Thymidine incorporation into Rhizobium meliloti

1979 ◽  
Vol 25 (6) ◽  
pp. 675-679 ◽  
Author(s):  
R. M. Behki ◽  
S. M. Lesley
Keyword(s):  
Carbon Dioxide ◽  
Thymidine Incorporation ◽  
Rhizobium Meliloti ◽  
Aminoisobutyric Acid ◽  
Low Concentrations ◽  
High Concentrations

Thymidine is rapidly catabolized to thymine, β-aminoisobutyric acid, and carbon dioxide by Rhizobium meliloti cells. The incorporation of labelled thymidine into the DNA of R. meliloti cells can be enhanced by the addition of low concentrations (10–20β μg/mL) of deoxyadenosine or other nucleosides (adenosine, uridine, guanosine). However, at high concentrations (>50 μg/mL) these compounds inhibit thymidine incorporation. Conditions to obtain highly radioactive DNA of Rhizobium are described.

Role of cell replication in regulation of Na-coupled hexose transport in LLC-PK1 epithelial cells

1986 ◽  
Vol 250 (2) ◽  
pp. C314-C318 ◽  
Author(s):  
A. Moran ◽  
J. S. Handler ◽  
M. Hagan
Keyword(s):  
Epithelial Cells ◽  
Ionizing Radiation ◽  
Thymidine Incorporation ◽  
Regulatory Process ◽  
Hexose Transport ◽  
Cell Replication ◽  
Response Data ◽  
Low Concentrations ◽  
High Concentrations

The glucose concentration in growth medium has been shown to regulate the number of sodium-coupled glucose transporters in LLC-PK1 epithelial cells. Epithelia grown in high concentrations of glucose express fewer transporters than epithelia grown in low concentrations of glucose. In the present work, the effect of a dose of ionizing radiation sufficient to block the incorporation of thymidine was examined in order to gauge the importance of cell replication in the hexose transport regulatory process. The low rate of thymidine incorporation in the plateau phase was completely eliminated by ionizing radiation. Under conditions of irradiation that completely blocked thymidine incorporation, down-regulation, namely the loss of alpha-methylglucoside-concentrating capacity, brought about by switching the epithelium from low to high glucose-containing medium, is independent of the irradiation and therefore most likely is also independent of cell replication. In contrast, the up-regulatory phenomenon is strongly impaired by radiation. This impairment may be due to specific radiation impairment of gene expression necessary for the up-regulatory process. It is apparent from the dose-response data that up-regulation is not inhibited by irradiation in a simple manner and is not inhibited at the same radiation dose as cell replication.

scholarly journals Stress-induced Ethanol Production in Fresh Fruit and Vegetables

HortScience ◽  
1996 ◽  
Vol 31 (4) ◽  
pp. 635d-635
Author(s):  
Charles F. Forney ◽  
Michael A. Jordan
Keyword(s):  
Carbon Dioxide ◽  
Ethanol Production ◽  
Fruits And Vegetables ◽  
Physiological Stress ◽  
Anaerobic Respiration ◽  
Highbush Blueberry ◽  
Carbon Dioxide Atmosphere ◽  
Low Concentrations ◽  
Off Flavors ◽  
High Concentrations

Fresh fruits and vegetables produce ethanol when they are held in atmospheres containing low concentrations of oxygen. Ethanol concentrations in the headspace of fresh Brassica vegetables held 24 hours in nitrogen at 20°C ranged from 5 to 110 mmol·m–3. The absence of oxygen induced anaerobic respiration and the production of ethanol in these vegetables. However, other stresses, including heat and high concentrations of carbon dioxide, can also stimulate the production of ethanol in fresh fruits and vegetables held in aerobic atmospheres. Fresh heads of broccoli dipped in 52°C water had increased concentrations of headspace ethanol 2 hours after treatment when held at 20°C in air. Concentrations were 6, 160, and 490 times greater in broccoli treated for 1, 2, or 3 minutes than in nontreated controls, respectively. Fruit of three highbush blueberry cultivars held in 25% carbon dioxide for 6 weeks at 0°C had 80 to 190 times more ethanol than fruit held in air. The 25% carbon dioxide atmosphere also induced blueberries to soften and develop off-flavors. Ethanol may be a fast and easy-to-measure indicator of physiological stress in stored fresh fruits and vegetables. Monitoring induced ethanol production could identify injurious storage environments or postharvest treatments. Possible mechanisms of stress-induced ethanol production will be discussed.

Coupling of methyl coenzyme M reduction with carbon dioxide activation in extracts of Methanobacterium thermoautotrophicum

1982 ◽  
Vol 152 (2) ◽  
pp. 840-847
Author(s):  
J A Romesser ◽  
R S Wolfe
Keyword(s):  
Carbon Dioxide ◽  
Co2 Reduction ◽  
Methanobacterium Thermoautotrophicum ◽  
Coenzyme M ◽  
Cell Extracts ◽  
Low Concentrations ◽  
Efficient Reduction ◽  
High Concentrations ◽  
Reduction Of Co2 ◽  
Stimulation Of

The stimulation of carbon dioxide reduction to methane by addition of 2-(methylthio)ethanesulfonate (CH3-S-CoM) to cell extracts of Methanobacterium thermoautotrophicum was investigated. Similar stimulation of CO2 reduction by CH3-S-CoM was found for cell extracts of Methanobacterium bryantii and Methanospirillum hungatei. The CH3-S-CoM requirement could be met by the methanogenic precursors formaldehyde, serine, or pyruvate, or by 2-(ethylthio)ethanesulfonate (CH3CH2-S-CoM), but not by other coenzyme M derivatives. Efficient reduction of CO2 to CH4 was favored by low concentrations of CH3-S-CoM and high concentrations of CO2. Sulfhydryl compounds were identified as effective inhibitors of CO2 reduction. Both an allosteric model and a free-radical model for the mechanism of CO2 activation and reduction are discussed.

Air-tight storage of grain; its effects on insect pests. I. Calandra granaria L.(Coleoptera, Curculionidae).

1955 ◽  
Vol 6 (1) ◽  
pp. 33 ◽  
Author(s):  
SW Bailey
Keyword(s):  
Carbon Dioxide ◽  
Respiratory Quotient ◽  
Insect Pests ◽  
Storage Conditions ◽  
Grain Storage ◽  
Low Concentrations ◽  
Cent Mortality ◽  
High Concentrations ◽  
Time Required

The responses of adult and immature Calandra granaria L. to high concentrations of carbon dioxide and low concentrations of oxygen have been determined. To bring about 100 per cent. mortality of all stages requires an increase of carbon dioxide to 40 per cent. or a decrease of oxygen to 2 per cent. The respiratory quotient of the species has been measured and it is shown that the death of the insects, under air-tight grain storage conditions, is due to the depletion of oxygen caused by the respiration of the insects and the grain and not to the accumulation of carbon dioxide. The adult insects are the most resistant stage and the first insects larvae the most susceptible. Estimates for the time required for the insects to die and for the amount of damage they cause before death are given.

The potential of higher plants with the phosphopyruvic acid cycle

1971 ◽  
Vol 179 (1056) ◽  
pp. 221-235 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Higher Plants ◽  
Apparent Lack ◽  
Acid Cycle ◽  
Carbon Reduction ◽  
Low Concentrations ◽  
Reduction Cycle ◽  
Artificial Environment ◽  
High Concentrations ◽  
Carbon Reduction Cycle

Optimal conditions for photosynthesis by intact higher plants are considered as those resulting in the maximum production of organic matter from carbon dioxide over a prolonged period of time. Photosynthetic yields may be limited by the ability of plants to fix and retain carbon from an atmosphere containing high concentrations of oxygen and low concentrations of carbon dioxide. In many plants photosynthetic capacity is decreased under these conditions as a result of loss of carbon from the photosynthetic carbon reduction cycle as glycollic acid. Photosynthesis is further decreased by the loss of carbon dioxide from the leaf during the further metabolism of this glycollate in photorespiratory processes. Other plants, tropical grasses in particular, are resistant to inhibition by high concentrations of oxygen. This resistance is associated with an apparent lack of photorespiration, a characteristic leaf anatomy, dimorphic chloroplasts and an ancillary mechanism for trapping carbon dioxide— the phosphopyruvic acid cycle. It is concluded that a tropical grass such as sugar cane could produce the optimum yield of organic material in an artificial environment.

EFFECT OF HIGH CONCENTRATIONS OF CARBON DIOXIDE AND OXYGEN ON THE RESPIRATION OF FULLTERM INFANTS

PEDIATRICS ◽  
1954 ◽  
Vol 14 (2) ◽  
pp. 104-113
Author(s):  
HERBERT C. MILLER
Keyword(s):  
Carbon Dioxide ◽  
Respiratory Insufficiency ◽  
Newborn Infants ◽  
Slight Effect ◽  
Asphyxia Neonatorum ◽  
Healthy Newborn ◽  
Low Concentrations ◽  
Pessimistic Attitude ◽  
Powerful Stimulus ◽  
High Concentrations

Five percent carbon dioxide added to 20% oxygen is a more powerful stimulus to respiration of healthy fullterm infants than is 100% oxygen. Fullterm infants hypoventilating as a result of exposure to low concentrations of oxygen had their minute volumes restored more rapidly and to a greater extent when 5% carbon dioxide was added to oxygen concentrations varying from 12 to 95% than when 100% oxygen was administered. The age of the infant appeared to have but slight effect on the response made to breathing 5% carbon dioxide or 100% oxygen. Infants under two or three hours of age were not tested. The value of adding carbon dioxide to air or oxygen in the treatment of "asphyxia neonatorum" has been discussed. Too little is known concerning the chemical, physiologic and anatomic changes occurring in this loosely termed condition or even in healthy newborn infants to warrant a pessimistic attitude towards the use of 5% carbon dioxide added to air or oxygen in the treatment of newborn infants with respiratory insufficiency.

scholarly journals HIGH CONCENTRATIONS OF RADON AND CARBON DIOXIDE IN ENERGY-EFFICIENT FAMILY HOUSES WITHOUT HEAT RECOVERY VENTILATION

2018 ◽  
Vol 26 (1) ◽  
pp. 64-74 ◽  
Author(s):  
Gábor GÉCZI ◽  
József BENÉCS ◽  
Krisztina KRISTÓF ◽  
Márk HORVÁTH
Keyword(s):  
Carbon Dioxide ◽  
Energy Efficient ◽  
Heat Recovery ◽  
Well Being ◽  
Efficient Operation ◽  
Low Concentrations ◽  
Viable Solution ◽  
High Concentrations ◽  
Materials Used ◽  
Carbon Dioxide Co2

The most significant factors of indoor air quality – besides temperature and humidity – are the concentrations of carbon-dioxide (CO2) and radon (222Rn). Radon seepage is caused by and affected by the materials used in walls and floors, the quality of insulation, cracks and even the amount of pipes running through the walls. The amount of CO2 is predominantly affected by the biological processes of the inhabitants, and possibly by potentially faulty HVAC systems. The energy efficiency related upgrades to family homes, which often only extend to window replacements and better insulation have a significant effect and could potentially increase concentrations of both radon and CO2 which has a significant effect on the well-being of the inhabitants. Our tests conducted in Hungary have proven that by using automated heat recovery ventilation (HRV) both energy efficient operation and low concentrations of radon and CO2 are achievable. Our results prove the significance and prevalence of the issue of higher concentrations of these pollutants, and offer a viable solution.

Neutrophil Elastase Potentiates Cathepsin G-lnduced Platelet Activation

1992 ◽  
Vol 68 (05) ◽  
pp. 570-576 ◽  
Author(s):  
Mary A Selak
Keyword(s):  
Neutrophil Elastase ◽  
Cell Activation ◽  
Thromboxane A2 ◽  
Creatine Phosphate ◽  
Dense Granule ◽  
Cathepsin G ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Low Concentrations ◽  
High Concentrations

SummaryWe have previously demonstrated that human neutrophil cathepsin G is a strong platelet agonist that binds to a specific receptor. This work describes the effect of neutrophil elastase on cathepsin G-induced platelet responses. While platelets were not activated by high concentrations of neutrophil elastase by itself, elastase enhanced aggregation, secretion and calcium mobilization induced by low concentrations of cathepsin G. Platelet aggregation and secretion were potentiated in a concentration-dependent manner by neutrophil elastase with maximal responses observable at 200 nM. Enhancement was observed when elastase was preincubated with platelets for time intervals of 10–60 s prior to addition of a low concentration of cathepsin G and required catalytically-active elastase since phenylmethanesulphonyl fluoride-inhibited enzyme failed to potentiate cell activation. Neutrophil elastase potentiation of platelet responses induced by low concentrations of cathepsin G was markedly inhibited by creatine phosphate/creatine phosphokinase and/or indomethacin, indicating that the synergism between elastase and cathepsin G required the participation of ADP and thromboxane A2. On the other hand, platelet responses were not attenuated by the PAF antagonist BN 52021, signifying that PAF-acether did not play a role in elastase potentiation. At higher concentrations porcine pancreatic elastase exhibits similar effects to neutrophil elastase, demonstrating that the effect of elastase was not unique to the neutrophil protease. While neutrophil elastase failed to alter the ability of cathepsin G to hydrolyze a synthetic chromogenic substrate, preincubation of platelets with elastase increased the apparent affinity of cathepsin G binding to platelets. In contrast to their effect on cathepsin G-induced platelet responses, neither neutrophil nor pancreatic elasatse potentiated aggregation or dense granule release initiated by ADP, PAF-acether, arachidonic acid or U46619, a thromboxane A2 mimetic. Moreover, unlike its effect on cathepsin G, neutrophil elastase inhibited thrombin-induced responses. The current observations demonstrate that elastase can potentiate platelet responses mediated by low concentrations of cathepsin G, suggesting that both enzymes may function synergistically to activate platelets under conditions where neutrophil degranulation occurs.

In Vitro Effects of Ethanol on Rabbit Platelet Aggregation, Secretion of Granule Contents, and Cyclic AMP Levels in the Presence of Prostacyclin

1989 ◽  
Vol 61 (02) ◽  
pp. 254-258 ◽  
Author(s):  
Margaret L Rand ◽  
Peter L Gross ◽  
Donna M Jakowec ◽  
Marian A Packham ◽  
J Fraser Mustard
Keyword(s):  
Cyclic Amp ◽  
Inhibitory Effect ◽  
Rabbit Platelet ◽  
Inhibitory Effects ◽  
Low Concentrations ◽  
Rabbit Platelets ◽  
High Concentrations ◽  
In Vitro Effects ◽  
Aggregation Of Platelets

SummaryEthanol, at physiologically tolerable concentrations, inhibits platelet responses to low concentrations of collagen or thrombin, but does not inhibit responses of washed rabbit platelets stimulated with high concentrations of ADP, collagen, or thrombin. However, when platelet responses to high concentrations of collagen or thrombin had been partially inhibited by prostacyclin (PGI2), ethanol had additional inhibitory effects on aggregation and secretion. These effects were also observed with aspirin- treated platelets stimulated with thrombin. Ethanol had no further inhibitory effect on aggregation of platelets stimulated with ADP, or the combination of ADP and epinephrine. Thus, the inhibitory effects of ethanol on platelet responses in the presence of PGI2 were very similar to its inhibitory effects in the absence of PGI2, when platelets were stimulated with lower concentrations of collagen or thrombin. Ethanol did not appear to exert its inhibitory effects by increasing cyclic AMP above basal levels and the additional inhibitory effects of ethanol in the presence of PGI2 did not appear to be brought about by further increases in platelet cyclic AMP levels.

Aggregation of Cat Platelets in Vitro

1970 ◽  
Vol 23 (03) ◽  
pp. 601-620 ◽  
Author(s):  
Th. B Tschopp
Keyword(s):  
Adenosine Monophosphate ◽  
Blood Collection ◽  
Base Line ◽  
Reversible Aggregation ◽  
Low Concentrations ◽  
Irreversible Aggregation ◽  
High Concentrations ◽  
Two Phases ◽  
Improved Technique

SummaryAggregation of cat platelets in the citrated plasma is examined by means of Born’s absorptiometer. A marked tendency of the platelets of this species to spontaneous aggregation necessitated first of all the development of an improved technique of blood collection.A hypothesis according to which 5-HT is released from the platelets, explains the absence of oscillations on the base line of the absorptiometer, the absence of platelet swelling, when ADP is added, and the effect of stirring on the aggregation curves in cat PRP. The average volume of cat platelets amounts to 10.46 μ3 when directly fixed in the blood, when fixed from PRP to 12.17 μ3, when fixed from stirred PRP to 13.51 μ3.In low concentrations (0.3-2 μM) ADP produce reversible aggregation; in narrowly restricted, individually dissimilar mean concentrations irreversible aggregation in two phases and in high concentrations, irreversible aggregation in one phase. Like ADP serotonin produces 2 phase irreversible aggregation in concentrations of 3-10 μM, but unlike ADP, the aggregation velocity decreases again with high 5-HT concentrations (>100 μM). Adrenaline does not produce aggregation and it is likely that adenosine and adenosine monophosphate inhibit the aggregation by serotonin but not by ADP. Species differences in the aggregation of human, rabbit and cat platelets are discussed.

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