell is about ten times the mean adult erythrocyte volume. The gestation age of an embryo can be determined from blood cell size distributions. The mode of the non‐nucleated population and the percentage of each population indicates the gestation age.

Size distribution of cells in density gradient fractions apparently indicate two size populations of non‐nucleated cells between the thirteenth and fifteenth days. The density of the non‐nucleated cells increases during gestation. It is suggested that the decrease in size and increase in density of non‐nucleated cells is due to the release of successively smaller reticulocytes from the liver.
Membrane phosphatase and active transport in red cells from different species
Authors: Vigliocco Ana M. , Rega Alcides F. , Garrahan Patricio J.
Published: February 2005

The K+‐dependent phosphatase activity from red cell membranes from different mammalian species shows a close relationship with both the rate of active potassium influx and (Na+ + K+)‐dependent ATPase activity. This finding supports the view that membrane phosphatase activity is related to the cation transport system.
In vitro immune response of primed mouse spleen cells as affected by the time of antigenic stimulation
Authors: Meiss H. K. , Agarossi G. , Martinozzi M. , Doria G.
Published: February 2005

Normal and primed spleen cells stimulated in vitro with sheep RBC showed a different behaviour in the 19 S PFC response. The immunologic capacity of primed cells, unlike that of unprimed cells, was impaired if the antigen addition to culture had been delayed for more than six hours. The requirement of primed cells for immediate reexposure to antigen varied with the time of preimmunization and was maximum when spleen cells had acquired in the donor the ability to display the highest response in vitro upon optimal restimulation. This phenomenon of antigen requirement of primed cells in vitro is at variance with the known immunologic behaviour of primed cells grown in vivo, and can be attributed to cellular changes unmasked by in vitro cultivation.
A new method of cloning mammalian tissue culture cells in suspension
Authors: Walters R. A. , Hutson J. Y. , Burchill B. R.
Published: February 2005

Chinese hamster cells (line CHO) were cloned in suspension with a carboxymethylcellulose‐containing medium, and the colonies were counted with an electronic particle counter after enzymatically degrading the carboxymethylcellulose with cellulase. Survival of x‐irradiated cells was determined by both the standard plating technique and the suspension technique, and comparable results were obtained.
The influence of diffusion in the external medium upon the determination of cytoplasmic diffusion coefficients
Authors: Løvtrup Søren , Mild Kjell Hansson , Berglund André
Published: February 2005

The exchange of isotopic water has been studied in ovarian eggs from three Anuran species (R. esculenta, R. pipiens and R. temporaria) by the automatic diver balance technique. The oocytes were treated with chemicals (digitonin, ethanol and formaldehyde) to remove the plasma membrane. The cytoplasmic diffusion coefficient for water was calculated with and without allowance for the influence of diffusion in the external medium. The former expedient was found necessary in order to obtain correct values. The chemical treatments gave different values, but there are sound reasons to believe that those obtained with digitonin (8.9, 15.3 and 10.8.10−6 cm2sec−1 for R. esculenta, R. pipiens and R. temporaria, respectively) are the correct ones. These results indicate that the rate of diffusion in the oocyte cytoplasm amounts to 50–75% of that of free diffusion.
Extraction of an actomyosin‐like protein from amoebae of Dictyostelium discoideum
Authors: Woolley David E.
Published: February 2005

An actomyosin‐like protein has been extracted from amoebae of Dictyostelium discoideum, V‐12. The purified protein exhibited a reversible change in viscosity upon addition of ATP, indicating an ATP sensitivity of 75–85% and a specific viscosity of 0.1. At low ionic strength in the presence of Mg++ and ATP the amoeba protein displayed the phenomenon of superprecipitation. The protein extract was found to be an adenosinetriphosphatase (ATP'ase) hydrolyzing ATP to ADP and inorganic phosphate. Both Mg++ and Ca++ at low ionic strength accelerated the ATP ase activity whereas at high ionic strength only Ca++ stimulated ATP hydrolysis. The ATP'ase activity was inhibited by ethylene‐diamine‐tetraacetic‐acid, Mersayl and p‐chloromercuribenzoate. The physico‐chemical and enzymatic properties of the extracted amoeba protein are qualitatively comparable to those of muscle actomyosin, and very similar in quantitative properties to smooth muscle actomyosin and the actomyosin‐like proteins of blood platelets, leucocytes and slime mold plasmodia. The significance of the presence of this actomyosin‐like protein in Dictyostelium amoebae is discussed in relation to amoeboid form and movement.
Correlation of adenosine phosphate levels with cellular morphology in Dictyostelium discoideum amoebae
Authors: Woolley David E. , Jones Peter C. T.
Published: February 2005

Prior to completion of aggregation and the beginning of multicellular differentiation, the amoebae of Dictyostelium discoideum assume two distinct phases with characteristic changes in cellular movement, shape and adhesiveness. These two phases of amoeboid behaviour have been studied with respect to the quantitative analysis of the intracellular adenosine phosphates, using both enzymatic and chromatographic techniques. A higher intracellular ATP level and energy‐charge has been found for the actively moving, non‐adhesive amoebae as compared to the flattened, mutually adhesive cells. The importance and possible role of ATP in regulating amoeboid form, movement and cell adhesion is discussed.
Argon laser micro‐irradiation of mitochondria in rat myocardial cells in tissue culture
Authors: Berns Michael W. , Gamaleja Nicolai , Olson Robert , Duffy Cecilia , Rounds Donald E.
Published: February 2005

Three types of lesions produced by argon laser micro‐irradiation of single mitochondria are described. A correlation between lesion severity and optical phase density and/or laser output power was observed. Cell survival was generally not affected by mitochondrial irradiation. As many as ten mitochondria were irradiated without cell death resulting. Absorption of the laser radiation was attributed to the natural chromophores, cytochromes c and c1.
From cell biology to immunology—A short trip
Authors: Herzenberg Leonard A.
Published: February 2005

Immunologic memory and immunoglobulin allotype suppression are discussed as problems in Cell Biology. Memory, the ability of an animal after a first antigenic exposure to give a heightened and faster immune response upon a second exposure to the same antigen, is shown to be a property of bone marrow‐derived cell lines. Expression of this memory depends on interaction with thymus‐derived cells from either non‐immunized or immunized mice.

Chronic allotype suppression is described for the first time. It is initiated by in utero or neonatal exposure of (SJL × BALB/c)F1 mice, allotype a/b, to anti b antibody. Suppression lasts for long periods and continues in irradiated recipients which have received lymphoid cells from suppressed donors. Selection against b allotype producing cell precursors can explain suppression.
The action of mendelian genes in human diploid cell strains
Authors: Krooth Robert S. , Sell Elizabeth K.
Published: February 2005

Some of the cells of every human being will grow outside the body as microorganisms. It is possible to show, in a variety of ways, that these cells resemble genetically the individual from whom they were obtained. Over 35 inherited human diseases and anomalies can now be studied in such cell lines.

Human diploid cell strains, biochemically marked by one or more mutant Mendelian genes, have proven particularly useful for the study of gene action in man and for the detection of genetic changes such as mutation and somatic cell hybridization. In addition, the strains have a number of clinical applications, including the antenatal diagnosis of inherited disease.

The failure of cultured human cells to display their phenotype at most loci continues to restrict their use in both genetics and medicine. There are reasons for hoping that this difficulty will eventually be solved, and some experiments bearing on the problem are already feasible.
An introspective view of penicillinase
Authors: Saz Arthur K.
Published: February 2005

Based both on a review of the literature dealing with penicillinase induction as well as published data from this laboratory, the thesis is presented that penicillinase serves an important metabolic function in producing cells, far more significant than the ability to hydrolyze certain penicillins. An attempt is made to implicate the enzyme in the sporulation process in sporeforming cells and in cell wall metabolism in non‐spore‐forming organisms.
Changes in the carbohydrate content of the KB cell during the growth cycle
Authors: Glick Mary Catherine , Gerner Edward W. , Warren Leonard
Published: February 2005

KB cells were grown in suspension culture and synchronized with a double thymidine block. Cells were removed at various times during the cell cycle and analyzed for sialic acid, fucose, mannose and galactose. The mannose, galactose, and fucose contents of the cells all showed a decrease during the mitotic phase. The content of sialic acid decreased, but later in the cycle. When the cell was not dividing the molar rations of sialic acid to fucose: mannose: galactose were approximately 2:5:3 when sialic acid was expressed as 1; the ratios dropped to approximately 1:3:1.5 throughout division. These results indicate that the glycoprotein and/or glycolipid contents of KB cells probably change throughout the cell cycle.
Metabolic effets of nucleosides in rat thymus cells in vitro
Authors: Thomson Marnie J. , Garland Maureen R. , Richards James F.
Published: February 2005

The incorporation of pyrimidine nucleosides into deoxyribonucleotides by rat thymocytes in vitro was decreased by the addition of any one of several nucleosides. In cells incubated with deoxyguanosine, the decrease was apparently caused by interference with the ribonucleotide reductase reaction, and at least part of the effect of deoxyadenosine was produced in the same way. While ara‐C also produced a decrease in labelling of deoxynucleotides, this was quantitatively less than the effect on DNA synthesis, and may have resulted from an indirect effect on the reductase by a deoxyribonucleoside triphosphate which accumulated due to a direct effect of an ara‐C derivative on the DNA polymerase. Cells incubated in the presence of adenosine showed a decreased labelling of deoxynucleotides and DNA due to inhibition of earlier steps in utilization of the labelled precursor, its uptake and phosphorylation. Guanosine, or a derivative, apparently reduced labelling of DNA and RNA even at concentrations which produced no alteration in uptake and phosphorylation of the precursor. An effect on the reductase was indicated.

Uptake and phosphorylation of the pyrimidine ribonucleosides seem to be separate processes, since each can vary independently of the other when cells are incubated in the presence of various concentrations of exogenous nucleosides.
Factors affecting the production of glutamine in cultured mouse cells
Authors: Barnes Paul R. , Youngberg Dean , Kitos Paul A.
Published: February 2005

Glutamine synthetase activity of NCTC clone 929 mouse cells (strain L) was studied as a function of the prior nutritional experience of the cells. Small enzyme increases were recorded in response to either glutamine depletion or chronic serum supplementation of the growth medium. Somewhat greater increases resulted from the administration of cortisol or certain other steroids, particularly if the hormone treatment was combined with glutamine withdrawal. High concentrations of glutamate in the medium did not augment the glutamine synthetase content of the cells and even caused an apparent decrease in it. The presence of glutamine in the culture medium resulted in a fairly rapid rate of disappearance of the glutamine synthetase of previously induced cells. The data suggest that glutamine and cortisol act independently on the cells in regulating the level of the enzyme.
Differential actions of insulin on enzyme activities in mammary organ culture
Authors: Rivera E. M. , Cummins E. P.
Published: February 2005

Mammary explants from midpregnant mice were cultured for 4, 24, 48, and 72 hours in the presence and absence of insulin. Changes in the activities of phosphoglucose isomerase (an enzyme of the glycolytic pathway for glucose metabolism) and of glucose‐6‐phosphate and 6‐phosphogluconate dehydrogenases (enzymes of the pentose phosphate pathway) were assessed at each culture interval. During the first four hours of culture, no significant effect could be attributed to insulin on the activity of these enzymes. Moreover, insulin had no detectable stimulatory effect on phophoglucose isomerase until 48 hours, at which time the hormone caused a marked increase in the activity of this enzyme over the next 24 hours. In contrast, insulin stimulated only a small increase in dehydrogenase activity at 24 hours, after which this hormone acted mainly to maintain the activity that was present initially. These results indicate differential actions of insulin on two groups of enzymes catalyzing the same substrate.
Cell surface negativity and the binding of positively charged particles
Authors: Weiss L. , Zeigel R.
Published: February 2005

The binding of positively charged, colloidal ferric oxide particles to the surfaces of Ehrlich ascites tumour cells, before and after incubation with neuraminidase and/or ribonuclease, has been studied by electron microscopy. An attempt has been made to correlate the amount of binding observed, with the electrophoretic mobilities of the cells under similar conditions to those under which they were exposed to the ferric oxide.

Although a progressive loss of staining was observed with progressive loss of cellular net surface negativity, neither property was predictable from knowledge of the other. Some of the difficulties inherent in quantitative staining techniques of this type are discussed.
The effects of lactose on human erythrocytes
Authors: Kollmann George , Shapiro Bernard , Martin David
Published: February 2005

Human erythrocytes suspended in isotonic lactose solution lost potassium and continued to lose potassium even when resuspended in isotonic sodium chloride. The same phenomenon was observed when the cells were suspended in an isotonic solution of the sodium salt of glutamate, a nonpenetrating anion. The presence of 5 mEq per liter of sodium chloride in the lactose or sodium glutamate suspensions greatly reduced the initial potassium loss and the potassium loss when the cells were resuspended in sodium chloride solution. Salts of nonpenetrating anions were less or not effective in blocking lactose damage. The results indicate that absence of penetrating anions in the suspending media is the initiating condition of lactose damage. Chloride and consequently potassium are lost from the erythrocyte. Changes in cellular ionic pattern and/or changes in the cell membrane result in a nontransient damage manifested by continued potassium loss by lactose‐treated cells resuspended in isotonic NaCl.
Responses of neuroblastoma cells to iontophoretically applied acetylcholine
Authors: Nelson P. G. , Peacock J. H. , Amano T.
Published: February 2005

Dissociated mouse neuroblastoma cells were studied in vitro by using intracellular microelectrodes for electrical stimulation and recording. Some, but not all cells, which exhibited well developed action potentials to electrical stimulation also showed changes in membrane potential to iontophoretically applied acetylcholine (ACh). The types of responses to ACh varied. Short latency depolarizing responses to pulses of ACh (similar to those obtained with skeletal muscle) as well as sustained depolarization to steady ACh application (D response) occurred. A longer latency prolonged hyperpolarizing response (H response) and bi‐ and triphasic combinations of H and D responses were also seen.

Pairs of cells showing morphologic contact were tested for the occurrence of effective synaptic coupling by placing intracellular microelectrodes in each cell. In none of 95 cases tested did spike activity produced by direct electrical stimulation of one cell elicit a synaptic potential of 200 μv or more in the other.
Hematopoietic stem cells from mice with erythroblastosis
Authors: Hajdik I. , Niewisch H. , Matioli G.
Published: February 2005

The infection of newborn mice with a mouse erythroblastotic virus increases the number of hematopoietic stem cells in the spleen. Upon retransplantation of these stem cells into intermediate recipient mice certain growth parameters (doubling time, self renewal and extinction probability, etc.) which are abnormal when measured by techniques which avoid the intermediate recipient step, appear to be reverted toward normal values. The “normalization” of the stem cells is explained by the change in the environment supporting CFU growth during transplantation.
Distinctions between rabbit lymph node cell populations responding to primary and secondary injections of keyhole limpet hemocyanin
Authors: Folds J. D. , Roszman T. L. , Stavitsky A. B.
Published: February 2005

Rabbits were injected once or twice into the hind foot pads with alum‐precipitated keyhole limpet hemocyanin. At the height of the primary or secondary responses individual rabbits were sacrificed for the preparation of lymph node cell suspensions from the regional lymph nodes. These cells were employed for the in vitro study of antibody synthesis by the incorporation of 14C‐leucine and the secretion of antibody by the time of appearance of radioactive antibody in the medium. The primary response cells rapidly synthesized and secreted IgM and IgG antibodies. The secondary response cells rapidly synthesized IgM and IgG antibodies, secreted IgG antibody promptly, but secreted the IgM antibody with a lag of six to ten hours. Microsomal fractions could not be prepared from the primary response cells, but were readily produced from the cells of the secondary response. The primary response cells contained mainly free ribosomes, those of the secondary response predominantly membrane‐bound ribosomes. It was postulated that IgM antibody was not secreted until it was glyco‐sylated in the Golgi apparatus and that the lag in secretion entailed the time for this rate‐limiting step to occur.
Susceptibility of primate‐mouse hybrid cells to SV40
Authors: Knowles Barbara B. , Barbanti‐Brodano Giuseppe , Koprowski Hilary
Published: February 2005

Primate‐mouse hybrid cells were challenged with SV40 DNA and monitored for their ability to produce virus. All of the hybrid cells had lost at least half of their primate chromosomes at the time of challenge. Only SV40 T‐antigen‐positive hybrid cells derived from an SV40‐transformed human parental cell produced SV40. This finding suggests that the chromosome(s) necessary for SV40 replication are easily lost on fusion of mouse and primate cells unless the parental cells are already SV40‐transformed.
Diffusion chamber and spleen colony assay of murine haematopoietic stem cells
Authors: Breivik Harald , Benestad Haakon Breien , Bøyum Arne
Published: February 2005

Mouse bone marrow cells have been cultured in diffusion chambers and their capacity to form spleen colonies in irradiated mice investigated after different culture periods. The number of spleen colony‐forming units (CFU) in the chambers decreased during the first day of culture. The number then increased rapidly to a level significantly above the original chamber value on the third to fifth day of culture. By that time large numbers of granulocytes and macrophages had also appeared.

Histological examination of spleen colonies showed that prior culturing did not alter the ratio between the different types of colonies.

Cultured bone marrow cells which were transferred to new chambers retained granulopoietic capacity. This capacity increased between the first and second day of primary culturing. At this time hydroxyurea injections to chamber hosts revealed that the progenitor cells were proliferating.

The results show that the granulopoietic progenitor cells of the chambers are stem cells, and that one progenitor cell type is identical with the CFU.
Haematopoietic stem cell content of murine bone marrow, spleen, and blood. Limiting dilution analysis of diffusion chamber cultures
Authors: Breivik Harald
Published: February 2005

Suspensions of mouse bone marrow cells, spleen cells, and blood leucocytes were cultured in diffusion chambers in dilution series in order to establish the minimum concentrations of haematopoietic stem cells (HSC). The observed frequencies of empty chambers after seven days of culture conformed to the expected frequencies of a null response in a Poisson distribution. The proportions of empty chambers could therefore be used to estimate the concentrations of HSC in the cell suspensions. The following numbers of HSC per 105 cells were found (with 95% confidence limits): Bone marrow: 50 (44–56). Spleen: 3.5 (2.8–4.3). Blood leucocytes: 1.4 (1.2–1.8). The mean (± standard error) HSC‐content per femur, spleen, and milliliter blood when pooling cells from three to six donor mice was 8240 ± 600, 7660 ± 490, and 56 ± 6.5 respectively.

For comparison, the HSC concentrations were also determined with the spleen colony technique; the ratio between the HSC‐concentrations of bone marrow, spleen, and blood determined with the diffusion chamber technique was similar to that determined with the spleen colony technique.
Genetics of somatic mammalian cells XII: Mutagenesis by carcinogenic nitroso compounds
Authors: Kao Fa‐Ten , Puck Theodore T.
Published: February 2005

Four known carcinogenic compounds, all of which contain the nitroso group, have been found to be effective in producing cell killing, chromatid breaks, mutagenesis and chromatid rearrangements in Chinese hamster ovary cells. Single cell survival curves revealed these agents to exhibit a 50,000‐fold difference in their mean lethal dose (Do) values. However, all agents yielded constant values for their efficiencies of production of chromatid breaks and single gene mutagenesis, but not chromatid rearrangements, when these were expressed in terms of the Do value of each agent. Three of the carcinogens produced single‐hit and one produced a multiple‐hit survival curve. The system offers distinct advantages in study of the interrelationships between mutagenic and carcinogenic actions in mammalian cells.
Properties of the mouse embryo conditioned medium factor(s) stimulating colony formation by mouse bone marrow cells grown in vitro
Authors: Stanley E. R. , Bradley T. R. , Sumner M. A.
Published: February 2005

The properties of the mouse embryo cell conditioned medium (ECM) colony stimulating factor(s) from six day mouse embryo cultures have been examined. The general properties were similar to those described previously for the human urine colony stimulating factor. The ECM colony stimulating activity (CSA) was not lost following treatment with nucleases, glycosidases, phospholipases and proteolytic enzymes with the exception of α‐chymotrypsin. ECM CSA was lost following mild periodate treatment.

Fractionation of ECM CSA revealed a slight size heterogeneity on gel‐filtration and on zone sedimentation in sucrose gradients. There was a discrepancy between the apparent molecular weights determined by gel‐filtration (70,000–150,000) and by zone sedimentation (64,000) as has been reported previously for other colony stimulating factors. A gross charge heterogeneity of ECM CSA was apparent on electrophoresis and DEAE‐cellulose chromatography, and a heterogeneity of the elution profile on stepwise elution from calcium phosphate gel was observed. This heterogeneity was still apparent in the presence of 6M urea and appeared to be unchanged following re‐chromatography on DEAE‐cellulose under the usual fractionation conditions. These studies suggested that the heterogeneity was not due to easily reversible combinations of active subunits.

The electrophoretic heterogeneity of six day ECM CSA was found to develop gradually from an electrophoretically monodisperse band at day 2 of culture. Experiments in which preparations containing concentrated monodisperse ECM CSA were added back to culture dishes during and after ECM production suggested that the development of heterogeneity was related to the production or release of factor(s) from the cells rather than the action on the colony stimulating factor(s) of an extracellular enzyme in the medium. Alteration of the electrophoretic mobility of six day ECM CSA by incubation with purified sialidase suggested the presence of sialic acid on the active molecules.

Purification procedures for the ECM factor(s) were not developed to any large extent primarily in view of the charge heterogeneity. The results of this study suggest that the ECM colony stimulating factor(s) is a glycoprotein(s).