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 18,428 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Spectrophotometric characteristics of bilirubin at low concentrations (0.005-2.500 mg/100 ml) have been studied under various physical conditions in order to gain a better understanding of the state of bilirubin when preparing "solutions" for laboratory use. Standing, minimal shaking, or stirring of the bilirubin preparations at pH 7.4 progressively reduced and altered the maximal spectral absorption of bilirubin (440 nm) in aqueous buffered media. The shift to 415-420 nm is attributed to oxidation of the pigment whereas shoulder formation is attributed to the formation of large size particles (flocculants). In the presence of antixidants (L-ascorbic acid and nitrogen gas) and EDTA the maximal absorption peak remained at 440 nm but decreased in magnitude concomitant with development of progressively increasing shoulder at 480-560 nm. In the absence of antioxidants and EDTA maximal absorption shifted to 415-420 nm and the magnitude of 480-560 nm shoulder formation was less. At the higher concentrations of bilirubin and with reduction in pH of the buffer in the absence of antioxidants, the shift to lower wave lengths was reduced and 450-560 nm shoulder formation was increased. In the absence of antioxidants and EDTA at the lower concentrations of bilirubin and in more alkaline media, the reduction at 440 nm and the shift of maximal absorption to the shorter wave lengths was enhanced. At pH 12, stirring of antioxidant-EDTA-containing solutions of bilirubin resulted in neither a shift of maximal absorption to the shorter wave lengths nor the formation of 480-560 nm shoulder. The formation of 480-560 nm shoulder was accompanied by the visual appearance of turbidity. The formation of flocculants when a "solution" is agitated indicates that significant portions of the pigment were in fact, not in solution and must have existed previously as a finely dispersed colloidal sol or supersaturated solution which progressed to a colloidal sol. Spectral curves of bilirubin, therefore, may represent a composite resulting from four physical states of bilirubin: (1) bilirubin truly in solution with the spectral peak at 440 nm; (2) bilirubin in the fine colloidal dispersion with spectral characteristics similar to those of bilirubin in solution; (3) bilirubin flocculant giving 480-560 nm shoulder; and (4) oxidation products of bilirubin with the spectral peaks lower than 440 nm. Increasing the pH of the aqueous media containing bilirubin (0.05 mg/100 ml) from 7.4 to 12.0 increased the molar extinction coefficient of bilirubin, E1M/440 1cm, progressively to a maximum at pH 12 of 6.35 X 10(4). Very dilute bilirubin preparations (0.005-0.050 mg/100 ml) in aqueous media, pH 7.4, exhibited spectral evidence of rapid oxidation (more so at higher pH), but spectral shoulder formation was still observed after mechanical agitation. Thus, the solubility of bilirubin in 0.1 M phosphate buffer at pH 7.4 appears to be less than 0.005 mg/100 ml.
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PMID:Spectrophotometric characteristics of bilirubin. 0 55

By shaking a dilute suspension of egg yolk with chloroform followed by low speed centrifugation (1500 g for 30 min) the water soluble proteins which include chicken IgG (IgY) separate from the emulsion of chloroform and lipophilic substances. The IgY may then be separated from the associated water soluble proteins by precipitation with 12% polyethylene glycol Mr 6000. The method called the chloroform - polyethylene glycol procedure was compared with the polyethylene glycol procedure which is currently being used. It was found that the chloroform - polyethylene glycol method yielded 2.57 times more IgY than the conventional polyethylene glycol method. The ratio of titres of IgY anti Jasus lalandii haemocyanin antibody purified by the two procedures was very nearly 2.57 indicating that the chloroform had no adverse effect on the antibody activity.
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PMID:Isolation of IgY from the yolks of eggs by a chloroform polyethylene glycol procedure. 236 27

Ten isolates of Pseudomonas aeruginosa obtained from the corneas of patients with Pseudomonas keratitis adhered to soft contact lenses in significantly greater numbers than did six isolates from other body sites (P less than .05). However, there was no predominant serotype among the 10 corneal isolates tested. Isolates grown statically in broth at 37 degrees C formed a pellicle and adhered two times as much to contact lenses as did isolates grown in broth while shaking which did not form a pellicle (P less than .01). The more adherent isolates (grown at 37 degrees C) were shown to be more hydrophobic than the less adherent bacteria (grown at 26 degrees C) by their propensity to accumulate at the interface between hexadecane and saline and their movement into polyethylene glycol from dextran. These corneal isolates agglutinated erythrocytes, a process that was inhibited by dilute solutions (as low as 0.01%) of three commonly used surfactants. These same surfactants inhibited the adherence of Pseudomonas aeruginosa to soft contact lens surfaces by as much as 52%. It is concluded that hydrophobic interactions may significantly contribute to the ability of Pseudomonas aeruginosa to adhere to contact lenses.
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PMID:The contribution of bacterial surface hydrophobicity to the process of adherence of Pseudomonas aeruginosa to hydrophilic contact lenses. 249 54

Methemoglobin formation was studied at near physiological hemoglobin concentration. The reaction proceeds at a faster rate when the concentration of hemoglobin is high (15-18 mM in heme) than when it is low (2 mM). Constant shaking of hemoglobin preparations during the incubation decreases the differences seen in the rates of autoxidation between concentrated and dilute samples. When red cell hemolysate is used instead of pure hemoglobin, similar results are obtained. A comparison of rates of methemoglobin formation in hemoglobin solutions under low air pressure (1/2 atm) with those under normal air pressure (1 atm) shows no differences between concentrated and dilute samples. There is also no significant difference between the rates of autoxidation of dilute and concentrated solutions when the reactions are carried out under one atmosphere of oxygen (100 percent O2). The study of one patient with hereditary spherocytosis demonstrated higher hemoglobin autoxidation rate in spherocytes, which have higher hemoglobin concentration, than in normal biconcave red cells. These results suggest that: a) the rate of hemoglobin autoxidation at red cell hemoglobin concentration is significantly faster than rates obtained by studying dilute solutions; b) although the accelerated oxidation might be related to multiple factors, one seems to be less accessibility of oxygen when the hemoglobin solution is highly concentrated.
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PMID:Hemoglobin autoxidation at physiological concentrations. 366 22

Cultures of Tetrahymena are routinely shaken to ensure proper access to oxygen. Recent work showed that growth of dilute cultures (inocula < 10(4) cells ml-1) of T. pyriformis was sensitive to shaking. Addition of oleic acid (9 microM) or linoleic acid (140 microM) before or at the onset of shaking gave considerable protection to the cells. A similar effect was seen with ergosterol (25 microM) and to some extent with cholesterol (100 microM). Octanoic acid (20 microM), palmitic acid (140 microM) and palmitoleic acid (100 microM) had no effect. Paraquat (230 microM), which induced peroxidation of unsaturated fatty acids, increased the effect of shaking-induced cell division stress. Such results may be due to changes in the membrane composition of Tetrahymena. It has not been possible to demonstrate differences in the 14C-oleic acid labelling of phospholipids of cells with and without shaking.
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PMID:Certain fatty acids and steroids protect Tetrahymena from cell division stress caused by shaking. 825 55

A total of 498 porcine embryos at various stages of development collected from superovulated gilts was used to investigate cryopreservation. First, blastocysts (BL), expanded blastocysts (ExB), and hatched blastocysts (HB) were used to determine the effect of exposure to concentrated solutions of ethylene glycol as cryoprotective additives (CPAs) on embryo survival. Then, survival of other embryos after vitrification by rapid cooling was determined. Based on their development after 48 h in culture, embryos were not injured by being exposed to 2.0 M ethylene glycol (EG) for 15 min or to 2.0 M EG for 5 min and then to a solution of 8.0 M EG in 7% polyvinylpyrrolidone (PVP) for 1 min. The CPAs were removed from the embryos by diluting them with 1.7 M galactose. To vitrify the embryos, they were exposed to 2.0 M EG for 5 min and then were pipetted directly into short columns of 8.0 M EG-PVP contained within (1.25-ml plastic straws and separated from long columns of 1.7 M galactose by an air bubble. The straws were plunged directly into LN2. After the straws were warmed rapidly in a 25 degrees C water bath, the embryos were immediately mixed with galactose within the straws by shaking them vigorously to mix the contents. In sequential experiments, three methods were used to dilute the CPA solutions. Method 1: Embryos in the EG-PVP-galactose mixture were expelled from the straws and rinsed and cultured in modified CZB medium (mCZB). Method II: Embryos in the mixture were placed briefly into 1.5 M EG and then rinsed and cultured in mCZB. Method III: Embryos in the mixture were rinsed in 1.0 M EG and then in 0.5 M EG and finally rinsed with mCZB and cultured. After 48 h in culture, the respective percentages of survival of embryos vitrified as BL, ExB, or HB were: Method I, 21, 32, and 13%; Method II, 9, 40, and 24%; Method III, 35, 85, and 71%. Of 20 additional ExB vitrified embryos diluted by Method III and transferred into a recipient, four developed into live piglets; two other recipients failed to litter although one had been pregnant for 65 days. These results demonstrate that porcine embryos can be successfully cryopreserved by rapid cooling in EG-PVP and by careful dilution of the CPA after warming.
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PMID:Piglets produced by transfer of vitrified porcine embryos after stepwise dilution of cryoprotectants. 950 Sep 30

It has previously been shown that a droplet fractionation process, simulated by shaking a separatory funnel containing a dilute protein solution, can generate droplets richer in protein than present in the original dilute solution. In this article, we describe an alternative method that can increase the amount of protein transferred to the droplets. The new method uses ultrasonic waves, enhanced by a bubble gas stream to create the droplets. The amount of protein in these droplets increases by about 50%. In this method, the top layer of the dilute protein solution (of the solution-air interface) becomes enriched in protein when air is bubbled into the solution. This concentrating procedure is called bubble fractionation. Once the protein has passed through the initial buildup, this enriched protein layer is transferred into droplets with the aid of a vacuum above the solution at the same time that ultrasonic waves are introduced. The droplets are then carried over to a condenser and coalesced. We found that this new method provides an easier way to remove the protein-enriched top layer of the dilute solution and generates more droplets within a shorter period than the separatory funnel droplet generation method. The added air creates the bubbles and carries the droplets, and the vacuum helps remove the effluent airstream from the condenser. The maximum partition coefficient, the ratio of the protein concentration in the droplets to that in the residual solution (approx 8.5), occurred at pH 5.0.
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PMID:Sonic wave separation of invertase from a dilute solution to generated droplets. 1084 59

The degradation process that takes place at room temperature when bis(2,4,4-trimethylpentyl)monothiophosphinic acid (R2P(S)OH), bis(2,4,4-trimethylpentyl)dithiophosphinic acid (R2P(S)SH) and tris(2,4,4-trimethylpentyl)phosphine sulfide (R3PS) are in contact with 5 M HNO3 has been studied by FT-Infrared, FT-Raman spectroscopy and by gas chromatography with mass spectrometry detection (GC-MS). An exposure period of ten days of the rough reagents to 5 M HNO3 causes complete oxidation of the compounds. This process mainly leads to the formation of nitrogen dioxide, elemental sulfur and the oxo-analogues of the reagents. For dilute solutions of the reagents it was observed that after 15 min of contact with phase-shaking, R2P(S)OH and R3PS are completely oxidized to yield R2P(O)OH and R3PO, respectively, whereas for R2P(S)SH, the oxidation process is less severe, because the dithioacid is still present in the oxidized mixture, the oxidation products being R2P(S)OH and R2P(O)OH.
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PMID:Determination of the degradation compounds formed by the oxidation of thiophosphinic acids and phosphine sulfides with nitric acid. 1213 76

A revised method to determine solubility of nitrogen in dilute pepsin, using 0.0002% pepsin in place of 0.2% in AOAC Official Method 971.09, was tested in 16 laboratories with 12 samples of fishmeal. Results were calculated according to 2 procedures: AOAC Official Method 971.09 and a method described in 1964 by researchers at the Torry Research Station (Aberdeen, Scotland), and generally referred to as the modified Torry method. Variations in the method of shaking and source of pepsin were also investigated. Pepsin solubility values were lower and more variable when calculated by the Torry procedure. The method of shaking apparently affected the result when calculated according to the Torry but not the AOAC method. The source of pepsin had no significant effect on between-laboratory variability, but a comparison of the 2 main sources within one laboratory resulted in highly significant differences. Based on this study, the International Fishmeal and Fish Oil Organization has adopted this new method, using 0.0002% pepsin but keeping the AOAC method of calculation. The type of shaker and source of pepsin are recommended but are not mandatory. The repeatability and reproducibility limits of this new method are 1.6 and 3.3% units of solubility, respectively.
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PMID:Determination of nitrogen solubility in dilute pepsin hydrochloric acid solution of fishmeal: interlaboratory study. 1247 2

A basic investigation on the removal of cadmium(II) ions from aqueous solutions by dead Sargassum sp. was conducted in batch conditions. The influence of different experimental parameters; initial pH, shaking rate, sorption time, temperature and initial concentrations of cadmium ions on cadmium uptake was evaluated. Results indicated that cadmium uptake could be described by the Langmuir adsorption model, being the monolayer capacity negatively affected with an increase in temperature. Analogously, the adsorption equilibrium constant decreased with increasing temperature. The kinetics of the adsorption process followed a second-order adsorption, with characteristic constants increasing with increasing temperature. Activation energy of biosorption could be calculated as equal to 10 kcal/mol. The biomass used proved to be suitable for removal of cadmium from dilute solutions. Its maximum uptake capacity was 120 mg/g. It can be considered an optimal result when compared to conventional adsorbing materials. Thus Sargassum sp. has great potential for removing cadmium ions especially when concentration of this metal is low in samples such as wastewater streams.
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PMID:Kinetic modeling and equilibrium studies during cadmium biosorption by dead Sargassum sp. biomass. 1506 29


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