bluuebunny/crossref_metadata_2025 huggingface dataset:
Calcium transport and distribution in ehrlich mouse ascites tumor cells
Authors: Levinson Charles , Blumenson Leslie E.
Published: February 2005

Data from isotopic uptake experiments were used to measure calcium fluxes and compartment sizes in ascites tumor cells. The data were analyzed with two kinetic models, A and B. In 80% of the experiments model A, which is based on one exchangeable calcium compartment, was rejected in favor of Model B, which predicts two exchangeable compartments. A statistical evaluation of the model's performance, when fit to the experimental data was used to select between the two models.

The results show that calcium was distributed between three cellular compartments in the ratio, non‐exchangeable (88%): rapidly exchanging (7%): slowly exchanging (5%). The undirectional fluxes suggested that calcium transport could be described as a series system with the temporal sequence: environment ⇄ rapidly exchanging ⇄ slowly exchanging.
The interaction of mengo virus ribonucleic acid with L, HeLa and human diploid cells: A comparative study
Authors: Tovell Dorothy R. , Garbutt Elizabeth W. , Yaremko Louise , Colter John S.
Published: February 2005

A study, designed to define the optimal conditions for infecting L, HeLa and human diploid cells with Mengo RNA, showed that the three cell types differ with respect to (a) the concentration of sucrose (in PBS) that produces maximum stimulation of infectious center (I.C.) formation (0.6 M, 1.2 M and 1.0 M for L, HeLa and human diploid cells respectively) and (b) the optimal combination of sucrose and dimethyl‐sulfoxide (DMSO). With all three cell types, diethylaminoethyldextran (DEAE‐D) was found to produce maximum stimulation of I.C. formation when present, in PBS, at a concentration of 100 μg/ml. Direct comparisons of I.C. formation in the three cell types using the sucrose, sucrose‐DMSO and PBS‐DEAE‐D media optimal for each revealed that (a) the best medium for titration in L and HeLa cells is PBS containing 100 μg DEAE‐D/ml, (b) DMSO produces a 4–8 fold increase in I. C. formation in L cells, but is only marginally effective in HeLa cells, and (c) the optimal medium for titration in human diploid cells is sucrose‐DMSO. The results of studies of the “uptake” of 3H‐Mengo RNA showed that there is no correlation between the amount of RNA that becomes cell associated and the number of I.C.'s that are produced in the cell population.
A kinetic study of the genetic control of hemopoietic progenitor cells assayed in culture and In vivo
Authors: Sutherland D. J. A. , Till J. E. , McCulloch E. A.
Published: February 2005

The kinetics of growth of bone marrow cells from normal or genetically anemic mice (Sl/Sld and W/Wv) were studied in irradiated normal and genetically anemic hosts. The parameters followed included total cellularity, the number of peroxidase positive cells, and the number of cells capable of forming colonies in vivo (CFU‐S) or in culture (CFU‐C). The results of these experiments demonstrate that W and Sl defects alter the growth of CFU‐C and peroxidase‐positive cells to a modest degree; that the defects are more obvious when studied in spleen rather than in bone marrow; and that there is no additivity of W and Sl defects.

Nineteen irradiated recipients of marrow from W/Wv mice were studied after three to six months. Of these, 18 showed host‐type erythrocytes, while in one mouse the erythrocytes had the size distribution of W/Wv cells. This finding indicated that occasionally genetically defective stem cells may repopulate irradiated hosts.
Beneficial effects of embryo extract on cultured rabbit cartilage cells
Authors: Ham Richard G. , Murray Louann W. , Sattler Gerald L.
Published: February 2005

Growth and the expression of cartilage‐like differentiation by adult rabbit chondrocytes is stimulated greatly by the Sephadex G‐25 macromolecular fraction of chicken embryo extract (CEEM). A small amount of fetal bovine serum or the macromolecular fraction of fetal bovine serum (FBSM) is also needed for growth. Medium F12 supplemented with CEEM plus FBSM supports moderate clonal growth of the rabbit chondrocytes with excellent expression of differentiated properties. The effects of CEEM on growth and the expression of differentiation have been quantitated by measurement of radioactive sulfate incorporation and total protein synthesis.
pH dependence of the effect of adenosine triphosphate and ethylenediaminetetraacetate on sodium and magnesium binding by cellular membrane fragments
Authors: Sanui Hisashi
Published: February 2005

The pH dependence of previously reported effects of adenosine triphosphate (ATP) and ethylenediaminetetraacetate (EDTA) on cation binding by rat liver microsomes was studied by an equilibration and washing procedure. Equilibration of microsomes in media containing 95 mM NaCl and 4 mM MgCl2 with pH varied from 4 to 8 resulted in an increase in bound cations from zero below pH 4 to 0.90 mmoles Mg and 0.34 mmoles Na/g N at pH 8; the ratio of bound Na/bound Mg increased from 0.15 at pH 5 to 0.38 at pH 8. Addition of 5 mM EDTA to the equilibration media produced striking changes in cation binding such that bound Na/bound Mg increased from 0.30 at pH 5 to 3.90 at pH 7 and decreased to 3.55 at pH 8. In the presence of added 10 mM ATP, bound Na/bound Mg increased from 0.10 at pH 5 to a maximum of 0.80 at pH 7. The observed changes could generally be correlated with known mass law relationships, although the system containing added ATP was complicated considerably by the hydrolysis of ATP. Results demonstrate that environmental pH is an important factor in determining the effect of ATP and EDTA on the cation binding pattern of cellular membranes. Because hydrogen ion is a product of ATP hydrolysis as well as of other metabolic reactions, the described interactions may be of particular significance in the molecular mechanisms of ATP effects on cation binding and transport in living cells.
Studies on colony formation in vitro by mouse bone marrow cells. II. Action of colony stimulating factor
Authors: Metcalf Donald
Published: February 2005

An analysis was made of some of the processes involved in the stimulation by colony stimulating factor (CSF) of cluster and colony formation by mouse bone marrow cells in agar cultures in vitro. Colony formation was shown to be related to the concentration and not the total amount of CSF. The concentration of CSF determined the rate of new cluster initiation in cultures and the rate of growth of individual clusters. Colony growth depleted the medium of CSF suggesting that colony cells may utilise CSF during proliferation. Bone marrow cells incubated in agar in the absence of CSF rapidly died or lost their capacity to proliferate and form clusters or colonies. CSF appears (a) to be necessary for survival of cluster‐and colony‐forming cells or for survival of their proliferative potential, (b) to shorten the lag period before individual cells commence proliferation and (c) to increase the growth rate of individual clusters and colonies.
Parathyroidectomy and the induction of thymic atrophy in normal, adrenalectomized and orchidectomized rats
Authors: Perris A. D. , Weiss L. A. , Whitfield J. F.
Published: February 2005

Parathyroidectomy or thyroparathyroidectomy in the male rat results in the severe atrophy of the thymus gland. This effect is not mediated by a secondary release of the cytolytic adrenal or gonadal steroids since it also occurs in adrenalectomized and orchidectomized animals. The loss of the parathyroid gland decreases the flow of thymic lymphocytes into mitosis; this inhibition of cell production leads to the marked decline in thymic weight. The effect can be partially prevented by administration of parathyroid hormone or calcium gluconate.
Further studies on the differentiation of a cell line of myeloid leukemia
Authors: Ichikawa Yasuo
Published: February 2005

A limited time of contact with a conditioned medium from embryo cells induced phagocytotic activity in a cell line of myeloid leukemia followed by the loss of colony forming and leukemogenic capacity. After two days in a high concentration of the conditioned medium, the colonies showed morphological changes which indicated the differentiation of this line of cells. The differentiation‐stimulating factor present in the conditioned medium was relatively thermolabile, while the growth‐stimulating factor was highly thermostable. Both factors could pass through a dialysis membrane.
SDS‐acrylamide gel electrophoresis and its application to the proteins of poliovirus‐and adenovirus‐infected human cells
Authors: Maizel Jacob V. , Summers Donald F. , Scharff Matthew D.
Published: February 2005

Sensitive techniques for acrylamide gel electrophoretic analysis have been applied to animal virus systems and have proven generally useful. Estimates of the number of kinds, molecular weights and number of molecules of proteins in almost any biological sample have been made with ease. As applied to the poliovirus‐HeLa cell system they reveal four major proteins in the virion and at least ten additional proteins in the infected cell. Some of the intracellular and particulate proteins undergo cleavage reactions following a unique translation in which the genome is apparently translated in toto as one large polypeptide of molecular weight greater than 200,000 daltons. The splits occur at three levels: (a) during synthesis; (b) at intermediate stages; and (c) co‐incident with maturation. In vitro studies on protein synthesis, RNA synthesis and virus assembly have substantiated and extended the in vivo observations. The structure of the adenovirion has been established in detail. Hexon, penton base, fiber and core polypeptides and certain relevant subviral structures have been identified. Nearly all of the proteins synthesized in the infected cells after 20 hours are viral. The major structural antigens (hexon and penton) predominate and are made in 10 to 50 fold excess but the internal core polypeptides are not produced in great excess. Studies on the synthesis of polypeptides and their assembly into morphological subunits and virions show that hexon and penton polypeptides are made in about four and two minutes respectively on cytoplasmic polyribosomes, that morphological subunits are formed within five minutes of synthesis of protein, and that there is a delay of greater than one half hour for entry of hexons into virions.
The distribution of rapidly hybridizing RNA sequences in heterogeneous nuclear RNA and mRNA from hela cells
Authors: Darnell James E. , Balint Robert
Published: February 2005

Both HnRNA and mRNA contain sequences derived from DNA which is reiterated many times in the cell genome. The degree of reiteration for sites binding HnRNA appears to be greater than for those DNA sites which bind mRNA.
Responsiveness of normal and transformed rat embryo cell cultures to poly I · poly C and interferon
Authors: Freeman Aaron E. , Uhlendorf Carol P. , Younkers Penny E. , Baron Samuel
Published: February 2005

A number of normal rat cell cultures as well as cultures transformed spontaneously, by chemicals, and/or by oncogenic viruses were tested for responsiveness to the interferon inducer polyinosinic·polycytidylic acid, or to exogenous interferon. Responsiveness, or lack thereof, had no correlation with subculture passage number, infection with RNA leukemia virus, morphological transformation by oncogenic RNA or DNA viruses, chemical treatment, or the ability of these cells to produce tumors in isologous host animals. The data indicate that lack of response to interferon or to the inducer is neither a necessary prerequisite nor an absolute result of cellular transformation of rat cells.
Cholinergic‐stimulated alkaline phosphatase secretion and phospholipid synthesis in guinea pig seminal vesicles
Authors: Lockwood D. H. , Williams‐Ashman H. G.
Published: February 2005

Incubation of slices of seminal vesicles of the guinea pig with cholinergic drugs led to an enhanced secretion of alkaline phosphatase. Incubation with carbamylcholine also stimulated the incorporation of P32 into the phospholipid fraction. Both cholinergic effects required a supply of energy since dinitrophenol was inhibitory. The stimulation of enzyme secretion and phospholipid synthesis by carbamylcholine was completely abolished by atropine. Omission of calcium ions from the incubation medium and pre‐treatment of the slices with ethylenediaminetetraacetic acid (EDTA) caused a marked reduction in alkaline phosphatase secretion induced by carbamylcholine but had no effect on incorporation of P32 into phospholipids. Adenergic agents such as epinephrine, norepinephrine and isoproterenol did not influence these two processes. Addition of cyclic AMP, dibutyryl cyclic AMP and a phosphodiesterase inhibitor was also ineffective. The incorporation of P32 into the various phospholipids of the seminal vesicle was examined. In the presence of carbamylcholine, there was a marked increase in the P32‐specific activities of phosphatidylinositol (nearly 6‐fold) and of phosphatidylserine (about 1.5‐fold). These observations indicate that the guinea pig seminal vesicle, a large hollow organ composed of a single layer of epithelium, is ideally suited for studies concerning the biochemistry of macromolecular secretion.
Shifts in nuclear and cytoplasmic nucleic acid content in temperature‐synchronized Tetrahymena pyriformis (HSM)
Authors: Lane Nancy M. , Padilla George M.
Published: February 2005

Nuclei were isolated by exposing temperature synchronized Tetrahymena pyriformis (HSM) to Triton‐X‐100. Cell division synchrony was induced with a repetitive 12‐hour temperature cycle (9.5 hours at 13°, 2.5 hours at 29°). Increase in nucleic acid content was biphasic: primarily during the last two hours of the cold period well in advance of the synchronous burst of division and secondarily in the last hour of the warm period. Nuclear RNA content rises almost two hours ahead of cytoplasmic RNA which shows a maximum 0.5 hour before the onset of the warm period. The DNA content reaches a peak 30 minutes later. On the basis of these shifts there appears to be not net synthesis of nucleic acids during cell division. The changes in RNA/DNA of the isolated macronuclei and micronuclei suggest enhanced RNA turnover, loss to the cytoplasm and enhanced ribonuclease activity prior to cell division. Cytoplasmic RNA also appears to be subject to enzymic degradation.
Uridine transport and RNA synthesis in growing and in density‐inhibited animal cells
Authors: Weber Michael J. , Rubin Harry
Published: February 2005

Both chick embryo fibroblasts and mouse 3T3 cells reduce the rate at which they incorporate H3 uridine into RNA as their growth becomes inhibited at high cell density. This reduction occurs as a function of the cell population density, and with chick embryo cells (in contrast to 3T3 cells) it is not accompanied by significant medium alterations. This indicates the importance of the cell population density in the control of cellular metabolism.

The decline in H3 uridine incorporation is paralleled by a decline in the rate of uptake of the isotope into the acid‐soluble pool, suggesting that decreased entry of H3 uridine into the cell, rather than a decreased rate of RNA synthesis, is responsible for the reduced rate of incorporation into RNA of density‐inhibited cells. This suggestion was confirmed by finding that when the restriction on uridine uptake was overcome by increasing the concentration of uridine in the medium, the density‐dependent inhibition of uridine incorporation was largely reversed. We conclude that, even though the rate of H3 uridine incorporation into RNA is reduced three‐ to five‐fold in density‐inhibited cells, the rate of synthesis of pulse‐labeled RNA continues at 70 to 85% of the rapidly‐growing rate.
Stabilizing effects of D2O on the microtubular components and needle‐like form of heliozoan axopods: A pressure‐temperature analysis
Authors: Marsland Douglas , Tilney Lewis G. , Hirshfield Michael
Published: February 2005

A systematic study of the resistance of heliozoan axopodia to pressure‐induced disintegrational changes has shown that progressively higher concentrations of D2O in the environing medium produce a progressively greater stability, not only as to the needle‐like form of the whole axopodia, but also as to their microtubular components. Also it was found that a higher temperature (25°C) yielded significantly higher stability values with identical degrees of deuteration, as compared with experiments performed at a lower temperature (20°C).
An improved heat‐stable glutamine‐free chemically defined medium for growth of mammalian cells
Authors: Nagle Stanley C. , Brown Bruce L.
Published: February 2005

A heat‐stable chemically defined medium, free of glutamine, is described for the growth of mammalian cells in suspension culture. The presence of L‐alanine in the defined medium permitted the omission of glutamine. A 22‐fold increase in the population of a substrain of mouse L cells was obtained (3.4 × 106 cells/ml) in six days with no medium replenishment during incubation. Maximum yields (27 × 106 cells/ml) were obtained by daily medium replacement and venting of cultures. Growth was also improved in a line of cat kidney cells and HeLa cells, and in another substrain of L cells.
Electrophoretic studies of muscle proteins. II. Complex formation between delta protein, myogen and myosin
Authors: Amberson William R. , Bauer Adelia C.
Published: February 2005

In actin‐free extracts of rabbit white muscles complexes form between delta protein, myogen (mainly glycolytic enzymes) and myosin, detectable in electrophoretic patterns of both limbs. The complexes are concentration sensitive, nearly absent when total protein is below 5 mgm/ml, but increasing at higher concentrations. At 65 mgm/ml about 60% is bound at 1°C.

Complex concentrations can be calculated by making Rayleigh fringe counts on two portions of the same solution, one more concentrated, the other diluted with buffer. A “fringe balance” can then be constructed which measures the forward movement, in the concentrated descending pattern, of those portions of myogen and myosin which have united with delta and moved with it in a fast position. Similar calculations are possible for the ascending limb.

When commercial aldolase or lactic dehydrogenase solutions are mixed with concentrated extracts from which most free myogen has been removed the patterns show that portions of the added enzymes have complexed with myosin and delta and move with them in fast positions.

Mixtures of pure aldolase and nearly pure myosin solutions also show com‐plexing, less well developed than when other enzymes are present. The glycolytic enzymes may have to unite with each other before they can readily complex with myosin and delta. There may be a lineal order of the glycolytic enzymes laid out along the fibrous proteins, permitting a rapid handling of their substrates.
Electrogenesis in mouse neuroblastoma cells In vitro
Authors: Nelson P. G. , Peacock J. H. , Amano T. , Minna J.
Published: February 2005

Intracellular microelectrode studies of passive membrane properties and action potential generation were carried out on cloned and uncloned mouse neuroblastoma cells in tissue culture. The cloned cells were studied between the eighth and tenth months and the uncloned cells between the third and fifth weeks after primary dissociation. Electrophysiologic measurements of cell membrane properties were made by passing stimulating current pulses across the cell membrane from an intracellular microelectrode and recording simultaneously from the same electrode, by means of a bridge circuit, the changes in membrane potential. The range of responses to electrical stimulation varied from passive increases in membrane potential to repetitive firing of action potentials. A 20 fold range in spike generating capability was found. Passive membrane properties (membrane potential, specific membrane resistivity, and specific membrane capacitance) were similar to those of sympathetic neurons in intact preparations. Seventy‐nine percent of the cloned cell line compared to 94% of the uncloned line were capable of generating action potentials. Less than 2% of the cloned cells showed repetitive firing whereas 23% of the uncloned cells had this property. As in several types of normal neurons, the action potential mechanism was largely, although not completely, blocked by iontophoretic and bath applied tetrodotoxin.
Oxygen toxicity in a fission yeast
Authors: Vaughan Gerald L.
Published: February 2005

Continuous exposure of synchronous cultures of Schizosaccharomyces pombe to 2.0 atmospheres oxygen beginning at any point in the first two‐thirds of the cell cycle prevented subsequent cell division. Similar exposure during the last one‐third of the cell cycle did not prevent cell division. The inhibition of division was totally reversible. Exposure to 2.0 atmospheres oxygen for 2.5 hours did not affect oxygen consumption. Oxygen at 1.0 atmospheres reduced growth rate and protein synthesis by 44%. Similar exposure to 1.0 atmospheres reduced transport of glycine‐14C, L‐leucine‐14C, and uracil‐14C by 95%, 73%, and 89% respectively. Analysis of the kinetics of uptake of these materials showed noncompetitive inhibition of transport by oxygen. The primary effect in rapidly appearing oxygen toxicity apparently involved interference with the transport capabilities of the cell membrane.
Mutation rate from asparagine requirement to asparagine non‐requirement
Authors: Morrow John
Published: February 2005

The mutation rate from asparagine requirement to asparagine non‐requirement has been measured using the Luria‐Delbrück Fluctuation test in the Walker 256 rat carcinosarcoma line grown in vitro. Non‐requiring variants are pre‐existing in the population, and are not induced by the selecting agent. The mutation rate was of the order of 1.4 × 10−6 per cell per generation to 3.5 × 10−6 per cell per generation. The relationship between the malignancy of the cell line and its unusual requirement for asparagine is discussed.
The biosynthesis of protamine during spermatogenesis of the mouse: Extraction, partial characterization, and site of synthesis
Authors: Lam D. M. K. , Bruce W. R.
Published: February 2005

A highly basic, testis‐specific, chromosomal protein (MP) can be extracted with acid from testis cells of the mouse, but not from mature spermatozoa. A similar protein (MP') can be isolated from spermatozoa if they are first disrupted with β‐mercaptoethanol and urea. The two proteins (MP and MP') are identical as characterized by polyacrylamide gel electrophoresis, Bio‐Gel P‐10 chromatography, amino‐acid analysis and equilibrium ultracentrifugation. They are presumably mouse protamine. Both measurements of the sedimentation velocities of testis cells which synthesize mouse protamine and of the activity of spermatozoa after a pulse label with radioactive arginine show that protamine is synthesized 19 days after the last meiotic S‐phase, that is, at an advanced stage of spermiogenesis.
Photo‐reversal of the circadian rhythm in the proliferative activity of the mouse small intestine
Authors: Sigdestad Curtis P. , Lesher S.
Published: February 2005

Mice (C57Bl) were placed for 35 days in a room with reversed light cycle; lights came on at 1800 hours and off at 0600 hours. At six hour intervals throughout the day three mice were injected with tritiated thymidine and sacrificed 30 minutes later. Crypts were dissected for radioautography and determination of disintegrations per minute per crypt, the number of cells in mitosis and the number of cells synthesizing DNA was determined. The results reported clearly demonstrate reversal of the circadian rhythm in the parameters tested.
Mutation rates in cells at different ploidy levels
Authors: Harris Morgan
Published: February 2005

Fluctuation tests of the Luria‐Delbrück type have been used to examine the frequency of spontaneous variations in cultures of diploid, tetraploid, and octaploid Chinese hamster cells. Resistance to 8‐azaguanine and altered response to thermal shock were chosen as marker systems. Mutation frequencies of approximately 10−6 and 10−5 have been estimated for heat resistance and azaguanine resistance respectively. Rates of mutation for these markers remain constant or decline slightly in cells with increasing numbers of chromosome sets. This trend is not in accordance with expectations based on the assumption of dominant, co‐dominant, or recessive changes at gene or chromosome levels. It is suggested that at least some variations may arise in somatic cells by stable shifts in phenotypic expression rather than by changes in genetic information.
Age‐related changes in hematopoietic stem cell populations of a long‐lived hybrid mouse
Authors: Chen Michael G.
Published: February 2005

Age‐related changes in the number and concentration of pluripotential and unipotential hematopoietic stem cells in the femoral bone marrow and spleen of BC3F1 mice were investigated. Pluripotential stem cells were assayed by the spleen colony technique, and unipotential stem cells were determined by an agar cloning method and by erythropoietin responsiveness in polycythemic mice. Changes with senescence were observed in the concentration of both uni‐ and pluripotential stem cells in the bone marrow; the size of the stem cell compartment in the marrow did not change significantly with age. Also, a reduction in the seeding of transplanted spleen colony‐forming units into the spleens of aged recipients was demonstrated. The implications of these findings for the kinetics of hematopoietic stem cell proliferation in aged animals are discussed.
Effect of 5‐bromodeoxyuridine on hyaluronic acid synthesis of a clonal hybrid line of mouse and Chinese hamster in culture
Authors: Koyama Hideki , Ono Tetsuo
Published: February 2005

A clonal hybrid line, B‐6, derived from the fusion of mouse and Chinese hamster cell lines, has an inheritable ability to synthesize and secrete hyaluronic acid (HA). In order to elucidate the control mechanism of expression of this differentiated function, we studied the effect of 5‐bromodeoxyuridine (BUDR), a thymidine (TDR) analog on the growth and HA synthesis of this hybrid line. The presence of BUDR at 0.5–1 μg/ml of medium had no effect on cell multiplication, but reduced HA production by approximately 25 to 40%. Treatment with 5 to 25 μg/ml of the analog resulted in about 15% decrease of the total cell growth, or 30% decrease of the viable cell growth, while mucopoly‐saccharide production was reduced by more than 70%. These results indicate that BUDR affects HA synthesis more strongly than it does cell growth.

Inhibition was found to be detectable after two days of culture with BUDR. This effect was prevented by the simultaneous addition of TDR in a concentration more than twice that of the analog. Furthermore the inhibitory effect was reversible, since a gradual but complete recovery of HA synthesis occurred after removal of BUDR from the medium. In contrast, the growth rate of B‐6 cells was discovered to be more sensitive than HA synthesis to the inhibitory action of either excess TDR or another analog, 5‐fluorodeoxyuridine (FUDR).
Cultures from adult rat liver cells I. Establishment of monolayer cell‐cultures from normal liver
Authors: Iype P. T.
Published: February 2005

Establishment of monolayer cell‐cultures from adult normal rat liver is described using cells isolated by a collagenase‐hyaluronidase perfusion technique. The cells plated originally were polygonal in shape and contained a large number of mitochondria. However, cells with less granules were also observed in the primary culture, after a few days of plating. In subsequent subcultures, the latter type of cells could be grown continuously. After an initial lag, the cells attained a doubling time of 55 hours and a plating efficiency of 20%. The cells are “normal” with respect to their karyology, morphology and growth pattern. Difficulties encountered during the culture and the possible uses of these cultured cells in studies on carcinogenesis in vitro are discussed.
Cation exchange binding of rubidium and cesium by rat liver cell microsomes
Authors: Sanui Hisashi
Published: February 2005

The rubidium and cesium binding characteristics of rat liver cell microsomes were studied by an equilibration, centrifugation and washing procedure. Concentration dependence experiments, in which microsomes were equilibrated in media containing 0 to 400 mM rubidium or cesium chloride at pH 6.9, yielded saturation type adsorption isotherms similar to those previously reported for sodium and potassium. Mass law analysis of the data yielded apparent dissociation constants of 21 × 10−3 eq/liter and 19 × 10−3 eq/liter for rubidium and cesium binding, respectively. The results indicate that cesium is bound slightly more strongly than rubidium, and that both these cations may be bound more strongly than sodium or potassium. The maximum binding capacity at pH 6.9 was approximately 1.3 meq rubidium or cesium/g nitrogen. Sodium, potassium, magnesium and calcium generally associated with the isolated microsomes decreased concomitantly with increasing bound rubidium or cesium, demonstrating the ion exchange nature of the binding. Results of pH‐dependence experiments showed that following equilibration of the microsomes in media containing approximately 96 mM rubidium or cesium at various pH values, bound rubidium or cesium was essentially zero at pH less than five, increased sharply between pH 5 and 7, and tended to level off at higher pH. The present results further characterize the cation binding properties of the microsomal material.
Selective and nonselective isolation of temperature‐sensitive mutants of mouse L‐cells and their characterization
Authors: Thompson L. H. , Mankovitz R. , Baker R. M. , Wright J. A. , Till J. E. , Siminovitch L. , Whitmore G. F.
Published: February 2005

Mutants of mouse L‐cells which are temperature‐sensitive for growth have been obtained by using both selective and nonselective isolation procedures on populations treated with the mutagen nitrosoguanidine. Selective isolation was carried out by utilizing a five‐day treatment with 3H‐TdR and ara‐C as selective agents at the nonpermissive temperature. Nonselective isolation was performed by isolating 1400 clones in the absence of selective agents and then testing them for temperature‐sensitivity. From this experiment we obtained a minimum estimate of 6 × 10−3 for the frequency of mutants in the mutagentreated population. The mutants were characterized by their plating efficiencies, growth in suspension culture, and uptake of isotopic precursors of DNA, RNA, and protein. A range in phenotypes was observed, and there appeared to be some differences between the mutants obtained by the two types of isolation procedures. In uptake experiments the most marked reductions in the rates of precursor incorporation were seen with 3H‐TdR, rather than 3H‐UR or 3H‐Leu. Different mutant lines showed considerable variation in the rate of cessation of DNA synthesis as well as the time required for termination of cell division. These experiments suggest that both types of isolation procedures are feasible for obtaining temperature‐sensitive mutants having a range of phenotypes.
Proliferation of hemopoietic stem cells in culture of embryonal liver of mice
Authors: Luria Elena A. , Samoylina Nina L. , Gerasimov Y. V. , Chertkov J. L.
Published: February 2005

The vinblastine technique was used to demonstrate that the proliferative capacity of colony‐forming cells in organ culture of embryonal liver of mice between the first and seventeenth day of cultivation is adequately high. The relative content of CFU increases in culture with a maximum between one and two weeks.
Effect of suppression of erythropoiesis on hematopoietic stem cells in the mouse
Authors: Preisler Harvey D. , Henderson Edward S.
Published: February 2005

Erythropoiesis was suppressed in CDF1 female mice using one of three different techniques: hypertransfusion, daily injections of low doses of actinomycin D, or post‐hypobaric polycythemia. Spleens and bone marrows of these mice contained increased numbers of stem cells as determined by transplantation into lethally irradiated syngeneic mice. These stem cells were capable of producing both erythrocytic and granulocytic progeny. An increase in the number of multipotential stem cells or increases in the numbers of both unipotential granulocytic and erythrocytic stem cells is compatible with these observations and implies that hematopoietic stem cells may have a basic rate of division that is in part independent of stimuli to differentiate. The implications of these findings for the possible modification of antineoplastic drug‐induced bone marrow toxicity are discussed.
Alterations in the rate of hemoglobin synthesis during chick embryogenesis
Authors: Grinnell Frederick , Lee John C.
Published: February 2005

The rate of synthesis of different hemoglobin (Hb) species — embryonic, primitive, definitive, and adult — in the circulating red cells of the chick embryo have been measured. On the fifth day of chick embryogenesis, there is a marked decrease in the capability of these red cells to synthesize Hb. The rates of synthesis of embryonic and primitive Hb decrease markedly compared to that of definitive and adult Hb. On the fourth day of embryogenesis nucleic acid synthesis drops sharply in these cells. These decreases in metabolic activity preceed the disappearance of the primitive erythrocyte from the chick embryo circulation. It appears that the primitive cell line is specifically shut off with respect to its metabolic activities and possibly destroyed at this time.
The effect of multivalent cations on the membrane potential of the ehrlich ascites tumor cell
Authors: Smith Thomas C. , Mikiten Terry M. , Levinson Charles
Published: February 2005

The effect of di‐ and trivalent cations on the membrane potential of the Ehrlich ascites tumor cell has been investigated using micro‐electrode techniques. In solutions free of multivalent cations the average membrane potential for 46 cells was 8.3 ± 0.5 mv (SE). However, the potentials were not stable and decayed with a half‐time of about six seconds. Addition of Ca++ decreased the rate of decay and concomitantly increased the membrane potential. The magnitude of these effects was a function of the Ca++ concentration. At the optimum concentration (2 mM), the half‐time of decay was increased to 12 seconds and the membrane potential was raised to 17.8 ± 1.7 mv (SE). The related alkaline‐earth cations, Sr++, Ba++ and Mg++ had similar effects on both the stability and magnitude of the membrane potential. The effect of La+++, which was qualitatively similar to that of the divalent cations, was also concentration dependent. However, 100‐fold lower concentrations were adequate to achieve comparable effects. Moreover, membrane potentials were stable for up to ten minutes in La+++‐containing solutions. Variations in intracellular Cl− content induced by temperature changes were paralleled by changes in membrane potentials. However, the potentials were not those expected for a simple Cl− electrode.
Response of multipotent (CFU) and granulocyte (diffusion chamber assay) progenitor cells and differentiating cells of murine haematopoietic tissues to a perturbation of the steady state
Authors: Breivik Harald
Published: February 2005

Regulation of haematopoiesis was investigated by studying the response of haematopoietic tissues of mice to a perturbation of the steady state by vinblastine (VLB). Progenitor cells were quantified ly limiting dilution analysis of diffusion chamber cultures of haematopoietic cells and by the spleen colony technique. The diffusion chamber technique appears to assay granulocyte progenitor cells and those multipotent progenitor cells that become committed to granulopoiesis during chamber culture. The spleen colony technique probably assays multipotent progenitor cells.

Decaying oscillatory responses to VLB were observed for progenitor cells as well as for differentiating cells in bone marrow. The period lengths of the diffusion chamber progenitor cell oscillations might indicate that these were induced by humoral feedback signal(s) from nonproliferative granulocytes. The oscillations of the multipotent progenitor cells of bone marrow were less pronounced and were earlier damped than those of the granulocyte progenitor cells. This may support the hypotesis that multipotent progenitor cells are regulated by more efficient mechanisms, which may depend on short range cell‐cell interactions rather than long range humoral regulators.
Sialic acid masked membrane antigens of clonal functional glial cells
Authors: Herschman H. R. , Breeding J. , Nedrud J.
Published: February 2005

Antisera have been prepared to clonal cultured rat astrocytic cells (C6 cells) and clonal human astrocytic cells (CHB4 cells). When cultured glial cells are grown in the presence of neuraminidase the serological activity of the cell membrane with homologous antiserum is increased extensively. A similar activation of serological activity can be effected by incubating washed harvested cells with this enzyme. Membrane bound N‐acetyl‐neuraminic acid is extensively reduced by either incubation. The activity responsible for promoting the enhanced serological activity co‐chromatographs and co‐electrophoreses with neuraminidase. Proteolytic digestion, unlike neuraminidase treatment, was unable to enhance the serological activity of cultured glial cells.
Stimulation of rabbit erythroblast multiplication and maturation in vitro by blood leukocytes: Cytological observations. III. Studies on erythropoiesis
Authors: Borsook Henry , Jiggins Susan , Wilson Rosina T.
Published: February 2005

Blood leukocytes incubated in vitro with rabbit‐marrow cells induced a several‐fold increase in basophilic erythroblasts and smaller increases in acidophils and reticulocytes. The main effect was nearly complete in one hour at 37°. Erythropoietin augmented the leukocyte effect; anti‐erythropoietin inhibited it with or without erythropoietin. The erythroblast increase came entirely from the marrow cells; the precursor cell class has not been identified, except that division of pre‐existing basophils appears to be excluded. Autologous and homologous leukocytes were about equally effective.

A method is described of measuring on stained smears changes in relative concentrations of different classes of cells induced experimentally. A method of preparing highly concentrated peripheral blood leukocytes is described.
Competitive in vivo proliferation of foetal and adult haematopoietic cells in lethally irradiated mice
Authors: Micklem H. S. , Ford C. E. , Evans E. P. , Ogden D. A. , Papworth D. S.
Published: February 2005

The relative proliferative capacity of haematopoietic cell populations derived from 22‐week‐old adult bone marrow and 14–18 day foetal liver has been studied in lethally irradiated syngeneic recipients by means of chromosome markers. Although starting at a disadvantage in terms of the number of colony‐forming units (stem cells) injected, the foetal liver‐derived populations steadily increased their relative numbers in the myeloid and lymphoid tissues over a period of several weeks until a plateau was reached. It is suggested that stem cells in foetal liver have, on average, a higher intrinsic capacity for self‐renewal than do those in bone marrow, and that this capacity falls to the adult level within about ten weeks of transfer.
Hypoplasia of the bone marrow in rats following removal of the parathyroid glands
Authors: Rixon R. H. , Whitfield J. F.
Published: February 2005

Removal of the parathyroid glands caused a marked and permanent lowering of the mitotic activity in rat bone marrow, which was followed by a pronounced decline (ca. 40%) in the size of the marrow's nucleated cell population. These changes occurred only when the hypocalcemia induced by the lack of parathyroid hormone (PTH) was maintained by feeding the animals a calcium deficient diet. Since the overall marrow hypoplasia was almost entirely due to strikingly large reductions (ca. 70%) in the size of the erythroid and lymphoid subpopulations, it is concluded that PTH and calcium are major physiological regulators of the proliferation of erythroid and lymphoid cells.
Electrogenesis of embryonic chick skeletal muscle cells differentiated in vitro
Authors: Kano Masaakira , Shimada Yutaka , Ishikawa Koichi
Published: February 2005

Electrogenesis of embryonic chick skeletal muscle cells differentiated in monolayer cultures was investigated. Muscle fibers in vitro generate spike potentials similar to those of fibers in vivo. However, other responses, plateaux resembling those in heart muscle, are also elicited. These results suggest that a functional differentiation exists in cultured muscle fibers.
Independent regulation of cytochromes and glycolytic enzymes in human fibroblasts
Authors: Pious Donald A. , Susor Walter A. , Benson Robert W. , Rutter William J.
Published: February 2005

Growth of cultured human fibroblasts in low oxygen resulted in reciprocal changes in the levels of cytochrome oxidase and several glycolytic enzymes. After five days' growth in low oxygen, cytochrome oxidase specific activity fell to 40% of the level of control cultures, while lactic dehydrogenase (LDH), aldolase, and triose phosphate dehydrogenase (TDH) levels were increased by 2‐ to 3‐fold. These changes were accompanied by a change in the LDH isoenzyme pattern resulting from an increase in the proportion of LDH A subunits; the aldolase electropherogram was unchanged. When fibroblasts were grown for five days in medium containing chloramphenicol, cytochrome oxidase specific activity fell to 10% of control values, but LDH, aldolase and TDH specific activities and LDH and aldolase electropherograms did not differ significantly from controls. These findings are interpreted to indicate that the increased accumulation of LDH, aldolase and TDH induced by low oxygen is not mediated by the rate of accumulation of cytochrome oxidase.
Synthesis of the small molecular weight monodisperse nuclear RNA's in contact‐inhibited cell cultures
Authors: Rein Alan , Penman Sheldon
Published: February 2005

The small molecular weight monodisperse nuclear RNA's are synthesized in contact‐inhibited cultures of 3T3 cells. The level of synthesis of these RNA's, and of ribosomal and transfer RNA's, appears to be only 8–20% of that observed in growing cultures. The synthesis of all of these relatively stable RNA species may thus be coordinately controlled.
Lymphopoiesis in the rat. I. The effect of pool size on lymphocyte production
Authors: Vaughan W. P. , McGregor D. D.
Published: February 2005

A method is described for measuring lymphopoiesis that enables the production of recirculating and non‐recirculating small lymphocytes to be estimated simultaneously. Using this technique, experiments were undertaken to determine whether the production of recirculating cells is influenced by the number present in the recirculating lymphocyte pool. The results suggest that neither a massive lymphocyte transfusion nor depletion of the pool by whole body irradiation or chronic lymph drainage affect the rate at which recirculating small lymphocytes are generated.
Lymphopoiesis in the rat. II. The effect of thymectomy
Authors: Vaughan W. P. , McGregor D. D.
Published: February 2005

Lymphopoiesis with respect to recirculating and non‐recirculating small lymphocytes was measured simultaneously in rats thymectomized as adults. Removal of the thymus at four to five weeks of age had a profound inhibitory effect upon the production of recirculating cells, whereas the formation of non‐recirculating lymphocytes was only slightly depressed. Thymectomy had approximately the same impact of lymphopoiesis as thymectomy and exposure of the animal to a large dose of whole body X‐ and γ‐irradiation. The latter finding, and the failure of a thoracic duct cell transfusion to augment lymphocyte production, accord with the view that the thymus is the principle intermediate source of recirculating small lymphocytes in the normal, unstimulated animal.
Volume changes of mammalian cells subjected to hypotonic solutions in vitro: Evidence for the requirement of a sodium pump for the shrinking phase
Authors: Rosenberg Howard M. , Shank Brenda Buckhold , Gregg Earle C.
Published: February 2005

A Coulter‐orifice pulse‐height analyzer system was used to measure volume spectra of mammalian cells in suspension at different times after the addition of an equal volume of water. In appropriate hypotonic medium, cultured mammalian cells rapidly increase in volume and then shrink, more slowly, approaching their initial volumes within 20 to 30 minutes at 37.5°C. The shrinking phase was found to be reversibly inhibited by ouabain and inhibited in both K+‐free and Na+‐free solutions; neither choline+ nor Li+ could substitute for extracellular Na+ in supporting the shrinking phenomenon but Rb+ and Cs+ were fairly good substitutes for K+.

Under conditions similar to those with which the shrinking phenomenon was observed with cultured cells, it was not found with either human or mouse red blood cells.

Two methods were used to determine intracellular Na+ and K+ content in osmotically shocked cells and in unshocked controls. An isotope equilibration method was employed with L5178‐Y mouse lymphoblasts and a chemical determination by flame photometry was used with Ehrlich ascites tumor cells. The K+ content was significantly reduced and the Na+ content was unchanged or somewhat increased in cells which had returned to their original volumes in hypotonic medium. The K+ content was even more reduced but the Na+ content was greatly increased in cells which were osmotically shocked in the presence of ouabain.
Studies on the bone marrow colony stimulating factor (CSF): Relation of tissue CSF to serum CSF
Authors: Sheridan J. W. , Metcalf D.
Published: February 2005

Fluctuations in the colony stimulating factor (CSF) content of submaxillary salivary gland, lung, kidney and spleen were studied in male C57BL mice which had been subjected to a variety of stimuli (endotoxin, x‐irradiation or polyadenylic‐polyuridylic acid complex) that caused elevations of the serum CSF. The temporal relationships and magnitudes of the rises in CSF were complex and differed from tissue to tissue according to the stimulus used. In the tissues examined not only was the measurable CSF content in each case found to equal or exceed the prestimulatory levels, but in some cases distinctly different forms of CSF were observed as shown by differences in the zone sedimentation, electrophoretic, and calcium phosphate binding characteristics of the material. The patterns of response to the stimuli investigated suggested that tissue injury either directly, or indirectly via the release of various cellular constituents, might mediate the release of CSF by various widely disseminated and/or differing cell types.
Nucleoside deaminase activity during the recovery of X‐irradiated, bone marrow‐protected mice
Authors: Basch Ross S. , Malathi V. G. , Silber Robert
Published: February 2005

Increased activity of the enzyme nucleoside deaminase is found in the spleens of mice protected from lethal whole‐body irradiation by transfusion of isogenic bone marrow cells. As few as 10,000 nucleated bone marrow cells produce a significant elevation in enzyme level. This increase precedes any detectable increase in hemoglobin synthesis and is temporarily associated with an increase in protein synthesis during the early stages of recovery. Hypertransfusion of the irradiated, protected mice eliminates most of the stimulus to erythroid differentiation and prevents the increase in nucleoside deaminase. The present studies indicate that this enzyme is present in a differentiated red cell precursor not found in the normal stem cell population.