bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mathematical model of influenza A virus production in large‐scale microcarrier culture
Authors: Möhler Lars , Flockerzi Dietrich , Sann Heiner , Reichl Udo 
Published: February 2005

AbstractA mathematical model that describes the replication of influenza A virus in animal cells in large‐scale microcarrier culture is presented. The virus is produced in a two‐step process, which begins with the growth of adherent Madin‐Darby canine kidney (MDCK) cells. After several washing steps serum‐free virus maintenance medium is added, and the cells are infected with equine influenza virus (A/Equi 2 (H3N8), Newmarket 1/93). A time‐delayed model is considered that has three state variables: the number of uninfected cells, infected cells, and free virus particles. It is assumed that uninfected cells adsorb the virus added at the time of infection. The infection rate is proportional to the number of uninfected cells and free virions. Depending on multiplicity of infection (MOI), not necessarily all cells are infected by this first step leading to the production of free virions. Newly produced viruses can infect the remaining uninfected cells in a chain reaction. To follow the time course of virus replication, infected cells were stained with fluorescent antibodies. Quantitation of influenza viruses by a hemagglutination assay (HA) enabled the estimation of the total number of new virions produced, which is relevant for the production of inactivated influenza vaccines. It takes about 4–6 h before visibly infected cells can be identified on the microcarriers followed by a strong increase in HA titers after 15–16 h in the medium. Maximum virus yieldVmaxwas about 1 × 1010virions/mL (2.4 log HA units/100 μL), which corresponds to a burst size ratio of about 18,755 virus particles produced per cell. The model tracks the time course of uninfected and infected cells as well as virus production. It suggests that small variations (<10%) in initial values and specific rates do not have a significant influence onVmax. The main parameters relevant for the optimization of virus antigen yields are specific virus replication rate and specific cell death rate due to infection. Simulation studies indicate that a mathematical model that neglects the delay between virus infection and the release of new virions gives similar results with respect to overall virus dynamics compared with a time delayed model. © 2005 Wiley Periodicals, Inc.
Prevention of naphthalene‐induced pulmonary toxicity by glutathione prodrugs: Roles for glutathione depletion in adduct formation and cell injury
Authors: Phimister A. J. , Nagasawa H. T. , Buckpitt A. R. , Plopper C. G. 
Published: February 2005

AbstractNaphthalene is metabolized in the lung and liver to reactive intermediates by cytochrome P450 enzymes. These reactive species deplete glutathione, covalently bind to proteins, and cause necrosis in Clara cells of the lung. The importance of glutathione loss in naphthalene toxicity was investigated by using the glutathione prodrugs (glutathione monoethylester or cysteine–glutathione mixed disulfide) to maintain glutathione pools during naphthalene exposure. Mice given a single intraperitoneal injection of naphthalene (1.5 mmol/kg) were treated with either prodrug (2.5 mmol/kg) 30 min later. Both compounds effectively maintained glutathione levels and decreased naphthalene–protein adducts in the lung and liver. However, cysteine–glutathione mixed disulfide was more effective at preventing Clara cell injury. To study the prodrugs in Clara cells without the influence of hepatic naphthalene metabolism and circulating glutathione, dose‐response and time‐course studies were conducted with intrapulmonary airway explant cultures. Only the ester of glutathione raised GSH in vitro; however, both compounds limited protein adducts and cell necrosis. In vitro protection was not associated with decreased naphthalene metabolism. We conclude that (1) glutathione prodrugs can prevent naphthalene toxicity in Clara cells, (2) the prodrugs effectively prevent glutathione loss in vivo, and (3) cysteine–glutathione mixed disulfide prevents naphthalene injury in vitro without raising glutathione levels. © 2005 Wiley Periodicals, Inc. J Biochem Mol Toxicol 19:42–41, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20052
Effects of nickel poisoning on expression pattern of the 72/73 and 94 kDa stress proteins in rat organs and in the COS‐7, HepG2, and A549 cell lines
Authors: Hfaiedh N. , Allagui M. S. , Feki A. El , Gaubin Y. , Murat J. C. , Soleilhavoup J. P. , Croute F. 
Published: February 2005

AbstractThe present study deals with the effects of Ni on the expression level of three stress proteins, namely, the cytosolic HSP72 and HSP73, and the reticulum‐associated GRP94. Experiments were carried out on “Wistar'' female rats daily injected with 4 mg NiCl2 per kg body weight for 1, 3, 5, and 10 days. Another set of experiments were carried out using cell lines, derived from the monkey kidney (COS‐7), and from human tumors of the lung (A549) and liver (HepG2). Cells were cultured for 4 days in the permanent presence of 100, 200, or 400 µM NiCl2. In control rats, stress proteins pattern was found to be tissue specific: two protein bands of 96 and 94 kDa were immunodetected with the anti‐GRP94 antibody in kidney and liver extracts, whereas only the 96 kDa band was present in ovary extracts. HSP73 was present in kidney, liver, and ovary whereas HSP72 was only found in kidney. In kidney of nickel‐treated animals, HSP73 and the 96 kDa proteins were overexpressed whereas HSP72 was strongly down regulated. No such effect was observed in liver or ovary. Similarly, in nickel‐treated cell lines, HSP72 was downregulated and GRP94 (96 kDa protein) was overexpressed. HSP73 expression appeared moderately increased in A549 cells but decreased in COS‐7 cells. Because long‐term caloric restriction was reported to reduce free radical generation in cells, the effect of 1 month food restriction (50%) was tested in rats as a possible way to lower oxidative damages induced by Ni. No significant effect on HSP expression was observed. © 2005 Wiley Periodicals, Inc. J Biochem Mol Toxicol 19:12–18, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20056
Cell Division: Pressure‐induced reversal of the antimeiotic effects of heavy water in the oocytes of the starfish, Asterias forbesi
Authors: Marsland Douglas , Hiramoto Yukio 
Published: February 2005

AbstractMeiotic activity in the öcytes of the starfish, Asterias forbesi, may be blocked by immersion in deuterated sea water (60% or more) as is judged by a stoppage in the breakdown of the germinal vesicles and a failure of the cells to form persistent polar bodies. These anti‐meiotic effects of heavy water were reversed in significant degree by application of suitable intensities (3,000 to 6,000 psi) of hydrostatic pressure. In this regard meiosis resembles mitosis, as studied previously in the first cleavage division of the sea urchin, Strongylocentrotus purpuratus.In studying germinal vesicle breakdown, immersion of the öcytes in deuterated (60, 70 and 80% D2O) sea water was initiated ten minutes after shedding and pressurization was established six minutes later. None of the non‐pressurized deuterated cells showed complete breakdown of the germinal vesicle, whereas complete breakdown was observed in a significant percentage of the pressurized deuterated specimen.In studying their capacity to form and maintain polar bodies, the öcytes were deuterated 60 minutes after shedding and pressurized six minutes later. Maximum release from deuterational blockage, as judged by the percentage of persistent polar bodies after one hour of treatment, was as follows: 85% at 2,000 psi for 50% D2O; 65% at 2,500 psi, for 60%; 77% at 3,000 psi for 70%; 55% at 3,500 psi for 80% and 65% at 3,500 psi for 90%. Persistence of polar bodies in the non‐pressurized deuterated cells did not exceed 15% in any medium containing 60% or more of D2O and the average persistence in such media was only 2.5%.Basic mechanisms which may account for the observed effects are discussed.
Temperature regulation in the echidna (Tachyglossus aculeatus)
Authors: Schmidt‐Nielsen Knut , Dawson T. J. , Crawford E. C. 
Published: February 2005

AbstractThe echidna (Tachyglossus aculeatus) maintained a body temperature of 30.7°C ± 1.03 s.d. (N = 23) at ambient temperatures (TA) between 0 and 25°C. It may, however, also become hypothermic at low TA. At TA = 30°C or above the echidna became hyperthermic. The thermoneutral range was about 20–30°C. At low TA the metabolic rate might be increased several fold. The thermal conductance was at a minimum at TA = 20°C, and was not further reduced at lower TA. At higher TA the thermal conductance increased up to five‐fold. The evaporation showed little change with increasing TA. At the highest TA we used (33°C) the evaporation on the average accounted for the dissipation of only about one‐third of the metabolic heat produced. These findings suggest that the echidna, although it can maintain its body temperature at low ambient temperature, cannot rely upon evaporation as the major avenue for heat loss at high ambient temperature.
A circadian rhythm of mating type reversals in Paramecium multimicronucleatum, syngen 2, and its genetic control
Authors: Barnett Audrey 
Published: February 2005

AbstractTwo new alleles, C and c, involved in mating type expression were demonstrated. A dominant allele, C(cycler), must be present for the expression of the rhythm involving a sequential alternation of the two complementary mating types (III and IV). Cultures can be entrained with light‐dark cycles. The phase of each clone can be characterized by its III to IV and IV to III transitions in relation to the zero hour of a given light‐dark cycle. Phase is a stable phenotypic trait during asexual reproduction, but following sexual reproduction it does not display Mendelian segregation. Instead phase is determined through nuclear differentiation, i.e., the trait is controlled by differently determined macronuclear alagen (caryonidal inheritance) which normally segregate at the second cell division after conjugation. The phase of a clone within its genetic limits is a function of the photofractions and the light intensities used in the entraining treatment. By examining a number of clones a variety of phase angles between the mating type cycle and the entraining light‐dark cycle are found. Dividing cells which are sexually unreactive and therefore do not express the rhythm can be entrained and following entrainment, phase is inherited through repeated cell replications at a rate greater than one fission a day in continuous darkness or continuous dim light. This result unique to this system indicates that the cellular processes underlying the phase and period of this circadian rhythm persist (unexpressed: sexual reactivity requires slight starvation) through repeated cell replications even when the division cycle is considerably shorter than the expressed circadian period. The rhythm has a circadian period in continuous darkness or light (tested for six days) of less than 24 hours. The reversal of mating type ceases in continuous light at higher intensities. Cells homozygous for the recessive allele, c(acyclic), do not reverse mating type but are either mating type III or IV, again as a consequence of nuclear differentiation. Since individual cells with the dominant allele express both mating types, differentiation for mating type can not involve the absence in the macronucleus of mating type determining factors.
Neural responses in the inferior colliculus of echolocating bats to artificial orientation sounds and echoes
Authors: Friend J. H. , Suga N. , Suthers R. A. 
Published: February 2005

AbstractThe responses of single units and evoked potentials to a pair of artificial sounds, mimicking theorientation sound and echo, and to tape recorded actual orientation sounds were studied in terms of recovery cycle. the recovery cycle of single units could be classified into four groups: (1) short suppression (4%), (2) delayed inhibition (11%), (3) temporal recovery with or without a supernormal phase (7%), and (4) undelayed inhibition (78%) lasting 4 to 26 msec. therefore the majority of neurons were not excited by the second sound (echo) of a pair when it was delivered within several milliseconds after the first (out‐going orientation sound). the duration of the recovery cycle was a function of the intensity of a pair of sounds. the weaker the first tone pulse relative to the second, the more rapid the recovery to the second. therefore, the reception of echoes is probably improved by contraction of middle ear muscles resulting in attenuation of self‐stimulation by the out‐going pulse.The collicular evoked potential consisted of two components, a fast one mainly due to the incoming fibers from lower levels and a slow one due to the main body of the inferior colliculus. The slow component showed slow recovery cycles as did the majority of single units while the fast one recovered very quickly. No noticeable difference in recovery cycles was found between awake and anesthetized animals. The functional meaning of inhibitory periods in the recovery cycle and role of the inferior colliculus in echo‐location are discussed.
The metabolism of L‐glutamate and L‐5‐Carboxypyrrolidone by mouse cells (NCTC clone 929) under conditions of defined nutrition
Authors: Kitos Paul A. , Waymouth Charity 
Published: February 2005

AbstractThe utilization of L‐glutamate by clone 929 mouse cells growing in a synthetic medium, MAL 294/2, was studied with the aid of carbon‐14 labeled L‐glutamate. The rate of consumption of extracellular glutamate was rapid even though the extracellular concentration of this substance has been found to remain constant or to increase. The rate of uptake during an interval of otpimal growth was calculated to be approximately 42 mμmoles/mg of cell protein per hour.Among the metabolic products that are derived from the carbon of glutamate and secreted from the cells are carbon dioxide, lactic acid, proline, alanine, alpha‐ketoglutaric acid and 5‐carboxypyrrolidone. Aspartic acid, although produced by the cells in amounts sufficient to meet the needs for growth, does not appear as an extracellular product of glutamate metabolism. Extracts of L cells were found to exhibit four times as much glutamic‐oxaloacetic as glutamic‐pyruvic transaminase activities. Failure to secrete aspartic acid must not be due to a deficiency in the transaminase. The transaminase concentrations are apparently not affected by variations in the concentrations of aspartic acid and alanine in the medium, both of which are absent from MAL 294/2.5‐Carboxypyrrolidone, although produced from L‐glutamate by L cells, is metabolically inert in this system. Likewise, mouse fetal lung cells, cultured in a similar way, use glutamic acid as extensively as L cells and fail to metabolize exogenous 5‐carboxypyrrolidone.
The effect of phytohemagglutinin on glucose‐U‐C14 oxidation by peritoneal and blood white cells of the rat
Authors: Hrachovec Josef P. 
Published: February 2005

AbstractIncubation of washed white cells with phytohemagglutinin (PHA) had a stimulatory effect on the rate of C14O2 evolution from uniformly C14‐labeled glucose by the cells. The intensity of this effect depended not only on the concentration of PHA, but also on the duration of soaking of the cells in protein‐free medium for tissue culture before PHA was added and on the length of incubation of the soaked cells with PHA before glucose‐U‐C14 was added. This effect of PHA on the rate of glucose‐U‐C14 oxidation by the cells was essentially the same, whether white blood cells or peritoneal white cells were used.
The glyceride fatty acid composition and lipid content of brown and white adipose tissue of the hibernator Citellus lateralis
Authors: Spencer W. A. , Grodums E. I. , Dempster G. 
Published: February 2005

AbstractGlyceride and total phosphatide levels of brown and white fat of Citellus lateralis have been followed throughout the year in biopsy samples.Extraction of the glycerides for fatty acid analysis is described. As much as 20% of the phosphatide of brown fat was found in the upper fat layer of a centrifuged tissue homogenate. This phosphatide appeared to be present as a low‐density lipoprotein, and may be associated with the lipid globules of the intact cell.Glyceride and phosphatide levels varied considerably in brown fat, and no particular level was consistently observed to be associated with any part of the hibernation cycle. Fatty acid composition of the glycerides also varied widely. The degree of unsaturation was not related to the hibernation cycle, although there appeared to be a differential utilization of fatty acids during a few weeks prior to spring arousal.A decrease in tissue glyceride levels was observed in both brown and white fat during arousal from hibernation at 2°C, the loss from brown fat being double the loss from white fat.
Electrophoretic mobility of mouse cells and homologous isolated nuclei
Authors: Mayhew E. , Nordling S. 
Published: February 2005

AbstractThe electrophoretic mobilities of Ehrlich ascites, sarcoma 37 ascites, mouse liver cells and their isolated nuclei were measured under similar environmental conditions. No differences in mobility were detected between cells and homologous nuclei from the same cell population and it was concluded that their surface charge densities were probably the same. The effect of neuraminidase on Ehrlich ascites and liver cells and nuclei was also determined; neuraminidase reduced the mobility of Ehrlich ascites cell nuclei as well as cells. The reduction in mobility of cells and nuclei prepared by a sucrose method was the same; however, the reduction in mobility of citric acid prepared nuclei was less than that of citric acid treated cells. The reduction in mobility of both liver cells and nuclei was small or insignificant. It is suggested that although cells and nuclei have similar electrophoretic mobilities, possibly different groups contribute to their surface charge.
Effects of inhibitor, competitors and temperature on transport of carbohydrate in Crithidia luciliae
Authors: Min Hong S. 
Published: February 2005

AbstractEffects of KCN (10−4 M), simultaneous presence of varying concentrations of D‐glucose and L‐sorbose, and temperature on transport of carbohydrate in C. luciliae have been studied. The rate of carbohydrate entrance is inhibited, in all sugars used, ranging from 19% to 70% inhibition at 0.5 mM external concentrations. However, this inhibitor does not affect transport from external concentrations of the order of 0.02 M. At 20 mM external concentration, the rate of L‐sorbose entrance is greatly inhibited by the simultaneous presence of D‐glucose, and the transport mechanism shows enormously greater affinity for glucose than for other monosaccharides. However, at 0.5 mM external concentration, the rate of sorbose entrance is not inhibited at all by the simultaneous presence of D‐glucose. In the temperature interval 15°–25°C, the Q10 for rate of entrance when the external concentration is 0.5 mM is 2.8 times larger than the Q10 when the external concentration is 20 mM. These data are interpreted as strongly suggesting two mechanisms for carbohydrate entrance: (a) facilitated diffusion, of importance only at high external concentrations; (b) an active transport mechanism, active at low external concentrations and dependent upon a supply of metabolic energy. These results are compared with those reported in the literature for other types of cells.
Amino acid requirements for attachment and outgrowth of the mouse blastocyst in vitro
Authors: Gwatkin R. B. L. 
Published: February 2005

AbstractArginine, cystine, histidine, leucine and threonine were needed for outgrowth of the mouse blastocyst in vitro. Omission of lysine, methionine, phenylalanine, tryptophane and tyrosine from the culture medium markedly reduced blastocyst outgrowth, but did not inhibit it completely; while omission of isolecine and valine reduced the extent of outgrowth only slightly. Blastocysts kept for seven days in a free‐floating condition by omitting arginine and leucine from the medium, grew out when these amino acids were added. Such behavior may be analogous to delayed implantation in utero and suggests that the free amino acid content of the uterus could be an important factor in the control of implantation. Blastocysts delayed from implanting in the uterus by ovariectomy were activated to outgrowth in a complete medium, but the intracellular changes associated with outgrowth occurred more slowly than in undelayed blastocysts.
The presence of ribonucleic acid within the peripheral zones of two types of mammalian cell
Authors: Weiss L. , Mayhew E. 
Published: February 2005

AbstractAn attempt has been made to locate RNA as a structural component of the peripheries of cultured cells derived from a human osteogenic sarcoma, and L1210 mouse leukaemia cells. In the case of cells derived from the osteogenic sarcoma, their detachment from glass was facilitated by incubation with ribonuclease; on removal from glass, they left cellular “footprints” behind, which were visulized in radioautographs of cells previously labeled with tritiated uridine, and removable with ribonuclease. The electrophoretic data show loss of charge by both types of cell following incubation with ribonuclease.These results are interpreted to indicate that RNA is a structural component of the peripheries of these cells. No attempt is made to speculate on the obvious biological improtance of these observations if they are applicable to cells in general.
Stimulation by normal and leukemic mouse sera of colony formation in vitro by mouse bone marrow cells
Authors: Robinson W. , Metcalf D. , Bradley T. R. 
Published: February 2005

AbstractUsing a modification of the agar gel method for bone marrow culture, serum from various strains of mice has been tested for colony stimulating activity. Ninety percent of sera from AKR mice with spontaneous or transplanted lymphoid leukemia and 40–50% of sera from normal or preleukemic AKR mice stimulated colony formation by C57B1 bone marrow cells. Sera from 6% of C3H and 30% of C57B1 mice stimulated similar colony formation. The incidence of sera with colony stimulating activity rose with increasing age. All colonies were initially mainly granulocytic in nature but later became pure populations of mononuclear cells.Bone marrow cells exhibited considerable variation in their responsiveness to stimulation by mouse serum. Increasing the serum dose increased the number and size of bone marrow cell colonies and with optimal serum doses, 1 in 1000 bone marrow cells formed a cell colony. Preincubation of cells with active serum did not stimulate colony formation by washed bone marrow cells.The active factor in serum was filterable, non‐dialysable and heat and ether labile.