bluuebunny/crossref_metadata_2025 huggingface dataset:
Orthophosphate excretion as related to RNA metabolism in Tetrahymena
Authors: Cline Sylvia G. , Conner Robert L.
Published: February 2005

Log phase cultures of Tetrahymena pyriformis W excrete orthophosphate, a purine, and a pyrimidine when suspended in a non‐nutrient buffered medium. Ribonucleic acid has been established as the primary source of these catabolic products. Thirty per cent of the total cellular RNA was degraded in three hours under the conditions of growth and suspension employed. The size of the phosphorus pools of these ciliates was determined during the period of RNA degradation; the internal acid‐soluble organic phosphate and the cellular orthophosphate pools remained constant for five hours at 20% and 5% of the total cell phosphorus respectively. The ultraviolet‐absorbing materials excreted with the orthophosphate were identified as hypoxanthine and uracil. A pentose, presumably ribose, was excreted in small quantities, but was not equivalent in amount to the orthophosphate and did not parallel the pattern of release of the anion. The excretion of orthophosphate, hypoxanthine, and uracil is correlated with the catabolism of RNA as it has been demonstrated in these cells.
Sodium transport inhibition by selective mitochondrial inhibitors in the urinary bladder of the toad
Authors: Hidalgo Cecilia , Canessa‐Fischer Mitzy
Published: February 2005

The effects of selective mitochondrial inhibitors on the short‐circuit current and oxygen consumption displayed by the isolated urinary bladder of the toad was studied.

Three types of compounds were used: (a) electron transfer inhibitors, Amytal, Cyanide and Antimycin A; (b) energy transfer inhibitors Guanidine, Oligomycin and Rutamycin; and (c) uncoupling agents, Carbonyl cyanide m‐chlorophenylhydrazone and 2–4 dinitrophenol.

The kinetics of inhibition of oxygen consumption indicated that the inhibitors tested were effectively reaching the mitochondria of the bladder cells.

Different kinetics of inhibition of short‐circuit current were obtained with the various inhibitors tested.

Uncouplers and electron transfer inhibitors rapidly blocked the short‐circuit current; energy transfer inhibitors only produced a slow and partial inhibition.

A site of energy‐coupling, tentatively identified with the intermediate formed in the energy transfer reactions closest to the electron transfer chain, is proposed.
The response of the early chick embryo heart to anoxia
Authors: Roberts Carmel Montgomery
Published: February 2005

Isolated 3‐ and 5‐day chick embryo hearts contain sufficient endogenous substrates to maintain their pulsatile activity for several hours under aerobic conditions, and even after five hours in substrate‐free medium the rates are 40 to 50% of the original rates. Carbohydrate appears to be an important component of the endogenous substrates since 1 mM 2‐deoxyglucose causes rapid failure of rate, and glycolysis appears to be a major energy pathway since the rate is depressed only about 50% by 2‐hour's exposure to 10 mM fluoroacetate. In nitrogen the hearts rapidly become asystolic in the absence of added substrate. Recovery of the rate occurs if oxygen is reintroduced within one hour, but longer periods of anoxia result in progressively less recovery, especially with the 3‐day hearts which appear to be particularly susceptible to irreversible damage. With 5.55 mM glucose as substrate there is little decrease in the original aerobic heart rate during five hours, and the hearts can tolerate total anoxia for five hours with rates only slightly less than the aerobic rates. The hypothesis of a preferential pentose phosphate pathway of glucose catabolism in the very young chick embryo heart is discussed, but no direct evidence in support of its existence is revealed in this study.
Tritiated‐histidine incorporation into Drosophila salivary chromosomes
Authors: Pettit Barbara J. , Rasch Robert W.
Published: February 2005

An autoradiographic study of H3‐histidine incorporation into nonhistone protein of explanted larval salivary gland chromosomes of D. virilis showed patterns of incorporation that were dependent upon the stage of larval development. The sequence of changes in the development of several puffs in a specific chromosomal region was followed using the appearance of pigment in the anterior spiracles as a means of larval staging. H3‐histidine incorporation into these puffs in prepupae occurred as the puffs were regressing in size and protein staining. Acid extraction of histone and nucleic acid failed to alter the character of the autographs; presumably a non‐histone protein is involved in the H3‐histidine incorporation. Other puff sites in the same prepupal chromosomes showed various patterns of isotopic amino acid incorporation indicating that the pattern reported for a specific region may not be true for all puff sites.
Effect of ATP, EDTA and EGTA on the simultaneous binding of Na, K, Mg and Ca by rat liver microsomes
Authors: Sanui Hisashi , Pace Nello
Published: February 2005

In the presence of Na, K, Mg and Ca at physiological pH, complexing agents can affect cation binding by rat liver microsomes in a manner not always readily predictable simply from a knowledge of individual formation constants. Increasing concentrations (0 to 20 mM) of the strong nonbiological complexing agent, ethylenediaminetetraacetate (EDTA), produced a sharp decrease almost to zero in bound Ca, an increase to a high plateau in bound Na and K and an initial increase followed by a sharp decrease in bound Mg. Increasing concentrations of the Ca‐preferring analogue of EDTA, ethylene bisglycol (β‐aminoethylether) tetraacetate (EGTA), produced similar changes except that bound Mg increased and remained elevated, indicating that this agent complexes Mg very weakly at physiological pH. The biological complexing agent, adenosine triphosphate (ATP), caused a gradual rectilinear and parallel decrease in bound Mg and Ca and a concomitant and parellel increase in bound Na and K at about 4°C and pH 6.4. Results with EDTA and EGTA suggest, however, that under different conditions, enhancement by ATP of divalent cation binding may be possible. Reactions of this nature may be of significance in ATP stimulated divalent cation uptake by subcellular particles.
Measurement of the electrical potential difference across the membrane of the ehrlich mouse ascites tumor cell
Authors: Aull Felice
Published: February 2005

The electrical potential difference (PD) across the membrane of the Ehrlich mouse ascites tumor cell has been measured with intracellular microelectrodes. The mean for 111 cells in control Ringer solution was − 11.2 mV ± 0.29 (SE), interior negative. When sulfate replaced chloride in the external medium the PD fell to − 2.8 mV if measured as soon as possible after mixing the cells with a sulfate medium, but when nitrate replaced chloride the PD fell only to − 8.5 mV. Cells equilibrated in nitrate had the same PD as those in control Ringer. These results indicate that the PD is sensitive to changes in the external chloride concentration and that nitrate can substitute for chloride electrically. However, since the PD for chloride, based on the Nernst equation and calculated on the basis of 70% exchangeability of cell chloride, is three times greater than the measured PD, it is hypothesized that sodium contributes significantly to the membrane potential in addition to chloride. On the other hand, potassium does not influence the PD to any great extent.
Ribonuclease of cultured mammalian cells
Authors: Flanagan John F.
Published: February 2005

KB cell ribonuclease has been purified 260‐fold and the fundamental properties have been studied. Though the enzyme is concentrated in the lysosomal fraction, appreciable quantities are present in the cell sap and nuclear fractions. Comparison of the optimal temperature and pH for activity, and the heat stability of enzyme from these three fractions suggests that only one species of this enzyme exists in these cells. The enzyme behaves as an endonuclease, cleaving synthetic pyrimidine polynucleotides to smaller oligonucleotides with cyclic 2′:3′ end‐groups. The final product is pyrimidine nucleoside 3′ monophosphate. Polyadenylic acid is not hydrolyzed. Of the properties examined in this study only two differences were noted between KB cell and pancreatic ribonuclease. KB cell enzyme acts optimally at pH 6 as opposed to an optimum at pH 7 to 8 for pancreatic enzyme. In addition ribonuclease from KB cells is definitely less stable to heating at 100°C than is the enzyme isolated from pancreas.
Variable duration of DNA synthesis in mammary gland cells during pregnancy and lactation of C3H/He mouse
Authors: Banerjee M. R. , Walker Ruby J.
Published: February 2005

Labeling index as well as the duration of DNA synthesis in alveolar cells of C3H mouse mammary gland at various stages of development was determined by autoradiographic methods. Labeling index of the alveolar cells is highest during pregnancy followed by a marked decrease in the lactating gland. The labeling index of the prelactating cells is significantly reduced after the same cells are transplanted into virgin females. Duration of DNA synthesis in the alveolar cells at eighth and fifteenth day of pregnancy is 14.1 and 8.2 hours respectively. During early lactogenesis, duration of DNA synthesis in the mammary alveolar cells was estimated as 8.5 hours. There is a 2–3 fold increase of the DNA replication time (21.5 hours) in the outgrowth cells of 15 day prelactating tissue after transplantation into virgin host.

A possible role of the hormones of pregnancy, estrogens and progesterone for stimulation of DNA synthesis in the prelactating tissue has been discussed. It has been suggested that the marked inhibition of DNA synthesis in the lactating tissue may be due to the increased stimulation of the same tissue by endogenous adrenocorticoid hormones. Variability of the duration of DNA synthesis (8.5–21.5 hours) in alveolar cells indicates that in mouse mammary gland, DNA synthetic time is not an unadjustable process. Control of DNA synthesis in mouse mammary gland cells by exogenous 17‐β‐estradiol and progesterone has been previously reported (Bresciani, '65). It is suggested that the same hormones of endogenous origin also may influence the duration of DNA synthesis and cell proliferation during mammogenesis.
Effects of helium group gases and nitrous oxide on hela cells
Authors: Bruemmer J. H. , Brunetti B. B. , Schreiner H. R.
Published: February 2005

The helium group gases and nitrous oxide at superatomospheric pressures depress multiplication of HeLa cells in monolayer cultures. The effectiveness of these gases in eliciting the pressure‐dependent response follows the order N2O, Xe > Kr > Ar > > Ne and He. The response correlates with lipid solubility of the gases.

Depression of growth by 4.2 atm Xe is reversible after exposure for one and two days. Cultures exposed to 7.2 atm Xe show irreversible damage including cytoplasmic vacuolization.

Cell attachment is strongly inhibited by Xe; 36% of the cell inoculum were not attached after 24 hours. Affinity for hydrophobic sites in the cell is suggested as determining the order of effectiveness of the gases in evoking the response.
Dynamic adhesion and separation of cells in vitro I. Mathematical analysis of the experimental system
Authors: Blumenson Leslie E.
Published: February 2005

The contact interaction between cells and thewalls of microchambers through which the cells are passing are quantitated in terms of parameters which are estimated from macroscopic experimental data. For this purpose, an analysis is made of the internal geometry of glass bead‐columns. A mathematical model is presented which describes the passage of cells down the column. This model relates the temporal pattern of the number of cells entering and leaving the bead‐column to the “dynamic adhesive” properties of a cell as it passes through a microscopic section of the bead‐column.
Erythrocyte membrane sulfhydryl groups and the active transport of cations
Authors: Rega Alcides F. , Rothstein Aser , Weed Robert I.
Published: February 2005

Parachloromercuribenzenesulfonate (PCMBS) has two opposing effects on the influx of Rb+ into red blood cells. The ouabain‐insensitive component, indicative of passive permeability of the membrane to cations, is increased whereas the ouabain‐sensitive or active transport component is inhibited. The increased passive permeability is paralleled by the action of PCMBS on net K+ efflux into a K+‐free medium. Inhibibition of active transport of Rb+ is paralleled by the inhibitory action of PCMBS on net Na+ efilux from Na+‐rich cells. Both effects are reversed rapidly by the penetrating sulfhydryl compound, cysteine, and considerably more slowly by the non‐penetrating sulfhydryl compound, ovalbumin. Measurements of PCMBS binding and of elution in the presence of cysteine and albumin indicate that only a fraction of the total sulfhydryl groups of the membrane is involved in either the effect on permeability or transport, and that the affected groups are located within the interior of the membrane.
The induction of multinuclearity in agitated and in aging cultures of Acanthamoeba sp. neff
Authors: James T. E. , Byers T. J.
Published: February 2005

Unagitated cultures of Acanthamoeba in the logarithmic growth phase have been observed to consist of over 99% mononucleates and less than 1% multinucleates. A small increase in the relative numbers of multinucleates occurs as the culture age and conditions for growth become limiting. A large increase in the proportion of multinucleates occurs during logarithmic growth, if the cultures are agitated by shaking or by the bubbling from a stream of air. After an initial increase and until the end of logarithmic growth, the numbers of multinucleates in the agitated cultures are maintained at a constant fraction of the total population. Proportions of multinucleates as high as 25% are observed during this period. A second increase in the relative numbers occurs as conditions for growth become limiting. Under these conditions, the multinucleates may exceed 50% of the total population. The factors inducing multinuclearity as well as the kinetics of the mononucleate and multinucleate accumulation curves are discussed.
The stimulation of amino acid incorporation into the protein of unfertilized sea urchin eggs by γ‐irradiation
Authors: Rustad Ronald C.
Published: February 2005

Control and γ‐irradiated sea urchin (Arbacia punctulata) eggs were incubated with H3‐leucine. No incorporation of the amino acid into the proteins of most unirradiated eggs was detectable by autoradiography. All irradiated eggs incorporated the amino acid and the amount of autoradiographic labelling varied greatly from cell to cell.
Electrophoretic studies of muscle proteins. I. Complex formation between delta protein and F‐actin
Authors: Amberson Willia R. , Bauer Adelia C.
Published: February 2005

Complex formation between delta protein and F‐actin has been demonstrated by electrophoretic technique. The high turbidity of F‐actin solutions has made it necessary to work at low concentrations of this protein (0.8 to 1.6 mg/ml). Delta protein concentrations were four to six times greater. At higher concentrations all F‐actin was bound to delta protein, on both limbs. The combination ratio was about 1:1 by weight. We call this complex “delta‐actin.” When the complex formed there was a slight fall in viscosity, indicating side‐by‐side union, but the turbidity greatly increased. The mobility of delta‐actin was always less than that of free F‐actin and sometimes also less than that of free delta protein.

We earlier reported that delta protein is probably a polymer of tropomyosin. Its sedimentation constant (4.4 to 6.0 S) is higher than the of any other form of tropomyosin so far described. It may be the native molecule, its structure preserved by our relatively simple method of extraction and purification.

The filaments of the I band may be composed of delta‐actin. Since delta protein also forms a complex with myosin the filaments of the A band may be composed of delta‐myosin. Delta protein may be a structural component which, in addition to other activities, may direct the building of both filament arrays and strengthen them.
Heterolysosome formation in mouse liver
Authors: Mego John L. , McQueen J. Donald
Published: February 2005

When formaldehyde‐treated 131I‐albumin was injected into mice, the total liver radioactivity did not change significantly from 5 minutes to 60 minutes after injection. There was a progressive increase with time in the amount of radioactivity associated with liver particles which could be released by osmotic shock; the quantity of material tightly bound to particles, but not releasable by osmotic shock, did not change. At five minutes after injection the liver particles did not release acid‐soluble radioactivity into the medium when incubated at 37°. These particles contain the injected protein in osmotically releasable form not associated with proteolytic enzymes and therefore correspond to phagosomes. At 10, 30 or 60 minutes after injection, the particles degraded the protein at similar rates but the activity ceased after 90 minutes incubation when only 50 to 60% of the osmotically releasable material was hydrolyzed. This cessation of activity was shown to be due to a thermal disruption of the particles during incubation.
Spedtral properties of a pigmented body in Hymenomonas sp.: An extra‐chloroplast organelle containing chlorophyll
Authors: Olson Rodney A. , Jennings William H. , Allen Mary Belle
Published: February 2005

In the chrysomonad Hymenomonas, a lamellar organelle of undefined function described previously in electron micrographs, is shown to be highly pigmented by absorption and fluorescence light microscopy. Absorption spectra of the lamellar organelle and the chloroplasts of Hymenomonas are presented. In comparison with the chloroplast the lamellar body appears to have an equal concentration of chlorophyll α and nearly three times the concentration of the 490 nm absorbing carotenoid. Fluorescence in the organelle is initially red as in the chloroplast; this is quickly replaced by an intense yellow emission. The rate at which the red fluorescence is replaced by the yellow is oxidation dependent and is quite rapid in the high intensity of the exciting light required for fluorescence micrographs. Possible roles of the organelle in cell metabolism or photochemistry which are considered and evaluated include: photosynthetic organelle, coccolithogenic organelle, symbiont and lysosome.
Tritiated thymidine effects on DNA, RNA, and protein synthetic rates in synchronized L‐cells
Authors: Krause Margarida O.
Published: February 2005

Exponentially growing L‐cells were synchronized by the double thymidine‐block method and exposed to high specific activities of tritiated thymidine. DNA, RNA, and protein synthetic rates were measured through one cell cycle with 1‐hour pulses of the appropriate C14‐labelled precursors. Equivalent doses of tritiated water were substituted for tritiated thymidine in some experiments. Total amounts of DNA and histones per nucleus were determined photometrically in Feulgen and fast‐green stained cells.

It was observed that incorporated tritiated thymidine has an effect distinct from that of tritiated water and that it enhances the incorporation of the precursors at specific stages of the cell cycle, to a degree roughly proportional to the dose. Photometric data indicated an increase in DNA net synthesis and a metabolic instability of histones in the H3‐thymidine‐treated cells, resulting in higher DNA:histone ratios.
Effects of D2O on the mechanism of pigment dispersal in the melanocytes of Fundulus heteroclitus: A pressure‐temperature analysis
Authors: Marsland Douglas , Meisner Donald
Published: February 2005

The melanocytes of isolated fish scales (Fundulus heteroclitus) immersed in 0.1 M aqueous KCl solution and in deuterated KCl solutions, in which 50–70% of the H2O was replaced by D7O, were observed at 300× magnification while they were subjected to increasing hydrostatic pressure, raised in increments of 1,000 psi in the range up to 16,000 psi. In one series of experiments the temperature was maintained at 20°C (± 0.2°), whereas in the other it was kept at 25°C (± 0.2).

Initially, all the melanocytes in the KCl media displayed a contracted, or punctate, form. With increasing pressures, gradually, expansion, or pigment granule dispersal, occurred but the degree of expansion at a given pressure depended upon the percentage of deuteration and the temperature. At 20°C in aqueous medium, total expansion, in which the pigment extended all the way out into the peripheral tips of melanocyte branches, occurred at 8,000–9,000 psi. At lower pressure, the intermediate values, expressed as a percentage of the total, fell along a smooth, slightly sigmoid curve. In the deuterated media, similar curves were obtained, but the pressure levels required to produce a given degree of expansion were significantly higher. Thus, maximum expansion required the imposition of 14,000 psi in the 50% D2O medium and of 16,000 psi in the 70%. Upon decompression, at the end of each experiment, the melanocytes quickly contracted, reaching a completely punctate form within 3–4 minutes.

Similar relationships were found at 25°C, except that all the pressure values were significantly higher than those at 20°C. In fact the values for 25°, with 50% deuteration, were very similar to those for 20°, with 70% D2O.

The evidence tends to confirm conclusions, previously submitted, namely, that, as expansion occurs, the cytoplasm of the unicellular pigmentary effectors of the fish undergoes a progressive process of solation and that contraction involves a reestablishment of the original firm gel structure. Thus the well known solational effects of high pressure tend to be counteracted by agencies, such as increasing deuteration and temperature, which are known to foster protoplasmic gelations generally.
Nucleotide action on spontaneous electrical activity of calcium deficient nerve
Authors: Kuperman Albert S. , Okamoto Michiko , Gallin Elaine
Published: February 2005

In concentrations having no effect on the evoked alpha‐A fiber spike, adenosine triphosphate (ATP), adenosine monophosphate (AMP) and several other nucleotides produced antagonism of spontaneous impulses in isolated desheathed frog nerve soaked in Ca free solution. ATP was only slightly more potent than AMP, indicating that high‐energy phosphate bonds and Ca complexing are not important for stabilizing action. Furthermore, sub‐effective concentrations of Ca potentiated the stabilizing action of ATP to a minimal degree and that of AMP not at all, suggesting a direct action of the nucleotide per se rather than a Ca‐nucleotide complex. Ca45 washout experiments showed that the nucleotides did not depress efflux of Ca from nerve axons but, in fact, caused release of Ca. It was proposed that nucleotide stabilization is associated with replacement of nucleotide lost from the excitable membrane into the Ca free medium.
Stability of division‐related protein and nucleic acid fractions in synchronized Tetrahymena
Authors: Byfield John E. , Scherbaum Otto H.
Published: February 2005

The kinetics of RNA synthesis have been studied under various growth conditions using synchronized Tetrahymena pyriformis GL. The curves obtained are approximately linear in growth‐supporting media but vary under other circumstances. The presence of amino acids in the medium stimulates RNA synthesis in Tetrahymena as it does in bacteria. Since these induced variations do not influence the essential features of the pre‐cytokinetic period it is inferred that fluctuations in the rate of RNA synthesis described by others are probably not essential features of temperature‐induced synchrony. In addition, the translational stability of division‐related templates at synchronizing temperatures has been investigated. The synthesis of proteins necessary for cytokinesis is shown to be greatly reduced under conditions simulating a heat‐shock. Inhibitor studies using cycloheximide indicate that protein synthesis is required longer into the cytokinetic phase than had previously been thought. Collectively the data are all compatible with the hypothesis that synthesis of division‐related proteins is drastically reduced in heat‐shocked Tetrahymena and that the basis for this reduction is hydrolysis of template RNA without concurrent translation.
Patterns of resistance to 2‐deoxy‐D‐glucose in pig kidney cells
Authors: Bailey Philip J. , Harris Morgan
Published: February 2005

Variants resistant to 2‐deoxy‐D‐glucose have been isolated from a clonal line of pig kidney cells by serial cultivation in the presence of inhibitor. Hexokinase activity may be affected directly in this system, since the oxidation of glucose to 6‐phosphogluconate by extracts from sensitive and resistant cells is blocked by the addition of 2‐deoxy‐glucose to the reaction mixture. This blockage was removed by the addition of glucose‐6‐phosphate to the system, but not by ATP. Resistant cells were found to accumulate significantly less 2‐deoxyglucose‐6‐phosphate than sensitive cells. The rate of phosphorylation of 2‐deoxyglucose, however, was higher in extracts from the resistant line. Alkaline phosphatase does not account for the reduced level of 2‐deoxyglucose‐6‐phosphate since this enzyme is not detectable in sensitive or resistant pig kidney cells. Increased acid phosphatase activity was observed in resistant cells, but extracts with high acid phosphatase activity proved incapable of hydrolyzing either 2‐deoxyglucose‐6‐phosphate or glucose‐6‐phosphate. In comparative growth studies, cells resistant to 2‐deoxyglucose proliferated more extensively than sensitive cells in a low glucose nutrient. They removed glucose more effectively from this medium, and were less stimulated by the addition of intermediates from the tricarboxylic acid cycle. The evidence suggests that resistance to 2‐deoxyglucose in the cells under study may be based on the ability of the resistant cells to proliferate at concentrations of glucose too low to support the growth of sensitive cells.
The repopulating potential and differentiation capacity of hematopoietic stem cells from the blood and bone marrow of normal mice
Authors: Lewis Jerry P. , Passovoy Mitchell , Freeman Mary , Trobaugh Frank E.
Published: February 2005

Using the hematopoietic colony technique, we have investigated the repopulating potential of bone marrow cells and leukocytes of blood from normal mice and have demonstrated that the frequency of hematopoietic stem cells in bone marrow is 50 to 150 times that of stem cells in the circulating blood. The differentiation capacity of these stem cells has also been examined. Results of comparative studies of the serial sections of hematopoietic colonies formed from marrow and blood leukocytes indicate that the differentiation capacity of stem cells from marrow and blood is similar, and that at least 80% of these cells differentiate along a single cell line. Thus, peripheral blood stem cells can effect a complete hematopoietic graft, establishing in the host, donor red cells, granulocytes, and platelets.

The possibility that blood leukocytes may serve as a potential source of stem cells for hematopoietic transplants has been considered. Although blood contains stem cells, their frequency is so low as to make it unlikely that they would become a useful source of precursor cells for transplantation purposes.
The influence of progressive growth on the specific catalase activity of human diploid cell strains. II. Effect of cellular genotype: A heterozygous strain
Authors: Pan Yue‐Liang , Krooth Robert S. , Takahara Shigeo
Published: February 2005

Human diploid cell strains develop progressively higher levels of specific catalase activity as they grow. Following subculture activity falls again. A diploid cell strain heterozygous for the gene for acatalasia I (acatalasemia) was found to develop specific catalase activity at proportionately the same rate as normal cell strains. Yet the mutant gene reduced the absolute level of specific catalase activity which the culture attained at any given point in time. In this respect the heterozygous acatalasia I strain resembles the homozygous acatalasia II strain previously reported.
The influence of progressive growth on the specific catalase activity of human diploid cell strains. III. Experiments bearing on the mechanism responsible for change in specific activity
Authors: Pan Yue‐Liang , Krooth Robert S.
Published: February 2005

It was shown previously that the specific catalase activity of human diploid cell strains falls immediately after subculture and then progressively rises in an exponential fashion. In this paper evidence is presented suggesting that the rise in catalase activity cannot be due to an accumulation within the cell of a small molecule which enhances enzyme activity in cell‐free extracts. It is also shown that activity per cell, as well as per unit cell protein, rises as the culture grows.

The rate of fall of specific catalase activity immediately after subculture is greater if the cells are at a low population density than if they are at a high one. The rate of fall can be made more sharp by increasing the frequency with which the cultures are fed.

It is shown that used medium, which has previously been incubated with cultured cells of the same strain, does not significantly change either the rate of fall of specific catalase activity following subculture, or the rate of its subsequent rise. It is postulated, as one possibility, that the cells liberate into the medium an enhancer of cell catalase activity which is highly labile. The steady state concentration of this enhancer in the medium might be expected to increase as the culture grew, but to decrease when the cells are subcultured into fresh medium or when the frequency of feedings is increased.
Cell volume regulation in mouse TA3 ascites tumor cells by exogenous ATP as measured by the coulter counter
Authors: Gasic G. , Stewart C.
Published: February 2005

Exogenous ATP can induce a marked cell enlargement in TA3 tumor cells which can be reversed or prevented by Ca and Mg. This regulatory effect on cell volume is specific for ATP. The mechanism probably involves changes in cell ionic content.
Sugar penetration into human blood platelets
Authors: McDonagh R. P. , Burns M. J. , Delaimi K. E. , Faust R. G.
Published: February 2005

The relative rates of penetration of pentoses and hexoses into human blood platelets were studied with a photoelectric densimeter. It was concluded that pentoses enter human platelets by free diffusion whereas hexoses penetrate into these cells by an altered diffusion process.
Membrane glycoprotein biosynthesis: Changes in levels of glycosyl transferases in fibroblasts transformed by oncogenic viruses
Authors: Bosmann H. Bruce , Hagopian Arpi , Eylar E. H.
Published: February 2005

Fibroblasts transformed by oncogenic viruses were found to have greater enzymic activities of four membrane glycoprotein:glycosyl transferases on a cell or protein basis then two non‐transformed fibroblastic lines. These enzymes are responsible for the synthesis of membrane glycoproteins; each of the four transferases studied, the polypeptide:N‐acetylgalactosaminyl, glycoprotein:galactosyl, fetuin:fucosyl and PSM:fucosyl transferases, was more than twice as active in the transformed cell lines using both endogenous and added receptor. The most pronounced differences occurred with the doubly (SV‐PY‐3T3) transformed fibroblasts in all cases; with the N‐acetylgalactosaminyl and galactosyl transferases the increase was 8–16 fold over the non‐transformed cells. It was demonstrated that these results do not arise from a changed level of glycosidase activities.
Optimal oxygen tension for human lymphocytes in culture
Authors: Andersen V. , Hellung‐Larsen P. , Sørensen S. F.
Published: February 2005

Human lymphocytes stimulated with phytohaemagglutinin in vitro show maximal 14C‐thymidine incorporation when the gas phase of the cultures contains 20% O2. The rate of DNA synthesis is more affected by hyperoxic conditions than by hypoxia. Cell viability, defined by dye exclusion, is considerably less dependent on pO2 than is cellular replication.
The metabolism of pyrimidine compounds by Tetrahymena pyriformis
Authors: Wykes J. R. , Prescott D. M.
Published: February 2005

The pyrimidine requirements for growth of T. pyriformis and for reversal of the growth inhibition caused by folate deprivation have been studied. The effects of thymidine and 5‐fluorodeoxyuridine have been shown to be quantitatively different from the effects of these compounds on growth and the rate of DNA synthesis in mammalian cells. Labelled nucleosides added to the medium have been found to be converted to the corresponding bases with the exception of deoxycytidine, which is first deaminated to deoxyuridine. As a result no deoxynucleosides other than thymidine specifically label DNA.

The results allow deductions to be made concerning the enzymes involved in pyrimidine utilization by this organism. It is suggested that pyrimidine utilization is always channeled through uracil in the case of those compounds that can supply the pyrimidine requirement for growth.
The dilution factor of intravenously injected hemopoietic stem cells
Authors: Matioli Gastone , Vogel Helmut , Niewisch Helgard
Published: February 2005

In order to measure the total number of stem cells present in a given preparation, it is necessary to know the fraction of stem cells which settle in the spleen and form macroscopically visible colonies. The intravenous injection does not allow a direct measurement of this fraction. However, its value is established by injecting stem cells directly into the spleen, thus minimizing the dilution of stem cells through the circulation. It has been measured with this procedure, that only 4% of intravenously injected stem cells form spleen colonies.
The continued requirement for inducer for the development of macrophage and granulocyte colonies
Authors: Paran Michael , Sachs Leo
Published: February 2005

Rat bone marrow cells were seeded as mass cultures or for cloning together with inducer required for colony formation, and at various times after seeding, the cells were re‐seeded for cloning either with or without inducer. The results indicate that the development of both macrophage (M) and granulocyte (G) colonies requires a continued supply of the inducer. No M or G colonies were produced when the inducer was replaced by erythropoietin.
The single cell origin of normal granulocyte colonies in vitro
Authors: Paran Michael , Sachs Leo
Published: February 2005

It has been shown by re‐cloning of colonies formed in vitro from rat bone marrow cells, that normal granulocyte colonies can originate from single cells. No mixed macrophage (M) and granulocyte (G) colonies were obtained after re‐cloning either M or G colonies. The results indicate, that clones of normal granulocytes and macrophages can be obtained in vitro, and that the mixed primary M and G colonies formed after seeding hematopoietic cells from animals presumably originate from a mixture of M and G cells.
Effect of exogenous ATP on the volume of TA3 ascites tumor cells
Authors: Stewart Carleton C. , Gasic Gabriel , Hempling Harold G.
Published: February 2005

When exogenous ATP is added to suspensions of TA3 ascites tumor cells suspended in Ca++ and Mg++ free media, a significant increase in cell volume can be measured. This increase is reversible upon addition of Ca++ and/or Mg++ back to the media.

The enlargement of these cells is temperature sensitive and specific for ATP; no other nucleotides, EDTA or ouabain were effective. The evidence suggest that this phenomena may be due to an alteration in membrane permeability and that the regulation of membrane permeability is an energy dependent process.
The effect of exogenous ATP on the electrolyte content of TA3 ascites tumor cells
Authors: Hempling H. G. , Stewart Carleton C. , Gasic Gabriel
Published: February 2005

In the presence of 1 mM ATP in the external medium, TA3 mouse ascites tumor cells showed a dramatic loss of potassium and gain of sodium down their respective concentration gradients. The volume changes detected by size discrimination with the Coulter counter have been adequately confirmed by densimetric techniques. Further, some experiments were so designed that net losses of both ions occurred and the cell shrank in response to ATP, a response which was predictable if the volume change was produced by a loss of cell water. We believe that ATP produces a major change in the passive permeability of the membrane to these ions and the effect may be due to a response of a contractile protein in the membrane to ATP.
Development of the mouse hematopoietic system. II. Estimation of spleen and liver “stem” cell number
Authors: Barker Jane E. , Keenan Mary Ann , Raphals Lisa
Published: February 2005

Colony‐forming cells (CFU), which have the general properties of hemopoietic “stem” cells, appear to be augmented in the mouse fetal liver from 12–18 days gestation and then decrease in the newborn. This finding suggests that few, if any, hemopoietic “stem” cells remain in the adult liver, an organ which appears to be unable to function erythropoietically, even at times of severe crises. In the spleen, and active adult as well as embryonic hematopoietic organ, the total number of CFU increases from 18 days gestation until at least 7 days after birth.

Spleen and liver CFU augmentation seems to occur in cojunction with an analogous expansion of non‐hematopoietic cells. The data suggests, in fact, that while there is an increase in the total number of liver CFU, there is also a dilution of liver CFU in the total cell population at successively later gestational ages.
Discrepancies between precursor uptake and DNA synthesis in mammalian cells
Authors: Smets L. A.
Published: February 2005

The incorporation of tritiated thymidine and deoxycytidine into DNA of x‐irradiated mammalian cells was studied. Both inhibition and stimulation were found due to pool changes rather than to effects on DNA synthesis, indicating that precursor uptake can be a misleading method to measure DNA synthesis rate.
Mitochondrial damage and inhibition of respiration in animal cell cultures treated with Triton WR‐1339
Authors: Zimmerman Eugene M. , Vaituzis Zigfridas , Hetrick Frank M.
Published: February 2005

Inhibition of cellular respiration by treatment with the nonionic detergent Triton WR‐1339 was found to be related to the cytotoxic response of cell to the surfactant. Respiration of sensitive cell lines (AV‐3 and HeLa) markedly inhibited by Triton concentrations as low as 125 μgm/ml. Conditionally sensitive lines (BHK‐21 and L‐929) were affected by 500 μgm/ml while the respiration of insensitive cultures (primary rat and chick embryo cells) was unaffected by this concentration. Macrocyclon, a cyclic analogue of Triton, failed to alter the respiration rate of any of the above cell cultures.

The levels of isocitric and succinic dehydrogenases in sensitive and conditionally sensitive cells were depressed within 2 hours after treatment with 500 μgm/ml of Triton was initiated and by 6 hours the activity was only 25% of the untreated controls. Similar results were obtained with mitochondrial preparations from these cells. Enzyme levels in insensitive cells were unaffected by Triton treatment.

Mitochondrial damage was the most striking characteristic noted in treated cells examined by electron microscopy. The mitochondria were quite distorted and had lost most of their cristae formation. This mitochondrial damage was seen in all cell types examined although the rate at which it occurred varied. With sensitive cultures, damage was pronounced within 6 hours after the addition of Triton while mitochondria from conditionally sensitive cells were not grossly affected until 48 hours and they appeared to repair the damage following the removal of Triton.
Curves of osmotic fragility calculated from the isotonic areas and volumes of individual human erythrocytes
Authors: Canham Peter B.
Published: February 2005

Theoretical osmotic fragility curves were calculated and drawn by computer using the van't Hoff equation and the isotonic areas and volumes of 1000 individual erythrocytes. We studied the influence on the calculated curves of theoretically altering the fraction of the volume which was osmotically active from 50 to 70%, and of altering the permissible stretch before hemolysis from zero to 10%. With the two assumptions–that the membrane does not stretch before hemolysis, and that the osmotically active fraction of the cell volume is 0.58–it was possible to duplicate the general shape of the standard fragility curve; the exact NaCl concentration, however, at which there was 50% hemolysis was approximately 0.1 gm/100 ml higher than found in vitro. The calculated osmotic fragility curves can be made quantitatively similar to in vitro ones if the following statements are true: the osmotically active volume is 58%, the permissible stretch of the membrane without lysis is 6%, the cell membrane resists a slight osmotic pressure gradient of approximately 0.1 atmospheres, and hemolysis is an all or nothing phenomenon. This set of values for the relevant factors is sufficient but not unique in causing the superposition of the calculated and experimental curves. The frequency distribution of the cells according to the hemolytic salt concentrations (the sodium chloride concentration at which an individual cell just hemolyzes) was skewed positively and was leptokurtic for each of the seven normal subjects studied.
Hemoglobin and ferritin synthesis in erythroid cells in prolonged marrow cell cultures
Authors: Gabuzda Thomas G. , Silver Ruth K. , Melvin Mary , Windus Constance , Sachs Carl
Published: February 2005

A method is described which maintains viable erythroid cells in tissue culture for periods from nine to twenty days. These cells appear predominantly as small round cells with scanty cytoplasm. They synthesize both heme and globin and are relatively more numerous free in suspension than in the adherent monolayer. Ferritin isomorph may serve as a convenient marker in tissue culture of cells of erythroid origin, suggesting that such cells may persist despite a completely transformed appearance and a loss of the ability to produce hemoglobin.
Studies on colony formation in vitro by mouse bone marrow cells. I. Continuous cluster formation and relation of clusters to colonies
Authors: Metcalf Donald
Published: February 2005

Colony formation in vitro by mouse bone marrow cells following stimulation by human urine was analysed over a 7‐day incubation period. There was a linear increase with time in the number of cell aggregates (clusters) developing in such plates. Early in the incubation period all clusters were granulocytic although later macrophage clusters developed. Although most fully developed colonies were composed of macrophages, mapping and transfer studies showed that at least half of these had initially arisen early in the incubation period as granulocytic clusters.
Control of multiplication of uninfected rat cells and rat cells converted by murine sarcoma virus
Authors: Temin Howard M.
Published: February 2005

The rate of multiplication of rat embryo fibroblasts in monolayer culture depends upon the amount of multiplication‐stimulating activity in the culture medium, as well as the efficiency of stimulation by and utilization of this activity. Multiplication‐stimulating activity is defined by its capacity to stimulate DNA synthesis and cell division in stationary populations of cells. Usually, multiplication stimulating activity is supplied as serum in cell culture media, but rat cells also produce it.

A comparison of multiplication of uninfected and Murine Sarcoma virus‐converted rat cells showed that converted cells multiplied at a greater rate than did uninfected cells, with the use of less or the same amount of multiplication‐stimulating activity; the converted cells produced cells produced an inhibitor of multiplication‐stimulating activity, and the efficiency of stimulation of DNA synthesis was similar for uninfected and converted cells. It appears that in the presence of serum the efficiency of utilization of multiplication‐stimulating activity is greater for converted cells than for uninfected rat cells.
Nuclear alterations in mammalian cells induced by L‐canavanine
Authors: Hare J. D.
Published: February 2005

Mammalian cells treated four hours with the L‐arginine analogue, L‐canavanine (Cana), develop alterations in nuclear architecture characterized by the formation of irregular aggregates of nucleoplasmic contents, frequently attached to the nuclear membrane. On the basis of previous studies showing that Cana is incorporated into nuclear proteins and inhibits DNA synthesis over similar periods of exposure, it is postulated that the formation of canavanyl protein‐DNA aggregates interfere with DNA replication.
Evidence for the existence of multipotential lympho‐hematopoietic stem cells in the adult rat
Authors: Nowell Peter C. , Hirsch Bruce E. , Fox Dianne H. , Wilson Darcy B.
Published: February 2005

Rats were given near‐lethal doses of x‐ray to produce clones of hemic cells marked by radiation‐induced chromosome abnormalities. Subsequently, bone marrow from these rats was injected into lethally irradiated mice to form erythropoietic spleen colonies; and peripheral blood lymphocytes from the same rats were stimulated to proliferate in a mixed lymphocyte interaction (MLI), an immunological response to histocompatibility isoantigens.

Chromosome markers indicated that in several instances the cells of an erythroid spleen colony and a proportion of the lymphocytes reacting in the MLI were progeny of the same stem cell in the donor rat. In addition, lymphocytes of the same radiation‐marked clone were shown to proliferate in response to several different histocompatibility isoantigens. The data indicate the presence in the adult rat of a primitive lymphohematopoietic stem cell capable of yielding both erythroid and lymphoid progeny. The findings also suggest that immunological specificity is determined during lymphoid differentiation, subsequent to the stem cell stage.
Density distribution analysis of In vivo and In vitro colony forming cells in developing fetal liver
Authors: Moore M. A. S. , McNeill T. A. , Haskill J. S.
Published: February 2005

The technique of buoyant density separation in gradients of Bovine Serum Albumin has been used to separate in vivo and in vitro colony forming cells (C.F.C.'s) in hemopoietic tissue of mouse fetal liver. Differences in the density distribution profiles showed that the in vivo and in vitro C.F.C.'s were different cell populations but the existence of an “out‐of‐phase” density association suggested that the two cell types were closely related.

Complex density heterogeneity of both cell populations was observed at later stages of liver development and was similar to that seen in adult marrow. A homogeneous population of in vivo and in vitro C.F.C.'s occupied a very light density position in 10.5 day fetal liver. The subsequent development of density heterogeneity was associated with progressive acquisition of higher density subpopulations. Transfer experiments showed the capacity of the lightest density cells from the earliest stage of liver hemopoiesis, to generate higher density colony forming cells in the environment of the adult marrow. Density determined differences in seeding efficiency of in vivo C.F.C.'s were observed but no evidence was obtained for differences in either in vivo or in vitro colony morphology in different density subpopulations.