bluuebunny/crossref_metadata_2025 huggingface dataset:
The possible mediation by cyclic AMP of the stimulation of thymocyte proliferation by vasopressin and the inhibition of this mitogenic action by thyrocalcitonin
Authors: Whitfield J. F. , MacManus J. P. , Gillan D. J.
Published: February 2005

Lysine vasopressin (antidiuretic hormone), like cyclic adenosine 3',5'‐monophosphate (cyclic AMP), rapidly (in less than 1 hour) stimulates the initiation of deoxyribonucleic acid synthesis and thereby increases the flow of cells into mitosis in rat thymic lymphocyte populations in vitro. This mitogenic action of vasopressin, again like that of cyclic AMP, is potentiated by caffeine, an inhibitor of the intracellular phosphodiesterase which catalyzes the degradation of cyclic AMP. On the other hand, vasopressin's mitogenic action (also like that of cyclic AMP) is blocked by imidazole, an activator of cyclic nucleotide phosphodiesterase activity. The hormone, thyrocalcitonin (calcitonin) which is known to block the cyclic AMP‐mediated mitogenic effect of parathyroid hormone by interfering with cyclic AMP action, also blocks the mitogenic action of vasopressin. The inhibitory effects of imidazole and thyrocalcitonin on vasopressin's mitogenic action are both overcome by the phosphodiesterase inhibitor, caffeine. It is concluded from these observations that the mitogenic action of vasopressin is mediated by cyclic AMP.
Variations in the synthesis and assembly of immunoglobulins by mouse myeloma cells: A genetic and biochemical analysis
Authors: Scharff M. D. , Bargellesi A. , Baumal R. , Buxbaum J. , Coffino P. , Laskov R.
Published: February 2005

The synthesis, assembly, and secretion of gamma globulin has been examined using cells from a mouse plasma cell tumor. The cells were then adapted to continuous culture and individual clones were obtained which differed from each other in the relative amounts of heavy and light chains synthesized, in the absolute amounts of gamma globulin being produced, and in the details of the assembly process. Finally, the kinetics, pathway, and completeness of assembly were examined in a variety of tumors and variants of these tumors.
Changes in ribosome‐polyribosome balances in chick muscle cells during tissue dissociation, development in culture, and exposure to simplified culture‐medium
Authors: Hosick Howard L. , Strohman Richard C.
Published: February 2005

The populations of polyribosomes, monomeric ribosomes, and ribosomal subunits are described from the time of tissue explantation to the time of complete muscle differentiation in primary cultures of chick muscle cells. There is extensive degradation of polyribosomes, and a net loss of ribosomes recovered, as cells of embryonic muscle are dissociated with proteolytic enzymes. The cells rapidly restore a high polysome: monomeric ribosome ratio. This recovery of the polyribosome population occurs before there is any detectable net increase in ribosome number. Ribosome production begins after a lag of approximately 15 hours in culture. Number of ribosomes/cell triples by 60 hours, at which time cell fusion (myotube formation) is complete. Unlike developing muscle in vivo, cultured cells have a very reduced pool of monomeric ribosomes. Medium simplification experiments done with fully differentiated cultures show, however, that monomers accumulate during starvation. These monomers reassociate to form polyribosomes during medium replenishment. Subunit complements are maintained at a constant level regardless of nutritional conditions. These features of cultured muscle are discussed as possible tools for further study of muscle development.
Nucleotide pools of Novikoff rat hepatoma cells growing in suspension culture. I. Kinetics of incorporation of nucleosides into nucleotide pools and pool sizes during growth cycle
Authors: Plagemann Peter G. W. , Erbe John
Published: February 2005

Results from kinetic studies on the incorporation of 3H‐5‐uridine and 3H‐8‐adenosine into the acid‐soluble nucleotide poor and nucleic acids by Novikoff hepatoma cells (subline N1S1‐67) in suspension culture indicate that the uridine transport reaction is saturated at about 100 μM and that for adenosine at about 10 μM nucleoside in the medium, and that above 100 μM simple diffusion becomes the predominant mode of entry of both nucleosides into the cell. The Km of the transport reactions is approximately 1.3 × 10−5 M for uridine and 6 × 10−6 M for adenosine. The incorporation of these nucleosides into both the nucleotide pool and into nucleic acids seems to be limited by the rate of entry of the nucleic acid synthesis from the rate of incorporation of nucleosides. Other complicating factors are a change with time of labeling in the relative proporation of nucleoside incorporated into DNA and into the individual nucleotides of RNA, the splitting of uridine to uracil by th ecells, the deamination of adenosine kto inosine and the subsequent cleavage of inosine to hypoxanthine.

Various lines of evidence are presented which indicate that the overall nucleotide pools of the cells are very small under normal growth conditions. During growth in the presence of 200 μM uridine or adenosine, however, the cells continue to convert the nucleosides into intracellular nucleotides much more rapidly than required for nucleic acid synthesis. This results in an accumulation of free uridine and adenosine nucleotides in the cells, the maximum amounts of which are at least equivalent to the amount of these nucleotides in total cellular RNA.
Nucleotide pools of Novikoff rat hepatoma cells growing in suspension culture. II. Independent snucleotide pools for nucleic acid synthesis
Authors: Plagemann Peter G. W. , Erbe John
Published: February 2005

Novikoff rat hepatoma cells (subline NlSl‐67) in suspension culture incorporate 3H‐5‐uridine into the acid‐soluble nucleotide pool more rapidly than into RNA, resulting in the accumulation of labeled UTP in the cells. When labeled uridine is removed from the medium after 20 minutes or 4.75 hours of labeling, the rate of incorporation of label from the nucleotide pool into RNA decreases to less than 10% of the original rate within five to ten minutes, in spite of the presence of a large pool of labeled UTP in the cells, and incorporation ceases completely if an excess of unlabeled uridine is present during the chase. Upon addition of 14C‐uridine to 3H‐uridine pulse‐labeled, chased cells, the 14C begins to be incorporated into RNA without delay and at a rate predetermined by the concentration of 14C‐uridine in the medium and without affecting the fate of the free 3H‐nucleotides labeled during the pulse‐period. The results are interpreted to indicate that uridine is incorporated into at least two different pools, only one of which serves as primary source of nucleotides for RNA synthesis. During active synthesis of RNA, the latter pool of free nucleotides is very small and rapidly exhausted when uridine is removed from the medium. However, UTP accumulates in this pool when cells are labeled at 4–6°, since at this temperature RNA synthesis is blocked while uridine is still phosphorylated by the cells, and the UTP is rapidly incorporated into RNA during a subsequent ten‐minute chase at 37°. From these types of experiments it is estimated that only 20–25% of the total uridine nucleotides formed in the cells from uridine in the medium is directly available for RNA synthesis and that the remainder becomes available only at a slow rate. Evidence is presented which suggests that one uridine nucleotide pool is located in the cytoplasm and another in the nucleus and that mainly the nuclear pool supplies nucleotides for RNA synthesis. The size of the latter pool is under strict regulatory control, since preincubation of the cells with 0.5 mM unlabeled uridine has little or no effect on the subsequent incorporation of 3H‐uridine, although it results in an increase of the overall cellular uridine nucleotide content to at least 5 mM. Other results indicate that adenosine is also incorporated into two independent nucleotide pools, whereas the cells normally appear to possess a single thymidine nucleotide pool.
Hemolysis in several animal species after rapid freezing of blood
Authors: Rapatz G. , Luyet B.
Published: February 2005

The effect of various freezing rates on the extent of hemolysis in human, bovine and ovine erythrocytes, which are known to have different cell volumes, water contents and permeabilities, was investigated. Blood in stainless steel capillary tubes was frozen at various rates by abrupt immersion of the capillaries into cooling baths at temperatures ranging from −20° to −130°C. Minimum lysis values were obtained at freezing temperatures of −40°, −50° and −70°C with, respectively, human, bovine and ovine blood. The smallest, highly permeable sheep erythrocytes were the least damaged at the highest freezing rates; the largest human cells with the highest water content, suffered the greatest damage; intermediate values were obtained with ox blood. At the lower freezing rates, the largest, human cells were the least damaged; the highest hemolysis values were obtained with the smallest, highly permeable sheep erythrocytes; ox blood again gave intermediate values. These results are in agreement with current views that, (1) very rapid freezing results in the formation of damaging intracellular ice; (2) injury associated with slow freezing is related to the extent of dehydration or to the increase in electrolyte concentration which accompanies ice formation; (3) minimum hemolysis is obtained under those freezing conditions in which osmotic dehydration has been sufficient to prevent the formation of intracellular ice, but has left enough water in the cells to prevent the damaging effects of dehydration and high electrolyte concentrations.
Distribution of UDP‐glucuronyl transferase among cell fractions of rat liver
Authors: Nyquist S. E. , Morre D. James
Published: February 2005

Microsomal UDP‐glucuronyl transferases (uridine‐5′‐diphosphate‐glucuronate glucuronyl transferase, acceptor unspecific, EC 2.4.1.17) function in detoxification of a wide range of aglycons containing phenolic, alcoholic, carboxylic or amino acceptor groups through formation of water‐soluble glucuronic acid derivatives. To localize this activity within a specific cell component, purified rough‐surfaced endoplasmic reticulum and Golgi apparatus fractions from rat liver were compared with total homogenates. The UDP‐glucuronyl transferase specific activity of the Golgi apparatus fractions was less than or approximately equal to that of the total homogenate whereas this activity was concentrated 3–8 fold in the rough‐surfaced endoplasmic reticulum fraction depending upon substrate. We conclude that the rough‐surfaced endoplasmic reticulum is the major site of glucuronide formation within the microsome fraction of normal rat livers.
The 5‐methylcytosine content of DNA: Tissue specificity
Authors: Kappler John W.
Published: February 2005

Using a new technique for the determination of the extent of DNA methylation by comparing the incorporation of radioactivity from deoxycytidine‐2‐C14 into DNA cytosine and 5‐methylcytosine (5MC), the 5MC content of DNA was found to be a tissue specific property in two systems: (1) mouse tissue culture cell lines, in which the level of 5MC varied from 2.97 ± 0.03% conversion of cytosine to 5MC in the DNA of a mouse melanoma line to 4.58 ± 0.18% in a primary teratoma line, and (2) the organs of the developing chick embryo, in which the level of 5MC varied from 3.60 ± 0.04% conversion of cytosine to 5MC in the DNA of the chorioallantoic membrane to 4.19 ± 0.02% in the brain.
Ultrastructural changes in sarcosomes after exposure of adult Calliphora erythrocephala to lethal and sub‐lethal high temperatures
Authors: Davison T. F.
Published: February 2005

The effects of lethal and sub‐lethal high temperatures on the morphology of intact flight muscle sarcosomes of adult Calliphora erythrocephala are described. Treatment of adult flies to lethal temperatures results in ultrastructural changes in the organisation of the cristae and the appearance of electron opaque inclusions. These changes have not been observed after sub‐lethal heat treatment, when 50% of the animals recover. It is suggested that changes in the ultrastructure of the intact sarcosomes may be correlated with changes in their ability to couple oxidative phosphorylation with α‐glycerophosphate. Age‐dependent changes in the sensitivity of sarcosomes are related to changes in the heat death point of the animal and suggest that the impairment of sarcosomal function may be one of the primary lesions in heat death of adult C. erythrocephala.
The effect of environment on lactate dehydrogenase isozymes of cultured somatic cells
Authors: Cribbs Richard M. , Kline Edward S.
Published: February 2005

The lactate dehydrogenases of HeLa cells grown in an anaerobic environment with either glucose or L‐lactate have a higher ratio of A to B sub‐units than do the same cells grown in an aerobic environment. This ratio is decreased when the anaerobic environment is made aerobic during cell growth, or when the cells are cultured for the entire growth period in aerobic conditions.
Effects of acronycine on nucleic acid synthesis and population growth in mammalian tumor cell cultures
Authors: Gout P. W. , Dunn B. P. , Beer C. T.
Published: February 2005

Acronycine — an alkaloid with antineoplastic activity against a wide range of experimental tumors — at concentrations of 0.5‐12 μg/ml rapidly inhibits RNA synthesis in L5178Y mouse lymphoma and IRC rat monocytic leukemia cultures. Culture growth is arrested only at acronycine concentrations which markedly inhibit RNA synthesis. DNA synthesis is inhibited at rather higher concentrations but this is not a prerequisite of the arrest of growth. It is suggested that the arrest of growth may be a consequence of the inhibition of RNA synthesis.

In both cultures arrest of growth coincides with the appearance of many cells with two apparently normal nuclei. Cells are not arrested in mitosis. It is shown these binucleated cells very probably arise from an inhibition of cell cleavage. Studies with synchronized cultures show that at low drug concentrations, more than one cell cycle may elapse before growth is arrested and binucleated cells appear, indicating the effect on cytokinesis is not immediate. The results suggest that the arrest of growth may be a result of a slow depletion of a component essential for cell cleavage. The disturbance at division is a major factor in arresting growth at low drug concentrations. At higher acronycine concentrations, when RNA synthesis may be inhibited by 80–90%, the cytotoxic effects appear earlier and are less specifically directed at cytokinesis; DNA synthesis is then also rapidly and markedly inhibited.
Demonstration of an ATPase at the cell surface of intact normal and neoplastic human cells in culture
Authors: Ågren G. , Pontén J. , Ronquist G. , Westermark B.
Published: February 2005

An ATPase reaction has been studied at the surface of intact normal and neoplastic human cells in culture. For this purpose a sensitive method has been developed which permits repeated monitoring of enzyme activity without interference with cellular viability.

Experiments could be performed with the cells cultured in a single dish. The cells were firmly attached to the supporting medium throughout the experiment. The incubation medium could easily be separated from the cells at the end of the reaction. There was no diffusion of the surface‐located ATPase into the incubation medium. Another advantage was the possibility of microscopic control of the appearance of the cells during the reaction.

High ATPase activity was found in glia‐like cells derived from normal adult brain cells while lines from gliomas had very low activity. One SV40 transformed glia line had an extremely low ATPase activity in contrast to the uninfected cells. Normal fibroblasts and sarcoma cells had about the same low activity as the glioma cells.
Regulation of specific functions of glial cells in somatic hybrids. I. Control of S100 protein
Authors: Benda Philippe , Davidson Richard L.
Published: February 2005

Hybrids were isolated between rat glial cells and mouse fibroblasts. Micro complement (C′) fixation was used to assay S100, a highly acidic protein specific for nervous tissues. The glial cells contain large amounts of S100. Extracts of the fibroblasts contain some C′ fixing material which is detected only at very high protein concentrations and which fixes C′ only weakly. The identity of this material is not known. The hybrids contain some C′ fixing material, but the concentrations of protein necessary to reach the point of antigen‐antibody equivalence is ten times greater with an extract of hybrids than with an extract of glial cells. This increase in the concentration of protein is associated with a decrease in the amount of C′ fixed. The possible significance of the C′ fixing material in the hybrids is discussed.
Phosphorus incorporation in the ehrlich ascites tumor cell
Authors: Levinson Charles , Gordon Edward D.
Published: February 2005

Data 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

Cell 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

The 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

Cultures 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

In 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

The 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

Mouse 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

Possible 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

Marmosets 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

The 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

Buoyant 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

A 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

The 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

Cell 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

In 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

Chinese 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

Density 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

Calcium‐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

Chinese 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

The 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

Using 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

Warming 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.
The relation between cell division rate and 3HTdR incorporation in organ culture
Authors: Simnett John D. , Fisher Jean M.
Published: February 2005

Rates of incorporation of labelled thymidine (RIT), radioautographic labelling index for DNA synthesis (LI) and mitotic incidence following colcemid metaphase arrest (MI) were measured in organ cultures of newborn and adult rat lung. In adult cultures these three parameters correlated well, being low after explantation and reaching a maximum after two to three days. In newborn cultures RIT fell several fold over the first 24 hours after explantation and, in this respect, did not correlate with LI and MI. The changes in RIT over the first 24 hours appear to be due to changes in the degree of competition between endogenous TdR and exogenous labelled TdR, probably caused by leakage of the intracellular thymidine pool following explantation. The report emphasizes the need to check RIT data against radioautographic evidence before accepting it as an index of DNA synthesis.
Relationship between the ratio of parental chromosomes and parental doubling times in chinese hamster‐mouse somatic cell hybrids
Authors: Labella T. , Amati P. , Marin G.
Published: February 2005

Somatic hybrids obtained by the selective method of Littlefield between a permanent line of Chinese hamster cells (Wg3) and one of mouse cells (3TP) showed a preponderance of biarmed (hamster) chromosomes. Under normal culture conditions (37°) the doubling time of the parental mouse cells was twice as long as that of the parental hamster cells. If the temperature of incubation was lowered (31°), the relative difference in doubling times was reduced; in hybrid lines obtained under these conditions, the proportion of biarmed chromosomes was also reduced.

Upon extended cultivation the average number of telocentric chromosomes progressively decreased in all hybrid lines tested, regardless whether these were started and maintained at 37° or at 31°. An inverse correlation was observed in hybrid cells between doubling time and relative proportion of biarmed chromosomes, suggesting that the karyotypic changes observed after extended culture were due to the selective overgrowth of cells with a high biarmed to telocentric ratio.
The temperature dependence of the exchange transport of glucose in human erythrocytes
Authors: Lacko L. , Wittke B. , Geck P.
Published: February 2005

The temperature dependence of the uptake of glucose by exchange transport is investigated at two pH values (7.5 and 5). The Arrhenius's energy of activation, the heat of activation, the free energy of activation and the entropy of activation are calculated. The parameters are different at pH 7.5 and 5. For both pH levels the heat of activation and the entropy of activation change abruptly at 20°C. This finding leads us to assume that at this temperature a change in the structure of the membrane takes place.
The effects of zinc and lanthanum on calcium uptake by mitochondria and fragmented sarcoplasmic reticulum of frog skeletal muscle
Authors: Batra S.
Published: February 2005

Calcium uptake by mitochondria and fragmented sarcoplasmic reticulum (FSR) isolated from frog skeletal muscle was studied. These fractions were characterized by electron microscopy, succinic dehydrogenase assay and by using mitochondrial inhibitors. With high (100 μM) Ca in the medium, the Ca accumulating capacity of the two fractions was similar. Zinc in concentrations of 5–10 μM in the medium had no effect on Ca uptake by either fraction whereas higher concentration of Zn (25 μM) reduced Ca uptake in both fractions. Five micromolar lanthanum lowered Ca uptake by 70% in mitochondria but had no effect on Ca uptake by FSR. With 10 and 25 μM La, Ca uptake by FSR decreased by 12 and 20% respectively. Addition of La (5 μM) to Ca‐loaded mitochondria had no effect indicating that La could only interfere with the Ca binding step and was unable to release Ca that was already stored. In the medium that originally contained low (10 μM) Ca FSR was able to reduce the Ca concentration below 0.1 μM. In contrast mitochondria, although possessing an equal capacity for Ca uptake were unable to accumulate Ca from the medium when Ca was lowered to approximately 4 μM. Presence of 5–10 μM La in the low Ca medium had no effect on the total amount of Ca taken up by FSR in two minutes but reduced the rate of Ca uptake significantly. The relation of the effects of Zn and La on the isolated fractions to their reported effects on the contractile response of skeletal muscle is discussed.
Electrophysiological observations on immature rat nerve cells grown in tissue culture
Authors: Lawson Sarah N. , Biscoe T. J.
Published: February 2005

Intracellular measurements were made on immature cultured rat neurons using single or double barrelled microelectrodes; 361 dorsal root ganglion, DRG, cells, 105 spinal cord cells and 12 cerebellar cells were studied. Membrane potentials recorded were in the range −25 mV to −50 mV. A statistically significant increase in membrane potentials with time in culture was found for DRG cells during 32 days in culture. This was not found for spinal cord cells.

Voltage‐current curves showed a non‐linearity in about 50% of DRG and spinal cord cells similar to anomalous rectification. Measurements made in DRG and spinal cord cells at ± 10 nA showed significantly greater average cell input resistance during hyperpolarising pulses than during depolarising pulses.

The calculated values of Rm and Cm for DRG and spinal cord cells were similar in magnitude to values given for other cells by other workers. The value for L, the dimensionless electrotonic length, was slightly higher than that calculated for motoneurones by other workers. Differences between these results and those of others working on neurons in vitro are ascribed to the immature nature of the cells studied here.
Myoglobin synthesis in cell cultures of red and white muscle
Authors: Heywood Stuart M. , Havaranis Amalia S. , Herrmann Heinz
Published: February 2005

Myoglobin synthesis was compared in cell cultures of leg (red) and breast (white) muscle of chick embryos. In leg muscle cultures a rapidly increasing amino acid incorporation into myoglobin begins two days after muscle cell fusion; in breast muscle cultures no comparable increase was observed. This qualitative difference in cultures of the two muscle cell types provides possibilities for the further study of the mechanism of myoglobin synthesis.
Isolation of temperature sensitive mammalian cells by selective detachment
Authors: Roscoe D. H. , Read Moira , Robinson Hildred
Published: February 2005

Temperature sensitive cells have been isclated from Syrian and Chinese hamster cells using a method based on selective detachment from a glass substrate. The Syrian hamster isolates occurred at a high frequency (about 1 in 103) and reverted rapidly; polyoma virus transformation conferred on cells the ability to grow, perhaps abnormally, in agar suspension. A slightly modified isolation technique was applied to Chinese hamster cultures and resulted in the isolation of at least one mutant (from a starting population of 5 × 108 cells) with a spontaneous reversion rate of less than one in 6 × 107. Treatment of the mutant with ethyl methane sulphonate induced reversion. It was concluded that selective detachment provided a useful method for the isolation of conditional lethal mutants of mammalian cells.
A temperature‐sensitive function in a Chinese hamster line affecting DNA synthesis
Authors: Smith B. J. , Wigglesworth N. M.
Published: February 2005

A temperature‐sensitive (ts) mutant of Chinese hamster cells (K12) is blocked at a step late in G1, required for the initiation of DNA synthesis. The ts lesion is recessive in interspecific hybrids.
Factors affecting pH‐dependent photo‐inhibition of division in Euglena gracilis
Authors: Cook J. R. , Kaiser H.
Published: February 2005

Visible light of moderate intensity (1200 ft‐cd) can severely inhibit cell division of a non‐photosynthetic mutant of Euglena gracilis when growth is supported by butanol, ethanol, or fumarate as sole carbon source. The degree of inhibition is pH dependent, being greatest at pH 4 to 5. A wide variety of other carbon sources permitted growth in the light without inhibition.