bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of endotoxin on murine stem cells
Authors: Quesenberry Peter J. , Morley Alec , Ryan Marie , Howard Donald , Stohlman Frederick
Published: February 2005

Previous studies showed that after 5 μg of Salmonella typhosa endotoxin there was an increase in colony stimulating factor temporally related to a fall in murine marrow in vitro colony forming cells (CFC). This was followed by differentiation along the marrow granulocytic pathway. The present studies showed that after 5 μg of endotoxin the peripheral blood CFC fell by approximately 50% at one hour, rose to a level ten fold that of control at six hours and then returned to control values by 48 hours. There was a progressive increase in the number of splenic CFC to ten fold that of control from 24 to 72 hours after endotoxin. These data imply a migration of CFC from the marrow to the spleen along with an in‐situ increase in splenic CFC. Thus, either migration or differentiation may explain the fall in marrow CFC after endotoxin.

Spleen colony forming units (CFU) in the marrow were measured by a transplantation technique and the transplantation fraction (f Fx) determined. A decrease in marrow CFU at 24 hours after endotoxin was secondary to a change in the f Fx. from 11.1% to 7.6%. There was however, an increased percentage of CFU in DNA synthesis in the interval of 6–48 hours after endotoxin, as judged by the hydroxyurea technique. As the marrow CFC fell within 20 minutes of endotoxin administration, the data suggest the CFC may be affected initially and that changes in the generative cycle of the CFU may be of a secondary nature.
A comparison of the effect of cytotoxic agents on agar colony forming cells, spleen colony forming cells, and the erythrocytic repopulating ability of mouse bone marrow
Authors: Millard R. E. , Blackett N. M. , Okell S. F.
Published: February 2005

Three assays for bone marrow progenitor cells have been used to determine the effect of single doses of two cytotoxic agents, cyclophosphamide and vinblastine. The assays employed were the agar colony forming and spleen colony forming assays and the crythroid repopulating ability.

In normal mice, there was little difference between the response of the progenitor cells assayed by the three methods, following cyclophosphamide: and no detectable difference following vinblastine.

Bone marrow from continuously irradiated mice and bone marrow regenerating seven days following transplantation was also studied: in both these situations the proliferation rate of the progenitor cells is increased. Cyclophosphamide was found to be only slightly proliferation dependent with each assay. However, vinblastine was strikingly proliferation dependent. In irradiated mice and also in regenerating marrow the agar colony forming cells were many times more sensitive to this agent than were the other progenitor cells.

These results show that under some but not all circumstances the agar colony forming and spleen colony forming cells behave similarly in C57BL mice, but are not a single population of cells.
The role of sulfhydryl groups in human neutrophil adhesion, movement and particle ingestion
Authors: Giordano Gerald F. , Lichtman Marshall A.
Published: February 2005

Recent studies have suggested that ectosulfhydryl groups may play a role in cell contact phenomena.

We have studied the possible role of ecto‐ and endosulfhydryl groups in the morphology, adhesiveness, random and directed (chemotaxis) motility and phagocytosis of human polymorphonuclear neutrophils. The rapidly penetrating sulfhydryl binding reagents HgCl2 and NEM inhibited adhesiveness, motility and phagocytosis when studied at > 0.1 mM in plasma or > 0.01 mM in buffer. The difference in inhibitory concentration was shown to be due to the difference in albumin content of the two media. D‐cysteine prevented the effect of HgCl2 and NEM on cell morphology, adhesiveness, motility and phagocytosis indicating that their effects were on cell sulfhydryl groups. PCMBS, a very slowly penetrating organic mercurial, had no effect on neutrophil morphology, adhesiveness, motility or phagocytosis. However, PCMBS inhibited platelet aggregation, assuring its potency. These studies indicate that ectosulfhydryl groups are either not present or not participants in the maintainence of structure and functions of human neutrophilic granulocytes.
The importance of the techniques employed during the enzymatic preparation of isolated liver parenchymal cells
Authors: Labrecque Douglas R. , Bachur Nicholas R. , Peterson Janice A. , Howard Roger B.
Published: February 2005

The endogenous respiration of isolated rat liver parenchymal cells prepared by two enzymatic techniques has been measured. Despite the production of a high percentage of viable cells by both methods, as measured by the exclusion of trypan blue, the cells obtained by one of the techniques consume oxygen at only one‐half the rate of those obtained by the other technique. It is suggested that the lower rate is the result of an insufficient oxygen supply and also a lack of control of the pH of the incubation medium during the preparation of the cells.
Deoxyglucose transport by uninfected, murihe sarcoma virus‐transformed, and murine leukemia virus‐infected mouse cells
Authors: Plagemann Peter G. W.
Published: February 2005

The initial rates of deoxy‐D‐glucose transport by cultures of growing and density‐inhibited mouse embryo cells and lines of mouse cells transformed spontaneously or after infection by murine leukemia virus or murine sarcoma virus were investigated as a function of the deoxyglucose concentration. The apparent Km for deoxyglucose transport was about the same for all types of cells (1–2 mM). The Vmax of secondary cultures of mouse embryo cells decreased from 6 nmoles/106 cells/minute for sparse cultures to less than 1 nmole/106 cells/minute for density‐inhibited cultures. The Vmax was about the same whether estimated in monolayer culture or in suspensions of cells dispersed by treatment with trypsin. The Vmax for deoxyglucose transport by the established cells, whether transformed spontaneously or by virus infection, was 4 to 25 times higher than that for density‐inhibited mouse embryo cells and was independent of the cell density of the cultures. Deoxyglucose transport was competitively inhibited by Cytochalasin B, Persantin, glucose and 3‐O‐methyl‐D‐glucose and the apparent Ki values of inhibition were similar for the mouse embryo cells and the various cell lines. Similarly, the sensitivity of the glucose transport systems to inactivation by p‐chloromercuribenzoate was about the same for all types of cells. The results suggest that the glucose transport system of the normal mouse embryo cells and the cells of the various established lines is qualitatively the same, but that the number of functional transport sites differs for the various cell lines and decreases markedly in mouse embryo cells with an increase in cell density of the cultures.
Anion transport in the Ehrlich ascites tumor cell: The effect of 2,4,6‐trinitrobenzene sulfonic acid
Authors: Levinson Charles , Villereal Mitchel L.
Published: February 2005

We have investigated the effects of the amino reactive reagent, 2,4,6‐trinitrobenzene sulfonic acid (TNBS) on anion transport (chloride and sulfate) and on the K+ content of Ehrlich ascites tumor cells. Incubation of tumor cells with TNBS (3 mM or 10 mM) results in a time dependent uptake of this molecule. Tightly bound TNBS caused a loss of K+ as well as inhibition of sulfate uptake. Although sulfate transport was inhibited by tightly bound TNBS (40% inhibition with 20 nmoles bound per 107 cells), reversibly bound TNBS exerted much greater inhibition. Kinetic analysis of sulfate transport in the presence and absence of TNBS suggests that: (1) tightly bound TNBS exerts a competitive inhibition by occupying membrane sites remote from the specific transport site, (2) TNBS reversibly interacts with a separate site also in a competitive fashion.

Increasing amounts of tightly bound TNBS resulted in an enhanced chloride influx. However, reversibly bound TNBS was without effect. These results are in contrast to the effect of TNBS on sulfate transport and show that TNBS, at least in this cell type, is not a general inhibitor of anion transport.
Macromolecular requirements for the initiation and maintenance of DNA synthesis during the cell cycle of Tetrahymena pyriformis
Authors: Jeffery William R.
Published: February 2005

The macromolecular reguirements for the initiation and maintenance of macronuclear DNA replication were studied in heat synchronized Tetrahymena pyriformis GL‐C. Previous work had established that macronuclear S periods could occur in a consecutive fashion without intervening cell divisions during a multiple heat shock treatment, as well as immediately following the synchronized cell divisions. Cycloheximide treatment prior to or during the S period which follows the first synchronized cell division resulted in abolition of the initiation of DNA synthesis or an almost immediate cessation of DNA synthesis in progress. Temporary inhibition of DNA synthesis occurred when cycloheximide was added late in the S period. Treatment with actinomycin D was found to block the initiation of DNA synthesis but did not appreciably affect the continuation of the S period. It was concluded that RNA synthesis was required for the initiation but not the maintenance of DNA replication, whereas protein synthesis was necessary for both processes.

The dependency of the initiation of an S period on prior RNA and protein synthesis was also shown to exist when a second consecutive S period was initiated without a preceding cell division. Treatment with actinomycin or cycloheximide prior to a supernumerary S period during a multiple heat shock treatment completely abolished the initiation of DNA synthesis. In T. pyriformis the synthesis of RNA and protein related to the initiation of the S period is tightly coupled to each cycle of DNA replication.
Primitive erythropoiesis in chick embryogenesis. III. Effect of FUdR on Hb synthesis
Authors: Campbell Graham Lem , Weintraub Harold , Holtzer Howard , Mayhall B. H.
Published: February 2005

A single hematocytoblast in the yolk sac of the chick embryo has been shown previously to give rise on the average to a clone of 128 erythrocytes. Furthermore, in any given generation the erythroid cell synthesizes a characteristic amount of hemoglobin (Hb). In these experiments day 4 embryos were treated with FUdR for 12 hours, and then reversed with thymidine. We have monitored both the passage of these erythroblasts through the cell cycle, and the effect of this perturbation on the Hb content of single cells. As a result of this disruption the amount of Hb synthesized in a given generation can be varied, but the final amount of Hb/cell in the mature erythrocyte is the same as in the untreated controls. Apparently the total amount of the Hb/cell does not in itself influence the passage of the cell through the cycle. The coefficients of variation of the Hb values in the mature erythrocytes from both normal an perturbed embryos are similar.
Alkaline phosphatase activity and the regulation of growth in transformed mammalian cells
Authors: Sela Ben‐Ami , Sachs Leo
Published: February 2005

The relationship between alkaline phosphatase activity and cell growth has been studied in hamster cells transformed by different carcinogens. About 90% of normal hamster embryo cells were constitutively positive for alkaline phosphatase activity (AP+). However, there were no AP+ cells in cell lines transformed after treatment with the chemical carcinogens dimethylnitrosamine or 4‐nitro‐quinoline‐N‐oxide and 0.02% and 4% AP+ cells in cell lines transformed by polyoma virus or Simian virus 40. The glucocorticoid hormone, prednisolone, induced alkaline phosphatase activity in 12% and 44% of the enzyme‐negative (AP−) cells in cell lines transformed by polyoma or Simian virus 40, but this hormone did not induce alkaline phosphatase activity in AP− cells from cell lines transformed after treatment with the chemical carcinogens. Treatment of polyoma transformed AP− cells with the mutagen N‐methyl‐N′‐nitro‐N‐nitro‐soguanidine produced AP+ cells, whereas no AP+ cells were found after mutagen treatment of AP− cells from the chemically transformed cell lines. Studies on spontaneous segregation in the polyoma transformed cell line has shown that AP+ cells segregated AP− cells both in vitro and in vivo, although no spontaneous segregation was observed from AP− to AP+ cells.

AP+ cells, compared to AP− cells, showed a decrease in DNA synthesis, cell multiplication, the ability to form colonies in soft agar and tumorogenicity in animals. AP− cells induced for alkaline phosphatase activity by prednisolone, showed the same growth properties in vitro as uninduced AP− cells. The decreased cell growth found in AP+ cells which were constitutive for alkaline phosphatase activity was therefore not found in the hormone induced AP− cells. The results indicate that constitutive alkaline phosphatase activity appears to be related to the regulation of cell growth and that AP− cells have a selective advantage over AP+ cells.
The non‐equivalence of mouse and human marrow culture in the assay of granulopoietic stimulatory factors
Authors: Lind D. E. , Bradley M. L. , Gunz F. W. , Vincent P. C.
Published: February 2005

Mouse bone marrow forms colonies of granulocytes and monocytic phagocytes when cultured in the presence of human plasma, urine or “feeder layers” prepared from human leukocytes. By contrast, human marrow produces colonies in the presence of leukocyte feeder layers but not in the presence of plasma or urine. It has been tacitly assumed that the response of mouse marrow to human blood leukocyte feeder layers is a measure of physiological substances released by those leukocytes which might control human granulopoiesis. This assumption however, has never been put to the test by comparing the response of mouse and human marrow to stimulation by leukocytes from the same individual. This has been done in the present study by using leukocytes from normal and leukemic subjects. Different human marrows responded similarly to stimulation by the same normal feeder layers, but there was no quantitative or qualitative correlation between the response of human and mouse marrows. Feeder layers from patients with acute granulocytic leukemia did not stimulate colony growth in normal human marrow but were as potent in stimulating mouse marrow colony growth as were feeder layers of normal leukocytes.

We conclude that different factors may stimulate human and mouse marrows and that assays of granulopoietic factors of human origin should in future be carried out in human rather than mouse marrows.
Chinese hamster cells exhibiting a temperature dependent alteration in purine transport
Authors: Harris J. F. , Whitmore G. F.
Published: February 2005

This paper reports the isolation of a phenotypically stable line of Chinese hamster ovary cells which exhibits a temperature dependent alteration in the transport of some purines. The alteration manifests itself for the uptake of guanine, hypoxanthine, azaguanine and guanosine but not for adenine, adenosine or thymidine. Studies with crude cell extracts suggest that, at the temperature the alteration is being expressed, the HGPRT activity is within the normal range. In cell‐cell hybridization studies the alteration behaves as a recessive genetic trait.
The localization of enzymatic activities involved in uridine nucleotides reactions in human erythrocytes
Authors: Boninsegna A. , Deana R. , Siliprandi Dagmar
Published: February 2005

Enzymatic activities involved in the transformations of uridine nucleotides by intact erythrocytes and their subfractions have been studied and the following enzymatic activities have been identified: UTPase, UDPase, UMPase and uridylate kinase.

UTPase activity was present exclusively in the stromal fraction while UMPase and uridylate kinase activities were specific in the soluble fraction. UDPase was present in both the stromal and soluble fractions.

This compartmentation in erythrocytes differs from that reported for the enzymes involved in adenine nucleotides transformations. Due to its sensitivity to Zn2+, uridylate kinase could be differentiated from adenylate kinase.
Selection for temperature‐sensitive mutants of diploid and tetraploid mammalian cells
Authors: McBurney Michael W. , Whitmore Gordon F.
Published: February 2005

Mammalian cell populations may be enriched for temperature‐sensitive (ts) mutants by the tritiated thymidine (3H‐TdR) suicide procedure (Thompson et al., '71). Such procedures were carried out on the near‐diploid Chinese hamster ovary (CHO) cell line and on a line made “tetraploid” by Colcemid treatment. Clones of ts mutants were obtained from the diploid line, but in spite of repeated attempts, no ts mutants were isolated from the tetroploid line. The phenotypes of the new diploid ts mutants recovered were consistent with the particular selection regime employed.
The role of humoral factors in the regression of leukemia in chickens as measured by in vitro colony formation
Authors: Silva R. F. , Dodge W. H. , Moscovici C.
Published: February 2005

Leukemic myeloblasts induced by avian myeloblastosis virus in the chicken formed small compact (type II) colonies in semi‐solid agar medium. Normal yolk sac cells from 12‐day old embryos formed large diffuse (type I) colonies under the same conditions. Type I colony formation (but not type II) was strictly dependent upon the presence in the medium of a colony stimulating factor (CSF) present in fresh chicken serum or conditioned medium. Serum CSF levels were determined for normal, leukemic, and birds which had spontaneously regressed from myeloblastic leukemia. When type I colony formation was used as the assay, serum CSF levels of leukemic birds were found to be significantly lower than levels in either normal or regressed birds. When the same sera were tested for their ability to induce type II colonies, leukemic birds demonstrated a significantly higher CSF level than either normal or regressed sera. Regressed chickens had serum CSF levels similar to normal birds.
Changes in the uptake of 2‐deoxy‐D‐glucose in Balb/3T3 cells chemically transformed in culture
Authors: Oshiro Y. , Dipaolo J. A.
Published: February 2005

Balb/3T3 cells transformed in culture by chemical carcinogens were shown to multiply in a medium supplemented with 2% calf serum or with 10% agamma new‐born calf serum. The cell lines that multiply well in medium supplemented with 10% agamma serum produced a higher incidence of tumors in X‐irradiated weanling mice than the lines that multiply poorly. The difference in 2‐deoxy‐D‐glucose uptake into exponentially growing transformed and un‐transformed cells was 50–100%. In crowded cultures untransformed Balb/3T3 cells ceased taking up the sugar, while chemically transformed cells continued at the same rate even at high cell densities; thus, the difference became greater in crowded cultures. When the serum concentration in the media was reduced from 10% to 2%, untransformed Balb/3T3 cells took up the sugar at a reduced rate, while chemically transformed cells were only slightly affected; agamma new born calf serum supplemented medium had no effect on sugar uptake in any of the cells. When the serum concentration was changed from 2% to 10%, untransformed cells increased sugar uptake followed by cell division. The immediacy (within 15 min) of the response in the sugar uptake to 10% serum concentration suggested that the increased uptake rate and the consequent higher concentration of the sugar (D‐glucose in normal situation) within Balb/3T3 cells triggered the cell cycle. Chemical carcinogens appear to alter permanently the uptake mechanism for a key nutrient.
Viral probe into the events of cellular (in vitro) aging
Authors: Pitha Josef , Adams Robert , Pitha Paula M.
Published: February 2005

Viral infection by vesicular stomatitis virus (VSV) as well as cellular protection against it were studied in cultured human diploid fibroblast cells (WI38 strain) of varying senescence (passage) level. Full protection against viral infection can be achieved by pretreatment of cells with an interferon inducer (complex of polycytidylate and polyinosinate) or by pretreatment with concentrates of interferon itself. The late passages (over 45) require higher concentration of both agents than the medium passages (25–45); a complete failure of protective mechanisms occurs only close to cellular death. Furthermore, effects of confluency and of duration of induction impulse were studied. WI38 cells are sensitive to VSV infection through their entire life span; however, during the last passage before their death by senescence, VSV replication is significantly decreased. It is concluded that even in relatively senescent cells (a) protection mechanisms which were not used previously can be activated, (b) synthesizing machinery necessary for efficient support of viral replication is sustained, and (c) release of lysosomal enzymes ending the viral replication does not begin sooner than with cells of earlier passage level.
Effect of 5‐bromodeoxyuridine on incorporation of RNA precursors in sea urchin embryos
Authors: Fitzmaurice Leona C. , Baker Robert F.
Published: February 2005

Exposure of early sea urchin embryos to 5‐bromodeoxyuridine (at concentrations up to 100 μg per ml) severely decreases the uptake of exogenous 3H‐uridine into RNA. However, the actual gross rate of DNA or RNA synthesis in these embryos appears not to be affected by the presence of 5‐bromodeoxyuridine.
Interaction of alcohols with the transport system of glucose in human erythrocytes
Authors: Lacko L. , Wittkeand B. , Geck P.
Published: February 2005

Alcohols inhibit the exchange transport of glucose in human erythrocytes. Comparing the inhibition by monohydroxy‐alcohols, which have different distribution coefficients between medium and membrane, shows that the degree of inhibition depends mainly upon the concentration of the alcohol in the membrane.

1‐butanol exerts a mixed‐type inhibition; Vmax decreases and Km increases. Since also the Km of the equilibrium transport increases upon the addition of the alcohol, the changes in the Km of exchange transport cannot be attributed solely to the differently affected mobilities of the loaded and free carrier, but the affinity of glucose to the transport system is reduced.

The transport system can bind two alcohol molecules. With one alcohol molecule bound the affinity of the transport system for the second alcohol molecule already increases.

The nature of the bond of the alcohols to the transport system is discussed and possible explanations for the cooperative effect upon the binding of the second alcohol molecule are offered.
The influence of sex steroids on calcium‐ and magnesium‐induced mitogenesis in isolated rat thymic lymphocytes
Authors: Morganand J. I. , Perris A. D.
Published: February 2005

Elevated calcium and magnesium concentrations promoted mitotic activity in rat thymic lymphocyte cultures. Oestradiol inhibited calcium‐ but not magnesium‐induced mitogenesis. One prerequisite for the mitogenic action of calcium is a raised intracellular concentration of cyclic adenosine 3′5′ monophosphate (cyclic AMP) but cyclic AMP‐induced mitogenesis was insensitive to oestradiol. This suggests that the steroid blocks the mitogenic process at a stage preceding the endogenous cyclic AMP elevation. Furthermore the mitogenic actions of adrenaline, which stimulates adenylate cyclase (the enzyme responsible for cyclic AMP biosynthesis), and caffeine, which inhibits phosphodiesterase (the enzyme which degrades cyclic AMP) were also insensitive to oestradiol inhibition. This precludes a direct effect of the steroid on these enzymes. However, oestradiol did inhibit the mitogenic action of parathyroid hormone (PTH). Since the mitogenic action of PTH probably involves increased calcium entry to the cell, oestradiol may block this ion influx.

The inhibition of calcium‐ and PTH‐induced mitogenesis must be attributable to some structurally specific action of oestradiol. The steroids cholesterol, progesterone and testosterone all failed to reduce calcium‐induced mitogenesis, whereas both α and β oestradiol were effective.

In addition to its insensitivity to oestradiol inhibition, magnesium‐stimulated mitosis was unaffected by both imidazole and calcitonin at concentrations which significantly reduced calcium‐stimulated proliferation. These findings are compatible with the thesis that magnesium‐induced mitogenesis does not involve the elevation of cyclic AMP concentrations.
The deoxyribonucleoside transport systems of cultured Novikoff rat hepatoma cells
Authors: Plagemann Peter G. W. , Erbe John
Published: February 2005

The transport of various deoxyribonucleosides by cultured Novikoff rat hepatoma cells (subline N1S1‐67) follows normal Michaelis‐Menten kinetics. The transport reactions are competitively inhibited by most heterologous deoxy‐ and ribonucleosides and by Persantin and Cytochalasin B. Comparisons of the transport kinetics of the various deoxyribonucleosides (Km and Vmax ) and of the Km/Ki ratios for the inhibitions indicate that deoxythymidine, deoxyuridine and 5‐fluordeoxyuridine are transported by a single system, whereas deoxycytidine and the purine deoxyribonucleosides are transported by other systems. The data suggest that deoxyadenosine, deoxyguanosine and deoxyinosine, are not transported by a single system, but the number of transport systems involved could not be established unequivocally. Similar comparisons also suggest that the deoxyribonucleosides are transported by different systems than the ribonucleosides. All deoxyribonucleoside transport systems are inhibited to about the same extent by Persantin (Ki = 1–2 μM) and Cytochalasin B (Ki = 4–12 μM). The inhibitions of deoxynucleoside transport resulted in corresponding apparent competitive inhibitions of their incorporation into nucleic acids.
Chromosome patterns of nontransformed variants from chemically transformed Balb/3T3 cells
Authors: Olinici C. D. , Evans C. H. , DiPaolo J. A.
Published: February 2005

Nine variant cell lines isolated from cloned 7,12‐dimethylbenz(a) ‐ahthracene transformed Balb/3T3 mouse cells by treatment with FUdR had growth parameters closely resembling nontransformed cells. Chromosome analysis of the variant lines demonstrated that six variants had a diminished number and three variants had an increased number of chromosomes compared to the parental transformed cell line. All variants had unique marker chromosomes not present in the parental transformed Balb/3T3 cells. The distribution of marker chromosomes and heterochromatin suggested that the initial event in variant formation was a reduction in chromosome number with a subsequent polyploidization of the reduced chromosome complement.
The effect of calcium concentration on ACTH stimulation of steroidogenesis in mouse adrenal tumor cells
Authors: Wishnow Rodney M. , Feist Patty
Published: February 2005

Calcium is required for ACTH stimulated steroidogenesis in adrenal tumor cells in tissue culture. In the absence of calcium, the dose of ACTH required to induce half maximum steroidogenesis was increased 30 fold. In contrast to intact adrenal glands or isolated adrenal cells, high doses of ACTH (50 mU/ml) maximally stimulated steroidogenesis in the absence of calcium. Growth for up to six days in medium with low calcium did not affect basal or ACTH induced steroidogenesis. The addition of calcium to cells incubated with ACTH produced a maximum steroidogenic response in 15 minutes. In contrast to intact adrenal glands, calcium is not required for adenosine‐3′,5′‐cyclic monophosphate (cyclic AMP) stimulated steroidogenesis in adrenal tumor cells. These experiments support the concept that calcium is important at the level of ACTH‐membrane receptor site interaction or activation of adenyl cyclase in adrenal tumor cells.
Plasma membrane ectoglycosyltransferase activity of L1210 murine leukemic cells
Authors: Bernacki R. J.
Published: February 2005

L1210 murine leukemia cells after treatment with Cl. perfringens neuraminidase at pH 7.0 incorporated six times more N‐acetylneuraminic acid‐[C14] than control cells when incubated for 30 minutes with cytidine 5′‐monophosphate N‐acetylneuraminic‐[C14] acid and three times more galactose‐[C14] when incubated with uridine diphosphate galactose‐[C14]. These sugars were incorporated in a 10% trichloracetic acid insoluble fraction and more than 75% of the incorporated N‐acetylneuraminic acid‐ [C14] could be removed by further treatment of these cells with neuraminidase. The incorporation of N‐acetylneuraminic acid‐ [C14] as a function of time was divided into two rates: a rapid one, active during the first 30 minutes followed by a slower one, similar to the rate observed with untreated cells. The addition of Ba++ and Ca++ ions at 8.3 mM increased the incorporation of N‐acetylneuraminic acid‐ [C14] by 25% while 8.3 mM EDTA decreased activity by 58% . The addition of Zn++ or Hg++ at similar concentrations abolished the incorporation almost completely. The optimal pH for the incorporation of N‐acetylneuraminic acid‐ [C14] by these neuraminidase treated cells was 6.5. These data suggest that ectoglycosyltransferases are present on the outer surface of the plasma membrane of L1210 cells and are able to catalyze the addition of radiolabeled nucleotide sugars onto macromolecular acceptors (cell surface glycoproteins and glycolipids) prepared by prior incubation of the cells with neuraminidase. Use of these procedures for labeling outer cell surfaces may also prove to be valuable for the study of plasma membrane glycoprotein and glycolipid structure, synthesis, and turnover.
Studies on a chinese hamster line that is temperature sensitive for the commitment to DNA synthesis
Authors: Smith B. J. , Wigglesworth N. M.
Published: February 2005

The Chinese hamster cell line K12 is temperature sensitive for the initiation of DNA synthesis and for the programming of rounding up to enter mitosis. Viability is lost expontentially after twelve hours at the non‐permissive temperature. This temperature sensitivity is reversed following exposure of K12 cells to SV40 virus.
Dynamic osmotic behavior of chick blood lymphocytes
Authors: Doljanski F. , Ben‐Sasson S. , Reich M. , Grover N. B.
Published: February 2005

The dynamic response of chick blood lymphocytes to hypotonic shock is investigated using electrical sizing techniques, and an attempt is made to characterize the mechanisms involved. The cells first swell rapidly, as expected, but then gradually return to their initial volume. Maximum volume is attained in 2 minutes and the return is complete within about 15 minutes at room temperature. This cycle is studied under different osmotic strengths, temperatures, and cation compositions; behavior following successive hypotonic and hypertonic shocks is also described. Metabolic inhibitors are shown to have no effect, even at relatively high concentrations, while ouabain (10−3 M) affects only the much slower second‐order return process that sets in when the main one is blocked by appropriate external cation concentration.

It is proposed that a large increase in membrane permeability to K+ occurs as the cell swells beyond its iso‐osmotic volume, but none to Na+. The experimental results are then explained by ascribing the swelling to water entering the cell until the osmotic pressure inside equals that outside, and the return phase to the electrochemical potential gradient for K+ forcing it out of the swollen cell together with the associated anion and water in proportions that preserve osmotic equilibrium. This latter is a non‐active process independent of Na+ whose direction can be reversed by using K+ as the cation in the external medium.

The existence in the literature of several related observations is pointed out and some of the implications of our findings are discussed briefly in terms of a corrugated membrane structure.
Release of cytoplasmic enzymes into culture fluid
Authors: Nose Kiyoshi , Nitta Keiko , Takaoka Toshiko , Katsuta Hajim
Published: February 2005

The release of enzymatic activities from cells grown in protein‐and lipid‐free synthetic media into culture fluids was investigated. Cell strains employed were the derivatives from mouse fibroblasts, rat liver parenchymal cells, rat ascites hepatoma cells and HeLa cells. Activities of acid DNase, acid RNase and alkaline phosphatase (ALP)‐I were detected in culture fluids as early as one day after renewal of medium, whereas those of β‐glucuronidase and acid phosphatase were not found. This release of enzymes was unlikely to be caused by cell disruption during cultivation.

The release of Dnase was inhibited by the addition of cycloheximide or actinbomycin D, whereas that of ALP‐I was not inhibited.
Factors affecting division rhythmicity in Euglena gracilis
Authors: Cook J. R.
Published: February 2005

In phototrophic culture of Euglena gracilis, good synchrony was found only under rather restricted programs of light‐dark cycles, and rather narrow ranges of temperature and light intensity, when cultures were flushed with air fortified with adequate amounts of CO2. When flushed with air alone, CO2 was found to be limiting, and while cell divisions were rhythmic, less than a doubling of cell number occurred in division bursts. With air as gas phase, rhythmic division activity was maintained over wide ranges of temperature, light intensity, and the ratio of light:dark in a given program; all these factors affected the amplitude of the division burst, however.
In vitro response of goldfish (Carassius auratus L.) dermal melanophores to cyclic 3, 5′‐nucleotides, nucleoside 5′‐phosphates and methylxanthines
Authors: Abramowitz Joel , Chavin Walter
Published: February 2005

cAMP, dbcAMP, cCMP, cGMP, theophylline and caffeine caused reversible melanosome dispersion within 5 minutes at 10 mM in the dermal melanophores of the black goldfish, Carassius auratus L. cTMP, cUMP, 5′‐AMP, 5′‐CMP, 5′‐GMP, 5′‐TMP, and 5′‐UMP did not produce melanosome dispersion or aggregation in this melanophore system. cAMP was the most effective nucleotide in the induction of melanosome dispersion; at 10 mM, cGMP and at 5 mM, dbcAMP were the least effective of those nucleotides inducing melanosome dispersion. At the 10 mM level dbcAMP required 30 minutes to evoke the same degree of melanosome dispersion as 5 minutes cAMP treatment. Theophylline was more effective than caffeine in eliciting melanosome dispersion. At 1 mM, theophylline and caffeine first induced melanosome dispersion which was followed by aggregation in the course of the 30 minute test period. These reactions suggest both a high melanophore phosphodiesterase activity and competitive inhibition of phosphodiesterase by theophylline and caffeine. Induction of melanosome dispersion by several cyclic 3′,5′‐nucleotides suggest multi‐nucleotide control of melanosome dispersion. These findings also support a proposed mechanism of prostaglandin induced melanosome dispersion as well as the “second messenger” hypothesis.
Effect of cAMP on nucleoside metabolism II. Cell cycle dependence of thymidine transport
Authors: Roller Barbra A. , Hirai Kanji , Defendi Vittorio
Published: February 2005

We have shown previously that adenosine 3′5′ cyclic monophosphate (cAMP) increased the transport of thymidine into monkey cells (CV‐1) without affecting DNA synthesis (Roller et al., '74). Using techniques of cell synchronization, cell separation and DNA synthesis inhibitors in CV‐1 and other cell lines, we now report that thymidine transport at low thymidine concentrations increases during the S phase of the cell cycle and that initiation of DNA synthesis is necessary for thymidine transport, although continuation of DNA synthesis is not necessary. Cyclic AMP alters nucleoside transport by increasing the Vmax for the transport reaction, but has no effect on the Km. Cyclic AMP is found not to affect the time in the cell cycle when thymidine transport occurs or the quality of the transport reaction, and only affects the amount of thymidine transported.
Heterogeneity of molecules with low molecular weight isolated from media conditioned by human leukocytes and capable of stimulating colony formation by human granulopoietic progenitor cells
Authors: Price G. B. , Senn J. S. , McCulloch E. A. , Till J. E.
Published: February 2005

Molecules of low molecular weight, able to stimulate colony formation by human granulopoietic cells, were prepared from media conditioned by normal and leukemic human peripheral blood leukocytes. When molecules from these sources were studied, heterogeneity was observed in their ability, after radioiodination, to bind and suicide granulopoietic progenitors, in their radiolabelled tryptic digestion products and in their biological activity as stimulators of granulocyte colonies.
The biosynthesis and turnover of nicotinamide adenine dinucleotide in enucleated culture cells
Authors: Rechsteiner Martin , Catanzarite Valerian
Published: February 2005

Nicotinic acid mononucleotide (NaMN) and nicotinamide mononucleotide (NMN) have been proposed as intermediates in the biosynthesis of nicotinamide adenine dinucleotide (NAD) from nicotinic acid and nicotinamide respectively. Although NaMN and NMN were not detected in acid extracts from whole D98/AH2 cells following pulses with 3H‐nicotinic acid and 3H‐nicotinamide, they were observed following pulses of enucleated cells. Several experiments indicate that enucleated cells are incapable of synthesizing NAD and that biosynthesis stops with mononucleotide formation. These results provide support for the idea, based upon fractionation studies, that NAD pyrophosphorylase (which catalyzes the reaction NMN or NaMN + ATP → NAD or desamido‐NAD) is localized exclusively in the nucleus.

Acid extraction and chromatography were also used to compare the stability of 3H‐NAD in enucleated and whole cells. In the presence of the glutamine analog, azaserine, the intracellular concentration of 3H‐NAD decreased exponentially with a half‐life of 4 hours in whole cells. In enucleated cells the intracellular concentration of 3H‐NAD decreased with a half‐life greater than 14 hours. The increased stability of NAD in enucleated cells was confirmed by autoradiography. These results demonstrate the key role of the nucleus in both the biosynthesis and turnover of NAD.
The origin of chicken hematopoietic colonies as assayed in semisolid agar
Authors: Dodge W. H. , Silva R. F. , Moscovici C.
Published: February 2005

This investigation was undertaken to determine whether primitive stem cells and/or fully differentiated macrophages were the source of in vitro colonies derived from hematopoietic tissues.

The chicken colony‐forming cell (CFC) present in uncultured yolk sac was a nonadherent, presumably undifferentiated cell. The efficiency of colony formation in this case was approximately 0.08%. In contrast to uncultured yolk sac, the CFC present in one‐week old yolk sac cultures was evidently a macrophage. Yolk sac cultures, which consisted of greater than 99% macrophages, produced colonies with an efficiency of 1–5% while cultures derived from peritoneal macrophages produced colonies with an efficiency of 10%. Silica selectively destroyed macrophages and reduced the colony forming efficiency of cells derived from yolk sac cultures.
Mutants of Chinese hamster cells resistant to adenosine
Authors: McBurney Michael W. , Whitmore Gordon F.
Published: February 2005

Chinese hamster cells do not grow in medium containing high concentrations of adenosine because pyrimidine biosynthesis is inhibited. Adenosine metabolism was examined in two mutant cell lines isolated on the basis of resistance to adenosine. One line was deficient in adenosine kinase suggesting that high intracellular AMP concentrations may block pyrimidine synthesis indirectly in wild type cells by inhibiting PRPP synthetase. Although no enzymatic defect could be identified in the other cell line, these cells inefficiently utilize adenosine supplied in the medium.
Effect of leucine on the temperature sensitive phenotype of a mammalian leucyl‐tRNA synthetase mutant
Authors: Molnar S. J. , Rauth A. M.
Published: February 2005

The concentration of leucine in the growth medium has been found to influence the expression of the temperature sensitive phenotype of a mutant of Chinese hamster ovary cells with an altered leucyl‐tRNA synthetase. Plating efficiency and growth studies showed that increasing the leucine concentration allows cells to survive at normally non‐permissive high temperatures and conversely decreasing the leucine concentration enhances the adverse effects of high temperature. A similar but smaller effect was noted with isoleucine. It is suggested that this observation may form the basis of a rapid test, useful in directing the investigation of the lesion in similar mutants to pathways involving specific amino acids.
The effects of ouabain on the cell mitotic cycle of mouse lymphoblasts
Authors: Cuff Joyce M. , Lichtman Marshall A.
Published: February 2005

The inhibition of cell proliferation by ouabain has been analyzed with respect to the cell cycle. Three lines of evidence indicate that growth rate is modified by altering to different degrees the rate of progress through stages of the cell cycle: (1) a three hour lag occurs between the time of ouabain addition and the inhibition of proliferation; (2) ouabain must be present at least two to four hours prior to the mitotic burst of synchronized cells for inhibition of mitosis to occur; (3) parasynchrony is observed when cells are resuspended in ouabain‐free medium after 12 hours of exposure to ouabain.

Analysis of the distribution of cells in each of the stages of the cell cycle at various times during ouabain treatment reveals a progressive increase in the fraction of cells in S with a concomitant decrease in the percent of cells in each of the other stages. These results indicate that the prolongation of the cell cycle time in the presence of ouabain is due primarily to an S stage block.
The effect of insulin on basal and hormone‐induced elevations of cyclic AMP content in cultured human fibroblasts
Authors: Rosenthal Judith W. , Goldstein Samuel
Published: February 2005

Studies were carried out on confluent cultures of human fibroblasts to explore the effect of insulin on basal and hormone‐induced elevations of intracellular cyclic AMP content during short‐term incubations in serum‐free medium. Insulin tended to decrease basal levels of cyclic AMP but this was not statistically significant. Similarly, insulin was unable to block the elevations of intracellular cyclic AMP content induced by PGE1, epinephrine and glucagon. Paradoxically, when cells were preincubated with insulin, PGE1‐stimulated cyclic AMP elevation was potentiated, possibly because insulin was conserving factors needed for a maximal PGE1 stimulus or retarding the leakage of cAMP itself. The results indicate that insulin has little or no direct effect on cyclic AMP metabolism in cultured human fibroblasts and is consistent with the known insensitivity of these cells to insulin for other parameters.
Conditionally lethal mutations in Chinese hamster cells. Characterization of a cell line with a possible defect in the krebs cycle
Authors: Defrancesco L. , Werntz D. , Scheffler I. E.
Published: February 2005

A variant Chinese hamster cell line has been isolated from a mutagenized population that has a markedly reduced ability to oxidize a variety of substrates via the Krebs cycle. The production of 14CO2 from 14C‐labeled compounds was measured using pyruvate, acetate, β‐hydroxybutyrate, palmitate and glutamate, and in all cases it was negligible in the mutant. In contrast to this, significant amounts of 14CO2 were produced from 14C‐aspartate and 14C‐succinate which suggests that some reactions of the Krebs cycle can take place and this conclusion is supported by tracer experiments with labeled compounds. The rate of respiration measured with a Clark oxygen electrode in the mutant was compared to several normal Chinese hamster cell lines and was found to be only 8%. Mitochondria appear to be present in normal numbers and with only minor differences in morphology. The measurement of difference spectra between oxidized and reduced states permits us to conclude that the cytochromes are all present and functional. These results lead us to believe that there may be a defect in the Krebs cycle between α‐ketoglutarate and succinate. Alternatively a defect in a structural component of the mitochondria or in the electron‐transport chain itself may be causing pleiotropic effects in the Krebs cycle and respiration.
Acetylcholine‐induced initiation of thymic lymphoblast DNA synthesis and proliferation
Authors: Macmanus J. P. , Boynton A. L. , Whitfield J. F. , Gillan D. J. , Isaacs R. J.
Published: February 2005

Low (5 × 10−9 M to 10−7 M) acetylcholine concentrations cause a calcium‐independent stimulation of the initiation of DNA synthesis and proliferation of lymphoblasts which are part of rat thymocyte populations suspended in vitro. A much higher (5 × 10−5 M) acetylcholine concentration also stimulates lymphoblast DNA synthesis and proliferation, but this action is calcium‐dependent. This proliferogenic response to acetylcholine is however not clearly mediated by either cyclic GMP or cyclic AMP.
The effect of the herbicide 2,4,5 trichlorophenoxy acetic acid (245T) on the growth and metabolism of Tetrahymena pyriformis
Authors: Silberstein Gary B. , Hooper Alan B.
Published: February 2005

The herbicide 2,4,5 trichlorophenoxy acetic acid (245T) at concentrations from 0.5 to 0.9 mM, was found to inhibit respiration and then growth in exponentially growing cultures of Tetrahymena pyriformis. Cell division was stopped for periods up to 60 minutes after which the cells recovered and division resumed. Recovery of oxygen utilization and cell division occurred in the presence of 245T. 245T was shown to inhibit mitochondrial oxygen utilization. Mitochondria from cells that had recovered from 245T treatment lost their sensitivity to low concentrations of the herbicide and sedimented deeper in a sucrose gradient than mitochondria from control cells.
Differentiation of erythroleukemic cells in vitro: Irreversible induction by dimethyl sulfoxide (DMSO)
Authors: Preisler Harvey D. , Giladi Miriam
Published: February 2005

The inclusion of DMSO in the media of suspension cultures of Friend erythroleukemia cells results in the erythroid differentiation of these cells. The studies reported here were directed towards answering two questions: (1) How long an exposure to DMSO is necessary to induce the differentiation of these cells; and (2) What is the fate of the differentiating cells when DMSO is removed from the medium. Exposure to DMSO for less than 24 hours failed to produce any detectable evidence of erythroid differentiation. On the other hand, culture in the presence of DMSO for 24 hours followed by culture in DMSO‐free medium for four additional days produced a small but detectable increment in the proportion of benzidine positive cells in the culture. Once the differentiation of an individual cell was initiated, the process continued after removal of DMSO from the medium. The cell became progressively more differentiated as evidenced by increases in the intensity of benzidine staining as well as in the rate of heme synthesis and heme content. However, when cells which had been induced to differentiate by DMSO were cultured in DMSO‐free medium for more than 3–4 days, they became vacuolated and apparently died. This latter phenomenon, as well as the more rapid proliferation of the undifferentiated cells in the culture, accounts for the observation that when new cultures are established from cultures which have been grown in the presence of DMSO for several days, the culture which results ultimately contains only differentiated cells.