Automatic gas tank switching system for CO2 incubators

Summary The use and construction of an automatic gas tank switching system are described. This device monitors the gas pressure in a CO₂ incubator gas system and automatically switches to a reserve tank when the main supply tank is depleted. The unit contains an alarm system that signals either a loss of power or of gas pressure in the supply system. This research was supported by National Cancer Institute Contract No 1-CP-33226, grants CA 13058 and CA 14680 and an institutional grant to the Michigan Cancer Foundation by the United Foundation of Greater Detroit.     

A respiratory valve for rapid switching between two gas mixtures.

We have devised a respiratory valve that facilitates rapid and silent breath-to-breath switching between two gas mixtures, under remote control. It utilizes two inspiratory Loven-type valve elements, one for each gas mixture, either of which can be held closed with an electromagnet. Any type of valve element can serve as the expiratory valve. We have used a small respiratory valve with goats and a larger model for both goat and human use.     

Automatic gas meter for laboratory fermenters

Summary A versatile, cheap and automated system is designed for the measurement of small gas flows produced in laboratory-scale fermentation processes. An automatic sampling device for programmed times is linked to the flow meter. The displacement of a liquid by the gas being measured is the principle on which both the meter and the sampling device are based. The operation of the system is controlled by a simple electronic circuit.     

CO2 gas exchange of the understory plantAsarum europaeum L. in November

The CO₂ gas exchange rates of the Central European perennial understory plantAsarum europaeum L. were measured in late autumn (October 30 to November 30) in its natural habitat day and night.During these measurements the temperature ranged from 0 to 15°C and the absolute air humidity from 3 to 10 mg H₂O·1^–1. Temperature and absolute air humidity over these ranges did not affect CO₂ net assimilation which was determined almost entirely by quantum flux density.CO₂ net assimilation was light saturated at about 100 M·m^–2·s^–1 quantum flux density. The uptake rate at this point was 4.3 mg·dm^–2·h^–1. The compensation point occurred at approximately 1 M·m^–2·s^–1.     

Control of self-incompatibility by CO2 gas in Brassica

Pollen tubes penetrated stigma papilla cells in flowers thatwere illegitimately (self) pollinated, after CO₂ treatment ofthese flowers. This shows that the self-incompatible reactionin Brassica can be removed by CO₂ gas. Ethylene gas was noteffective. (Received May 16, 1969; )     

CO(2)-controlled sampling of alveolar gas in mechanically ventilated patients.

A newly designed gas-sampling device using end-tidal CO(2) to separate dead space gas from alveolar gas was evaluated in 12 mechanically ventilated patients. For that purpose, CO(2)-controlled sampling was compared with mixed expiratory sampling. Alveolar sampling valves were easily controlled via CO(2) concentration. Concentrations of four volatile substances were determined in the expired and inspired gas. Isoflurane and isoprene, which did not occur in the inspired air, had ratios of end-tidal to mixed expired concentrations of 1.75 and 1.81, respectively. Acetone and pentane, found in both the inspired and expired air, showed ratios of 0.96 and 1.0, respectively. Precision of concentration measurements was between 2.4% (isoprene) and 11.2% (isoflurane); reproducibility (as coefficient of variation) was 5%. Because the only possible source of isoflurane and isoprene in this setting was patients' blood, selective enrichment of alveolar gas was demonstrated. By using the new sampling technique, sensitivity of breath analysis was nearly doubled.     

Mechanical properties of hydrocolloid gels filled with internally produced CO2 gas bubbles.

Agar (2%), alginate (1% algin), and kappa-carrageenan (1.5%) gel specimens were prepared from mother solutions that contained 0-2.5% sodium bicarbonate (agar and carrageenan) or calcium carbonate (alginate). Upon immersion in a citric acid bath (0-2%), the carbonate reacted with the diffusing acid to produce numerous carbon dioxide bubbles. The compressive strength and deformability of the gas-filled gels so produced were determined using a Universal testing machine and compared with those of pure gels and gels containing the carbonate but not subjected to the process after various immersion times. While the agar and alginate gels retained considerable mechanical integrity even after several hours, the carrageenan gels disintegrated after about 2-5 h. Under similar conditions, the number of bubbles produced in the agar gels was about twice that in the alginate gels, an observation that cannot be explained solely by stoichiometric considerations.     

An effective time for CO2 gas treatment in overcoming self-incompatibility in Brassica

An investigation was made to determine the effective time forCO₂ treatment in overcoming self-incompatibility in Brassica.CO₂ was effective when supplied to a self-pollinated flowerwhile hundreds of pollen grains were germinating on the stigma.Since the effective time coincides with the attachment of pollentubes to papilla cells, it is thought that CO₂ produces a metabolicchange in these cells during attachement. ¹Part of a thesis submitted for the Dr. of Agr. degree by thesenior author at Tohoku University. ²Present address: Faculty of Agriculture, Kobe University, Nada-ku,Kobe, Japan. (Received December 7, 1972; )     

A multienzyme complex for CO2 fixation.

Acetyl-coenzyme A carboxylase from Euglena gracilis strain Z was isolated as a component of a multienzyme complex which includes phosphoenolpyruvate carboxylase and malate dehydrogenase. The multienzyme complex was shown to exist in crude extracts and was purified to a homogeneous protein with a molecular weight of 360,000 by gel filtration. The ratio of the activities of the constituent enzymes was acetyl-CoA carboxylase:phosphoenolpyruvate carboxylase:malate dehydrogenase, 1:25:500. The complex is proposed to operate in conjunction with malic enzyme, which is present in Euglena, to facilitate the formation of substrates, malonyl-CoA, and NADPH, for fatty acid biosynthesis. The interaction of the enzymes may represent a means of control of acetyl-CoA carboxylase activity in organisms which do not possess an enzyme subject to allosteric regulation. The acetyl-CoA carboxylase activity from Euglena is unaffected by citrate and isocitrate.     

Use of plant leaf as CO2 gas sensing probe

Intracellular potential (ICP) of a spiderwort (Commelina communis) leaf drastically changed to CO₂ gas exposure. A leaf of C. communis was attached on a slide glass under a microscope. The stem of the leaf was dipped in a bathing solution composed of 0.1 M phosphate buffer (K₂HPO₄-KH₂PO₄, pH6.5) and 0.1 M NH₄Cl.The ICP was measured with a glass capillary electrode referred to another electrode dipped in the bathing solution. When CO₂ gas was applied to the leaf under illumination, the ICP shifted sharply to the negative direction about 100mV, and then turned towards the positive direction. Finally the ICP reached a level about 50 mV higher than the initial level. When CO₂ supply was stopped, the ICP returned to the initial level immediately.When light was shielded or CO₂ concentration was decreased lower than 20%, the response curve showed a single phase. The intensity of the response was positively correlated with CO₂ concentration lower than 20% both under illumination and shielded conditions. In contrast, no response was observed, when N₂ gas or air (CO₂ content is 0.03%) was applied independent of light conditions. The responsiveness to CO₂ maintained for 10 days being set still on the slide glass. These results demonstrate the promising property of plant leaf as a CO₂ gas sensing element.     

CO2 gas exchange and phosphoenolpyruvate carboxylase activity in leaves of Zea mays L.

Important gas exchange characteristics of C4 plants depend on the properties of phophoenolpyruvate carboxylase (PEPC), the enzyme catalysing the primary fixation of CO2 during C4 photosynthesis. In this study, the relationship between intracellular resistance for CO2 fixation (r_i) at high photosynthetically active photon flux densities (PPFD) and maximum PEPC activity in vitro (V_pm) was examined in leaves of Zea mays L. The analysis allowed the estimation of the Michaelis constant K_p of the enzyme for CO2 (or the equivalent number for bicarbonate) in vivo. At low PPFD (below 100 mol m-2 s-1) the initial slopes of the curves describing net CO2 uptake rate A as a function of intercellular CO2 concentration c_i increased with increasing PPFD. The increase (i. e. a decrease in r_i) was interpreted as due to a reversible activation of PEPC by light. Including this assumption into a model of C4 photosynthesis enabled us to reproduce A(c_i) response curves measured at low levels of PPFD. Fitting the model to experimental data resulted in values for K_I, the PPFD at which PEPC reaches half of its full activation, of about 200 mol m-2 s-1. Similar results were derived from the dependence of r_i on PPFD. The analysis of the relationships between r_i and V_pm and between r_i and PPFD, as well as fitting of the model to gas exchange data all gave rise to estimates for the resistance for CO2 transfer within mesophyll cells that are comparable with those known from C3 plants.     

The enzyme system for the entrance of 14CO2 in the dark CO2-fixation of brown algae

High activity of phosphoenolpyruvate (PEP)-carboxykinase, orADP: oxalacetate (OAA) carboxy-lyase activity (a kind of EC4. 1. 1. 32) was discovered in enzyme extracts or partiallypurified preparations obtained from the brown algae, Eiseniabicyclis, Dictyota dichotoma, Spatoglossum pacificum; and Hizikiafusiformis. Enzyme activities were determined by measuring theradioactivity incorporated in the products of dark ¹⁴CO₂-fixationand by spectrophotometric determinations. Except for the lowactivity of "malic enzyme" (EC 1. 1. 1.40), no activities ofother carboxylases, i.e. PEP-carboxylase, PEP-carboxytransphosphorylase,and pyruvate carboxylase could be detected in algal extractsprepared under various conditions. Malate dehydrogenase (EC1. 1. 1. 37), fumarase (EC 4. 2. 1. 2), and glutamic: oxalacetictransaminase (EC 2. 6. 1. 1) were also detected. The algal PEP-carboxykinase required ADP and Mn²⁺ for maximumactivity in the carboxylation reaction; and ATP and Mn²⁺, butnot GTP, for maximum activity in both the decarboxylation andOAA-¹⁴CO₂-exchange reactions. The optimum pH of purified PEP-carboxykinase was in the regionof 7.0 to 7.3 in both the carboxylation and decarboxylationreactions, and its Km values for HCO₃^–, PEP, and ADP were10 mM, 0.3 mM, and 0.07 mM, respectively, in the carboxylationreaction, and values for OAA and ATP were 0.05 mM and 0.4 mM,respectively, in the decarboxylation reaction. Furthermore,the decarboxylation reaction was markedly inhibited by 20 mMHCO₃^–. The physiological role of PEP-carboxykinase as the enzyme responsiblefor the entrance reaction of the dark CO₂-fixation is discussed. ¹ Contributions from the Shimoda Marine Biological Station ofTokyo Kyoiku University, No. 236. This work was supported inpart by a Grant-in-Aid for Co-operative Research from the Ministryof Education, Japan and Matsunaga Science Foundation (to T.Ikawa). ² Present address: Department of Antibiotics, the National Instituteof Health, Shinagawa, Tokyo, Japan. (Received February 22, 1972; )     

Controlling self-incompatibility by CO2 gas treatment in Brassica campestris: structural alteration of papillae cell and differential gene expression by increased CO2 gas

Self-imcompatibility is a controlling genetic mechanism to prevent self-pollination for Chinese cabbage (Brassica campestris), one of the major vegetable crops in Korea. To maintain inbred lines of the crop plant, a method in that high CO2 gas is treated to the pistils to overcome the self-incompatibility and thereby self-pollens can successfully make germination and fertilization has been widely used in seed companies. Despite the common utilization of this method, any molecular and cellular studies on how the self-incompatibility is removed from the Chinese cabbage plant have not been done. In this study, we show that the increased CO2 gas causes a structural alteration of the papillae cell and thereby the self-incompatibility is removed from the Chinese cabbage plant, allowing the self-pollens to germinate and penetrate the papillae cell. Also, gene expression in the pistil treated with CO2 gas was studied by DD/RT-PCR and reverse northern hybridization experiments. The results suggest that the failure in self-incompatible reaction resulted not only from the structural alteration of the papillae cell but also from change in the pistil component production that is either positively or negatively regulated by the environmental stimulation.     

A gas phase chromatography method for determination of low dissolved CO2 concentration and/or CO2 solubility in microbial culture media

CO₂ concentration in aqueous samples was derived from determination of the CO₂ content in the gas phase at equilibrium with the liquid by gas chromatography. This technique was used to measure low dissolved CO₂ concentrations, down to 10^–6 mol/L, and CO₂ solubility in microbial culture media. The method gave results with an accuracy within 10%, and appeared thus as reliable and sensitive. It could be considered as a valuable tool to study CO₂ mass transfer in bio-processes.