Uptake of 2,6-diaminopurine-2-14C by 2,6-diaminopurine-sensitive and -resistant L strain mouse cells grown on plastic discs

1970 ◽  
Vol 48 (11) ◽  
pp. 791-800 ◽  
Author(s):  
D. G. R. Blair ◽  
G. J. Hebert
Keyword(s):  
Transport System ◽  
Enzyme System ◽  
Sampling Technique ◽  
Metabolic Enzyme ◽  
Adenine Phosphoribosyltransferase ◽  
Short Term ◽  
Simple Diffusion ◽  
L Cells ◽  
Mouse Cells ◽  
Short Incubation Time

The short-term uptake of 2,6-diaminopurine-2-14C by 2,6-diaminopurine-sensitive (DAP-s) or -resistant (DAP-r) L cells was studied by means of a "disc sampling" technique. Monolayers of cells were grown on plastic discs which were subsequently incubated for various periods of time in cell growth medium containing 2,6-diaminopurine-2-14C. At 37 °C the uptake of DAP-2-14C by DAP-r cells was relatively linear with respect to the extracellular concentration of DAP-2-14C, whereas the uptake by DAP-s cells was characterized by the phenomenon of saturation. The uptake of DAP-2-14C by DAP-s cells was greatly reduced by lowering the temperature to 4 °C, and a Q10 value of 1.8 was calculated. Under conditions of low temperature and (or) short incubation time, which limited DAP metabolism in DAP-s cells, the uptake of DAP-2-14C by DAP-s and DAP-r cells was similar, suggesting similar permeability. However, the involvement of an enzymatic transport system, as well as the intracellular metabolic enzyme system, in DAP-s cells was not ruled out. The data suggest that permeability is not a major factor in the resistance of L cells to DAP, but the overall uptake of DAP is facilitated by the presence in DAP-s cells of adenine phosphoribosyltransferase, which catalyzes the formation of DAP ribonucleotide, and possibly of an enzymatic transport system, whereas the entry of DAP into DAP-r cells, which lack, or have very low amounts of, adenine phosphoribosyltransferase, appears to be by simple diffusion.

The toxicity of adenine and of purine-analogs to 2,6-diaminopurine-sensitive and -resistant L-strain mouse cells

1970 ◽  
Vol 16 (8) ◽  
pp. 775-781 ◽  
Author(s):  
D. G. R. Blair ◽  
S. J. Peesker ◽  
D. C. Cross
Keyword(s):  
Amino Acids ◽  
Mammalian Cells ◽  
Culture Medium ◽  
Cell Multiplication ◽  
Aminobenzoic Acid ◽  
Adenine Phosphoribosyltransferase ◽  
L Cells ◽  
Purine Analogs ◽  
Mouse Cells ◽  
Low Levels

The toxicity of adenine, hypoxanthine, and several purine-analogs to 2,6-diaminopurine (DAP)-resistant (DAP-r) and -sensitive (DAP-s) murine L cells has been tested in tissue culture. Resistance of DAP-r cells to DAP and 8-azaadenine was found to be stable over a period of about 5 years. DAP-r cells were cross-resistant to 8-azaadenine, less sensitive than DAP-s cells to 6-thioguanine and hypoxanthine, and more sensitive than DAP-s cells to 6-mercaptopurine and 8-azaxanthine.The concentration of adenine required to inhibit cell multiplication by 50% was 1.37 times greater for DAP-r cells than for DAP-s cells, although DAP-r cells lack, or have very low levels of, adenine phosphoribosyltransferase, which catalyzes adenosine 5′-monophosphate formation from adenine. Adenine toxicity to DAP-r and DAP-s cells could not be prevented by 4-amino-5-imidazolecarboxamide, guanine, hypoxanthine, xanthine, purine ribonucleosides, including adenosine, pyrimidine ribonucleosides, or thymidine. Purine and pyrimidine deoxyribonucleosides, amino acids, and vitamins were supplied in the cell culture medium. Increased concentrations of thiamine, calcium pantothenate, or p-aminobenzoic acid also did not prevent adenine toxicity.It is concluded that the toxicity of adenine to DAP-r and DAP-s L cells likely occurs by the same mechanism in both types of cell. This mechanism does not include the formation of adenosine 5′-monophosphate as an activation step, and does not involve the synthesis of thiamine, pantothenate, amino acids, purines, or pyrimidines which has been involved in other cases of adenine toxicity to bacterial and mammalian cells. A hitherto unknown mechanism seems to be operative.

Molecular biology of enzyme adaptations in higher eukaryotes

Genome ◽  
1989 ◽  
Vol 31 (1) ◽  
pp. 272-283 ◽  
Author(s):  
Donal A. Hickey ◽  
Bernhard F. Benkel ◽  
Charalambos Magoulas
Keyword(s):  
Molecular Biology ◽  
Tissue Specificity ◽  
Enzyme System ◽  
Direct Interaction ◽  
Evolutionary Genetics ◽  
Short Term ◽  
Eukaryotic Genes ◽  
Higher Eukaryotes ◽  
The Relationship

Multicellular eukaryotes have evolved complex homeostatic mechanisms that buffer the majority of their cells from direct interaction with the external environment. Thus, in these organisms long-term adaptations are generally achieved by modulating the developmental profile and tissue specificity of gene expression. Nevertheless, a subset of eukaryotic genes are still involved in direct responses to environmental fluctuations. It is the adaptative responses in the expression of these genes that buffers many other genes from direct environmental effects. Both microevolutionary and macroevolutionary patterns of change in the structure and regulation of such genes are illustrated by the sequences encoding α-amylases. The molecular biology and evolution of α-amylases in Drosophila and other higher eukaryotes are presented. The amylase system illustrates the effects of both long-term and short-term natural selection, acting on both the structural and regulatory components of a gene–enzyme system. This system offers an opportunity for linking evolutionary genetics to molecular biology, and it allows us to explore the relationship between short-term microevolutionary changes and long-term adaptations.Key words: gene regulation, molecular evolution, eukaryotes, Drosophila, amylase.

scholarly journals Short-Term Debt and Financial Performance of Small and Medium Scale Enterprises in Buganda Region, Uganda

2020 ◽  
Vol 9 (4) ◽  
pp. 58-69
Author(s):  
Henry Mugisha ◽  
Job Omagwa ◽  
James Kilika
Keyword(s):  
Financial Performance ◽  
Small And Medium Enterprises ◽  
Low Cost ◽  
Linear Regression Analysis ◽  
Sampling Technique ◽  
Primary Data ◽  
Short Term ◽  
Cross Sectional ◽  
Capital Shortage ◽  
Qualitative Approaches

Short-term debt is regarded as an important source of financing for Small and Medium-sized enterprises (SMEs). This is because it can be easily accessed and useful during times of emergent working capital shortage. However, short-term debt is the least researched among the components of capital structure, which explains why its contribution to the financial performance of small and medium-sized businesses still lacks empirical validation especially in the Ugandan context. This paper sought to determine the effect of short-term debt on financial performance of Small and Medium Enterprises in Uganda. The study adopted a descriptive cross-sectional research design to collect and analyse the data. Stratified random sampling technique was used to select SMEs while purposive sampling technique was used to select one key respondent from each of the sampled 453 SMEs in Uganda. Primary data was collected using survey questionnaire. Data was analysed using descriptive statistics and simple linear regression analysis. The findings indicted that short-term debt had a negative and significant effect on financial performance of SMEs as measured by return on assets. The study provides empirical evidence to support the propositions in the extant literature that short-term debt significantly hampers financial performance of SMEs. The study recommends that SMEs should adopt low cost operation procedures to improve profitability. This would lead to accumulated profits that can be used for investment purposes as a means of driving growth among the SMEs without resorting to borrowing. This paper suggests that further research should be conducted to establish the justification for the negative and significant effect of short-term debt on financial performance using qualitative approaches.

scholarly journals ANALISIS PENGARUH KEBIJAKAN HUTANG TERHADAP KINERJA KEUANGAN

2020 ◽  
Vol 9 (1) ◽  
pp. 35
Author(s):  
Ari Triadi Wijaya ◽  
Muhammad Ali Fikri
Keyword(s):  
Data Analysis ◽  
Financial Performance ◽  
Stock Exchange ◽  
Sampling Technique ◽  
Free Variable ◽  
Short Term ◽  
Return On Equity ◽  
Total Debt ◽  
Research Population

This study aims to determine the effect of debt policy on  financial performance of coal companies listed on the Indonesia Stock Exchange. Policy debt is proxied by short term debt (STD), long term debt (LTD), and total debt (TD), while financial performance is proxied by return on equity (ROE). This research carried out for 3 (three) years, namely 2015-2017. This research is a causal research with a quantitative approach, whereas based on the level of exploration of this study, including associative research. Population research is a coal company listed on the Indonesia Stock Exchange for the period 2015-2017. Samples obtained were based on purposive sampling technique, and obtained 21 company. Data analysis technique used panel data regression. Regression with using the free variable short term debt (STD), long term debt (LTD), and total debt (TD). Based on the results of data analysis, STD has no significant effect on ROE. Variable LTD has a significant effect on ROE. The TD variable has no significant effect with ROE. so the STD and LTD variables are able to influence the ROE variable explained by other factors outside this research model.

The (Na++K+) activated enzyme system and its relationship to transport of sodium and potassium

1974 ◽  
Vol 7 (3) ◽  
pp. 401-434 ◽  
Author(s):  
Jens Chr. Skou
Keyword(s):  
Transport System ◽  
Enzyme System ◽  
Membrane Bound ◽  
Hydrolysis Of ◽  
Sodium And Potassium

It seems to be the membrane bound (Na++K+)-activated enzyme system which transforms the energy from a hydrolysis of ATP into a vectorial movement of sodium out and potassium into the cell against electrochemical gradients, i.e. this systems seems to be the transport system for sodium and potassium (see, for example, review by Skou, 1972; Hokin & Dahl, 1972).

scholarly journals Amino Acid Changes in Proteins 2B and 3A Mediate Rhinovirus Type 39 Growth in Mouse Cells

2005 ◽  
Vol 79 (9) ◽  
pp. 5363-5373 ◽  
Author(s):  
Julie R. Harris ◽  
Vincent R. Racaniello
Keyword(s):  
Amino Acid ◽  
Viral Replication ◽  
Host Cell ◽  
Viral Rna ◽  
Nonstructural Proteins ◽  
Viral Receptor ◽  
Viral Growth ◽  
L Cells ◽  
Cell Components ◽  
Mouse Cells

ABSTRACT Many steps of viral replication are dependent on the interaction of viral proteins with host cell components. To identify rhinovirus proteins involved in such interactions, human rhinovirus 39 (HRV39), a virus unable to replicate in mouse cells, was adapted to efficient growth in mouse cells producing the viral receptor ICAM-1 (ICAM-L cells). Amino acid changes were identified in the 2B and 3A proteins of the adapted virus, RV39/L. Changes in 2B were sufficient to permit viral growth in mouse cells; however, changes in both 2B and 3A were required for maximal viral RNA synthesis in mouse cells. Examination of infected HeLa cells by electron microscopy demonstrated that human rhinoviruses induced the formation of cytoplasmic membranous vesicles, similar to those observed in cells infected with other picornaviruses. Vesicles were also observed in the cytoplasm of HRV39-infected mouse cells despite the absence of viral RNA replication. Synthesis of picornaviral nonstructural proteins 2C, 2BC, and 3A is known to be required for formation of membranous vesicles. We suggest that productive HRV39 infection is blocked in ICAM-L cells at a step posttranslation and prior to the formation of a functional replication complex. The observation that changes in HRV39 2B and 3A proteins lead to viral growth in mouse cells suggests that one or both of these proteins interact with host cell proteins to promote viral replication.

scholarly journals Genetic instability at the adenine phosphoribosyltransferase locus in mouse L cells.

1982 ◽  
Vol 2 (3) ◽  
pp. 250-257 ◽  
Author(s):  
J A Tischfield ◽  
J J Trill ◽  
Y I Lee ◽  
K Coy ◽  
M W Taylor
Keyword(s):  
Chinese Hamster Ovary ◽  
Hot Spot ◽  
Chinese Hamster Ovary Cells ◽  
Human Fibroblasts ◽  
Chinese Hamster ◽  
Ovary Cell ◽  
Adenine Phosphoribosyltransferase ◽  
Ovary Cells ◽  
L Cells ◽  
A Site

Resistance to adenine analogs such as 2,6-diaminopurine occurs at a rate of approximately 10(-3) per cell per generation in mouse L cells. This resistance is associated with a loss of detectable adenine phosphoribosyltransferase activity. Other genetic loci in L cells have the expected mutation frequency (approximately 10(-6)). Transformation of L cell mutants with Chinese hamster ovary cell DNA results in transformants with adenine phosphoribosyltransferase activity characteristic of Chinese hamster ovary cells. No activation of the mouse gene occurs on hybridization with human fibroblasts. That this high frequency event is the result of mutation rather than an epigenetic event is supported by antigenic and reversion studies of the 2,6-diaminopurine-resistant clones. These results are consistent with either a mutational hot-spot, a locus specific mutator gene, or a site of integration of an insertion sequence.

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