An apparatus to measure the rate of oxygen evolution while maintaining pO2 constant during photosynthetic growth in closed culture vessels capable of operation at increased hydrostatic pressures

A double polarographic device is described which permits regulation of dissolved oxygen concentration at any preset pO₂ in suspensions or cultures of photosynthetic algae. It also simultaneously permits measurements of the rate of oxygen evolution during photosynthesis. The apparatus is designed to operate in closed vessels in the absence of a gas phase, and may be used at increased pressures tested up to 500 atmospheres. Regulation of oxygen levels was maintained constant at various preset concentrations equivalent to atmospheric pO₂ values ranging between 0.02 and 0.21 at 25°C.     

Aquatic insect larvae as indicators of limiting minimal contents of dissolved oxygen

Minimal concentrations of oxygen are limiting factors for limnic biocenoses. It should therefore be possible to use biocenose structure to infer minimal oxygen concentrations that have occured, provided the tolerance of the organisms concerned is known. A simple apparatus used to measure LC₅₀ of oxygen for aquatic insect larvae with tracheal gills is described. Lethal concentrations found in some Ephemeroptera differ between species. Usually, they are strongly temperature dependent. In the species so far studied, confidence intervals are very small and suggest that such insect larvae could be used as bioindicators of minimal oxygen concentrations (even of short term ones), especially in thermically stable waters.     

Photosynthetic electron transport and anaerobic metabolism in purple non-sulfur phototrophic bacteria

Purple non-sulfur phototrophic bacteria, exemplifed byRhodobacter capsulatus andRhodobacter sphaeroides, exhibit a remarkable versatility in their anaerobic metabolism. In these bacteria the photosynthetic apparatus, enzymes involved in CO₂ fixation and pathways of anaerobic respiration are all induced upon a reduction in oxygen tension. Recently, there have been significant advances in the understanding of molecular properties of the photosynthetic apparatus and the control of the expression of genes involved in photosynthesis and CO₂ fixation. In addition, anaerobic respiratory pathways have been characterised and their interaction with photosynthetic electron transport has been described. This review will survey these advances and will discuss the ways in which photosynthetic electron transport and oxidation-reduction processes are integrated during photoautotrophic and photoheterotrophic growth.     

An Apparatus for Dosing Laboratory Fermenters with Suspensions

S ummary : The construction and operation of an apparatus for dosing laboratory fermenters semicontinuously with suspensions is described. The apparatus periodically measures a volume of slurry and then injects it into the fermenter. A control unit determines how often the cycle of operations is performed.     

Verfahren und Analysenautomat zur Bestimmung von Nährlösungskomponenten und Stoffwechselprodukten

A continuous flow system with an enzyme electrode and with a new type of measuring instrument, the BIOXY-Meter, is described as an example for the determination of glucose. The BIOXY-Meter combined with various biosensors may be used in biotechnology and in other fields for the solution of a number of analytical problems. Measuring principle is the reduction of oxygen. The peak of first derivation of the current-time-curve is proportional to oxygen consumption and to decrease of substrate concentration. Enzyme fixation with common adhesive and a device for automated saturation of measuring samples with air in the sampler are also described. With the apparatus 60 samples per hour are analyzed for glucose. The linear measuring range is 0.1 mMol to 1.5 mMol with a coefficient of variation of V_k = 0.93 per cent. The described type of enzyme electrode is stable for 2 to 12 weeks or 1,000 to 5,000 measurements.     

Vitamin analysis with use of a yeast electrode

A vitamin B₁ (thiamin)-sensitive electrode has been devised by combining an oxygen electrode with a yeast-containing membrane. The assembly was used for assaying thiamin at concentrations down to 10^?11 gl^?1. The analytical procedure developed should allow the measurement of 10–20 samples per hour. The performance of the yeast electrode was improved when alginate membranes reinforced with a nylon network were used. An apparatus for preparing such membranes is described together with a magnetic membrane holder facilitating handling of membranes in combination with electrodes.     

Method for Simultaneous Measurement of Radioactive and Inactive CO(2) Evolved from Soil Samples During Incubation with Labeled Substrates

An apparatus is described which allows the simultaneous, continuous, and highly sensitive analysis of inactive and radioactive CO₂ evolved from ¹⁴C-supplemented soils or other materials. The apparatus consists of a control unit, a commercially available conductometric CO₂ analyzer, and fraction collector. A number of model experiments were conducted to demonstrate the potentials of the apparatus. These included analysis of the time course of priming action, when ¹⁴C-glucose was added to soil, separation of CO₂ respiration peaks caused by simultaneous degradation of radioactive and inactive soil supplements, and study of the effects of a fungicide, Benomyl, on degradation of ¹⁴C-labeled glucose. In the last experiment, partial degradation of the fungicide could also be followed.     

Method for Simultaneous Measurement of Radioactive and Inactive CO2 Evolved from Soil Samples During Incubation with Labeled Substrates

An apparatus is described which allows the simultaneous, continuous, and highly sensitive analysis of inactive and radioactive CO₂ evolved from ¹⁴C-supplemented soils or other materials. The apparatus consists of a control unit, a commercially available conductometric CO₂ analyzer, and fraction collector. A number of model experiments were conducted to demonstrate the potentials of the apparatus. These included analysis of the time course of priming action, when ¹⁴C-glucose was added to soil, separation of CO₂ respiration peaks caused by simultaneous degradation of radioactive and inactive soil supplements, and study of the effects of a fungicide, Benomyl, on degradation of ¹⁴C-labeled glucose. In the last experiment, partial degradation of the fungicide could also be followed.     

Isolation of cu -Antitrypsin in a New Preparative Electrophoresis Apparatus

The construction and operation of an apparatus is described which enables α-antitrypsin to be isolated from human serum by preparative electrophoresis in polyacrylamide gel. The initial pass through the chamber yields a fraction that is predominantly albumin and several α₁-proteins. After removal of albumin by affinity chromatography, a second pass through the chamber separates the individual α₁-proteins. A volume of 50 ml of serum may be accommodated by the chamber, and the recovery of activity in each step is greater than 60%. The entire procedure may be completed in 36 hrs.     

A pilot plant apparatus for continuous phased culture--some observations on oxygen usage by Candida utilis during the cell cycle

An inexpensive scale-up of the cyclone column apparatus (Can. J. Microbiol., 11 , 893 (1965)) is described which is suitable for pilot plant studies on the 10 liter scale. Details of its construction and operation are given. Experimental with phased cultures of C. utilis growing in the equipment are reported during which studies of dissolved oxygen and oxygen uptake were made over the cell cycle. Changes in both oxygen parameters occurred during the cycle and were useful as monitors of the growth. Cell of C. utilis were found to be very sensitive to changes in oxygen supply during the early stages of the cell cycle.     

A method for the control of the dissolved oxygen tension in microbial cultures

A method for the control of dissolved oxygen tension in growing microbial cultures is described. The apparatus consists of a motor-driven air sparge pipe which may be lowered or raised to give a variable point of entry of the air stream into the culture liquid and hence a variable gas dispersion and gas–liquid contact time. Control of the sparge pipe position is by means of a feedback control loop consisting of a dissolved oxygen probe, an on/off controller, and a reversing electric motor which drives the sparge pipe. The difficulty presented by the relatively slow response of the oxygen probe has been overcome by incorporating an adjustable rate of control action.     

Laboratory-Produced CO(2) Calibration Gases

A simple, inexpensive apparatus for making mixtures of accurately known amounts of CO₂ and CO₂-free atmospheric air is described. Calibration gases with CO₂ contents of 200 to 1500 microliters per liter produced with the apparatus had concentrations which were within 10 microliters per liter of the target concentration.     

Continuous Culture of Ruminal Microorganisms in Chemically Defined Medium: I. Design of Continuous-Culture Apparatus

An apparatus is described which has been used for successful continuous culture of the ciliates from the rumen of cattle. Automatic control of feeding rate, pH, oxidation-reduction potential, temperature, stirring rate, aeration rate, salinity, and volume of the culture is provided for, using standard commercial equipment, whenever possible. The operation of this apparatus is described.     

An observation chamber for a high-pressure stopped-flow apparatus

A new design of the observation window to observation chamber seal is described for the Berger rapid stopped-flow apparatus. This design permits reliable operation of the apparatus and retains the features of a square non-deviating observation path with flush windows. Incorporation of fiber optic light guides for the observation path has made the apparatus insensitive to vibration artifacts. A demonstration reaction of calcium binding to EGTA is presented; the reaction, which is 90% complete complete within 2 ms, illustrates the capability of this apparatus for examining fast reactions.     

瑞芬太尼对急性高容量血液稀释后颅内动脉瘤夹闭术患者脑氧代谢以及术后认知功能的影响

目的:探究瑞芬太尼对急性高容量血液稀释(AHH)后颅内动脉瘤夹闭术患者脑氧代谢以及术后认知功能的影响。方法:选择2015年5月至2016年12月期间在我院进行颅内动脉瘤夹闭术的92例患者作为研究对象,并将其随机均衡分为研究组和对照组,每组46例,研究组给予瑞芬太尼治疗,对照组给予硝酸甘油治疗。对两组患者AHH前(T0)、AHH后(T1)、降压前(T2)、降压后30 min(T3)、动脉瘤夹闭术后5 min(T4)等时间点的平均动脉压(MAP)、心率(HR)进行记录,在T2-T4时间点对颈内静脉球部血、桡动脉血两处位置的动、静脉血氧饱和度(SAO_2、SjvO_2)、动脉血氧分压(PAO_2)、静脉血氧分压(PjvO_2)进行统计,计算动脉氧含量(CAO_2)、颈内静脉氧含量(CjvO_2)、动脉颈内静脉球部血氧差(Da-jvO_2)、颈内静脉球部动脉乳酸差(VADL)和脑氧摄取率(CERO_2)。在术前、术后3 d、术后7 d采用简易智力状态量表(MMSE)对两组患者的认知功能进行评估。结果:相对于T2时间点,在T3、T4时间点,两组患者MAP均出现显著降低(P0.05);对照组患者HR显著升高,研究组患者HR显著降低(P0.05)。两组患者SaO_2均为100.00%,在T3、T4时间点研究组SjvO_2、CjvO_2显著高于T2时间点,且较对照组患者升高,差异均有统计学意义(P0.05),Da-jvO_2、CERO_2显著低于T2时间点,且较对照组患者降低,差异均有统计学意义(P0.05)。PaO_2、CaO_2、PjvO_2、VADL组间比较差异均无统计学意义(P0.05)。术前、术后3 d、术后7 d两组患者的MMSE评分比较均无统计学差异(P0.05),术前、术后7 d两组患者的MMSE评分均高于术后3 d的MMSE评分(P0.05)。结论:瑞芬太尼对急性高容量血液稀释进行颅内动脉瘤夹闭术,能够有效维持患者机体血流动力学稳定,同时还可以对脑氧代谢率进行有效控制,相对于硝酸甘油进行急性高容量血液稀释,瑞芬太尼优势较为明显,但对于认知功能无明显的改善作用。     

A simple apparatus for the continuous monitoring of 14CO2 production from several small reaction mixtures

A simple apparatus is described which permits the continuous monitoring of ¹⁴CO₂ production from ten separate reaction mixtures simultaneously. The device is relatively simple and inexpensive to construct, makes use of small disposable incubation vials, and allows complete trapping of all ¹⁴CO₂ evolved in scintillation vials, where it can be easily counted. The use of this apparatus to determine the rates of metabolism by glomeruli of ¹⁴C-labeled substrates to ¹⁴CO₂ is described.     

Design and operation of a simple continuous-culture apparatus

A versatile and simple continuous-culture apparatus is described. With this apparatus, independent control of limiting growth factors and other nutrilites is possible and the conditions of each experiment are reproducible. In view of the synchronized speed of the feeder syringes, flow variation troubles are not encountered. The device allows the performance of growth experiments at different dilution rates simultaneously in a single run which makes the comparison of the results more reliable. The operation of the device has been tested successfully with a study of adenine deaminase induction in yeast.     

Nitrogen-limited continuous culture ofRhodopseudomonas capsulata growing photosynthetically or heterotrophically under low oxygen tensions

A continuous culture apparatus is described, which allows cultivation of photosynthetic bacteria anaerobically in the light and semiaerobically in the dark at constant oxygen tensions. The growth-parameters 1. substrate concentration at half maximum growth rate (K _s) and 2. yield (Y) forRhodopseudomonas capsulata are calculated.An automatic control system of the oxygen partial pressure in the culture medium is elaborated. It is shown, that the discontinuous regulation with a control unit in connection with two magnetic valves, which give short pulses of either oxygen-free gas or gas mixed with oxygen, is an economic, practicable and reliable method.The yield coefficientY during growth limited by ammonium sulfate is variable due to the synthesis of nitrogen independent metabolites, such as poly--hydroxybutyrate. The storage of poly--hydroxybutyrate in continuous culture is a function of both the actual concentration of ammonia and of theC/N ratio. At very low growth rates (1/6 µ _m ) the poly--hydroxybutyrate content increases amounting to 33% of the dry weight.In semiaerobically dark grown cells (pO₂: 5 mm Hg) the protein and bacteriochlorophyll content increased definitely on dry weight basis with increasing growth rates. In contrast, in anaerobic light cultures only a small increase of the bacteriochlorophyll level but no change of the protein content per dry weight of cells was observed at increasing growth rates.     

A NEW FORM OF DIFFERENTIAL MICRORESPIROMETER

1. A microrespirometer suitable for measuring oxygen uptakes from 0.1 to 10λ per hour is described. 2. The sensitivity of the instrument may be readily altered by substituting different sizes of capillary tubing. 3. By means of replaceable brass plugs the chamber volume of this instrument may be varied from 700 to less than 40λ. 4. No thermostat is required for the operation of the instrument at room temperature. 5. It may be charged at one temperature and used at a widely different one. 6. The chambers may be filled with any desired gas mixture. 7. Two solutions may be mixed during the course of an experiment. 8. The entire apparatus may be sterilized.     

Effects of hyperoxia on biomarkers of oxidative stress in closed-circuit oxygen military divers

Oxygen toxicity is a problem in diving which can have fatal consequences in the water. When divers use closed-circuit oxygen rebreathing apparatus they are taking only oxygen 100% and this hyperoxic exposure increases the generation of reactive oxygen species (ROS) in biological tissues. The objective of the present study is to evaluate the effects of hyperoxia on biomarkers of oxidative stress in closed-circuit oxygen military divers. Fifteen professional divers of Spanish Navy Diving Center participated in a training program which consisted of one-hour immersion at seven metres of depth breathing oxygen 100% with closed-circuit oxygen rebreathing apparatus. The training went on two or three times per week for the first six weeks and once a week for the last six weeks. Serum total antioxidant status (TAS), levels of glutathione peroxidase (GPx), nitrates (NO₃ ^?) and urinary concentrations of 15-isoprostane F_2t were measured. The results show that TAS decreased significantly after 6 weeks (mean 1.38 versus 1.23 mmol/l), with a slight increase at the end (mean 1.31 mmol/l). GPx and F₂-isoprostanes were significantly lower after 6 and 12 weeks and NO₃ ^? was significantly lower after 6 weeks and remained unchanged until the end. In summary, professional divers who use closed-circuit apparatus and therefore breathe oxygen 100%, do not suffer an important oxidative hyperoxia-induced stress, probably due an adaptive process after hyperoxia. The age and good physical form of the subjects studied could probably enhance the adaptive process to hyperoxia.