bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phosphorus incorporation in the ehrlich ascites tumor cell
Authors: Levinson Charles , Gordon Edward D. 
Published: February 2005

AbstractData from isotopic uptake experiments were used to measure the kinetics of labelling of cellular phosphate, ATP and ADP in the Ehrlich ascites tumor cell. The results show that steady state phosphate exchange flux was 0.333 ± 0.052 (S.E.) μmoles per 107 cells per hour at 37°, and that the specific activity of phosphate was the same as Pγ ATP. Metabolic inhibition reduced the phosphate flux by 30–50%. A model, based on oxidative phosphorylation and the adenylate kinase reaction is used to interpret the labelling sequence of Pβ ATP and Pβ ADP, and its dependence on Pγ ATP.
A two‐step growth curve from undisturbed cultures of Tetrahymena pyriformis
Authors: Winet Howard , Jahn Theodore L. 
Published: February 2005

AbstractCell counts from T. pyriformis cultures conform to a two‐step logistic growth curve if such populations are left undisturbed until sampling and, sampled only once. This curve, drawn according to the integral function

and confirmed by a reduced asymptote technique, displays an inflection acceleration near 5 × 103 cells/cm3 which can be explained as an effect of the onset of bioconvective fluid instability in the culture.
Electrical properties of chick skeletal muscle fibers developing in cell culture
Authors: Fischbach Gerald D. , Nameroff Mark , Nelson Phillip G. 
Published: February 2005

AbstractThe membrane properties of individual skeletal muscle cells were studied with intracellular microelectrodes as the fibers developed, in vitro, from mononucleated precursor cells. Passive membrane constants were determined from analysis of transmembrane potential responses to pulses of current assuming the myotubes could be represented as sealed, finite cylinders. Resting membrane potentials increased from 10–15 mV in the shortest, youngest myotubes to ca. 60 mV in the longest, most mature fibers. The increase in membrane potential was not associated with a change in membrane resistivity. Action potentials occurred spontaneously in the most mature cells and repetitive spikes could be evoked by depolarizing current pulses. Spikes and twitches could be evoked in young myotubes provided the membrane was first hyperpolarized to 60–70 mV. Apparently the membrane potential is the rate limiting factor in the maturation of excitation‐contraction mechanisms.
Density dependent stimulation of thymidine incorporation in BHK2l cells by active material released from the same cells
Authors: Stoker M. G. P. , Clarke G. D. , Thornton Maureen 
Published: February 2005

AbstractCultures of BHK2l cells continuously release into serum‐free medium, active materials which stimulate the incorporation of thymidine in non‐confluent, but not in confluent cultures of homotypic cells. The activity is not removed by centrifugation at 30,000 g for four hours, but is non‐dialysable and retained by membranes with a nominal limitation for MW 25,000. Activity is stable at 4° for several weeks, but destroyed in 30 minutes at 56°. BHK2l cells also release active material capable of enhancing the effect of added serum. This is also heat labile and its action is density‐dependent.
Evidence for cortical control of macronuclear behavior in Stentor
Authors: de Terra Noël 
Published: February 2005

AbstractIn Stentor, the changes in macronuclear morphology which occur during oral differentiation are known to be regulated by a corresponding series of cytoplasmic changes. The present experiments were designed to determine whether these changes are transmitted to the nucleus through the endoplasm or through the cortex. When two stentors in different stages of regeneration are grafted together, they normally become synchronized with respect to macronuclear behavior. The experimental results described in this paper show that the stimulus responsible for synchronizing the nuclei of such graft complexes is transmitted with greatly decreased efficiency when the two graft components are separated by a continuous barrier of reversed cortex but share a common endoplasm. When the cortical barrier is incomplete, nuclear synchronization almost always occurs. These findings indicate that the cytoplasmic signals regulating macronuclear morphology are transmitted to the nucleus from the cortex; they further suggest that the synchronizing stimulus travels through the cell membrane rather than the cortical fibrillar system and that it is not released into the endoplasm but acts on the subcortically located macronucleus at close range.
Effects of caffeine on the intracellular distribution of calcium in frog sartorius muscle
Authors: Borys H. K. , Karler Ralph 
Published: February 2005

AbstractThe influence of caffeine on the intracellular distribution of calcium in the frog sartorius muscle was studied by differential centrifugation in an attempt to identify the locus of action of this alkaloid. The problem was approached in two ways. In the first, the locus of action was sought by relating the kinetic functions of 45Ca washout curves of muscles to changes in the distribution of 45Ca in the isolated fractions from the same muscles. It was not possible to make any correlation of the 45Ca‐washout curves to the activity in the fractions; the relative distribution of this nuclide remained essentially unchanged at 1‐, 2‐, and 3‐hour intervals along the curve. The washout curves appear to be the net effect of a complex interaction of the calcium in pools containing both readily exchangeable calcium and calcium which has a slow exchange or turnover rate. The second approach centered upon the examination of the effect of caffeine on the intracellular distribution of 45Ca and of calcium among the cellular fractions. Caffeine treatment resulted in a distinct increase in the calcium content of the mitochondrial fraction and a decrease in the calcium of the microsomal fraction. Electron micrographic studies revealed significant morphological changes in the whole muscle and in the isolated mitochondrial fraction after the muscle had been exposed to caffeine in a concentration producing irreversible contracture or rigor (10 mM). The increase in calcium content of the mitochondrial fraction after caffeine treatment may be due to an actual accumulation of calcium by the mitochondria or may be the consequence of the appearance of granular vesicles in the fraction.
Adherence column and buoyant density separation of bone marrow stem cells and more differentiated cells
Authors: Metcalf D. , Moore M. A. S. , Shortman K. 
Published: February 2005

AbstractMouse bone marrow cells were separated by adherence column and albumin density gradient procedures, assaying for spleen colony forming units (in vivo CFU's), agar colony forming cells (in vitro CFC's) and cluster forming cells. Column filtrates were enriched for CFU's whereas in vitro CFC's and cluster‐forming cells were enriched in adherent fractions. Gradient separation of these column fractions gave density distribution profiles indicating the non‐identity and heterogeneity of CFU's and in vitro CFC's.
Tissue sources of bone marrow colony stimulating factor
Authors: Sheridan J. W. , Stanley E. R. 
Published: February 2005

AbstractPossible tissue sources in C57BL mice of the serum factor stimulating colony formation in vitro by mouse bone marrow cells have been investigated.A reproducible technique employing batch chromatography on calcium phosphate gel was developed for the extraction and assay of material with colony stimulating activity from mouse tissues. Sixteen hematopoietic and non‐hematopoietic tissues from C57BL mice were found to vary widely in their content of extractable activity. Characterisation of the colony stimulating factors (CSF's) from these tissues by assay of stepped concentrations of eluate showed that CSF's from most tissues were similar in chromatographic behavior, but all differed significantly from those of serum in being both more disperse and more firmly bound to calcium phosphate gel. Male submaxillary salivary gland gave the richest yield of CSF. CSF from this source displayed a greater dispersity on and affinity to calcium phosphate, a lower electrophoretic mobility and a smaller average sedimentation coefficient than that from any other source investigated. Colony morphology appeared to be identical for all tissue sources investigated.
In vitro proliferation and differentiation of hemic precursor cells from marrow and blood of naturally chimeric marmosets
Authors: Porter R. P. , Gengozian N. 
Published: February 2005

AbstractMarmosets are unique in that they are “always” blood cell chimeras. When the nucleated cells from the bone marrow and from the peripheral blood of marmosets were incubated in the appropriate culture fluid they were shown capable of extensive proliferation in vitro. Two patterns of cellular proliferation, adherent and nonadherent, occurred in the same culture vessel. Repeated passage of nonadherent cells in RPMI 1640 medium supplemented with calf serum resulted in relatively long‐term fluid bulk cultures showing myelocytic differentiation and megakaryocytic maturation. As myelocytic maturation became the predominant feature of cultures mitoses of the precursors diminished. About half of 41 marrow‐derived cultures underwent extensive proliferation lasting about two months, as evidenced by an increasing cellularity and the presence of dividing cells. Such active growth occurred in one culture for over 120 days. The natural blood‐cell chimerism of marmosets was demonstrated in vitro by cytogenetic analyses of metaphases from four relatively long term marrow cultures. The ratios of male and female cells remained either relatively stable or changed slowly with time in culture. Cells having both diploid and polyploid number of chromosomes were identified male or female, suggesting chimerism in myelocytic and megakaryocytic series. Marmoset lymph node and spleen cells proliferated as lymphoid cultures for various lengths of time up to five weeks but these cells did not differentiate into hemic cell lines. Attempts to culture human and rodent hemic tissue by the procedure used on marmoset tissue were unsuccessful.
Studies on the surface of chick blastoderm cells. I. Electrophoretic mobility and pH‐mobility relationships
Authors: Zalik Sara E. , Sanders Esmond J. , Tilley Carol 
Published: February 2005

AbstractThe electrophoretic mobilities (E.P.M.) and pH‐mobility relationships of chick blastoderm cells at successive developmental stages were determined. Mobilities in 0.145 M NaCl, pH 7.2, showed a wide spread and decreased from a mean value of 1.63 μ/sec/V/cm in the prestreak blastoderm, to 1.49 in the intermediate streak and 1.34 in the head process stages. Cell surface charge density changes as detected by E.P.M. were observed in all regions of the embryo.pH‐mobility relationship studies showed that two cell populations differing in their approximate isoelectric point appeared at the intermediate streak and head process stages. Neuraminidase treatment indicated that the contribution of sialic acid residues to the negatively charged groups at the cell surfaces is very small at the stages studied.
Purification and characterisation of the in vitro colony forming cell in monkey hemopoietic tissue
Authors: Moore M. A. S. , Williams N. , Metcalf D. 
Published: February 2005

AbstractBuoyant density gradient separation of Rhesus monkey bone marrow, spleen and blood leukocytes has demonstrated a reproducible and homogeneous light density distribution profile of cells capable of forming hemopoietic colonies in agar culture (in vitro colony forming cells — CFC). High resolution density gradient separation performed on a light density fraction of bone marrow produced on average a 100‐fold enrichment of in vitro CFC with the most enriched fractions containing the majority of the in vitro CFC population present in the original marrow. Fractions were routinely obtained in which up to 23% of cells formed colonies and 33% were capable of proliferating to some degree upon stimulation. Tritiated thymidine suiciding showed the active proliferative status of the in vitro CFC and application of autoradiography and morphological characterisation to highly enriched density fractions has shown that the in vitro CFC in normal marrow is a transitional lymphocyte. Single cell transfer experiments have shown that in vitro CFC's formed colonies containing both granulocytes and macrophages, formally demonstrating the clonal origin of in vitro colonies and the common origin of granulocytes and macrophages.
The partial purification from calf serum of a fraction with multiplication‐stimulating activity for chicken fibroblasts in cell culture and with non‐suppressible insulin‐like activity
Authors: Pierson Robert W. , Temin Howard M. 
Published: February 2005

AbstractA multiplication‐stimulating activity for chicken embryo fibroblasts has been purified approximately 6000‐fold from calf serum by a three step procedure. The partially purified multiplication‐stimulating activity stimulated DNA synthesis, mitosis, and growth of cultured chicken embryo fibroblasts. In addition, the active step 3 material was shown to have non‐suppressible insulin‐like activity and to be an inhibitor of trypsin activity.The activity appeared to be associated with a small protein and was heat stable, but sensitive to dithiothreitol and to periodate.
Sodium and potassium content and membrane transport properties in red blood cells from newborn puppies
Authors: Miles P. R. , Lee Ping 
Published: February 2005

AbstractThe intracellular sodium and potassium concentrations and membrane transport properties for these ions were investigated in red blood cells from newborn puppies and adult dogs. At birth the intracellular concentrations of sodium and potassium are much higher than those found in adult dog red cells. During the first few weeks of life the intracellular concentrations of these ions gradually decrease until the adult level is reached. Changes in the membrane transport properties develop concurrently. The rate of active potassium influx, as measured by ouabain‐sensitivity, and the pump to leak ratio are greater in red cells from newborn puppies than in those from adult animals. No ouabain‐sensitive sodium efflux could be demonstrated in red cells from older puppies or adult dogs. When either puppy or adult dog red cells are depleted of ATP (by incubation at 37°C with no substrate), potassium permeability increases, and the permeability of the membrane to sodium decreases. The addition of adenosine reverses the effect of depletion.
Ion transport by ouabain resistant and sensitive ehrlich ascites carcinoma cells
Authors: Mayhew E. 
Published: February 2005

AbstractCell division, net Na+‐K+ and amino‐acid transport of cultured Ehrlich ascites is reversibly inhibited by Ouabain at a final concentration of 1 × 10–3M. A line of Ehrlich ascites cells resistant to the growth inhibiting effects of Ouabain has been developed. These cells behave similarly to Ouabain‐sensitive cells in the following respects doubling time, S phase time, chromosome number, cell surface charge density, rate of incorporation of C14 Uridine and 3H‐Thymidine, sensitivity to Digoxin and Digitoxin, steady state Na+, K+ levels and rate of loss of K+ and gain of Na+ in cold.Ouabain resistant cells differ from sensitive cells only with respect to the effect of ouabain on active Na+, K+ transport. Although Ouabain inhibits active Na+, K+ transport in sensitive cells it has no significant effect in resistant cells.
The pH dependence of exchange transport of glucose in human erythrocytes
Authors: Lacko L. , Wittke B. , Geck P. 
Published: February 2005

AbstractIn glucose exchange transport into red blood cells the rate of glucose uptake showed two pH dependent maxima, with the larger at approximately pH 7.5 and the smaller one at pH 3.In the studied pH range the relation between the rate of glucose uptake and the substrate concentration followed Michaelis‐Menten kinetics. While the maximal velocity (V) reflected the pH changes of the media, the Michaelis constant (Km) remained constant.The dissociation constants of the groups of the free carrier and the carrier‐glucose complex were the same. The pK of the acidic group was 5.2 and of the basic group 9.5.Glucose was not bound to groups of the carrier which dissociated protons in the pH range of three to nine.By rearranging the equation for the pH dependence of the relative influx a more definitive graphic determination of the pK values was produced.
Effects of cold treatment on synchronous Chinese hamster cells treated in mitosis
Authors: Nagasawa H. , Dewey W. C. 
Published: February 2005

AbstractChinese hamster mitotic cells (95% in mitosis with 85% in metaphase and 10% in anaphase) were shaken loose from monolayer asynchronous cultures and stored at 1°C for up to 28 hours. During this period, the mitotic index did not decrease and the cells remained cytologically normal. However, over a four‐hour period, metaphase cells located within 1.8 minutes of anaphase, 10% of the metaphase population, were able to move into anaphase; this point of 1.8 minutes corresponds in time to that reported for the spindle activation marker. When the cells were warmed to 37°C, they were delayed in entering G1 and S (35 and 70 minutes, respectively, after a 4‐hour treatment). This delay of 70 minutes was maintained for three cell cycles, during which a high degree of synchrony was maintained. Cold treatment for 12 hours produced delays into G1 and S of 50 and 110 minutes, respectively. A fraction of the metaphase cells (12 or 50% after treatments of 4 or 12 hours, respectively) evidenced chromosomal aggregation, were unable to complete cytokinesis, and appeared in the next division as tetraploid cells. These tetraploid cells were unable to survive and produce macroscopic colonies. It is concluded that this decrease in viability is caused by irreversible effects on the spindle and/or centriolar components in metaphase cells located prior to the spindle activation marker.
Induction of cell division: Role of cell membrane sites
Authors: Sivak Andrew 
Published: February 2005

AbstractDensity dependent inhibition of cell replication is released in stationary cultures of BALB/c‐3T3 fibroblasts by the potent tumor promoter for mouse skin, phorbol myristate acetate (PMA). The saturation density of these cultures, which is dependent on the serum concentration of the medium, is increased by PMA. Cell division, which can be induced by PMA or serum in stationary monolayers of BALB/c‐3T3 cells, is not blocked by several inhibitors of proteolytic enzymes or the plant lectins, concanavalin A or wheat germ agglutinin. Induction of cell replication by PMA or serum does not appear to be dependent on proteolytic activity, and the membrane sites associated with this induction appear to be distinct from the agglutinin‐binding sites.
Studies of calcium influx into squid giant axons with aequorin
Authors: Hallett Mark , Carbone Emilio 
Published: February 2005

AbstractCalcium‐influx associated with the action potential was studied in squid giant axons using an EDTA‐free preparation of aequorin as a probe. Associated with an individual action potential there was a transient increase in aequorin luminescence and the time course of this increase was examined on a kinetic basis. The luminescent response associated with a train of action potentials was compared with that expected on the basis of superposition of individual responses. The analyses of luminescence curves produced by long trains of action potentials were complicated by failure of superposition. A long pulse of inward current was found to produce a very large enhancement of luminescence.
Genetics of somatic mammalian cells. XV. Evidence for linkage between human genes for lactic dehydrogenase B and serine hydroxymethylase
Authors: Jones Carol , Wuthier Paul , Kao Fa‐Ten , Puck Theodore T. 
Published: February 2005

AbstractChinese hamster ovary cells with a deficiency in Serine Hydroxymethylase which produces a specific glycine auxotrophy (gly− A) were fused with human cells from a variety of sources and the resulting hybrids analyzed for human gene linkage. Of 102 hybrid clones examined 65 possessed both glyA and lactic dehydrogenase B markers, 35 possessed neither marker. Two clones were found with altered glycine responses which were not linked to LDH‐B. The data indicate linkage between genes responsible for serine hydroxymethylase activity and lactic dehydrogenase B. Evidence for absence of linkage between these and a variety of other genes is also presented.
Sulfhydryl groups during the s phase: Comparison of cells from G1, plateau‐phase G1, and G0
Authors: Harris J. W. , Teng S. S. 
Published: February 2005

AbstractThe non‐protein sulfhydryl (NPSH) content of cells moving into S from G1, plateau phase G1, and G0 was measured. Chinese hamster ovary (CHO) cells accumulated in G1 by growth into plateau phase contain only one‐fourth the NPSH concentration of cycling C1 cells or G1 cells accumulated by brief growth in isoleucine‐deficient medium. Upon dilution of plateau cultures with fresh medium, cellular NPSH content increases rapidly, reaching the same level as that in cycling cells within four hours. This increase is prevented by cycloheximide but not by actinomycin D or hydroxyurea. Neither CHO cells cycling in vitro nor salivary gland G0 cells stimulated with isoproterenol in vivo show significant changes in intracellular NPSH concentrations during S phase. This suggests that the concentration of intracellular NPSH (glutathione) remains constant during the cell cycle except when cells are grown to plateau phase in exhausted or deficient medium, in which case normal degradation exceeds synthesis and the gross level falls until fresh medium is provided and synthesis, apparently on preexisting RNA templates, accelerates.
Azaguanine resistant hamster cell lines not deficient in hypoxanthine‐guanine phosphoribosyl transferase
Authors: Morrow John , Colofiore Joseph , Rintoul David 
Published: February 2005

AbstractUsing a serial selection technique in which Chinese hamster cells were treated first with 8‐azaguanine and then subsequently with HAT medium it was found that approximately 15% of azaguanine resistant clones were also resistant to HAT. Several such clones were subcultured and found to be stably resistant to azaguanine, in some cases at a higher level than the usual azaguanine resistant mutants which are HAT sensitive. Measurements of hypoxanthine‐guanine phosphoribosyl transferase levels were in some cases lower than the parental line but in three of the clonal lines were higher than the parental strain. The fact that azaguanine resistant lines constitute a biochemically heterogeneous population underscores the importance of careful characterization of mammalian cell culture variants.
The effect of temperature on nucleotide pool formation in Tetrahymena pyriformis
Authors: de Barros Ademar V. , de Castro Jacy F. , de Castro F. T. 
Published: February 2005

AbstractWarming of exponentially growing T. pyriformis to 34°C results in severe inhibition of nucleotide pool formation. The utilization of the pool for stable RNA synthesis is poorly affected at the high temperature. It thus appears that the synthesis and processing of ribosomal RNA precursors are not primarily impaired at 34°C.