bluuebunny/crossref_metadata_2025_split huggingface dataset:
Expression of the neuron‐specific protein, 14‐3‐2, and steroid sulfatase in neuroblastoma cell hybrids
Authors: Arthur McMorris F. , Kolber Alan R. , Moore B. W. , Perumal A. S. 
Published: February 2005

AbstractThree series of neuroblastoma X fibroblast hybrid clones were isolated from crosses between mouse or human fibroblasts and mouse or human neuroblastoma cell lines by virus‐mediated cell fusion. The expression of 14‐3‐2 protein (an acidic protein specific to neurons) and steroid sulfatase activity was studied in parental and hybrid cell lines. Steroid sulfatase was extinguished in hybrids when only one parent expressed the enzyme, but was expressed in one hybrid combination in which both parents expressed the enzyme. The neuron‐specific 14‐3‐2 protein, on the other hand, continued to be expressed in all three series of neuroblastoma x fibroblast hybrids. In most cases where these pheno‐types were expressed, they also exhibited temporal modulation; that is, specific activity is low during logarithmic growth and increases markedly during stationary phase. The glial‐specific protein S‐100 is absent from all parents and hybrids. The results are discussed in terms of mechanisms of regulation of differentiated phenotypes in mammalian cells.
Maturation of membrane function: The permeability of the rat erythroblastic leukemic cell to water and to non‐electrolytes
Authors: Hempling H. G. , Wise W. C. 
Published: February 2005

AbstractThe erythroblastic leukemia produced in Long‐Evans rats by the administration of 7, 8, 12 trimethylbenz (a) anthracene has been used as a model of the most immature form of the erythrocyte series. In conjunction with studies of the maturation of several other membrane functions, the permeability of this cell to water and to certain definitive non‐electrolytes was measured with osmotic methods. The hydraulic conductivity, Lp was 6.2 micro (minute)−1, (atm)−1 at 25°C, quite high and characteristic of mature erythrocytes, but different from values of 0.65 for immature myeloid cells. The effect of temperature provided an energy of activation of 4.4 kCal/mole, also typical of mature mammalian erythrocytes but again different from 13 to 18 kCal/mole for immature myeloid cells. Urea was compared to thiourea. The permeability coefficient for urea was 76.7 micra (minute)−1 ± 13.8 (S. E.); the value for thiourea was 1.55 micra (minute)−1 ± 0.18 (S. E.). Phloretin at 0.25 mM inhibited urea permeability by 90% with 50% inhibition occurring at 0.05 mM. Inhibition was reversible. Permeability to the glycols was also compatible with mature erythrocytes. We infer from these findings that the structure which underlies these basic, passive membrane functions is laid down early and persists after loss of nucleus and subsequent maturation.
The binding of cationized ferritin at the surfaces of ehrlich ascites tumor cells: The effect of pH and glutaraldehyde fixation
Authors: Subjeck J. R. , Weiss L. 
Published: February 2005

AbstractThe densities of cationized ferritin (CF) particles binding to the surfaces of cultured Ehrlich ascites tumor cells were determined at pH 7.4, where the ferritin stain was applied either prior to or following glutaraldehyde fixation. The densities were also determined with CF adjusted to pH 1.9 and applied after fixation. For all fixed samples there was a higher density of particles bound to microvilli than to the spaces between them. Treatment with neuraminidase removed more particles from microvilli than from the intermicrovillus spaces, but did not reduce the levels of binding to the same value.When cationized ferritin is applied prior to fixation, an aggregation of the CF particles at the cell surface was observed, with the internalization of some clusters. This effect was independent of neuraminidase treatment.
Relationship of energy production to gluconeogenesis in renal cortical tubules
Authors: Suzuki Tadao , De Hartog Maria , Gordon Edwin E. 
Published: February 2005

AbstractIsolated tubules prepared by collagenase treatment of rat renal cortex retained their ultrastructural integrity and responded to added lactate and succinate with an increase in gluconeogenesis and respiration. Inhibition of the mitochondrial respiratory chain with rotenone, or energy conservation sites with oligomycin caused a marked reduction in respiration and ATP content thereby completely inhibiting net gluconeogenesis. Dissociation of gluconeogenesis from respiration was accomplished with quinolinic acid and hydrazine, inhibitors of gluconeogenesis. At 5 × 10−3 M quinolinic acid, gluconeogenesis from succinate was inhibited approximately 50% and from lactate nearly 100%. This concentration of quinolinic acid did not affect oxygen uptake or the ATP content of tubules in the presence or absence of substrate. Hydrazine at 10−3 M resulted in approximately 75% inhibition of glucose formation from succinate and complete inhibition from lactate without interfering with respiration or ATP content. The increased mitochondrial energy generation, as manifested by accelerated respiration was independent of gluconeogenesis. The unchanging cell ATP concentration with a higher respiratory rate upon addition of exogenous substrate bespeaks increased ATP turnover. ATP utilization for the substrate‐induced enhancement of gluconeogenesis could not account for the increment in ATP hydrolysis.
Growth limitation of 3T3 mouse fibroblasts by available growth surface area and medium components
Authors: Thrash Cornelia R. , Cunningham Dennis D. 
Published: February 2005

AbstractStudies with untransformed fibroblasts demonstrate that growth of these cells in culture can be limited by the availability of both growth surface and medium components. Experiments using cells grown on coverslips, in which the only variable was available growth surface, indicate that when the medium to cell ratio is high, surface area is the principal factor limiting growth. At low medium to cell ratios, however, growth of cells is predominantly limited by medium components. The final number of cells per culture is almost directly proportional to available surface area when the culture medium is changed daily.
Isolation and studies of the granules of the amebocytes of Limulus polyphemus, the horseshoe crab
Authors: Mürer Erik H. , Levin Jack , Holme Randi 
Published: February 2005

AbstractGranules were isolated from the cytoplasm of the amebocytes of Limulus polyphemus, the horseshoe crab, by disruption of cells obtained from blood which had been drawn into 2 mM propranolol. The granules subsequently were purified by centrifugation through a sucrose gradient that contained heparin. Extracts of the granules were prepared by freezing and thawing the granule preparations in distilled water.Transmission and scanning electron microscopy of the granules revealed round or ovoid particles. However, only one type of granule appeared to be present. The ultraviolet spectrum of the extract of amebocyte granules demonstrated a peak at 277 nm at pH 7.4, and a shift into two peaks of 281 nm and 290 nm at alkaline pH. Analytical ultracentrifugation revealed a pattern similar to that observed with lysates prepared from intact amebocytes. Polyacrylamide gel electrophoresis, in the presence of urea at pH 4.5, demonstrated patterns similar to those observed with amebocyte lysate. Extracts of the granules were gelled by bacterial endotoxin.The blood of the horseshoe crab contains only one type of cell, the amebocyte. Previous studies have shown that the blood coagulation mechanism of Limulus is contained entirely within amebocytes. The current studies suggest that the granules, which pack the cytoplasm of these cells, contain all of the factors required for the coagulation of blood, including the clottable protein. The intracellularly localized coagulation system is released from amebocytes when their granules rupture during cell aggregation.
Chromosome balance and the control of malignancy
Authors: Bloch‐Shtacher Navah , Sachs Leo 
Published: February 2005

AbstractThe Giemsa banding pattern of the chromosomes has been analyzed in a line of transformed golden hamster cells, revertant and re‐revertant cells and their tumors. The transformed and re‐revertant cells were malignant in vivo and had gained an additional chromosome 57. Revertants with a suppression of malignancy lost this additional chromosome 57 and gained an additional chromosome 72. The tumors produced by segregants from the revertant cells were malignant, although to a lower degree than transformed and re‐revertant cells. These tumors had lost the additional chromosome 72 found in revertants and gained one or two 512 chromosomes. The results support the hypothesis that the balance between genes for expression and suppression controls malignancy. The data indicate that chromosome 72 carries genes for suppression and that chromosomes 57 and 512 carry genes for expression of malignancy. The genes on chromosome 57 seem to result in a greater degree of expression than the genes on chromosome 512. The chromosome balance that controlled malignancy in these cells, also controlled the expression and suppression of transformed properties in vitro.
Non‐histone protein synthesis during G1 phase and its relation to dna replication
Authors: Gerner Eugene W. , Meyn Raymond E. , Humphrey Ronald M. 
Published: February 2005

AbstractThe kinetics of non‐histone chromosomal protein (NHCP) synthesis were studied in Chinese hamster ovary (CHO) plateau phase cells stimulated to proliferate and were compared to NHCP synthesis kinetics in two populations of synchronous G1 traversing cells. In all cases, NHCP synthesis rates increase 3‐ to 5‐fold as cells traversed G1 and attained maximum values one hour before semi‐conservative DNA replication began. Similar to results in synchronous G1 cells, the molecular weight distributions of the NHCP fraction from stimulated plateau phase cells underwent only minor changes, measured by sodium dodecylsulfate (SDS) polyacrylamide gel electrophoresis, as these cells moved toward S phase. Yet, during this progression after plateau phase and in the transition from early G1 to late G1 in synchronous cells, the total NHCP fraction increased significantly (1.5–2‐fold) in amount per cell. These data indicate that plateau phase cells are similar to early G1 cells, both in terms of their amounts of non‐histone per cell and in their subsequent NHCP synthesis kinetics as they move toward S phase. These results extend previous findings which suggested that NHCP synthesis was coupled to DNA replication and demonstrate that the increased NHCP synthesis and accumulation in chromatin may be a biochemical marker for G1 progression.
Degradation of abnormal proteins in heLa cells
Authors: Hendil Klavs B. 
Published: February 2005

AbstractThe experiments show that abnormal proteins are degraded faster than normal ones in HeLa cells. Among the fragmentary proteins made in the presence of puromycin, those with low molecular weight are least stable. Proteins made after incubation with 5‐fluorouracil or in the presence of some amino acid analogues are also unstable. Breakdown of proteins made in the presence or absence of puromycin is nearly unaffected by cycloheximide and is independent of pH between 7 and 8.
Formation of thymidine kinase and deoxycytidylate deaminase in synchronized cultures of chinese hamster cells temperature‐sensitive for DNA synthesis
Authors: Kit Saul , Jorgensen George N. 
Published: February 2005

AbstractCytosol thymidine kinase (TK) and deoxycytidylate (dCMP) deaminase formation was investigated in synchronized cultures of K12 Chinese hamster cells which have a temperature‐sensitive lesion affecting the initiation of DNA synthesis. Enzyme formation was found to be cycloheximide‐sensitive and also temperature‐dependent. Beginning at about six hours after addition of medium with 10% calf serum to serum‐depleted K12 cultures, cytosol TK and dCMP deaminase activities increased when the cultures were incubated at 36.5°, but not at 40.5°. When cultures were shifted from 36.5° to 40.5° at 4, 6, or 8 hours after serum addition, TK activity continued to increase, though not to the level observed at ten hours in cultures maintained at 36.5°. Actinomycin D addition at the time of serum reversal or four hours later blocked the TK increase normally observed at the permissive temperature at ten hours. However, when actinomycin D addition was delayed for six or eight hours after serum addition, the increase in TK measured at ten hours resembled that observed in the temperature shift‐up experiments. The results provide evidence that the mutation in K12 Chinese hamster cells most likely blocks the progression through G1 into S and suggest that transcription or post‐transcriptional processing required for TK formation is affected.
Membrane transport in synchronized ehrlich ascites tumor cells: Uptake of amino acids by the A and L system during the cell cycle
Authors: Tupper Joseph T. , Mills Barry , Zorgniotti Flavia 
Published: February 2005

AbstractUsing the double thymidine block technique. Ehrlich ascites tumor cells (ELD) carried in continuous spinner culture have been synchronized. Simultaneous monitoring of 3H‐thymidine incorporation, cell number and mitotic index yielded a cell cycle time of approximately 13.5 hours. This is composed of an S period of 3–4 hours, G2 of 6–8 hours and M of 1–2 hours. No appreciable G1 is present.Ehrlich cells synchronized in this manner were used to investigate the characteristics of two neutral amino acid transport systems during progression through the cell cycle. Unidirectional influx via the Na‐dependent system A was studied using C14‐alpha‐aminoisobutyrate (AIB) as substrate. The Na‐independent system L was monitored using 3H‐leucine and 14C‐cycloleucine as substrates. Transport by the A system was minimal in M and early S. It underwent a three‐fold increase during late S and early G2. In mid G2 the transport via this system rapidly dropped and remained low again through M and early S. The intracellular/extracellular ratios of AIB indicate that the system is actively transporting AIB throughout the cell cycle. The minimum ratios of approximately 3 were achieved during early M and the maximum ratios of approximately 9 were achieved in late S, early G2. The uptake of leucine and cycloleucine by the L system was quite different during the cell cycle. Maximal unidirectional influx by this system occurred during early and mid S period. Upon progression into G2 the transport rate dropped and remained reduced throughout M. Intracellular/extracellular ratios of leucine or cycloleucine were near unity at the peak of the transport activity (early S) and dropped to values of 0.5 to 0.6 throughout the remainder of the cycle. This result indicates that inward transport by the L system is, for the most part, non‐active in growing cells.
The nature of the cells generating B‐Lymphocyte colonies in vitro
Authors: Metcalf D. , Wilson J. W. , Shortman K. , Miller J. F. A. P. , Stocker J. 
Published: February 2005

AbstractB‐lymphocyte colonies were grown in semi‐solid agar from mouse spleen or lymph node cells in the presence of mercaptoethanol with or without added sheep red cells. High levels of colony‐forming cells were present in the spleen or normal mice and nu/nu (athymic) mice but colony‐forming cells were rare in the thymus and not detected in activated T‐lymphocyte populations. Colony‐forming cells were θ‐negative and most exhibited Fc receptors. Most colony‐forming cells had the sedimentation velocity of small lymphocytes, were non‐adherent and had a buoyant density similar to B‐lymphocytes. Colony‐forming cells were radiosensitive (Do 60 rads) and sensitive to cortisone. Colony formation was potentiated by the addition of adherent spleen cells or peritoneal macrophages. It is concluded that most cells forming B‐lymphocyte colonies are themselves characterisable as B‐lymphocytes.
Surface interactions between mammalian sperm and egg: Variation of spermatozoa concentration as a probe for the study of binding in vitro
Authors: Hartmann John F. , Hutchison Cameron F. 
Published: February 2005

AbstractThe pre‐penetration binding interactions between gametes of the golden hamster were investigated in vitro. Binding between capacitated spermatozoa and the surface of eggs, that is the zonae pellucidae with intact vitelli, as a function of the concentration of spermatozoa, followed a sigmoidal curve. This was in sharp contrast to the linear binding obtained with mechanically isolated zonae pellucidae (zonae lacking vitelli). Penetration of eggs as a function of the concentration of spermatozoa paralleled the binding curve that occurred between gametes. The binding curve obtained with uncapacitated spermatozoa and eggs was not sigmoidal but was linear after a slight lag and parallel to the curve obtained with uncapacitated spermatozoa and isolated zonae pellucidae. Taken together these results support previous work which implicated a vitelline factor in the binding reaction between the surfaces of eggs and capacitated spermatozoa. By scoring binding at one minute intervals it was possible to relate the rapid uninterrupted binding that occurs between capacitated spermatozoa and isolated zonae pellucidae with the equally rapid but transient and vitellus‐influenced binding that occurs between gametes. It was concluded that the vitelline factor acts by preventing most of the early type of binding that occurs between spermatozoa and isolated zonae pellucidae and not by terminating the early, rapid, initial binding as previously postulated. Thus, this early binding never occurs between most of the gametes that finally bind 30 to 40 minutes later and, therefore, does not play a role in the establishment of the late binding step which leads to penetration.
Increased susceptibility of murine teratocarcinoma cells to simian virus 40 and polyoma virus following treatment with 5‐bromodeoxyuridine
Authors: Speers Wendell C. , Lehman John M. 
Published: February 2005

AbstractCultures of the multipotential stem cell, embryonal carcinoma (EC), of a murine teratocarcinoma were treated with 5‐bromodeoxyuridine (BrdU). Within 2–4 days at concentrations of 1–50 m̈gm/ml of BrdU, there was a marked change in the morphology of cells observed by light and electron microscopy. A comparison of the growth potential showed that for up to four days the BrdU‐treated cultures were similar to untreated cultures. When these BrdU‐treated cells were infected with Simian virus 40 (SV40) and polyoma virus (Py), there was an increase in susceptibility of the treated cells. The untreated embryonal carcinoma cells were refractory. These results suggest that BrdU modifies the embryonal carcinoma cells to allow infection with two DNA viruses.
Degradation of abnormal proteins in HeLa cells
Authors: Prouty Walter F. 
Published: February 2005

AbstractCanavanine, an arginine analog, is incorporated into HeLa cell protein when cells are incubated in the absence of arginine, and this incorporation can result in the production of nonfunctional enzymes or abnormal proteins. The cells degrade these abnormal proteins up to three times more rapidly than normal cell proteins. The capacity for selective degradation of abnormal proteins is not limited to HeLa cells since human fibroblasts also showed increased degradative rates following exposure to canavanine. In addition, enhanced degradation is not a peculiar property of canavanine incorporation since other amino acid analogs also promoted protein degradation. Thus, mammalian cells have the capacity to recognize and selectively degrade abnormal proteins.
Energy metabolism in respiration‐deficient and wild type chinese hamster fibroblasts in culture
Authors: Donnelly M. , Scheffler I. E. 
Published: February 2005

AbstractThis paper presents a comparison of energy metabolism in wild type and respiration‐deficient Chinese hamster cells. From previous work (DeFrancesco et al., 75) it was concluded that the mutant satisfies essentially all of its energy requirements from glycolysis and in this study we measure precisely the amount of glucose consumed and lactate produced per milligram increment of protein in exponentially growing cultures. From these measurements we calculate the amount of ATP derived from glycolysis (and hence the total energy requirement for normal proliferation) to be 105 ± 15 μmoles ATP/δ mg protein in the mutant. It is 63 ± 10 μmoles ATP/δ mg protein derived from glycolysis in wild type cells. We present evidence that the total energy requirement of wild type cells is similar to that of the mutant, suggesting that ∼40% of the energy requirement is derived from respiration. The oxidation of glutamine appears to be more significant than the complete oxidation of glucose to CO2 in these Chinese hamster fibroblasts. The amount of ATP required by the mutant cells per milligram increment of protein is relatively independent of pH.
Density regulation of amino acid transport in cultured, androgen‐responsive tumour cells
Authors: Robinson Jeffery H. 
Published: February 2005

AbstractIn androgen‐responsive cells, activity of a sodium‐dependent transport system for neutral amino acids is shown to be density‐dependent, whereas activity of a sodium‐independent system is not. Transport of the nonmetabolizable amino acid, α‐aminoisobutyric acid (α‐aib) was largely sodium‐dependent, whereas transport of cycloleucine (cyleu) was by both sodium‐dependent and sodium‐independent systems. The Km for cyleu transport changed with density because only the sodium‐dependent portion of this transport was density‐dependent. By contrast, the Vmax for α‐aib transport changed with density, indicating that either the amount of functional membrane carrier or the activity of the sodium pump was affected.
Reversible independent alterations in glucose transport and metabolism in cultured human cells deprived of glucose
Authors: Salter Donald W. , Cook John S. 
Published: February 2005

AbstractWe have measured uptake of 3H‐hexoses into diploid human cells by exposing them to brief pulses of isotopic sugar during the log‐growth, subconfluent‐growth, and confluent‐growth (contact inhibited) phases of the strain HSWP derived from human skin. 3H‐deoxyglucose appears to be taken up three times faster than 3H‐glucose. After exposure to 3H‐glucose for longer than one minute, the cells excrete ∼70% of the isotope into the medium as lactate. If lactate production (and hence excretion) is abolished by treating the cells with iodoacetic acid or dinitrofluorobenzene, neither of which inhibits transport, the uptake of 3H‐glucose is found to be in fact somewhat larger than that of 3H‐deoxyglucose. If cells are deprived of glucose for 24 hours, apparent uptake of 3H‐glucose is enhanced 10‐fold or more. This latter increase is accounted for by 2‐ to 3‐fold enhancement of true transport plus retention of > 90% of the radioactivity, since little lactate is formed or excreted in glucose‐deprived cells. Deoxyglucose, galactose, or pyruvate when present during glucose deprivation each have quantitatively different effects on the cells' capacity to produce lactate from a short pulse of glucose, but none of them prevents the enhancement of hexose transport. After restoration of 5 mM glucose to starved cells, their metabolism returns to normal (in the sense that ∼70% of the glucose taken up in a pulse is again excreted as lactate), with a half‐time of 0.5 hour; but the transport of hexoses returns to control levels much more slowly, with a half‐time of ∼6 hours. The two processes appear to be independently regulated.