bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of phenethyl alcohol on yeast cells
Authors: Burns Victor W. , Wong D.
Published: February 2005

An investigation of the physiological effects of phenethyl alcohol (PEA) on exponentially growing yeast cells is reported. RNA, DNA, protein and aminoimidazole ribotide syntheses and glucose uptake and incorporation are inhibited by PEA at concentrations of 0.1% to 0.3%. Two classes of response curves are found and the sensitivities of processes in each class to PEA differ. Glucose incorporation and RNA synthesis are the most sensitive processes in their respective classes. The effects of PEA at 0.3% or less are largely or completely reversible. It is deduced that PEA inhibits intracellular processes as well as the cell membrane.
Clonal growth of differentiated rabbit cartilage cells
Authors: Ham Richard G. , Sattler Gerald L.
Published: February 2005

Single cell suspensions have been prepared from rabbit cartilage by collagenase digestion in the presence of fetal bovine serum. When inoculated into medium F12 supplemented with 5% fetal bovine serum and 5% rabbit serum, the cartilage cell suspensions yield large healthy colonies of epithelial‐like cells with an average plating efficiency of 47%. At the end of a 14 day incubation period, the centers of many of the colonies are thickened into multilayered aggregates. Such colonies exhibit serveral cartilage‐like properties, including metachromatic staining with toluidine blue, dense brown staining with bismark brown, bright green staining with alcian green, and a refractile matrix which can be seen with the phase contrast microscope to surround the living cells. Similar properties have also been observed in second and third passage subcultures.
Development of 3T3‐like lines from Balb/c mouse embryo cultures: Transformation susceptibility to SV40
Authors: Aaronson Stuart A. , Todaro George J.
Published: February 2005

Balb/c mouse embryo cultures that are carried under a rigid transfer schedule that minimizes cell‐cell contact evolve into permanent lines that possess properties very similar to 3T3. From the same embryo cultures, a transfer schedule where cell‐cell contact is extensive leads to lines (Balb/3T12) that form multiple cell layers and have saturation densities up to 25‐fold higher than the Balb/3T3 lines. All the lines are hypotetraploid.

Comparison of the Balb/3T3 lines with 3T3 reveals similar morphology, ability to grow at high dilution, low saturation density, and high susceptibility to transformation by SV40 virus. The Balb/3T12 lines, which are continually maintained at high cell density, show little improvement in cloning efficiency. Infection with SV40 produces transformants that can be selected by their ability to form colonies at low cell densities. Using the appropriate selective system for each line, it appears that SV40 T antigen induction and transformation in Balb/3T3 and Balb/3T12 are comparable.
Coupling of excitation and cessation of cyclosis in Nitella: Role of divalent cations
Authors: Barry William H.
Published: February 2005

The effect of external divalent cation salt solutions upon the association of an action potential and cessation of cytoplasmic streaming in Nitella was studied. Nitella cells remained excitable when immersed in solutions of CaCl2, MgCl2, BaCl2, and SrCl2. Cessation of streaming coincident with excitation occurred in solutions of CaCl2 or SrCl2 but not in solutions of MgCl2 or BaCl2. In cells exposed to solutions containing mixtures of MgCl2 and CaCl2, or MgCl2 and SrCl2, it was the [Ca]/[Mg] or [Sr]/[Mg] which determined the effect of an action potential upon the rate of streaming, rather than the absolute concentrations Ca++ or Sr++. The implications of these data are discussed with respect to the structure involved in the generation of cytoplasmic streaming and the relation of streaming to other types of biological motion.
Triggering of the cell cycle in an organized tissue In vitro
Authors: Harding C. V. , Wilson W. L. , Wilson J. R. , Reddan J. R. , Reddy V. N.
Published: February 2005

The rabbit lens can be maintained in culture under conditions which retain the block to proliferation characteristic of many of the cells in the normal tissue in vivo. Proliferation and cell migration subsequently can be triggered at will by the addition of serum to the medium. Serum is not required throughout the whole period of culture in order to elicit this response but only during an initial period which ends prior to the onset of both DNA synthesis and mitosis. The duration of this period of serum‐dependency is specifically related to the location (and hence the state of organization) of the cells within the epithelial layer. Some of the characteristics of the serum factors which promote these reactions and the conditions of culture which affect their activity are reported.
Changes in DNA polymerase activity associated with cell fusion in cultures of embryonic muscle
Authors: O'Neill M. , Strohman R. C.
Published: February 2005

In cultures of differentiating chicken embryo muscle cells there is a steep decline in DNA polymerase activity which closely parallels the time of rapid cell fusion and the formation of multinucleated myotubes. The DNA polymerase activity remaining in the cultures is almost completely associated with single unfused cells. Cell fusion does not require a confluent culture and fusion capability appears to be severely reduced in the remaining single cells following an approximately ten hour time period during which the majority of fusion takes place. A model is presented to explain the observed kinetics of cell growth and cell fusion in vitro.
The rate of attachment of amoebae to the substratum: A study of nuclear‐cytopolasmic relationships
Authors: Lorch I. J.
Published: February 2005

The rate of attachment to the substratum was found to be a strain specific character of certain large free‐living amoebae. Two strains, which differed significantly in this respect, were compared with regard to the rate of attachment of enucleated cytoplasm, nuclear‐cytoplasmic hybrids and amoebae injected with cytoplasm from another strain. It was found that both the nucleus and the cytoplasm of the more rapidly attaching strain were able to transmit this character to amoebae of the more slowly attaching strain. The possible mechanisms underlying attachment and transmission of the rate of attachment are discussed.
Relationship between uridine kinase activity and rate of incorporation of uridine into acid‐soluble pool and into RNA during growth cycle of rat hepatoma cells
Authors: Plagemann Peter G. W. , Ward Gary A. , Mahy Brian W. J. , Korbecki Michal
Published: February 2005

Uridine kinase activity measured in cell‐free extracts of Novikoff rat hepatoma cells grown in suspension culture fluctuates about 10 fold during the growth cycle of the cells. Maximum specific activity (units/106 cells) is observed early in the exponential phase and then decreases progressively until the stationary phase. The rate of incorporation of uridine into the acid‐soluble pool by intact cells fluctuates in a similar manner and both the rate of uridine incorporation by intact cells and the uridine kinase actvity of the cells increase several fold before cell division commences following dilution of stationary phase cultures with freshmedium. Regardless of the stage of growth, uridine is rapidly phosphorylated to the triphosphate level by the cells.

The rates of incorporation of uridine into the nucleotide pool and into RNA by intact cells fluctuate in a similar manner during the growth cycle. However, evidence is presented that indicates that alterations in the rate of incorporation of uridine into RNA are not simply due to changes in the rate of phosphorylation of uridine, but are regulated independently.

Inhibition of protein synthesis by treating cells with puromycin or actidione causes a marked inhibition of incorporation of uridine into RNA, but has little effect on the phosphorylation of uridine to UTP for several hours. Thus the depression of incorporation of uridine into RNA probably reflects a decrease in the rate of RNA synthesis as a result of inhibition of protein synthesis. Inhibition of RNA synthesis by treating cells with actinomycin D does not affect the rate of conversion of uridine to UTP and thus results in the accumulation of labeled UTP in treated cells.
Control of cell multiplication in uninfected chicken cells and chicken cells converted by avian sarcoma viruses
Authors: Temin Howard M.
Published: February 2005

The increased multiplication of converted chicken cells in the presence of limited amounts of serum results from more efficient utilization of multiplication‐stimulating activity rather than increased binding or uptake of this activity.
Phenotypically variant adrenal tumor cell cultures with biochemical lesions in the ACTH‐stimulated steroidogenic pathway
Authors: Schimmer Bernard P.
Published: February 2005

Four clonal adrenal tumor cell lines which exhibit biochemical lesions in the ACTH‐stimulated steroidogenic pathway have been isolated. Two of these cell lines, designated Y‐6 and OS3, appear to contain their lesions at points proximal to cyclic AMP formation in the ACTH‐stimulated steroidogenic pathway. Growth of Y‐6 and OS3 as tumors in isogenic mice results in a restoration of ACTH sensitivity in both cell lines by mechanisms which do not appear to involve selection or fulfillment of specific nutritional requirements. Growth of Y‐6 and OS3 as tumors in heterogenic mice results in restoration of ACTH sensitivity in Y‐6 but not in OS3, suggesting that the biochemical lesions in these cell lines are at different loci. Two other cell lines, designated OS1 and OS4, possess biochemical lesions in the steroidogenic pathway beyond the formation of cyclic AMP and before the formation of pregnenolone. Growth of OS1 and OS4 as tumors in isogenic mice results in the repair of the biochemical lesions in these cells distal to cyclic AMP formation in the ACTH‐stimulated steroidogenic pathway. The four cell lines described are potentially useful in elucidating the mechanism of action of ACTH in adrenal cells as well as in determining the factors required for maintaining differentiated function in cultured cells.
The influence of conditioned media and nonessential amino acid supplementation on the growth of cells in vitro
Authors: Oellermann Rolf A. , Miller Elsa M.
Published: February 2005

The growth enhancing effect of media conditioned by cells from established lines (BHK and L60) is comparable to that of media conditioned by cells of primary origin (chick embryo). However, the properties of the conditioned media from these two systems show marked differences: the growth enhancing factors in the former are dialyzable and heat‐stable, in contrast to the non‐dialyzable and heat‐labile factors in the latter.

Media conditioned for only four hours by BHK or L60 cells stimulated cell growth. Amino acid analyses revealed that non‐essential amino acids had appeared in these conditioned media.

To verify this as the metabolic basis of conditioning by cells from established lines, media containing dialyzed serum were supplemented with each of six non‐essential amino acids, and assayed on BHK and L60 at various population densities. Serine was the most stimulatory and alanine the most inhibitory of the amino acids tested.

Mixed supplementation of the medium showed that when low levels of alanine and serine were added simultaneously, cell growth was enhanced but any increase in the level of alanine required an increase in the level of serine also to achieve growth stimulation.
DNA‐mediated transformation of mammalian cells in culture. Increased transforming efficiency following sonication
Authors: Roosa Robert A. , Bailey Ellen
Published: February 2005

A series of 100 experiments was completed to determine if DNA is capable of transforming the genotype of a murine lymphoma (P388) in cell culture. The test system was concerned with the transformation of cells from 8‐azaguanine (AZG) sensitivity to resistance. By the use of this marker, it was determined that transformation by DNA did occur, and that the efficiency of transformation was greatly increased by sonication of the DNA. A statistical analysis of 100 experiments demonstrated that the increase in the number of resistant cells after treatment with sonicated resistant DNA (R‐DNA) was statistically significant (χ2 > 4.25, 0.05 > p > 0.02) in 66% of the experiments. DNA from sensitive parental cells and DNA from other sources produced no effect while DNase and UV treatment abrogated effective transformation by either sonicated or nonsonicated R‐DNA. RNase was without effect.

Sucrose gradient analysis of sonicated and nonsonicated R‐DNA demonstrated that the peaks which correspond to the highest specific transforming activity are not altered by sonication and do not coincide with the OD260 peaks, in spite of the fact that sonication shifted the peak of maximum OD260 to a slower sedimenting region of the gradient. The major portion, however, of the transforming material did shift after sonication to the slower sedimenting region of the gradient and did coincide with the OD260 peak.

The hereditary stability of the transformed cells was established by cloning a representative number of transformants, growing them in the absence of AZG for an extended period and then testing their ability to grow in graded concentrations of AZG. In addition, DNA extracted from transformants successfully transformed sensitive cells.
Interaction of calcium and local anesthetics with skeletal muscle microsomes
Authors: Bondani Augusto , Karler Ralph
Published: February 2005

The influence of Ca++, several drugs, and pH on the binding of Ca++ by skeletal muscle microsomes was studied in vitro. A mass‐law graphic analysis revealed the presence of three distinct species of Ca++‐binding sites in the microsomes, and the binding at only one of these sites was antagonized by local anesthetics and quinidine. These drugs also decreased the maximum Ca++‐binding capacity of the microsomes. Caffeine and ouabain exerted no effect on the binding at any of the sites. Procaine was also bound by microsomes, and this binding was antagonized by Ca++, which also decreased the maximum procaine‐binding capacity of microsomes. The sites that bind procaine and Ca++ are not identical because the maximum‐binding capacities of the interacting sites are distinctly different. The influence of pH on the ability of drugs to antagonize Ca++ binding indicates that the displacing activity increases as the percentage of the drug in the nonionized form increases. All of the data obtained in the above studies are consistent with the interpretation that quinidine and local anesthetics of the procaine type noncompetitively antagonize the binding of Ca++ by microsomes. The pharmacological significance of a noncompetitive interaction may be related to the property of local anesthetics and quinidine to increase contractile tension in skeletal muscle rather than to their ability to stabilize the cell membrane.
The diversity of sulfhydryl groups in the human erythrocyte membrane
Authors: Shapiro Bernard , Kollmann George , Martin David
Published: February 2005

Human bank blood erythrocytes were exposed to the mercurials p‐chloromercuribenzoate (PCMB), chlormerodrin (CM), p‐chloromercuribenzenesulfonate (PCMBS), and 1‐bromomercuri‐2‐hydroxypropane (BMHP) for different time intervals, at different concentrations and in combination with n‐ethylmaleimide (NEM) added before, and 2‐mercaptoethylguanidine (MEG) and reduced glutathione (GSH) added after the mercurial. Binding patterns of the mercurials to the cells and effects on permeability of the cells were measured. The results indicate that the erythrocyte membrane contains multiple classes of sulfhydryl groups, alteration of which has a variety of effects on cell permeability. PCMB, chlormerodrin and PCMBS react with at least three classes of sulfhydryls, two of which are associated with the sodium‐potassium barrier and, when altered, result in potassium loss, sodium accumulation and hemolysis. BMHP reacts with at least two classes of sulfhydryls, one of which is associated with permeability, and, when altered, results in hemolysis in isotonic solutions of choline chloride or lactose. The results provide additional insight into the structure and function of the erythrocyte membrane.
Histidase function in human epidermal cells
Authors: Barnhisel Mary L. , Priest Robert E. , Priest Jean H.
Published: February 2005

The activity of histidase was studied in (1) epidermal tissue scraped from human infant foreskin, (2) fibroblast‐like cells in monolayer serial culture from human foreskin, and (3) epithelial‐like (epidermal) outgrowth from foreskin primary explants. Foreskin epidermal tissue without in vitro culture and epidermal outgrowth in primary culture from explants of foreskin showed equivalent mean levels of histidase activity, 5.22 × 10−3 and 5.01 × 10−3 μMoles urocanic acid produced per milligram protein per minute. Under the same assay conditions, there was no measurable histidase activity in cultured fibroblast‐like cells from foreskin at various times after subculture. The Km for enzyme from human foreskin epidermal tissue ranged between 2 and 5 × 10−3 M histidine. Ability to demonstrate the presence or absence of this tissue‐specific enzyme function in cultured cells suggests a useful means for studying differentiation, as well as a more precise way to identify epidermal origin of cultured cell types than morphological characteristics alone would permit.
Hemopoietic stem cell distribution in tissues of fetal and newborn mice
Authors: Niewisch Helgard , Hajdik Irene , Sultanian Ishkhan , Vogel Helmut , Matioli Gastone
Published: February 2005

The variations in the distribution of hemopoietic stem cells in fetal tissues are concomitant with changes in the electrophoretic pattern of hemoglobin. The data presented here are consistent with the hypothesis that the embryonic stem cells can be transformed into adult stem cells in the liver of 15 to 16 days old fetuses.
Mammalian cell fusion III. A hela cell inducer of premature chromosome condensation active in cells from a variety of animal species
Authors: Johnson R. T. , Rao P. N. , Hughes H. D.
Published: February 2005

The phenomenon of premature chromosome condensation (PCC) is induced in unstimulated horse lymphocytes, bovine spermatozoa, Chinese hamster ovary cells, embryonic chick fibroblasts and erythrocytes, Xenopus kidney and mosquito cells by fusing each of these cell types with HeLa cells blocked in mitosis. Thus it becomes possible to visualize chromosomes even from non‐multiplying cells of heterologous species, such as, chick erythrocytes and bovine spermatozoa.
The effect of drugs on the rate of proteolysis in Vitro within secondary liver lysosomes
Authors: Bertini Francisco , Bari Daniel R.
Published: February 2005

The in vitro hydrolysis rate of intravenously injected 131 I‐albumin inside mouse liver phagolysosomes was studied for this type of secondary lysosome, when incubated at pH 5.0 and 37°C in the presence of different drugs. While vitamin A alcohol and etiocholanone showed inhibitory effects, suitable concentrations of chloroquine activated that intraparticulate hydrolysis. On the contrary cortisone, in various concentrations, did not alter the hydrolysis rate of the labeled albumin. Neither cortisone nor chloroquine modified the inhibitory effect of vitamin A. The hypothesis that the drugs act on the hydrolysis rate because they modify the stability of this type of secondary lysosome is forwarded.
The relationship of DNA synthesis to protein accumulation in the cell nucleus
Authors: Auer G. , Zetterberg A. , Foley G. E.
Published: February 2005

The relationship between DNA synthesis and protein accumulation in cell nucleus and cytoplasm has been investigated by the use of a combination of ultramicrointerferometric and ultramicrospectrophotometric methods.

5‐Fluoro‐2'‐deoxyuridine (FUdR) inhibited DNA synthesis, resulting in inhibition of cell proliferation in G‐1 and early S‐phase. However, synthesis and accumulation of protein continued in the presence of FUdR, as indicated by a 54% increase in the average dry mass value per individual cell during 18‐hour exposure to FUdR; due primarily to protein accumulation in the cytoplasm, the average cytoplasmic dry mass increased by as much as 85%, while the dry mass of the nucleus increased by only 21%.

The dry mass values of individual nuclei were well‐correlated to the nuclear DNA content throughout the period of exposure to FUdR. In contrast to the continued accumulation of protein in the cytoplasm during inhibition of DNA synthesis, protein accumulation in the nucleus was inhibited. When cells were released from inhibition of DNA synthesis by the addition of 2'‐deoxythymidine, the nuclear DNA content and nuclear dry mass increased in near‐synchrony, there being some evidence that DNA synthesis was initiated somewhat prior to initiation of increase in nuclear dry mass.

Thus, it appears that DNA synthesis (or an increase in nuclear DNA content) is intimately related to the regulation of protein accumulation in the nucleus.
Transformation of granulocytes to macrophages in bone marrow colonies in vitro
Authors: Metcalf Donald
Published: February 2005

Single cells from developing two day granulocytic bone marrow colonies were transfered in agar cultures. After three to five days, 48 of 239 transfered single cells had transformed to single macrophages or proliferated to form aggregates of pure macrophages or mixed macrophage‐granulocyte aggregates. Some granulocytes in colonies developing in vitro from bone marrow cells appear to have the capacity to transform to macrophages.
Stimulation by serum of multiplication of stationary chicken cells
Authors: Temin Howard M.
Published: February 2005

When serum was added to cultures of stationary chicken fibroblasts, there was an increase in the percentage of cells synthesizing DNA after a delay of about five hours. If the serum was removed before DNA synthesis began, some cells were still found to start DNA synthesis and to enter mitosis. The delay between the time of addition of serum and the start of DNA synthesis was not affected by the type of serum, the concentration of serum, nor the means of preparing the stationary cells. However, all of these factors affected the proportion of cells stimulated by serum.

If two pulses of serum were given immediately following each other, their effects were synergistic. If there were twelve hours between them, there was no effect of the first pulse. These results were summarized in a new model of the cell cycle which subdivided the G1 phase into Gla, b, and c.

The effects of serum were seen in a balanced salt solution, and were sensitive to several metabolic inhibitors.
The effect of pH, potassium, sodium, bicarbonate, and chloride ions and glucose on the buoyant density distribution of human erythrocytes in bovine serum albumin gradients
Authors: Kneece W. C. , Leif R. C.
Published: February 2005

The effect of pH on the buoyant density of human erythrocytes at 4°C in bovine serum albumin (BSA) gradients has been reinvestigated. The results obtained disagree with those found by Legge and Shortman. This disagreement is due to a difference in the way “isotonic” is defined. The results in this pH study were obtained by keeping the total concentration of cations constant rather than the total concentration of solutes. This study demonstrated that when the pH of the BSA gradient is maintained between 5.7 and 7.2, by varying only the concentrations of bicarbonate and chloride ions, the value of ρtmed, the buoyant density at the truncated median of the density distribution, for human erythrocytes changes in a complex manner, but does not increase anywhere as much as previously found. The bicarbonate ion apparently is partially excluded from the human erythrocyte.

Upon extrapolation to the physiological concentration of the bicarbonate ion (27.50 meq/liter), the buoyant density was found to decrease with the increasing pH.

Variations in the (K+/Na+) ratio of the BSA gradient media, at a constant pH and total cation concentration, do not appear to affect significantly the buoyant density of the human erythrocyte. Increasing the concentration of glucose from 5.55 to 11.10 meq/liter also did not significantly affect the buoyant density of these cells.
Phosphate transport in ehrlich ascites tumor cells and the effect of arsenate
Authors: Levinson Charles
Published: February 2005

The effect of extracellular Pi and arsenate on Pi‐transport in Ehrlich ascites tumor cells has been studied. Pi‐transport can be described by Michaelis‐Menten kinetics; the maximal flux equal to 44 mmoles (kg cell water)−1 hour−1 and Km equal to 3.3 × 10−4 M. Arsenate is a competitive inhibitor of Pi‐transport with an inhibition constant (Ki) equal to 2.41 × 10−3 M.

The data support the hypothesis that cellular Pi is regulated by the cell membrane through the mediation of a carrier system.
Phagocytosis and the sialic acid of the surface of polymorphonuclear leukocytes
Authors: Noseworthy John , Korchak Helen , Karnovsky Manfred L.
Published: February 2005

Treatment of polymorphonuclear leukocytes with sialidase release about one‐half of the total sialic acid of the cells. Such treatment affects neither phagocytic ingestion nor glycolysis. These results are in contrast to earlier data in the literature that indicate suppression of both functions mentioned upon desialation of these cells. The presence of an inhibitor of glycolysis that contaminated the crude enzyme previously used is suggested.
Stimulation of uptake of tritiated thymidine into mouse marrow cells in culture by a factor from L‐cell conditioned medium
Authors: Austin P. E. , McCulloch E. A. , Till J. E.
Published: February 2005

Uptake of 3H‐thymidine into suspension cultures of mouse marrow cells was stimulated by the addition of serum‐free conditioned medium harvested from cultures of mouse L‐cells. Characterization of the “conditioning factor activity” (CFA) by gel filtration, ion exchange chromatography, velocity sedimentation, polyacrylamide gel electrophoresis and susceptibility to trypsin digestion indicated that the CFA detected by stimulation of 3H‐thymidine uptake is the same as the CFA detected previously by its ability to stimulate colony formation by marrow cells in vitro. The 3H‐thymidine uptake assay was used to investigate the kinetics of disappearance of CFA as a function of time in the presence of mouse marrow cells. The CFA recoverable from the cultures decreased rapidly during the first day, and approached background levels by the fifth day. There was no evidence of inhibitory substances in the depleted media. Even if the cultures continued to receive fresh conditioned medium at daily intervals, 3H‐thymidine uptake decreased sharply after the fifth day, indicating that the marrow cells had lost their capacity to respond to CFA.
Expression of differentiated functions in hepatoma cell hybrids. II. Aldolase
Authors: Bertolotti Roger , Weiss Mary C.
Published: February 2005

A study of aldolases in rat hepatoma clones and subclones has revealed that they synthesize all three forms of aldolase monomers: A (the ubiquitous glycolytic isozyme), B (the form characteristic of the liver) and C, and that in vitro–in vivo passage results in a reversible modulation in aldolase A activity.

Three kinds of somatic hybrids, between rat hepatoma cells and either mouse fibroblasts or rat epithelial cells, have been studied. In each case, aldolase B, found only in the hepatoma parent, was absent in the hybrid cells. The absence of aldolase B in the somatic hybrids seems not to be due to trivial factors (species differences, inactivation of all hepatoma aldolase genes, increase in ploidy or loss of chromosomes); it is concluded that extinction of this differentiated function of the hepatoma parent reflects a genetic regulatory phenomenon.
Arrest of chinese hamster cells in G2 following treatment with the anti‐tumor drug bleomycin
Authors: Tobey Robert A.
Published: February 2005

Upon addition of bleomycin (BLM) to suspension cultures of Chinese hamster cells (line CHO), cells closer to prophase than 56 minutes continue dividing at the normal rate, whereas cells at earlier positions in the cell cycle either fail to reach mitosis altogether (at 200 μg/ml) or enter mitosis and divide at a reduced rate at lower drug concentrations. At 100 μg/ml of BLM (the rate of cell division slowed to a doubling time of 167 hours), initiation and termination of DNA synthesis occur at normal rates, resulting in an accumulation of cells with a G2 DNA content in the first 130 minutes of G2. Bleomycin effects are not readily reversible. The rates of incorporation of leucine, uridine, or thymidine into cells treated for six hours with 100 μg/ml of BLM were 90, 85, and 80%, respectively, of the values obtained in control cultures, suggesting that the effects of BLM on cell‐cycle traverse cannot be correlated with gross inhibition of macromolecular synthesis.
The influence of calcium on the cyclic AMP‐mediated stimulation of DNA synthesis and cell proliferation by prostaglandin E1
Authors: Whitfield J. F. , Macmanus J. P. , Braceland B. M. , Gillan D. J.
Published: February 2005

Prostaglandin type E1 (PGE1) rapidly stimulates cyclic AMP formation and the initiation of deoxyribonucleic acid (DNA) synthesis in rat thymic lymphocytes suspended in vitro by reactions which are not affected by wide variations in the extracellular calcium concentration. On the other hand, the operation of the associated reaction(s) responsible for the subsequent progression of the stimulated cells into mitosis is profoundly affected by the extracellular calcium level. If the maximum intracellular cyclic AMP concentration is in the lower range of stimulatory values (e.g., 150 × 10−8 picomoles per cell as produced by an exposure to 0.5 μg of PGE1 per milliliter of medium), an extracellular calcium concentration of 0.5 to 1.0 mM is needed to obtain maximum cell proliferation, but not the maximum stimulation of DNA synthesis. Contrariwise, if the cellular cyclic AMP content is raised to a much higher level (260 × 10−8 picomoles per cell) by exposure to a greater PGE1 concentration (5.0 μg per millilter), cell proliferation is maximally stimulated in calcium‐free medium and increasing the extracellular calcium concntration above 0.2 mM actually prevents the stimulation of cell proliferation (but does not affect the stimulation of DNA synthesis). Thus, the ultimate translation of PGE1's early cyclic AMP‐mediated reactions into increased cell proliferation is determined by both the intracellular cyclic AMP level and the extracellular calcium concentration.
Hemopoietic colony studies. VI. Increased eosinophil‐containing colonies obtained by antigen pre‐treatment of irradiated mice reconstituted with bone marrow cells
Authors: Jenkins V. K. , Trentin J. J. , Speirs R. S. , McGarry M. P.
Published: February 2005

The cellular response to an intraperitoneal injection of antigen (tetanus toxoid) was studied in reconstituted animals in order to determine the mechanism of control of eosinophil granulocytopoiesis. Antigen treatment of the marrow cell donors did not consistently increase the number of spleen and bone marrow colonies in recipient animals or change the percentage of eosinophil or other hemopoietic colony types. Antigen pre‐treatment of the irradiated recipients increased the percentage of eosinophil‐containing colonies in the spleen and femoral bone marrow without significantly changing the total number of either spleen or marrow colonies. Antigen treatment of both the bone marrow cell donor and recipient produced a further increase in the percentage of eosinophil‐containing colonies in the marrow cavity, but not in the spleen. Antigen treatment of the irradiated recipient increased the number of eosinophilic cells (but not the total number of cells) in both the peritoneal cavity and the bone marrow. Antigen treatment of both the marrow donor and recipient produced a further increase in the number of eosinophilic cells in the peritoneal cavity, but not in a single femur. Since antigen treatment of the marrow recipient, or recipient and donor, but not of the marrow donor alone, results in increased eosinophilic cell and colony numbers, the effect of antigen appears to be mediated through some host factor(s), perhaps the eosinophilic hemopoietic inducing microenvironment (HIM), rather than directly on the hemopoietic stem cells.
Cloning of mouse myeloma cells and detection of rare variants
Authors: Coffino Philip , Baumal Reuben , Laskov Reuven , Scharff Matthew D.
Published: February 2005

Cultured mouse myeloma cells have been cloned in soft agar using a modification of the method established by Pluznik and Sachs ('65, '66) and by Bradley and Metcalf ('66). A linear relationship existed between the number of cells plated and the number of colonies produced. Conditions for obtaining optimum cloning efficiency and colony size were determined for the MPC‐11 cell line. Feeder cells of mouse, human and rabbit origin and conditioned growth medium obtained from mouse cultures and had an enhancing effect on colony formation. Immunoglobulin production by cloned cells was detected by overlaying the clones with anti‐immunoglobulin antiserum. The antiserum had no adverse effect on cloning efficiency or colony size. A reconstruction experiment was performed to show that the plate assay could reliably detect rare variants of immunoglobulin producing cells. The plate assay was validated by studying immunoglobulin production following recovery of clones from dishes and their growth to mass suspension culture. Immunoglobulin formation in these cultures was assessed by a Ouchterlony immunodiffusion of the supernatant medium, and by incubating the cells with radioactive amino acids and analyzing the intracellular and secreted immunoglobulin on polyacrylamide gels.
Multiple sensitivity of single taste cells of the frog tongue to four basic taste stimuli
Authors: Sato Toshihide
Published: February 2005

The electrical response of the taste cells of the frog fungiform papillae to four fundamental taste solutions (NaCl, acetic acid, quinine‐HCl and sucrose) was studied by using the intracellular recording technique. The average value of resting membrane potential was 22.5 mV, inside negative. Each of the four taste solutions applied to the tongue produced a slow depolarizing potential, the receptor potential, on which no spike potential was superimposed. The amplitude of the receptor potentials increased linearly as a function of the logarithm of the concentration of the stimulus. Amplitudes of depolarizations to a given taste stimulation varied from one cell to another even within a single taste bud. Most of the cells responded to more than two of the four basic taste solutions. Sensitivity patterns in terms of the number of effective solutions and the relative effectiveness of different kinds of solutions were variable among cells. Statistical analysis suggests that at the receptor membranes of the taste cells, the sensitivities for the four basic stimuli are independent and random.
Ammonia effects in cultures of normal and transformed 3T3 cells
Authors: Visek W. J. , Kolodny G. M. , Gross P. R.
Published: February 2005

3T3 and SV‐40 transformed 3T3 mouse fibroblasts were cultured in media with serum and antibiotics plus ammonia (NH3 z NH4+) added as NH4C1. Both cell lines cultured without added ammonia showed normal morphology and multiplication even though ammonia in the medium at the end of the culture period ranged from 35 to 48 μg/ml. Ammonia concentrations being significantly higher in media removed from cells at the end of the culture period than in media incubated identically without cells, verified that cells released substantial quantities of ammonia in addition to components of the medium which underwent spontaneous breakdown. Both cell lines showed changes in morphology and highly significant reductions in cell multiplication which increased progressively as the concentration of added ammonia on the initial day of culture was increased to 35μg/ml. Control 3T3 cultures released significantly greater quantities of ammonia per cell than control cultures of transformed cells but their multiplication was more adversely affected by added ammonia. There were downward shifts in pH of the culturing medium for both cell lines as culture age increased at all concentrations of added ammonia, However, significant reductions in cell multiplication resulted from additions of ammonia that did not produce significant changes in extracellular pH. The data show that studies upon the effects of pH of the medium on cultured cells require control of ammonia concentrations.
Contact inhibition of what? An analytical review
Authors: Martz Eric , Steinberg Malcolm S.
Published: February 2005

Quite a number of phenomena having to do with cells' influences upon one another's movements have come to be regarded as expressions of “contact inhibition.” However, no single, central mechanism has been shown to underlie them all. Consequently, the term “contact inhibition” should not be used without operational modifiers. Inhibitions of individual cell movements imputed to be mediated by cell‐cell contacts include inhibition of overlapping (which results in monolayering), of colony expansion, of cell speed (nuclear translocation), of ruffling, of orthogonal movement (proposed to explain spontaneous parallel alignment of cells), and of neighbor exchanges.

The six inhibitions listed above are operationally distinct, and only two (overlapping and colony expansion) are known to result from a common mechanism. A seventh phenomenon, so‐called “contact inhibition of cell division” (more operationally termed postconfluence inhibition of cell division) is in a separate category and is not considered here.

Evidence eliminating action‐at‐a‐distance is available only for the first three, and hence only these should at present be termed contact inhibitions. Inhibition of neighbor exchanges is yet hypothetical; at its extreme, it would immobilize cells in a confluent monolayer, but such immobilization has been found not to occur.

Contact inhibition of overlapping, the most studied of the six, is not displayed by invasive cells with respect to normal cells; invasive tumor cells overlap freely upon normal cells, although not necessarily upon one another. Contact inhibition of overlapping, and its loss by invasive cells, can readily be interpreted, by means of the differential adhesion hypothesis, as consequences of cell‐type‐specific differences in cell‐cell and cell‐substratum “strengths of adhesion.” These strengths of adhesion are formulated as specific interfacial free energies, which are the only parameters of cellular adhesiveness that have been rigorously shown to determine equilibrium configurations of cell populations.
Loss of density‐dependent regulation of multiplication of BALB/3T3 cells chemically transformed in vitro
Authors: Oshiro Y. , DiPaolo J. A.
Published: February 2005

Balb/3T3 cells show density‐dependent regulation of multiplication with the final cell density depending on serum concentration in the media. Chemically transformed Balb/3T3 cells (Balb/3T3‐D) pile up on each other, multiply to a high cell density, but have decreased DNA synthesis at very high cell densities. Balb/3T3‐D cells require less serum for multiplication compared with original Balb/3T3 cells. A rat serum fraction and a bovine β‐globulin fraction stimulate the multiplication of Balb/3T3 cells but only slightly stimulate Balb/3T3‐D cells indicating different serum factors stimulate growth of these two cell types. The multiplication properties of Balb/3T3‐D cells are very similar to those of SV‐40 transformed 3T3 cells, however, these properties were brought about by a single treatment by a chemical carcinogen, without an exogenous virus. The transformation altered the contact of cells to one another, indicating a permanent chemical change in the membrane structure.
Clone size variation in the human diploid cell strain, wi‐38
Authors: Merz George S. , Ross John D.
Published: February 2005

By mapping the location of isolated single cells; and then counting the number of cells at each location as a function of time. it was possible to accumulate data on the growth history for each of a large group of clones. The clone size distribution, its mean and standard deviation were computed for each day in culture. Variations in schedule of medium change and time of exposure to trypsin, did not measurably affect variation in clone size. Neither could clone size variation be accounted for on the basis of (1) occurrence of nondividing cells nor (2) presence of heritable growth rate variants in the population. It is probable that clone size variation under our conditions is primarily a consequence of a highly variable interdivision time among the constituent cells.
Action spectrum for a low intensity, rapid photoinhibition of mechanically stimulable bioluminescence in the marine dinoflagellates Gonyaulax catenella, G. acatenella, and G. tamarensis
Authors: Esaias Wayne E. , Curl Herbert C. , Seliger Howard H.
Published: February 2005

The mechanically stimulable bioluminescence of members of the Gonyaulax catenella group can be maximally photoinhibited by exposure to as few as 1013 quanta/cm2, a factor 104 times smaller than that required for comparable photoinhibition in Gonyaulax polyedra and all other photosynthetic bioluminescent dinoflagellates investigated. Following an irradiation pulse there is an initial time lag of one minute, followed by a rapid decrease in mechanical stimulability to approximately 1% of the dark unirradiated control with a firstorder rate constant as high as 0.01 sec−1. Action spectra for all three species imply a pigment with a single absorption band having a maximum at 562 nm and a half band width of 105 nm within the spectral range 325 nm to 775 nm. Photoinhibition appears to decrease either the sensitivity of the shear receptor mechanism or the efficiency of signal transmission in the dinoflagellates, since chemically stimulable bioluminescence is unaffected by these exposures.
Calcium transport in isolated bone cells I. Bone cell isolation procedures
Authors: Dziak Rosemary , Brand John S.
Published: February 2005

Bone cells were isolated by collagenase‐hyaluronidase digestion of 19–20 day‐old fetal rat calvaria. It is shown that contamination from calcified matrix can give erroneously high values for total cell calcium and can mask intracellular calcium exchange.

Filtration of the cell suspension through 35 μ mesh nylon net and a five minute treatment with a cold pH 6.0 isotonic salt solution removed the contamination. Total calcium for cells prepared in this manner was 16.8 mmoles/kg wet weight. 45Ca uptake studies revealed an active component of calcium exchange.
The membrane potentials of fibroblasts in different environments
Authors: Bard J. , Wright M. O.
Published: February 2005

The membrane potentials of human embryonic lung fibroblasts have been measured in different cellular environments. Sparse cells on plastic have a mean membrane potential of −8.5 mV. As the cells progress to dense culture, the mean membrane potential rises to −14.7 mV. The mean membrane potential of fibroblasts in human embryonic lung fragments by comparison was found to be −16.5 mV. Sparse cells on collagen, at the same density as the sparse cells on plastic, have mean membrane potentials of −10.8 mV.

Sparse cells on plastic migrating from dense cellular areas, following a cut being made in a thick sheet of cells, have mean membrane potentials of −5.9 mV.

The significance of these results in relation to cellular environments has been discussed.
Electrical sizing of particles in suspensions IV. Lymphocytes
Authors: Ben‐Sasson S. , Patinkin D. , Grover N. B. , Doljanski F.
Published: February 2005

The factors involved during the pumping of a particle suspended in an electrolyte through a small cylindrical orifice across which exists an electric field are reviewed, and their practical application to cell volume measurement in terms of orifice geometry and particle properties is considered. Procedures are described to determine whether a particular cell type satisfies the operational criteria of a rigid, non‐conducting sphere, for which the theoretical expressions can be reduced to an especially simple form under appropriate conditions.

Experimental results are presented for the case of chick, mouse and human lymphocytes, all of which are shown to satisfy the above requirements. Volume distributions are provided for chick blood lymphocytes and compared with those from various lymphatic organs; representative data are also reported for different types of mouse lymphocytes. Human blood lymphocytes are found to have normally‐distributed diameters (p > 98%), a property not shared by their volumes or their surface areas, nor by blood lymphocytes from the chick or from patients with chronic lymphatic leukemia. A possible implication of this finding is mentioned briefly.
Change of chromatin morphology during the cell cycle detected by means of automated image analysis
Authors: Sawicki Wojciech , Rowinski Jan , Swenson Ronald
Published: February 2005

Mouse embryo fibroblasts growing asynchronously in vitro stained with Feulgen method and their nuclear chromatin was analysed by means of the image analysing computer Quantimet 720D. Cells with 2C, 3C and 4C content of DNA were considered as being in G1, middle S and G2 phase of cell cycle, respectively. It was found that the projected area of nuclei increases during the cell cycle and that the mean optical density of chromatin increases from G1 through S to G2 phase. The curves showing the areas of chromatin at different optical density thresholds are different for cells in G1, S and G2 phase. The results demonstrate cyclic changes in chromatin morphology in the interphase nuclei during the cell cycle.
Cell properties after repeated transplantation of spontaneously and of SV40 virus transformed mouse cell lines. I. Growth in culture
Authors: McFarland V. W. , Mora P. T. , Schultz A. , Pancake S.
Published: February 2005

“Spontaneously” or SV40 virus transformed AL/N mouse cell lines were passed repeatedly through syngeneic mice. Cell lines were re‐established in culture from minced pieces of tumors in the presence of concentrated fetal calf serum or from tumor cells dispersed by trypsin. The aim of this study was to compare the two cell lines in regard to the selection processes which operate during such procedures by characterization of the resulting cell lines. Measurements of growth in tissue culture on substratum showed no significant difference between any of the transformed cell lines. The SV40 transformed cells and its derivative cells had a low anchorage requirement for growth. The greatest anchorage requirement for growth was in the normal untransformed cells and in the derivative cells from the “spontaneously” transformed cells which were established from minced tumors. The spontaneously transformed cells and all derivative cells had high tumorigenicity in vivo (TD50 < 102). The SV40 transformed cells had no observable tumorigenicity (TD50 > 108), except when injected into irradiated mice (TD50 = 107). The derivative cell lines obtained from such a tumor had increased tumorigenicity (TD50 = 1–5 × 105 in the immunocompetent mice, 5 × 104 in the irradiated mice). The SV40 transformed derivative cells maintained their SV40 specific T antigen and their susceptibility to lysis by specific antiserum.