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PubMed2000

Analysis of phospholipid molecular species in brain by (31)P NMR spectroscopy.

Techniques are described for the (31)P NMR analysis of glycerophospholipid (PL) headgroup and molecular species in brain. The (31)P NMR spectrum of PLs from human temporal cortex, solubilized in aqueous Na cholate, typically showed 3 major resonances, assigned to phosphatidylcholine (PC) molecular species containing 0, 1, or 2 fully saturated acyl chains. Less species resolution was obtained for the other PL headgroups under these conditions. Alkylacyl- and alkenylacyl-PC were readily discerned using the CHCl(3)-CH(3)OH-H(2)O solvent method. The chain-length, temperature, and species dependences of the (31)P NMR chemical shifts were explored in model PLs. Assignments of signals from phosphatidylethanolamine (PE) subclasses were confirmed in the sodium-cholate system by lipase-mediated selective hydrolysis of bovine-brain PE. The utility of (31)P NMR to monitor enzymatic PL oxidation was further demonstrated. Possible changes in PL composition with postmortem interval (PMI) in rat brain were examined. No significant changes were seen in PL headgroup or PC species composition with PMI at up to 18 hours. Where comparable, the Na-cholate-solubilization and solvent methods gave similar quantitative results for headgroup analysis on the same samples. The present work demonstrates the feasibility and utility of the dual system for analysis of PLs in brain. Magn Reson Med 44:215-223, 2000.

Aged↗
PubMed2006

Individual dissolution of single-walled carbon nanotubes in aqueous solutions of steroid or sugar compounds and their Raman and near-IR spectral properties.

The individual solubilization of single-walled carbon nanotubes (SWNTs), achieved by using ten different anionic-, zwitterionic-, and nonionic-steroid biosurfactants and three different sugar biosurfactants, was examined. Aqueous micelles of anionic cholate analogues, such as sodium cholate (SC), sodium deoxycholate (SDC), sodium taurocholate (STC), sodium taurodeoxycholate (STDC), sodium glycocholate (SGC), as well as N,N-bis(3-D-gluconamidopropyl)cholamide (BIGCHAP) and N,N-bis(3-D-gluconamidopropyl)deoxycholamide (deoxy-BIGCHAP), exhibited good abilities to dissolve the SWNTs individually. Aqueous micelles of nonionic biosurfactants, such as sucrose monocholate (SMC), n-octyl-beta-D-glucoside (OG), n-decyl-beta-D-maltoside (DM), and n-decanoyl-N-methylglucamide (MEGA-10), could dissolve the SWNTs, however, the solubilization abilities were weaker than those of the anionic cholate analogues. In sharp contrast, the solubilization abilities of the zwitterionic micelles of 3-[(3-cholamidopropyl)dimethylammonio]propanesulfonic acid (CHAPS) and 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxypropanesulfonic acid (CHAPSO) were very low, and almost zero for OG. It is evident that the chemical structures, in particular the substituent groups of the surfactants, play an important role in the solubilization of SWNTs. The near-IR photoluminescence behaviors of the SWNTs dissolved in aqueous micelles and in 1 mM biosurfactants were investigated. The chirality indices of the SWNTs dissolved in these solutions depend on the chemical structures of the biosurfactants. The Raman spectra of the SWNTs dissolved in a 1 mM solution of SC suggest the selective extraction of the metallic SWNTs. Finally, a possible solubilization mechanism using steroid surfactants is described. The SWNTs dissolved individually in water-containing biocompounds are useful in many areas of nano- and materials chemistry.

Journal Article↗
PubMed1996

Analysis of macrolide antibiotics by capillary electrophoresis.

Capillary electrophoresis was utilized in the study of the macrolide antibiotics (i.e. pharmaceutical glycoconjugates) clarithromycin, erythromycin, oleandomycin, troleandomycin, and spiramycin. In order to assist in analyte solubilization, two buffer systems using acetonitrile were developed. The first system involved 30 mM sodium cholate and 20% acetonitrile in 80 mM sodium phosphate, pH 6. This buffer permitted the baseline resolution of all five glycoconjugated antibiotics. In addition, erythromycin was separated from its derivatives estolate and ethylsuccinate. In the absence of surfactants, a higher acetonitrile quantity, 65%, was used in the second buffer system, with 35 mM sodium phosphate, pH 6. Selectivity between oleandomycin and clarithromycin was reversed in this system compared to the cholate buffer, indicating solute interaction with the cholate micelles in the previous system. Calibration linearity and detection sensitivity were improved in the high acetonitrile buffer, due to decreased background absorbance. It was demonstrated that both buffer systems can be utilized for the visualization of minor components that may be present in bulk pharmaceuticals.

Acetonitriles↗
PubMedDate not supplied

Physiologic cholestasis II: serum bile acid levels reflect the development of the enterohepatic circulation in rats.

We have shown that serum bile acid concentrations are elevated in human infants reflecting physiologic immaturity of the enterohepatic circulation. To define further the ontogeny of bile acid metabolism in mammals, we examined maturational changes in the serum concentration of total cholate conjugates by radioimmunoassay in fetal, neonatal, suckling, and mature Sprague-Dawley rats. Fetal (21st day) levels were low (1.4 +/- 0.23 microM; X +/- S.E.), possibly due to minimal enterohepatic cycling in utero. The concentrations in samples obtained minutes after birth, prior to suckling were significantly elevated (12.6 +/- 2.37; p less than 0.001 vs. fetal); these high values persisted after feeding was initiated (6 hr = 13.5 +/- 0.99), but fell at 12 hr (5.2 +/- 0.81) and remained unchanged for the duration of the first day. Serum values fluctuated briefly, being 9.6 +/- 0.73 on Day 4, and the rose progressively through the suckling period (Day 10 = 7.2 +/- 9.57; Day 14 = 10.4 +/- 1.70; Day 21 = 16.8 +/- 1.93); there was a dramatic peak after weaning (Day 28 = 21.8 +/- 1.53). The serum concentration of cholate conjugates then fell (5.6 +/- 0.68 on Day 42) to achieve adult levels by 56 days (4.0 +/- 0.55), a value substantially different from that of all developing animals (p less than 0.025). These data corroborate studies which suggest that a period of physiologic cholestasis occurs in the developing rat. Serum cholate conjugate concentrations likely reflect interrelated morphologic alterations (bile canalicular structure and portal blood flow) and physiologic changes (bile acid synthesis, pool size, and transport) occurring in the enterohepatic circulation during early life.

Age Factors↗
PubMed1994

Deficiency of bile acid transport and synthesis in oval cells from carcinogen-fed rats.

Freshly isolated oval cells, which we obtained from the livers of rats fed a choline-deficient/DL-ethionine-supplemented diet, did not transport bile acids. Compared with freshly isolated rat hepatocytes they took up only negligible amounts of [3H]taurocholate or [14C]cholate. The cells bound small amounts of radioactive bile acids. This portion of the total cell-associated radioactivity was enhanced on membrane permeabilization. In contrast to cultured liver parenchymal cells from untreated rats, no bile acid synthesis was detected in cultured oval cells. Cultured oval cells also lost the ability to conjugate exogenously added cholate (100 mumol/L) with taurine or glycine. However, when liver parenchymal cells were isolated from carcinogen-fed rats, bile acid uptake was diminished compared with that in hepatocytes from control animals. In particular, the maximum values of taurocholate and cholate uptake were decreased by 75% and 50%, respectively, whereas the Michaelis-Menten constant values were not altered. The study demonstrates that (a) oval cells lack typical liver parenchymal cell-specific properties such as bile acid uptake, bile acid synthesis and conjugation of bile acids with taurine/glycine and therefore do not contribute to bile acid dependent bile formation (b) proliferating in livers of rats fed a choline-deficient/DL-ethionine-supplemented diet are part of the bile duct epithelial cell compartment); and (c) bile acid uptake is reduced in liver parenchymal cells of rats fed a choline deficient/DL-ethionine-supplemented diet, and this effect is due to a decrease in transport capacity without a decrease in transport affinity.

Animals↗
PubMed1998

Accurate separation of biliary lipid aggregates requires the correct intermixed micellar/intervesicular bile salt concentration.

The intermixed micellar/intervesicular bile salt (BS) concentration (IMC), composed of BS monomers and simple micelles, is in dynamic equilibrium with mixed micelles and vesicles. Accurate separation of biliary lipid aggregates is believed to depend on accurately measuring the IMC. Using centrifugal ultrafiltration, we measured the IMC of cholesterol-supersaturated model biles that were physiologically composed. Gel chromatography was performed using eluants containing the following: 1) the IMC; 2) the same BS composition as the IMC but higher or lower BS concentrations; 3) the same BS concentration as the IMC, but with more hydrophilic or hydrophobic BS; and 4) 10 mmol/L cholate. Compared with an eluant containing the same BS composition as the IMC, an eluant containing the same relative BS composition but 75% of the IMC increased the proportion of cholesterol in vesicles and decreased the vesicular cholesterol/egg yolk phosphatidylcholine (EYPC) ratio. In contrast, an eluant containing 150% of the IMC entirely transformed vesicles to micelles. Eluants containing slightly more hydrophobic or more hydrophilic BS eliminated or increased vesicular cholesterol content, respectively. An eluant of 10 mmol/L cholate overestimated vesicular cholesterol and in concentrated biles reproducibly produced an incompletely separated intermediate peak, possibly because of re-equilibration between mixed micelles and vesicles. Further, in concentrated biles, fractions eluting at volumes corresponding to mixed micelles were visibly turbid, irrespective of the eluant used. The correct IMC allows accurate separation of biliary lipid aggregates, but differences in BS concentration or composition substantially alter the vesicular percentage of cholesterol as well as the cholesterol/EYPC ratio. Elution with 10 mmol/L cholate may introduce artifactual gel-filtration peaks and inadequate separation of particles with widely differing molecular weights, both of which have confused previous analyses of biliary lipid aggregates.

Bile↗
PubMed1984

The detergent solubility properties of a malarial (Plasmodium knowlesi) variant antigen expressed on the surface of infected erythrocytes.

Four detergents have been compared for identification of the Plasmodium knowlesi variant antigen on infected erythrocytes by immunoprecipitation analysis. Erythrocytes infected with late trophozoite and schizont forms of cloned asexual parasites were labeled by lactoperoxidase-catalyzed radioiodination and extracted either with the anionic detergents sodium dodecyl sulfate (SDS) or cholate, the neutral detergent Triton X-100, or the zwitterion 3-[(3-cholamidopropyl)dimethylammonio]-1-propane sulfonate (CHAPS). After addition of Triton X-100 to SDS and cholate extracts, parallel immunoprecipitations of the four extracts were performed using rhesus monkey antisera of defined agglutinability. Identical results were obtained with clone Pk1(A+), which has 125I-variant antigens of Mr 210,000 and 190,000, and with clone Pk1(B+)1+, which has variant antigens of Mr 200,000-205,000. SDS yielded maximal levels of immunoprecipitated 125I-variant antigens. Variant-specific immunoprecipitation was detected in some experiments with Triton X-100 and cholic acid but with significantly lower recovery than with SDS. CHAPS extraction did not yield the variant antigens on immunoprecipitation. The variant antigens could also be identified in Triton X-100-insoluble material by subsequent extraction with SDS, indicating that failure to recover these proteins in the Triton X-100-soluble fraction is due to failure of this detergent to extract the variant antigens rather than to degradation during extraction. We suggest that the 125I-variant antigens either have a structure that renders them intrinsically insoluble in Triton X-100, cholate, or CHAPS, or that they are associated in some way with host cell membrane components that also resist solubilization by these detergents.

Animals↗
PubMed1993

sn-1,2-diacylglycerol cholinephosphotransferase from pig liver: mixed micellar assay and kinetic analysis of the partially pure enzyme.

sn-1,2-Diacylglycerol cholinephosphotransferase from pig liver microsomes was partially purified through a procedure involving solubilization with sodium cholate and chromatography on Sepharose 6B. The resulting preparation was 19-fold enriched with respect to microsomes and was shown to be very sensitive to different detergents. Sodium cholate gave the best yields in activity. In a mixed micellar assay with Triton X-100 a strong dependence of the enzyme activity on the concentration of mixed micelles was observed, due to Triton X-100 acting as an inactivator. Soja phosphatidylcholine added exogenously protected the enzyme against detergent inactivation and stimulated the enzyme activity. Dioleoyl-phosphatidylcholine had a similar stimulatory effect, whereas didecanoyl- or dioctanoyl-phosphatidylcholine did not; thus long-chain phosphatidylcholines seem to be essential in the activation of cholinephosphotransferase. In a mixed micellar assay with sodium cholate no inactivation of the enzyme could be detected and it was found that soja phosphatidylcholine stimulates the activity in a greater extent than in Triton X-100 mixed micelles. The phospholipid activates the enzyme in a noncompetitive way with an activation constant of 176 mol%. Km was estimated as 1.54 mol% with a Vmax = 30 nmol/min/mg protein. Those results support an activation mechanism by phosphatidylcholine interacting at sites different from the active center. The high activation constant led to the conclusion that cholinephosphotransferase requires a lipidic boundary for full activation. No activation by substrate was observed. Short-chain diacylglycerides such as dihexanoyl-, dioctanoyl-, or didecanoylglycerol can be used as substrates although the enzyme in this case has only 5 to 10% of the activity it has for dioleoylglycerol or egg diglycerides.

Animals↗
PubMed2000

Bile Salt Anion Sorption by Polymeric Resins: Comparison of a Functionalized Polyacrylamide Resin with Cholestyramine.

Cholestyramine and a cross-linked polyacrylamide resin with lateral alkyl quaternary ammonium groups (QPDA12) were used to study their ability to bind several bile salt anions (including the cholate, glycocholate, taurocholate, and chenodeoxycholate), individually and competitively, from phosphate buffer solutions at room temperature. The latter resin showed high affinities for all the bile salt anions examined, while cholestyramine exhibited a high affinity only for the more hydrophobic chenodeoxycholate. However, for the binding with cholestyramine, cooperative effects were more pronounced, leading to the enhancement of sorption at higher concentrations. The Langmuir equation and its modified versions were used in the interpretation of both individual and competitive binding of bile salts. The data from competitive binding studies indicated that the presence of the tightly bound chenodeoxycholate did not significantly diminish the ability of QPDA12 resin to bind cholate. However, for cholestyramine, the sorption of chenodeoxycholate increased the relative binding affinity for the more hydrophilic cholate, revealing a novel "cooperative" effect involving different bile salt anions. The latter results suggest that the observed higher affinity of QPDA12 is brought about predominantly through the hydrophobic interactions with the pendant alkyl groups rather than with the resin backbone. Copyright 2000 Academic Press.

Journal Article↗
PubMed1998

In vitro morphological and functional characterization of isolated porcine hepatocytes for extracorporeal liver support: bile acid uptake and conjugation.

Recently, researchers have focused on the use of bioartificial liver (BAL) to support patients with fulminant hepatic failure (FHF). We have developed a cell-based BAL, consisting of porcine hepatocytes in a hollow-fiber bioreactor. To better characterize BAL metabolic functions in vitro, bioreactors were inoculated with 48-h-cultured, microcarrier-attached hepatocytes and perifused with recirculating human plasma that contained either 1 microCi of [24-14C] plasma-enriched cholate or 1 microCi of [24-14C] plasma-enriched taurocholate. Bile acids were sampled hourly and separated into four fractions (unconjugated, glycoconjugated, tauroconjugated, and sulfated) for radioactivity determination. Following 3 h perifusion, the glycoconjugated and sulfated bile acid fractions in the bioreactor extrafiber space were significantly elevated when compared to the recirculating plasma. During perifusion with taurocholate-enriched plasma, a relative decrease in the tauroconjugated fraction and an increase in the glycoconjugated fraction were observed. Cholate was accumulated by hepatocytes to a level threefold lower than taurocholate; however, a significant proportion of radioactivity (<25%) was detected in the glycoconjugated fraction. Ultrastructural examination of microcarrier-attached hepatocytes illustrated that the features typical of metabolically active liver cells were maintained. Our data demonstrate the ability of BAL to clear bile acids from the circulation, to accumulate cholate and taurocholate, and to conjugate a substantial amount of cholic acid.

Animals↗
PubMed1980

Comparative studies on the uptake of 14C-bile acids and 3H-demethylphalloin in isolated rat liver cells.

The inward transport of bile acids in isolated hepatocytes completes with the uptake of phallotoxins. Cholate, taurocholate and glycocholate added 30 s prior to phallotoxins reduce their uptake in a concentration dependent manner. 100 microM bile acids suppress the uptake of phallotoxins completely. Several compounds known to inhibit the bile acid transport reduce the phallotoxin uptake to similar degree. Hepatocytes exposed to reagents reacting preferentially with amino groups of proteins lose their up take of both bile acids and phallotoxins. In hepatocytes isolated from 5 day old rats the uptake of both phallotoxins and cholate is reduced as compared to cells from adult controls. AS-30D ascites hepatoma cells, known to be insensitive to phallotoxins are unable to take up both phallotoxins and cholate. The results are consistent with our working hypothesis of a very similar mechanism for the uptake of bile acids and phallotoxins.

Alkaloids↗
PubMed1981

Competitive inhibition of the uptake of demethylphalloin by cholic acid in isolated hepatocytes. Evidence for a transport competition rather than a binding competition.

Cholic acid inhibits the uptake of demethylphalloin (DMP), in a competitive manner. The bile acid increases the Michaelis constant but not Vmax of the inward transport. The inhibition constant Ki for cholate was found to be 8 microM. Cholate competes for the transport system but not for intracellular binding of phallotoxins. Various experimental data presented in this paper exclude an accumulation of phallotoxins in hepatocytes by intracellular binding only. Preincubation of hepatocytes with small concentration of either (3H)-demethylphalloin or (14C)-cholate and subsequent treatment with high concentrations of the non-labelled compounds reduces the intracellular concentration of both radioactive substrates. In accordance with earlier findings the above results suggest a common component needed for the transport of both phallotoxins and cholic acid.

Alkaloids↗
PubMed1982

Lack of intestinal transport of [3H]-demethylphalloin: comparative studies with phallotoxins and bile acids on isolated small intestinal cells and ileal brush border membrane vesicles.

Several earlier studies suggested that the uptake of phallotoxins by liver cells is a carrier mediated process using a transport system normally handling bile acids (see Frimmer 1982). In this study we have shown whether ileal cells, well known to transport bile acids too, are able to take up phallotoxins. Isolated epithelial cells prepared from guinea pig ileum accumulated [14C]-cholate, whereas [3H]-demethylphalloin ([3H]-DMP) was not taken up. The same observation was made with isolated jejunal cells but the uptake of [14C]-cholate was much slower. [3H]-DMP, however, was partly bound to intestinal cells. This process was not inhibited by cholate, iodipamide, oligomycin and carbonylcyano-chlorophenylhydrazone (CCCP), compounds known to decrease the uptake of phallotoxins into liver cells. Substituting Na+ for choline+ and also Cl- for SCN- did not influence the binding of [3H]-DMP. Frozen intestinal cells from the guinea pig bound two time more [3H]-DMP after thawing compared with intact cells. Supplementary uptake experiments on isolated brush border membrane vesicles from rat ileum revealed that phalloidin does not inhibit taurocholate uptake and that taurocholate does not interfere with [3H]-DMP binding. The results suggest that [3H]-demethylphalloin is not recognized by the bile acid carrier of the guinea pig and the rat ileum. It is concluded that the transport system for bile acids present in ileal cell is different from that of liver cells.

Alkaloids↗
PubMed1978

Interaction of fusidates with bile acid uptake by isolated rat hepatocytes.

The interaction of fisidic acid and two of its conjugates with carrier-mediated uptake of bile acids was investigated in isolated rat hepatocytes. All three fusidates inhibited the uptake of both cholate and taurocholate competitively suggesting a direct interaction of fusidates with bile acid carrier. The inhibition constants for all three fusidates for the inhibition of cholate uptake were significantly different from the respective inhibition constants for the inhibition of taurocholate uptake. This would indicate that both cholate and taurocholate are transported by more than one carrier into hepatocytes. The results may also indicate that taurine conjugated bile acids may be transported preferentially by one transport system while unconjugated bile acids may be preferentially transported by another transport system.

Animals↗
PubMed1978

Inhibition of hepatic uptake of bile acids by rifamycins.

The effect of rifamycin SV and rifampicin on hepatic acid uptake was studied using isolated rat hepatocytes in presence and in absence of albumin. The drugs inhibited cholate uptake more than taurocholate uptake and the inhibition was of non-competitive type. In presence of 3% albumin the inhibitory effect of the drugs was more for cholate and less for taurocholate uptake than in absence of albumin. Neither the binding of bile acids nor that of the drugs to albumin was altered by one another. Thus the effect in presence of albumin cannot be explained by the binding of the drugs and bile acids to albumin alone. It is suggested that albumin interacts with hepatic bile acid uptake process and this interaction with cholate uptake is different from that with taurocholate uptake. This additional and different effect of albumin may explain the effect of the drugs in presence of albumin. The results may be of clinical significance in rifamycins treatments.

Albumins↗
PubMed1985

Plasma secretin in response to pure bile salts and endogenous bile in man.

The effect of exogenous bile salts on plasma concentrations of secretin was studied by infusion of chenodeoxycholate, cholate, glycocholate, and taurocholate into the duodenum of normal subjects. The effect of endogenous bile on plasma secretin was studied by ingestion of a liquid test meal, by reinfusion of postprandial duodenal aspirates with known contents of bile salts, and by stimulation of gallbladder contraction by cholecystokinin. Each experiment was performed in groups of seven subjects. The relative secretin-releasing potencies of glycocholate, cholate, taurocholate and chenodeoxycholate (2.25 mmol) were 1.0:1.3:1.9:3.2. Hydrochloric acid (0.5 mmol) was, on a molar basis, approximately ten times more potent than sodium cholate. The effect of taurocholate was diminished when a liquid meal was used as vehicle instead of saline. Endogenous bile did, in no circumstance, elicit release of secretin. It is concluded that although bile salts have the ability to stimulate secretin release, endogenous secretin release is of minor, if any, importance for secretin release when physiological conditions are approached.

Bile↗
PubMed1982

Partial purification of the Na+-dependent D-glucose transport system from renal brush border membranes.

A membrane extract enriched with the Na+ -dependent D-glucose transport system was obtained by differential cholate solubilization of rat renal brush border membranes in the presence of 120 mM Na+ ions. Sodium ions were essential in stabilizing the transport system during cholate treatment. This membrane extract was further purified with respect to its Na+-coupled D-glucose transport activity and protein content by the use of asolectin-equilibrated hydroxylapatite. The reconstituted proteoliposomes prepared from this purified fraction showed a transient accumulation of D-glucose in response to a Na+ gradient. The observed rate of Na+-coupled D-glucose uptake by the proteoliposomes represented about a sevenfold increase as compared to that of the reconstituted system derived from an initial 1.2% cholate extract of the membranes. Other Na+-coupled transport systems such as L-alanine, alpha -ketoglutarate and phosphate were not detected in these reconstituted proteoliposomes.

Animals↗
PubMed1986

Tyrosinase activity in human ocular malignant melanoma.

We examined tyrosinase activity in pigmented specimens from three cases of ocular malignant melanoma. Tissue (cholate-trypsin-treated) extract was prepared in cholate-phosphate buffer by homogenization, centrifugation, trypsin digestion, and hydroxylapatite column chromatography. Tyrosinase activity was spectrophotometrically assayed as dopa (L-3,4-dihydroxylphenylalanine) oxidase activity. Tyrosinase activity was detected in the cholate-trypsin-treated extracts. Enzyme activity was inhibited by phenylthiourea but not by 3-iodo-tyrosine. The enzyme was inactivated when extract was preheated or digested with pronase. We believe that our findings confirm the presence of tyrosinase activity in ocular malignant melanoma.

Aged↗