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PubMed1991

Surface heterogeneity of bovine sperm revealed by aqueous two-phase partition.

Ejaculated, bovine sperm have been subjected to multiple partition in aqueous two-phase systems. This partition, carried out in a countercurrent fashion, reveals heterogeneity of the sperm population with respect to surface properties. The sperm, when partitioned in phase systems that detect non-change associated surface properties (change-insensitive) are largely distributed as two distinct populations. In charge-sensitive phase systems (which principally detect cell surface molecules carrying charge) the sperm do not show any obvious surface heterogeneity. Considerable heterogeneity is revealed in affinity-ligand phase systems containing palmitic acid coupled to one of the phase components-poly(ethylene glycol). There is a difference in surface heterogeneity between sperm which have been washed in buffer or left unwashed, direct from the ejaculate. This is indicative of weak adsorption of proteins to the sperm surface in seminal fluid. These results show that bovine ejaculated sperm is a heterogeneous cell population having unequal distributions of a number of different surface molecules.

Animals↗
PubMed1982

Preparative countercurrent chromatography for isolation of charge density-fractionated heparin.

A preparative method is described for continuous flow fractionation of heparin according to charge density in two-phase systems of butanol-hexadecylpyridinium chloride/aquaous NaCl. The separation is carried out on a "Slowly-Rotating Coil" device for countercurrent chromatography with 6 coil units and a sample capacity of 80 mg heparin. A turbidometric method is described which can be used to rapidly quantify the distribution of heparin. Characterization of fractions showed that linear charge density, binding constant for acridine orange, and specific activities in a "global" plasma anticoagulant assay and in a specific activities in a specific biochemical thrombin-inhibition assay varied with the NaCl concentration in the eluting phase. Some partial resolution of the two functional activities was observed. The fractions are much more homogeneous in composition than are the usual heparin preparations and may be useful as standards or in structure-function studies.

Acridine Orange↗
PubMed2004

Countercurrent chromatographic separation: a hydrodynamic approach developed for extraction columns.

In countercurrent chromatography (CCC) both stationary and mobile liquids undergo intense mixing in the variable force field of a coil planet centrifuge and the separation process, like the separation in conventional solvent extraction column, is influenced by longitudinal mixing in the phases and mass transfer between them. This paper describes how the residence time distribution (or the elution profile) of a solute in CCC devices and the interpretation of experimental peaks, can be described by a recently developed cell model of longitudinal mixing. The model considers a CCC column as a cascade of perfectly mixed equal-size cells, the number of which is determined by the rates of longitudinal mixing in the stationary and mobile phases. Experiments were carried out to demonstrate the validation of the model and the possibility of predicting the partitioning behaviour of the solutes. The methods for estimating model parameters are discussed. Longitudinal mixing rates in stationary and mobile phases have been experimentally determined and experimental elution profiles are compared with simulated peaks. It is shown that using the cell model the peak shape for a solute with a given distribution constant can be predicted from experimental data on other solutes.

Countercurrent Distribution↗
PubMed1985

Large-scale preparative countercurrent chromatography for separation of polar compounds.

Gram quantity separations of polar compounds (tryptophyl-leucine and valyl-tyrosine) have successfully been accomplished with the use of a horizontal coil planet centrifuge. Two columns of different length fluorinated ethylene propylene tubing but of same internal diameter (0.55 cm) were coaxially coiled around a holder 7.5 cm or 15 cm in diameter and used to assess the preparative capabilities of the apparatus in terms of stationary phase retention and sample peak resolution. Optimal operating conditions derived from preliminary studies with the short column were applied to a column 7 times in length and volume. Volume capacities were 114 ml and 750 ml respectively. A hydrophilic solvent system of n-butanol, acetic acid and water (4:1:5) was used with both the aqueous and non-aqueous phases being used as the mobile phase. Preliminary studies revealed that the hydrodynamic distribution of the two phases was independent of the helical diameter while peak resolution was sensitive to both helical diameter and rpm setting.

Chemical Phenomena↗
PubMed2005

[Preparative isolation and purification of cinnamoyl-C-glycoside chromone from aloe vera by high-speed countercurrent chromatography].

Aloe chromone is a group of anti-inflammatory and anti-tyrosinase constituents found in aloe vera leaves. High-speed countercurrent chromatography (HSCCC) is reported for the preparative isolation and purification of a chromone from aloe vera. The crude extract was obtained by a series of pretreatment of aloe vera leaves and extracted from decolorizing active carbon with methanol. Then the extract was distributed between dichloromethane and water, and the organic part was then subjected to HSCCC for the isolation of chromone constituents. The chromone compounds with a high performance liquid chromatographic grade (>95%) was isolated through two step HSCCC separations by employing two solvent systems composed of chloroform-methanol-water and dichloromethane-methanol-water at volume ratios of 4/3/2 and 5/4/2, respectively. The chromone was finally identified as cinnamoyl-C-glycoside chromone by ultraviolet (UV), fast atom bombardment mass spectrometry (FAB-MS), nuclear magnetic resonance (1H NMR and 13C NMR).

Aloe↗
PubMed2004

Mixed acid fermentation of paper fines and industrial biosludge.

This paper uses countercurrent fermentation to anaerobically convert paper fines and industrial biosludge to carboxylate salts using a mixed culture of acid-forming microorganisms. Using the MixAlco process, the carboxylate salts can be thermally converted to ketones and hydrogenated into mixed alcohol fuels. Continuum particle distribution modeling (CPDM) correlated batch fermentation data to countercurrent fermentation data, allowing the prediction of product concentrations and conversions over a wide range of solid loading rates and liquid residence times. For 80% paper/20% biosludge, the predicted product concentrations agreed with the data within 7.7%. The predicted conversion agreed with the actual conversion within 27.8%. By correcting for varying selectivity, the predicted conversion agreed with the actual conversions within 15.2%. For 40% paper/60% biosludge, the predicted product concentrations agreed with the data within 9.6%. The predicted conversion agreed with the actual conversion within 28.3%. By correcting for varying selectivity, the predicted conversion agreed with the actual conversions within 15.4%. For both the 80/20 and 40/60 cases, CPDM predicts that 90% conversion is possible with a 20 g/l product concentration, 300 g/l substrate concentration, 16 day liquid residence time, and 2.5 g/(ld) solids loading rate. Before proceeding to an industrial plant, these predictions must be verified in a pilot plant.

Acids↗
PubMed2003

Localization of Mg2+-sensing shark kidney calcium receptor SKCaR in kidney of spiny dogfish, Squalus acanthias.

We recently cloned a homologue of the bovine parathyroid calcium receptor from the kidney of a spiny dogfish (Squalus acanthias) and termed this new protein SKCaR. SKCaR senses alterations in extracellular Mg2+ after its expression in human embryonic kidney cells (Nearing J, Betka M, Quinn S, Hentschel H, Elger M, Baum M, Bai M, Chattopadyhay N, Brown E, Hebert S, and Harris HW. Proc Natl Acad. Sci USA 99: 9231-9236, 2002). In this report, we used light and electron microscopic immunocytochemical techniques to study the distribution of SKCaR in dogfish kidney. SKCaR antiserum bound to the apical membranes of shark kidney epithelial cells in the following tubular segments: proximal tubules (PIa and PIIb), late distal tubule, and collecting tubule/collecting duct as well as diffusely labeled cells of early distal tubule. The highly specific distribution of SKCaR in mesial tissue as well as lateral countercurrent bundles of dogfish kidney is compatible with a role for SKCaR to sense local tubular Mg2+ concentrations. This highly specific distribution of SKCaR protein in dogfish kidney could possibly work in concert with the powerful Mg2+ secretory system present in the PIIa segment of elasmobranch fish kidney to affect recycling of Mg2+ from putative Mg2+-sensing/Mg2+-reabsorbing segments. These data provide support for the possible existence of Mg2+ cycling in elasmobranch kidney in a manner analogous to that described for mammals.

Animals↗
PubMed1997

Effects of anastomoses on solute transcapillary exchange in countercurrent systems.

OBJECTIVE: To investigate effects of anastomoses between the descending vasa recta (DVR) and the ascending vasa recta (AVR) on the distribution of small solutes in the interstitial fluid of the renal medulla. METHODS: Countercurrent capillary loops, surrounded by a secretory epithelium, were used to model microvessels in the renal medulla. Anastomoses between the DVR and AVR were modeled as a decrease in cross-sectional area of the vessels and a decrease in flow velocity from the base to the tip of the capillary loop. When experimental data were used to evaluate parameters of the model, it was seen that diffusive transport of solute in the axial direction of the capillary was negligible, and the equations could be greatly simplified. RESULTS: General formulae of the solute concentration distribution were derived for different degrees of shunting between the two limbs of the capillary loop. Analytical solutions for the steady-state solute distribution were obtained when the sizes of capillaries and flows in them were assumed to decrease linearly with the distance from the base to the tip of the capillary loop. When the effects of reduction in the size of the limbs were compared with the effects of reduction of flow velocities on solute distribution, it was found that, in the presence of anastomoses, change in flow velocity increases the axial gradient of the solute concentration more than change in the cross-sectional area. The combined effects of a decrease in flow velocity and cross-sectional area can easily double the axial gradient of the solute concentration for a modest degree of anastomotic shunting. CONCLUSIONS: In this study, we separated effects of anastomotic flow between the DVR and AVR from other factors affecting the complicated countercurrent solute exchanges in the renal medulla. Results from the model show that anastomoses increase the solute concentration in the medullary interstitium and also the axial gradient of the solute concentration there.

Animals↗
PubMed1992

Behaviour of ejaculated spermatozoa from bull, boar and ram during thin-layer countercurrent partition in aqueous two-phase systems.

Ejaculated spermatozoa from bulls, boars and rams were subjected to thin-layer countercurrent partition in aqueous two-phase systems composed of dextran T500 and polyethylene glycol 6000 (PEG) in sucrose-based Hepes-buffered media. In the basal system, the great majority of spermatozoa tended to partition with the dextran-rich bottom phase; however, by including very low levels of phosphate, they could be made to partition increasingly with the PEG-rich top phase (complete at 10 mM phosphate). A procedure was developed for carrying out four separations simultaneously under identical conditions, whereby it could be shown that distribution varied with the number of spermatozoa in the sample. In the case of bull, the effect of cell number could be reduced considerably by inclusion of small quantities of seminal plasma in the phase system, but no such effect was found for ram or boar. Considerable variation in distribution pattern was seen between samples, which did not appear to be due to technical inconsistency. Livability in the phase systems was also variable, and we believe that PEG may exert a detergent-like effect on the sperm surface that is exacerbated in highly defined media free of protective proteins.

Animals↗
PubMed1986

Countercurrent centrifugal elutriation (CCE) recovery profiles of hematopoietic stem cells in marrow from normal and 5-FU-treated mice.

Data presented in this report describe countercurrent centrifugal elutriation (CCE) recovery profiles of hematopoietic colony-forming cells (CFC) in marrow from normal and 5-fluorouracil-(5-FU) treated mice. Of the total nucleated cells, 75%-95% were recovered, and up to 80% of CFC were recovered after CCE of bone marrow from normal mice. Red blood cells and the majority of lymphocytes were collected in fractions well separated from the CFC. In addition, the CCE recovery profiles of populations of CFC (i.e., BFU-E, CFU-E, GM-CFC, and HPP-CFC) were distinct. The distribution of recovered day 8 CFU-S was different from the distribution of day 12 CFU-S. The CCE recovery profiles of CFC in regenerating marrow from 5-FU-treated mice were shifted to fractions of larger cells, presumably in cell cycle. These data demonstrate that CCE is useful as a method of further characterizing qualitative and quantitative changes in populations of CFC occurring after various hematopoietic-influencing regimens.

Animals↗
PubMed1990

Specific binding of 125I-rErythropoietin to Friend polycythemia virus-transformed erythroleukemia cells purified by centrifugal elutriation.

We have used countercurrent centrifugal elutriation (CCE) to determine the distribution of cells with respect to cell volume and buoyant density for an erythroleukemia cell line (JG6) transformed by the polycythemia strain of Friend virus (FV-P), and to determine the effect of inducing the cells to differentiate with dimethylsulfoxide (DMSO) on this distribution. CCE made it possible to obtain suspensions of modal JG6 populations virtually free of dead cells and uniform with respect to volume and buoyant density. These modal populations were assayed for specific binding of erythropoietin (Epo). Between 500 and 550 Epo receptors per cell were detected. These belonged to a single class having a dissociation constant of 0.36 nM. DMSO induction of differentiation of the JG6 cells had no effect on the number of Epo receptors expressed.

Cell Differentiation↗
PubMedDate not supplied

Flow distributions in hollow fiber hemodialyzers using magnetic resonance Fourier velocity imaging.

Distribution of flow within the hollow fibers and the dialysate compartment of hemodialyzers is difficult to measure; previous work has suggested that flow distributions may be non uniform. Magnetic resonance Fourier velocity imaging was used to determine flow distributions within the hollow fibers and dialysate compartment of three commercial hemodialyzers (CA170, CT190, and F60A). Distilled water was pumped without pulsatility through the hollow fibers and the outflow was circulated in a countercurrent direction through the dialysate compartment. Steady state flow distributions were determined simultaneously in both directions using input flow rates of 300 and 600 ml/min. Flow distributions within the hollow fibers were relatively uniform in most hemodialyzer cross sections, approximately Gaussian, and similar for all hemodialyzers. Flow distributions in the dialysate compartment were non uniform and skewed to high flow rates. High flow in the dialysate compartment was largely outside the fiber bundle for the CA170 and CT190 hemodialyzers. Local regions containing both low flow within the hollow fibers and high flow in the dialysate compartment were observed for the F60A hemodialyzer, and these regions became more prominent at a flow rate of 600 ml/min. The results of this study demonstrate that flow distributions within the hollow fibers and dialysate compartment of hemodialyzers can be simultaneously determined using magnetic resonance Fourier velocity imaging. It is concluded that the distribution of flow within the hollow fibers of hemodialyzers is relatively uniform but in the dialysate compartment it is not uniform and depends upon hemodialyzer design.

Fourier Analysis↗
PubMed2004

Use of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate in countercurrent chromatography.

Room temperature ionic liquids (RTIL) are molten salts that are liquids at room temperature. Their liquid state makes them possible candidates as solvents in countercurrent chromatography (CCC), which uses solvents as both the mobile and stationary phases. The study focuses on 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM PF(6)), an easy to synthesize and purify RTIL whose melting point is -8 degrees C. It is shown that BMIM PF(6) behaves like a solvent of significant polarity (comparable with that of ethanol). The ternary phase diagram water-acetonitrile-BMIM PF(6) is given, because it was necessary to add acetonitrile to reduce the ionic liquid viscosity. The 40:20:40% w/ w water-acetonitrile-BMIM PF(6) biphasic liquid system was found to be appropriate as a biphasic liquid system for CCC. Different aromatic solutes, including bases, acids, and neutral compounds, were injected into the CCC column to estimate their distribution constants between the ionic liquid-rich phase and the aqueous phase. The resulting K(il/w) constants were compared with the corresponding literature octanol-water partition coefficients, K(o/w). The important drawbacks in the use of RTIL in CCC are clearly pointed out: high viscosity producing pressure build-up, UV absorbance limiting the use of the convenient UV detector, and non-volatility precluding the use of the evaporative light-scattering detector for continuous detection.

Countercurrent Distribution↗
PubMed2000

Organic-walled dinoflagellate cysts in western equatorial Atlantic surface sediments: distributions and their relation to environment.

In contrast to the wide range of studies carried out in temperate and high-latitude oceanic regions, only a few studies have focused on recent and Holocene organic-walled dinoflagellate cyst assemblages from the tropics. This information is, however, essential for fully understanding the ability of species to adapt to different oceanographic regimes, and ultimately their potential application to local and regional palaeoenvironmental and palaeoceanographic reconstructions. Surface sediment samples of the western equatorial Atlantic Ocean north of Brazil, an area greatly influenced by Amazon River discharge waters, were therefore analysed in detail for their organic-walled dinoflagellate cyst content. A diverse association of 43 taxa was identified, and large differences in cyst distribution were observed. The cyst thanatocoenosis in bottom sediments reflects the seasonal advection of Amazon River discharge water through the Guyana Current and the North Equatorial Countercurrent well into the North Atlantic. To establish potential links between cyst distribution and the environmental conditions of the upper water column, distribution patterns were compared with mean temperature, salinity, density and stratification gradients within the upper water column (0-100m) over different times of the year, using correspondence analysis and canonical correspondence analysis. The analyses show that differences in these parameters only play a subordinate role in determining species distribution. Instead, nutrient availability, or related factors, dominates the distribution pattern. The only possible indicators of slightly reduced salinities are Trinovantedinium applanatum and Lingulodinium machaerophorum. Four assemblage groups of cyst taxa with similar environmental affinities related to specific water masses/currents can be distinguished and have potential for palaeoenvironmental reconstruction.

Journal Article↗
PubMed1964

THERMOREGULATORY AND ADAPTIVE BEHAVIOR OF BROWN ADIPOSE TISSUE.

Brown adipose tissue has been shown to be a strongly thermogenic effector organ in homeothermic animals exposed to cold and in hibernators during cold-induced arousal from deep hibernation. Because of the anatomical distribution of brown fat and the utilization of vascular countercurrent heat exchange, this cold-induced thermogenic response protects the animal by contributing heat to the vital organs of the thorax, the cervical and thoracic segments of the spinal cord, and the sympathetic chain. Evidence indicates that control of thermogenic activity of brown fat is mediated by the sympathetic nervous system.

Acclimatization↗
PubMed1996

Theoretical studies of steady-state transcapillary exchange in countercurrent systems.

OBJECTIVE: As a first step in modeling microvascular exchange in the renal medulla, we developed mathematical models to explore the effects of blood flow, permeability, and anatomical arrangement of microvessels on the steady-state distribution of solute in the blood and the interstitial fluid (ISF). METHODS: Single capillaries and countercurrent capillary loops were used to model microvessels that were surrounded by a secretory epithelium over either the whole or part of the capillary length. Solute concentration in the vessels and the ISF were derived analytically. We also derived approximate solutions that ignored axial diffusion of solute. RESULTS: The full and approximate solutions were in good agreement with data based on measurements in the renal medulla. Model results revealed that concentration in the ISF falls rapidly with distance beyond the region of solute secretion and equilibrates with the concentration in capillaries, even with countercurrent exchange between the two limbs of the capillary loop. The ratio of the product of the permeability and area to the flow of the afferent limb, gamma 1, is an important parameter. When gamma 1 > 4, countercurrent exchange in a capillary loop facilitates a greater ISF concentration gradient than with a single capillary. Changes in flow also have a greater effect on this gradient. CONCLUSION: The model of countercurrent exchange presented here not only demonstrates the sensitivity of interstitial concentration gradients of solute to flow through capillary loops but also reveals the importance of the absolute value of gamma 1 in determining the magnitude and direction of these gradients.

Animals↗
PubMed2005

Conversion of municipal solid waste to carboxylic acids using a mixed culture of mesophilic microorganisms.

Waste biomass was anaerobically converted to carboxylate salts by using a mixed culture of acid-forming microorganisms. Municipal solid waste (MSW) was the energy source (carbohydrates) and sewage sludge (SS) was the nutrient source (minerals, metals, and vitamins). Four fermentors were arranged in series and solids and liquids were transferred countercurrently in opposite directions, which allows both high conversions and high product concentrations. Fresh biomass was added to Fermentor 1 (highest carboxylic acid concentration) and fresh media was added to Fermentor 4 (most digested biomass). All fermentations were performed at 40 degrees C. Calcium carbonate was added to the fermentors to neutralize the acids to their corresponding carboxylate salts. Iodoform was used to inhibit methane production and urea was added as a nitrogen source. Product concentrations were up to 25 g/L, with productivities up to 1.4 g total acid/(L liquid d). Mass balances with closure between 93% and 105% were obtained for all systems. Continuum particle distribution modeling (CPDM) was applied to correlate batch fermentation data to countercurrent fermentation data and predict product concentration over a wide range of solids loading rates and residence times. CPDM for lime-treated MSW/SS fermentation system predicted the experimental total acid concentration and conversion within 4% and 16% respectively.

Biodegradation, Environmental↗
PubMedDate not supplied

Diffusive-convective mass transfer rates for solutes present on both sides of a dialyzer membrane.

The transport (J) of waste products across dialyzer membranes is known to be proportional to the blood inlet concentration (Cbi) according to J = KCbi, where K is the clearance. For solutes present on both sides of the membrane, like sodium chloride, it has been shown that under certain conditions the transport rate will depend linearly also upon the dialysis fluid inlet concentration Cdi according to J = KbCbi -KdCdi. Kb and Kd are generalized clearances, which depend upon flow rates and membrane permeability but are independent of the concentrations. We have extended the results of Ross et al. in three ways. First, they only considered ultrafiltration (UF) that is equally distributed along the dialyzer. This is an unrealistic assumption, especially in hemodiafiltration and hemofiltration treatments with large UF rates (Quf) leading to large pressure drops along the dialyzer. Our approach allows for an arbitrary UF distribution. Second, it was possible to incorporate the more realistic model of Villaroel et al. for the local combination of diffusion and convection. Finally, we allow an arbitrary distribution of blood among the different fibers. All of these results are valid in both cocurrent and countercurrent configurations. With a sieving coefficient of 1, a good approximation for small solutes, we were also able to show that Kd = Kb - Quf, irrespective of the UF distribution along the dialyzer. This is an important result that, for example, provides a theoretical foundation for allowing a nonzero Quf in conductivity based clearance measurements.

Diffusion↗