Use Of Sodium Sulfite Research Articles

Antimicrobial PDMS Surfaces Prepared through Fast and Oxygen-Tolerant SI-SARA-ATRP, Using Na2SO3 as a Reducing Agent.

Poly(dimethylsiloxane) (PDMS) is an attractive, versatile, and convenient material for use in biomedical devices that are in direct contact with the user. A crucial component in such a device is its surface in terms of antimicrobial properties preventing infection. Moreover, due to its inherent hydrophobicity, PDMS is rather prone to microbial colonization. Thus, developing an antimicrobial PDMS surface in a simple, large-scale, and applicable manner is an essential step in fully exploiting PDMS in the biomedical device industry. Current chemical modification methods for PDMS surfaces are limited; therefore, we present herein a new method for introducing an atom transfer radical polymerization (ATRP) initiator onto the PDMS surface via the base-catalyzed grafting of [(chloromethyl)phenylethyl]trimethoxysilane to the PDMS. The initiator surface was grafted with poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) brushes via a surface-initiated supplemental activator and reducing agent ATRP (SI-SARA-ATRP). The use of sodium sulfite as a novel reducing agent in SI-SARA-ATRP allowed for polymerization during complete exposure to air. Moreover, a fast and linear growth was observed for the polymer over time, leading to a 400 nm thick polymer layer in a 120 min reaction time. Furthermore, the grafted PDMAEMA was quaternized, using various alkylhalides, in order to study the effect on surface antimicrobial properties. It was shown that antimicrobial activity not only depended highly on the charge density but also on the amphiphilicity of the surface. The fast reaction rate, high oxygen tolerance, increased antimicrobial activity, and the overall robustness and simplicity of the presented method collectively move PDMS closer to its full-scale exploitation in biomedical devices.

Effects of growth stage and growing degree day accumulations on triticale forages: 2. In vitro disappearance of neutral detergent fiber

The use of winter triticale (X Triticosecale Wittmack) in dairy-cropping systems has expanded greatly in recent years, partly because of its value as a forage crop but also to improve land stewardship by providing winter ground cover. Our objectives were to use 2-pool and 3-pool nonlinear models to characterize in vitro disappearance of neutral detergent fiber (NDF) and then describe the relationship between estimated parameters from those models with plant growth stage or growing degree days (GDD) >5°C for winter triticale forages harvested during 2016 and 2017 in Marshfield, Wisconsin. Forages were harvested from replicated field plots each year at growth stages ranging from stem elongation to soft dough. All NDF analyses included use of sodium sulfite and heat-stable α-amylase with residual fiber corrected for contaminant ash (asNDFom). Nonlinear 3-pool models for in vitro disappearance of asNDFom that included fast (Bfast) and slow (Bslow) disappearance pools as well as an associated disappearance rate for each (Kdfast and Kdslow, respectively) were easily fitted provided that a single discrete lag time was applied to both Bfast and Bslow pools to reduce the number of parameters to be estimated. An unresolved issue related to fitting 3-pool decay models was the incomplete recovery of asNDFom from immature triticale forages at 0 h, which was partially resolved with 2 approaches that produced similar estimates of Kdfast and Kdslow. Most parameters obtained from 2- and 3-pool decay models for asNDFom could be related to growth stage or GDD using polynomial regression techniques, often with high coefficients of determination (R2). For 3-pool models of asNDFom disappearance, Bslow increased with plant maturity, but the associated Kdslow ranged narrowly from 0.011 to 0.015/h and could not be related to growth stage or GDD by quartic, cubic, quadratic, or linear regression models. Despite different cultivars coupled with substantial differences in precipitation across years, single endpoint estimates of in vitro disappearance of asNDFom after 24, 30, or 48 h of incubation were closely related (R2 ≥ 0.906) to growth stage and GDD by linear or quadratic regression models that were generally similar across production years. Typical recommendations for harvesting triticale at boot stage to facilitate the planting of a double crop are strongly supported by the extensive 30-h in vitro disappearance of asNDFom at that growth stage, which was 63.1 and 64.8% of asNDFom during 2016 and 2017, respectively.

SO2 Removal from the flue gas by hollow fibre membrane contactor

The combustion of fossils fuels is the main source of the environmental problems, such as acid rain, photochemical smog, and ozone depletion. To solve these problems, the appropriate technology to remove acid gasses such as SO2 is urgently required. In this work, SO2 removal was conducted using polypropylene and polysulfone-based hollow fiber membrane contactors. Water and sodium sulfite were used as sorbents. The results showed that the use of sodium sulfite as a sorbent provided 2 times higher SO2 permeation than water. Moreover, permeate flux of polypropylene membrane was higher than polysulfone membrane since the hydrophobic membrane is more suitable as membrane contactor for flue gas cleaning. In addition, a comparison between membrane contactor and conventional scrubber showed that membrane contactor can reduce the contact volume up to 27 times smaller than those used in the conventional scrubber.

Effects of correcting for microbial contamination and the use of sodium sulphite in neutral detergent fibre analyses on the ruminal fibre degradability of several feeds

SUMMARYSodium sulphite is used in an optional way to remove insoluble proteins from neutral detergent fibre (NDF) residue. To determine whether the recovery of both NDF and insoluble nitrogen (N) in NDF solution (NDIN) are altered by its use, both parameters were measured in a set of 12 feeds, including cereal grains: maize (MG), rye (RG) and wheat (WG); cereal co-products: maize gluten feed (MGF), distilled dried grains from barley (DDGB) and wheat (DDGW) and wheat bran (WB); protein concentrates: rapeseed meal (RSM) and expeller palm kernel (EPK); dehydrated sugar beet pulp (DBP) and oat (OH) and ryegrass (RGH) hays. Associated effects on thein situeffective degradability (ED) of both NDF and NDIN were also studied in DDGW, WB, RSM, EPK, DBP, OH and RGH. Also, ED of acid detergent fibre (ADF) and its N (ADIN) were studied in hays. Errors due to microbial contamination in the rumen on the ED of NDF, ADF, NDIN and ADIN were also established in these last seven samples using15N infusion methods. Three rumen and duodenum cannulated wethers were used in the study. The sulphite use in NDF solution led to reductions (DDGB, DDGW, RSM and OH) and increases (RG, WG, WB and DBP) of the NDIN proportion, as well as the contribution of crude protein to NDF. These variations were associated with irregular effects on NDF residues and on ED of both NDIN and NDF. As a consequence, sulphite use does not assure the reduction of the insoluble protein contamination and it may even increase it. This methodology may also alter the degradability estimates of NDIN or NDF. Mean ruminal microbial contamination in NDF was 7·0, 10·8, 13·3, 5·4, 12·0, 35·3 and 20·0 g/kg in WB, DDGW, RSM, EPK, DBP, OH and RGH, respectively. The associated contents of microbial N in NDIN were: 59·3, 29·9, 26·2, 19·8, 37·3, 441 and 150 g/kg, respectively. Microbial contamination in ADF and ADIN (g/kg) was 3·6 and 94·5 in OH and 1·7 and 41·2 in RGH. Not correcting this contamination led to consistent undervaluations of ED of NDIN and NDF in all tested feeds, although errors only reached significance for NDIN in hays and DBP. Microbial-corrected ED of NDIN was 0·685, 0·826, 0·481, 0·389, 0·166, 0·718 and 0·425 in WB, DDGW, RSM, EPK, DBP, OH and RGH, respectively, whereas values for ADIN were 0·504 (OH) and 0·469 (RGH).

Improvement and validation of the method to determine neutral detergent fiber in feed

To improve the performance of the analytical method for neutral detergent fiber in feed with heat-stable α-amylase treatment (aNDFom), the process of adding heat-stable α-amylase, as well as other analytical conditions, were examined. In this new process, the starch in the samples was removed by adding amylase to neutral detergent (ND) solution twice, just after the start of heating and immediately after refluxing. We also examined the effects of the use of sodium sulfite, and drying and ashing conditions for aNDFom analysis by this modified amylase addition method. A collaborative study to validate this new method was carried out with 15 laboratories. These laboratories analyzed two samples, alfalfa pellet and dairy mixed feed, with blind duplicates. Ten laboratories used a conventional apparatus and five used a Fibertec(®) type apparatus. There were no significant differences in aNDFom values between these two refluxing apparatuses. The aNDFom values in alfalfa pellet and dairy mixed feed were 388 g/kg and 145 g/kg, the coefficients of variation for the repeatability and reproducibility (CV(r) and CV(R) ) were 1.3% and 2.9%, and the HorRat values were 0.8 and 1.1, respectively. This new method was validated with 5.8% uncertainty (k = 2) from the collaborative study.

Performance Evaluation of an Oxidation Ditch System with a Disc Aerator

Problem statement: The oxidation ditch system has been used to treat various types of wastewaters. Several types of aerators are used to supply the treatment process with oxygen. Among these devices, the disc aerator has certain advantages regarding foam generation over the brush and paddle type rotors, but the main disadvantages of this aerator is the limited oxygenation capacity. The main objectives of this study were to study the effects of various design parameters and system operation parameters on the oxygenation capacity of the system. Approach: A bench scale oxidation ditch system equipped with a disc aerator was used to gain better understanding of the phenomena of oxygen transfer and to study the effects of hole diameter, number of holes per disc, disc thickness, disc speed, immersion depth and number of discs on the oxygenation capacity of the system. The unsteady state method with sulphite oxidation was used to deoxygenate the water. The test involved chemical removal of dissolved oxygen from water followed by oxygenation. The power consumed was measured, the oxygen transfer coefficient was determined and both the oxygenation capacity and oxygenation efficiency were calculated. Results: The oxygen transfer coefficient was affected by the immersion depth, hole diameter, disc speed, disc thickness and number of discs, with the disc speed having the greatest effect. The results showed that three physical processes simultaneously contributed to oxygen transfer by the disc aerator: bubble aeration, eddy aeration and surface aeration. Conclusion: The use of sodium sulphite with cobalt chloride for deoxygenation of the water via the oxidation ditch was effective and the results were very consistent and repeatable. The aerator disc of 2.55 cm thickness, 1.92 cm diameter and 48 holes was found to achieve the highest oxygenation capacity. The system is anticipated to provide a broad range of oxygen transfer rates under actual conditions (23-164 mgO2/L-h) to meet varying process demands encountered in aerobic treatment systems.

Determination of chloramphenicol by differential pulse voltammetry at carbon paste electrodes – The use of sodium sulfite for removal of oxygen from electrode surface

The possibility of determination of chloramphenicol by differential pulse voltammetry at four different carbon paste electrodes, in the full pH range (2–12) of Britton–Robinson (BR) buffer was investigated. Electrodes were prepared by mixing spectroscopic graphite powder or glassy carbon microbeads with mineral oil (Nujol) or tricresyl phosphate. Under optimal conditions (BR buffer pH 12, the electrode prepared from glassy carbon microbeads and tricresyl phosphate), linear calibration graph was obtained only in 10–5 M chloramphenicol concentration range. Determination of lower concentrations of chloramphenicol was complicated by irreproducible peak of oxygen from the carbon paste which overlapped with peak of chloramphenicol. Addition of sodium sulfite removed the oxygen peak without influence on the peak of chloramphenicol. Under optimal conditions (electrode paste made from glassy carbon microbeads, BR buffer pH 10 and 0.5 M sodium sulfite), straight calibration line was obtained in the 10–6 and 10–5 M chloramphenicol concentration range. Limit of determination was 5 × 10–7 mol/l.

The amino acid profiles of the whole plant and of four plant residues from temperate and tropical forages.

This study compared the amino acid (AA) profile of five residues (original forage, borate-phosphate buffer residue (BPR), neutral detergent fiber residue with (NDF+) and without (NDF-) sodium sulfite, and acid detergent fiber residue (ADF). Fourteen grasses and legumes from tropical and temperate regions were used in this study. The use of sodium sulfite did not affect the NDF concentration, but the NDF insoluble protein was lower (P < 0.05) in the NDF+ than in the NDF- (3.9 vs 4.5% DM, respectively). For all of the amino acids tested, the amino acid content, expressed as a percentage of CP, was lower in the ADF residue than in the original forage. There were no differences in the amino acid concentrations of the NDF- and NDF+ extracts (P > 0.05). Only in the case of methionine was there a difference in the amount of amino acid when the original forage was compared with the BPR (1.84 vs 1.45 % CP). When the AA profile of each residue was corrected for the AA content of the ADF, no difference was observed between the AA profile of the original forage and of the BPR (P > 0.05). Similar to the result without correction for the amino acids in ADF, the AA profiles of the NDF+ and NDF- fractions were similar (P > 0.05). From this result, we infer that the sodium sulfite had similar effects on all AA in the NDF residue that we tested. There were differences in amino acid concentrations in the original forage and the NDF residues for several amino acids (Met, Cys, Lys, Thr, Arg, Ile, Leu, and Phe) (P < 0.05). When the amino acid values of the original forage and the BPR were used with animal data in the Cornell Net Carbohydrate and Protein System model, few differences in animal predicted performance were evident. These findings suggest that the AA profile of the original forage can be used to predict the AA profile of the undegraded intake protein instead of using the borate-phosphate buffer residue for amino acid analyses. This would simplify obtaining feed amino acid values for use in the Cornell Net Carbohydrate and Protein System.

A simplified method for the cultivation of extreme anaerobic Archaea based on the use of sodium sulfite as reducing agent.

The extreme sensitivity of many Archaea to oxygen is a major obstacle for their cultivation in the laboratory and the development of archaeal genetic exchange systems. The technique of Balch and Wolfe (1976) is suitable for the cultivation of anaerobic Archaea but involves time-consuming procedures such as the use of air locks and glove boxes. We describe here a procedure for the cultivation of anaerobic Archaea that is more convenient and faster and allows the preparation of liquid media without the use of an anaerobic chamber. When the reducing agent sodium sulfide (Na2S) was replaced by sodium sulfite (Na2SO3), anaerobic media could be prepared without protection from oxygen outside an anaerobic chamber. Exchange of the headspace of serum bottles by appropriate gases was sufficient to maintain anaerobic conditions in the culture media. Organisms that were unable to utilize sulfite as a source for cellular sulfur were supplemented with hydrogen sulfide. H2S was simply added to the headspace of serum bottles by a syringe. The use of H2S as a source for sulfur minimized the precipitation of cations by sulfide. Representatives of 12 genera of anaerobic Archaea studied here were able to grow in media prepared by this procedure. For the extremely oxygen-sensitive organism Methanococcus thermolithotrophicus, we show that plates could be prepared outside an anaerobic chamber when sulfite was used as reducing agent. The application of this method may faciliate the cultivation and handling of extreme anaerobic Archaea considerably.

Methods for Hatching Margined Madtom Eggs

We used the margined madtom Noturus insignis as a model species to develop egg-hatching techniques for other madtom species. Twelve methods were tested at water temperatures between 22°C and 30°C, but only one method produced consistent, high hatches of madtom eggs. Use of broodfish to incubate eggs was not effective because they ate their tank-spawned egg masses. Consequently, madtom eggs must be artificially incubated. Use of sodium sulfite, Na2SO3, to facilitate artificial incubation by separating madtom egg masses is not effective because it causes premature hatching and subsequent low survival of larvae. Agitation strong enough to tumble eggs and high temperature appear to be key in consistently producing good hatches. We obtained hatch rates greater than 65% for 14 of 16 margined madtom egg masses by incubating them at 28-30°C within a 6-mm-bar-mesh plastic basket positioned over an air stream strong enough to keep egg masses in constant motion. The larvae hatched in about 7 d at 28°C, and the mean number of degree-days for hatching was 205 ± 14 (N = 6).

Some comments on the determination of microcystin toxins in waters by high-performance liquid chromatography

This paper describes some of the problems that may arise during the analysis of microcystin toxins and nodularin using the method described by Lawton, Edwards and Codd (Analyst, 1994, 119, 1525). Difficulty may be caused by the appearance of additional peaks in the HPLC chromatograms as a result of leaching of material from the C18 trifunctional (C18t) solid-phase extraction cartridges, and co-elution of other organic compounds in the water makes it difficult to identify toxins using their characteristic UV spectra, expecially at low toxin concentrations. Samples containing chlorine must be treated with sodium thiosulfate since the presence of chlorine results in low toxin recoveries, especially of nodularin. The published method specifies the use of sodium sulfite and acidification with trifluoroacetic acid for the removal of chlorine, but application of this procedure has been shown to produce inconsistent toxin recoveries, and zero percentage recoveries were recorded in 71% of the analyses performed with treated waters having a microcystin LR concentration of 0.4 µg l–1. The use of microcystin LR as an ‘internal standard’ to adjust the recovery of other microcystin toxins is at best qualitative.

Effects of Incubation Time and Sodium Sulfite upon in-vitro Digestibility Estimates and Sample Filtering Time

We conducted 2 experiments to quantify the effects of incubation time, filtering method, forage type, and associated interactions on the precision and accuracy of in-vitro digestibility as estimates of in-vivo digestibility. Experiment I used 10 incubation times and alfalfa (Medicago sativa L.), kleingrass (Panicum coloratum L.), prairie grass, and wheat straw (Triticum aestivum L.) hays to determine whether a single incubation time should be employed to estimate digestibility of a variety of forages. Additionally, 2 second stage neutral detergent extraction methods were evaluated to determine sodium sulfite effect on fiber recovery and filter time. An interaction existed between incubation time and in-vitro estimates of digestibility. The use of sodium sulfite increased (P<0.05) digestibility estimates (1.3 units) across all hays and decreased filtering times by as much as 9.5 min/sample. Experiment II utilized 3 hays (alfalfa, kleingrass, and wheat straw), 4 incubation times and 4 neutral detergent extraction methods in an effort to isolate where the changes in neutral detergent fiber (NDF) estimates due to sodium sulfite occurred and if a method could be developed to maximize filtering speed without compromising the accuracy of digestibility estimates. Use of sodium sulfite in the rinse water did not affect apparent NDF recovery and decreased filtering time by approximately 10 min. when compared to no sulfite additions. Results of this study confirm previous observations that a single incubation period should not be used to estimate in-vivo digestibility. Addition of sodium sulfite to the rinse water provides a viable means to decrease sample analysis time without jeopardizing the accuracy of digestible NDF estimates.

Sodium sulfite and extrusion affect the nutritional value of soybean products for nursery pigs (1994)

A total of 150 weanling pigs (14.2 lb avg body wt) was used in a 28-d growth assay to determine the effects of using sodium sulfite as an extrusion enhancer for soy products. Treatments were: 1) soybean meal (SBM), 2) SBM + sodium sulfite, 3) extruded SBM, 4) SBM extruded with sodium sulfite, 5) extruded whole soybeans, and 6) whole soybeans extruded with sodium sulfite. For d 0 to 14, pigs fed SBM had greater average daily feed intake (ADFD, although they had poorer efficiency of gain (F/G) than pigs fed the extruded soy products. Also, pigs fed sodium sulfite showed a trend for greater average daily gain (ADG) and F/G compared to pigs fed diets without sodium sulfite. The positive response to sodium sulfite continued into Phase II (d 14 to 28), where pigs fed sodium sulfite had greater ADG and ADFI compared to those not fed sodium sulfite. Pigs fed extruded soybeans in Phase II had greater ADG than pigs fed extruded SBM. Overall (d 0 to 28), pigs fed diets with sodium sulfite consumed more feed, gained faster, and tended to have improved efficiencies of gain rompared to those fed diets without sodium sulfite. Also, pigs fed extruded soybeans had greater rates and efficiencies of gain than pigs fed extruded SBM. Thus, in conclusion, sodium sulfite improved growth performance of weanling pigs. Also, extruded soybeans supported greater growth performance than extruded SBM, but pigs fed extruded soybeans responded less to the use of sodium sulfite as an extrusion enhancement than pigs fed the other treatments.; Swine Day, Manhattan, KS, November 17, 1994

Host—guest stabilized room temperature phosphorescence in β-cyclodextrin/ bromoalcohol solutions from 2-naphthyl-oxy-acetic acid and 1-naphthyl-acetic acid

Room temperature phosphorescence (RTP) from 2-naphthyl-oxy-acetic acid (NOA) and 1-naphthyl-acetic acid (NAA), with stabilization by use of β-cyclodextrin (β-CD) as a host system, has been examined. 2-Bromoethanol and 2,3-dibromopropanol have been evaluated as external heavy atom perturbers to enhance the rate of intersystem crossing and, consequently, populating the triplet state for phosphorescence emission. The deoxygenation of the solutions was achieved chemically by use of sodium sulphite. The spectral characteristics of the phosphorescence emission from these relatively polar compounds and the optimization of the chemical variables involved are reported. The role of the bulkiness of the bromoalcohol employed, in comparison with the unoccupied space of the interior of the cyclodextrin cavity by the guest, is an important factor in the attainment of an effective RTP emission, and should be taken into account in the selection of the appropriate external heavy atom for the observation of RTP from other organic molecules of interest by this approach. 2,3-Dibromopropanol seems a more adequate bromoalcohol than 2-bromoethanol for the observation of RTP emission in the systems investigated.

Floatability of chalcopyrite in the presence of dialkyl-thionocarbamate and sodium sulfite

The use of sodium sulfite in the flotation of sulfide ores using a dialkyl-thionocarbamate as collector enables us to obtain, in most cases, a good selectivity for copper sulfide from other sulfides. However, under certain conditions, we observe some possibilities of chalcopyrite depression. The results related here attempt to delineate the parameters leading to a deterioration in the selectivity of the chalcopyrite flotation. The roles of mill type, pH regulator, more or less pronounced superficial oxidation, pollution by iron from the mill, etc. are considered. The conjunction of grinding without iron oxide pollution (by using a stainless steel mill), the presence of galena-pyrite mixture, Ca 2+ ions, and oxidizing conditions, has the effect of strongly depressing the chalcopyrite.

The use of sodium sulphite to improve the flotation selectivity between chalcopyrite and galena in a complex sulphide ore

The processing of complex sulphide ores by the sequential method of flotation requires maximal selectivity. In particular, the entrainment of galena into the chalcopyrite concentrate obtained with a dialkylthionocarbamate-type collector must be minimized. Use of sodium sulphite, in association with alkaline-earth or metal hydroxides released by the ore, helps to reduce the entrainment of lead into the copper ore. We have observed these phenomena with pure minerals and then with a natural ore. Observations of the electrokinetic potential and surface adsorption phenomena of galena suggest a mode of action of Ca 2+ and Ba 2+ ions or metal hydroxides. The species formed by barium on galena were detected by diffuse reflectance infrared interferometry.

Cyclodextrin-induced fluid solution room-temperature phosphorescence from acenaphthene in the presence of 2-bromoethanol

A 1:1 stoichiometric ratio and a formation constant of 130 1 mol −1 were obtained for the binary inclusion complex between acenaphthene and β-cyclodextrin (CD). On addition of 2-bromoethanol, effective quenching of the fluorescence emission and enhancement of the room-temperature phosphorescence (RTP) of acenaphthene is observed. The use of 2-bromoethanol as an external “heavy atom” to obtain room-temperature phosphorescence in fluid solutions is discussed. The RTP emission from acenaphthene included in β-CD was optimized and characterized. The apparent formation constant of the ternary associate was determined to be 880 1 mol −1 by the use of RTP enhancement in the presence of 1% 2-bromoethanol. The data indicate a ternary association between acenaphthene, β-CD and the bromo alcohol. The use of sodium sulfite, for chemical deoxygenation, to obtain RTP emission from a non-heavy atom-containing luminophor is shown to be feasible. The kinetics of the deoxygenation reaction were established and a photochemical catalytic effect on the reaction was demonstrated.

Glycerol production by anaerobic vacuum fermentation of molasses on pilot scale

The use of sodium sulphite as a steering agent for enhancing the yield of glycerol during anaerobic ethanol fermentation is well established. Several studies have been reported in the literature using free as well as immobilized cells of Saccharomyces cerevisiae. In these studies it was observed that a relatively high concentration of sulphite in the fermentation broth, typically 40-100 g/l, was required to obtain a commercially significant yield of glycerol on sugar fermented. However, the dosing of large quantities of sulphite generally resulted in reduced viability of the microorganisms and slow fermentations. The glycerol concentration in the fermented broth was generally observed to be in the range 20-40 g/l. The low productivity coupled with the high cost of sulfite rendered the process commercially unattractive. In order to reduce the sulphite requirement, whilst at the same time increasing the productivity, a modified vacuum fermentation was developed in the laboratories. The process was successfully estabilished on a pilot scale and typical data obtained on scaleup are reported below. 8 references.

Single-Column Chromatographic Analysis of Labeled Glutamine and Other Amino Acids in Whole Blood

A method is presented for single-column analysis of the concentrations and specific activities of the free amino acids in both whole blood and plasma. Interference from glutadiione in whole blood was eliminated by the use of sodium sulfite although losses of about one-half of the cystine and methionine occurred. Seventy-five percent±1 of the glutamine was recovered consistently in both whole blood and plasma so that corrections for this loss readily could be made. Elimination of the baseline shift due to ammonia was accomplished by passing the buffers through ion-exchange columns before entering the sample loops. There were several significant differences between amino acid concentrations and specific activities in whole blood and in plasma, indicating that care should be taken in interpreting data on metabolism of amino acids.

Morphological Adaptations of Cyprinodontoids for Inhabiting Oxygen Deficient Waters

A previously unrecognized morphological adaptation of fishes to oxygen depletion is described. Natural oxygen depletion was simulated by use of sodium sulfite. It was demonstrated that some fishes are adapted to permit use of an oxygen rich layer of water at the atmosphere-water interface. Representative cypronodontoids (Fundulus notatus, Gambusia affinis, and Poecilia reticulata) exhibited maximum adaptation and the greatest survival ability of the species tested. Notemigonus crysoleucas, Brachydanio rerio, Lepomis macrochirus, and L. cyanellus, representing other suborders, showed less adaptation to these conditions and correspondingly lower survival. Micropterus salmoides seemed unadapted for survival in oxygen depleted waters. Carassius auratus exhibited a physiological adaptation, but used the oxygen rich surface water as a supple-