High Concentrations Of Polyethylene Glycol Research Articles

Clinical Usefulness of TSAb Assay with High Polyethylene Glycol Concentrations

We previously demonstrated the stimulatory effect of polyethylene glycol (PEG) on thyroid-stimulating antibody (TSAb)-IgG-stimulated cAMP production (thyroid stimulating (TS) index) in porcine thyroid cell (PTC) assay. In the present study the clinical usefulness of the practical method using high PEG concentrations was examined. TS activity using PEG 22.5% precipitated fraction (PF) was significantly higher compared to standard TSAb activity using 12.5% PF from TSAb-positive serum, but the maximum TS activity was observed with PEG 12.5% PF + 4% PEG or PEG 22.5% PF + 2% PEG. In all cases of untreated Graves’ patients, TSAb activity determined by PEG 22.5% PF was higher compared to standard TSAb activity using PEG 12.5% PF from test serum, but the highest TSAb activity was observed by PEG 12.5% PF + 4% PEG without increased cAMP production to normal serum. TSAb was positive in 85% (40/47), 98% (46/47) and 100% (47/47) of untreated Graves’ patients by the method of PEG 12.5% PF, PEG 22.5% PF and PEG 12.5% + 4% PEG, respectively. Increased TSAb activity by PEG 12.5% PF + 4% PEG method was also observed even if the standard TSAb activity using PEG 12.5% PF method was negative in the euthyroid states of Graves’ patients during antithyroid drug therapy. The stimulatory effect of PEG on TS activity was not found in other thyroidal diseases [thyroiditis chronica (with high serum TSH), thyroid stimulation-blocking antibody (TSBAb)-positive sera (with low serum TSH), adenomatous goiter, subacute thyroiditis, and thyroid cancer]. The stimulatory effect of 5% PEG on TS activity produced directly by small amounts of Graves’ serum (50 μl) was also found, although the sensitivity was lower than with PEG-precipitated IgG from 0.2 ml serum. The clinical usefulness of the sensitive TSAb assay using PEG-precipitated IgG or direct serum assay in the presence of high PEG concentrations was demonstrated.

Transformation of sapstaining fungi with hygromycin B resistance plasmids pAN 7-1 and pCB1004

Protoplasts were produced by treating the yeast-like cells of O. piceae and O. quercus with high concentrations of Novozym 234 (20 mg ml−1). Transformants with resistance to hygromycin B were obtained by transforming the protoplasts with the plasmids pAN7-1 and pCB1004 containing the hygromycin B phosphotransferase (hph) gene. For all isolates tested, transformation efficiencies ranged between 103 and 105 transformants μg−1 vector DNA. High polyethylene glycol concentration (66%) increased the transformation efficiency. Integration of the hph gene into the transformant genome was verified by a polymerase chain reaction and dot DNA hybridization analysis. There was no evidence of mitotic instability of hygromycin B resistance in the transformants.

Crystallization of multiple forms of bovine seminal ribonuclease in the liganded and unliganded state

Bovine seminal ribonuclease (BS-RNase) is an intriguing homodimeric enzyme which exists as two conformational isomers, characterized by distinct catalytic and biological properties, referred to as M×M and M=M. Reduction of inter-chain disulfide bridges produces a stable monomeric derivative (M) which is still active. This paper reports the screening and optimization of crystallization conditions for growing single diffraction-quality crystals for the various BS-RNase forms. The crystallization trials were performed using both the vapor diffusion and microbatch methods. The M×M dimer was crystallized in the free form from polyethylene glycol (PEG) 4000 at pH 8.5 and as a complex with the substrate analog uridylyl(2′– 5′)guanosine (UpG) from an unbuffered ammonium sulfate (AS) solution. These two crystal types diffract X-rays to 2.5 and 1.9 Å resolution, respectively. Two different crystal types were obtained both for the M=M dimer and for the monomeric derivative. (M=M)a crystals, grown from PEG 4000 (8% w/v) at pH 5.6, diffract X-rays to 4.0 Å. At higher PEG concentration (15% w/v) a different crystal type was obtained, (M=M)b, which showed a better diffraction limit (2.5 Å). For the monomer, type (M)a and (M)b crystals, diffracting X-rays to 2.5 Å resolution, were obtained from AS at pH 6.5 and from PEG 4000 at pH 8.5, respectively. A comparison with previously crystallized forms of the dimer M×M and its complexes with uridylyl(2′–5′)adenosine and 2′-deoxycytidylyl(3′–5′)-2′-deoxyadenosine is also presented. The three-dimensional structure analysis of (M×M)·UpG and (M=M)b is in progress.

Clinical significance of a sensitive assay for thyroid-stimulating antibodies in Graves' disease using polyethylene glycol at high concentrations and porcine thyroid cells.

The Inui and Ochi group recently reported that cAMP production by porcine thyroid cells (PTC) was augmented more by polyethylene glycol (PEG) 22.5% precipitated fractions from almost all Graves' sera than those of PEG 12.5%. In the present study, thyroid stimulating immunoglobulin (TSI) activity was determined with PTC and prepared crude Ig fractions precipitated by two different concentrations of PEG (final concentrations 13.5% and 22.5%) from sera obtained from 117 Graves' patients. The activity of TSI determined by the PEG 13.5% assay and activity determined by the PEG 22.5% assay were designated as thyroid-stimulating antibody (TSAb) and sTSAb, respectively. At first we studied 55 TSAb-positive patients with untreated hyperthyroid Graves' disease and classified them according to the TSAb activity-below 500% (group 1) and above 500% (group 2). The positive stimulatory effect, arbitrarily defined as the ratio of sTSAb to TSAb, being more than 1.2, was observed in 85% of patients, and group 1 had a significantly (P<0.025) greater stimulatory effect (34/35, 97.1%) than group 2 (13/20, 65%). Subsequently, in 29 TSAb-negative patients, sTSAb was measured and detected in 26 (89.7%). Finally, sTSAb, TSAb and TBII were compared between patients presenting with recurrent Graves' disease and those with silent thyroiditis after withdrawal of antithyroid drug treatment for Graves' disease. sTSAb was detected in all 14 relapsed patients, but none of the 9 patients with silent thyroiditis had detectable sTSAb. In contrast, TSAb and TBII activities were found in only 7 (50.0%) of the 14 relapsed cases. The present paper demonstrated that the assay with a higher PEG concentration was found to be sensitive, specific and useful for the diagnosis and follow-up of Graves' disease after drug withdrawal, although the underlying mechanism remains unclear.

Phase Behavior and Structural Changes in Tetraethylorthosilicate-Derived Gels in the Presence of Polyethylene Glycol, Studied by Rheological Techniques and Visual Observations

A study has been done on how different concentrations and molecular weights of polyethylene glycol (PEG) affect the phase behavior of the sol–gel reaction. The sol–gel reaction of tetraethylorthosilicate (TEOS) in acidic media in the presence of PEG has been studied by means of visual observations and rheological investigations. The observations revealed that a macrophase separation occurred at intermediate concentrations for the two highest molecular weights of PEG. The proposed mechanism was bridging flocculation between organic and inorganic polymers. At high concentrations of PEG, steric stabilization took place and thus the phase transition evolved without a macrophase separation. Gelation times have been determined by visual observations and two different rheological methods, and there were no significant differences in the gelation times determined by the different methods. Flow curves revealed Newtonian, shear thinning, rheopectic, and thixotropic flow behavior at different stages of the sol–gel reaction, giving information about the structure formed. At the gelation point a viscoelastic scaling law G′(ω) ∼ G″(ω) ∼ ωnhas been observed with values for the critical exponent n in the range of 0.71–0.83. Values of the critical exponent have been used for gaining information about the degree of branching of the gel when comparing different phase behavior and growth mechanisms. It was shown that the phase-separated gels were less branched and more open than the others.

Increase of thyroid stimulating activity in Graves' immunoglobulin-G by high polyethylene glycol concentrations using porcine thyroid cell assay.

Cyclic adenosine monophosphate (cAMP) production during a 5-hour incubation using porcine thyroid cells (PTC) was stimulated significantly more by polyethylene glycol (PEG) 22.5% precipitated fractions (ppt frs) than by PEG 12.5% ppt frs from almost all Graves' sera. However, the thyrotropin (TSH) binding inhibition (TBI) activities of the PEG 12.5% and 22.5% ppt frs using porcine thyroid membranes were similar, and did not change in the 5-hour incubation. When the PEG 12.5% ppt fr from Graves' serum and the PEG 22.5% ppt fr from normal human serum (NHS) were coincubated, cAMP production was also stimulated as much as by the PEG 22.5% ppt fr from Graves' serum. When purified thyroid stimulating antibody (TSAb)-immunoglobulin G (IgG) and the PEG 22.5% ppt fr from NHS were coincubated, increased cAMP production was also observed, whereas bovine thyrotropin (bTSH) did not produce this effect. When purified TSAb-IgG and PEG solutions were coincubated, maximum increases in cAMP production (approximately 10-fold) with 5% PEG were found, whereas no increase was observed using bTSH. The stimulatory effect of high PEG concentrations on thyroid stimulating activity was observed by TSAb-IgG in salt-free or salt-containing medium (<0.15 mol/L NaCl concentration) but not by either TSAb-IgG conjugated to protein A-sepharose 4B or the inactivated TSAb-IgG by the treatment of 70 degrees C for 10 minutes. No stimulatory action by PEG was found with the thyroid stimulating substances such as GTPgammaS, forskolin, or pituitary adenylate-cyclase activating polypeptide (PACAP). The increased thyroid stimulating activity of Graves (IgG) at high PEG concentrations suggests the existence of some factors influencing the ability of TSAb to stimulate thyroid cells, although the exact mechanism remains to be clarified.

The response of DNA macromolecules to an elongational flow field and coil—globule transition of DNA

Large DNA molecules are known to exhibit a conformational change between the coil and globule states with the addition of polyethylene glycol (PEG). We investigated the coil—globule transition of T4DNA by observing the response of the molecule to a well-defined elongational flow field, where the response was monitored by the flow-induced birefringence. The flow-induced birefringence ( Δn) increased with the strain rate for solutions of low PEG concentration, indicating that the DNA molecule is in an extended coil state. There were no Δn response at high PEG concentration solutions, where the DNA molecule is in a well-developed globule state. The dependence of Δn on PEG concentration is in agreement with the PEG concentration dependence of DNA size, which was directly measured by a fluorescence micrograph method. A comparison of the results by the flow birefringence method with those by the fluorescence micrograph method indicated that the globule of the DNA molecule near the coil—globule transition is deformed by the elongational flow field. The elongational flow technique was proven to be a useful method for investigating the coil—globule transition of large DNA molecules.

Effects of abscisic acid and high concentrations of PEG on Hevea brasiliensis somatic embryos development

The effects of polyethylene glycol (PEG) and abscisic acid (ABA) were analysed on Hevea brasiliensis somatic embryos development. The presence of osmoticum greatly reduced the phenomenon of secondary embryogenesis and improved the conversion of proembryonic masses (PEMs) into torpedo-shaped embryos, while the addition of exogenous ABA favoured only the formation of globular-stage embryos. The development of embryos with a desirable morphological appearance (regular shape with a smooth and well-defined epidermis) was only observed in the presence of PEG in the solid culture media. The endogenous level of ABA was lower with these culture conditions than in control one (less than 10 nmol/g), indicating that PEG would not act through an endogenous ABA synthesis. However, the addition of 10 −5 M of ABA in the presence of the osmoticum increased its endogenous level (higher than 150 nmol/g) and the conversion into torpedo-shaped embryos but did not modify their morphological appearance. This effect of ABA was PEG-dependent and the best development occurred in the presence of 140 g/l PEG and 10 −5 M ABA. Further, the use of sucrose or PEG as osmotica has been discussed and an original method to achieve solid media with high concentrations of PEG has been proposed.

Polymer induced fusion and leakage of small unilamellar phospholipid vesicles: effect of surface grafted polyethylene-glycol in the presence of free PEG

We investigated the effect of surface grafted polyethylene glycol (PEG) in the presence of free PEG on leakage and fusion of small unilamellar vesicles. High concentrations of free PEG (MW 2000) caused leakage and fusion of small unilamellar vesicles. Addition of distearoyl phosphatidylethanolamine-polyethylene glycol (DSPE-PEG), a lipid containing a covalently bonded PEG at the headgroup, to the membrane forming solution reduced leakage and fusion induced by free PEG drastically. The inhibitory effect of this surface grafted PEG was a function of the concentration of DSPE-PEG in the lipid mixtures and increased continuously up to 10 mol%, at which leakage or fusion almost vanished. From our studies we concluded that surface grafted PEG acts as a steric barrier inhibiting the close approach of liposomes which is necessary for fusion.

The Response of DNA Macromolecule to an Elongational Flow Field and Coil-Globule Transition of DNA

It is known that large DNA molecules exhibit a conformational change between the coil and globule states with the addition of polyethylene glycol (PEG). We investigate the coil-globule transition of T4DNA by making use of the response of the molecule to a well-defined elongational flow field, where the response was monitored by the flow-induced birefringence. The flow-induced birefringence (Δn) increases with strain rate in elongational flow field -for the solutions of low PEG concentration indicating that the DNA molecule is in an expanded coil state. There are no Δn response at high PEG concentration solutions where the DNA molecule is in a well developed globule state. The dependence of Δn on PEG concentration accords with the PEG concentration dependence of DNA size which were directly measured by fluorescence micrograph method. Comparison of the flow birefringence and the fluorescence micrograph suggested that the globule of DNA molecule near the coil-globule transition point is soft and deformed by the elongational flow field though the well developed globule is rigid and in undeformed state. It is concluded that the elongational flow technique can be a useful method to investigate the coil-globule transition of large DNA molecules.

Interaction of polyethyleneglycol-phospholipid conjugates with cholesterol-phosphatidylcholine mixtures: sterically stabilized liposome formulations.

The purpose of this study was to investigate polyethyleneglycol (PEG)-phosphatidylethanolamine (PE) conjugate interaction with cholesterol-phospholipid mixtures in an attempt to explain the effect of cholesterol on liposome circulation time. Differential scanning calorimetry, NMR, electron microscopy, dynamic light scattering and fluorescence spectroscopy were the major methods used. Studies performed in the absence of cholesterol indicated the formation of three distinct physical states depending on the chain length of PEG in PEG-PE. Mixed micelle formation was observed at concentrations of PEG(1,000)-DPPE above 7 mol-% of lipid. Phase separated lamellae were observed at all concentrations of PEG( 12,000)-DPPE (Bedu-Addo et al. Pharm. Res. 13:710-717 (1996)). Upon incorporation of high concentrations of cholesterol >30 mol% into the lipid bilayer, the formation of phase separated lamellae was completely inhibited and the formation of mixed micelles significantly reduced. At high concentrations of PEG(1,000)-PE, solubilization of the bilayer occurred with preferential solubilization of cholesterol over phosphatidylcholine. Maximum steric stabilization (surface protection) was observed with low concentrations of short chain PEG-PE and high concentrations of cholesterol. The study provides a physical mechanism for the following observations: the blood circulation time is significantly increased or decreased with liposomes highly enriched with cholesterol or PEG-PE respectively.

Characterization of PEG-mediated electrofusion of human erythrocytes

Polyethylene glycol (PEG) and electrofusion were applied together in a simple and highly efficient cell fusion method. PEG (8000 M(r)) was used to bring human erythrocytes into contact, and a single 4.4 kV/cm, 80 microseconds duration pulse was applied to cell suspensions. The fusion yield (FY) is PEG concentration-dependent. A maximum FY (50%) was found at about 10% PEG. Higher PEG concentrations (> 10%) suppressed FY caused by colloid osmotic shrinkage. Morphological changes, such as colloidal osmotic swelling and shrinking, and the expanding and contraction of fusion lumen, when suspension media were changed from PBS to isotonic 15% dextran solutions, was examined by microscopy. FY was found to depend on both simple osmotic and colloidal-osmotic swelling. From the swelling behavior, we propose two types of electropores: the pre-fusion sites between cell pairs, and electropores on each individual cell connecting intracellular and extracellular space. The latter type is responsible for the colloidal osmotic swelling and shrinking of cell which, together with simple osmotic swelling, is responsible for expanding the pre-fusion sites into fusion lumens. Resealing of electropores resulted in reducing FY, but the FY can be restored by simple osmotic shock. Apparently, PEG plays two opposite roles in this fusion method; one is to promote pre-pulse and post-pulse cell-cell contact, protecting pre-fusion sites, and the other suppresses FY by colloid osmotic shrinkage of cells after pulsing, especially when high PEG concentration is used. 10% PEG 8000 represents the optimal combination of these properties.

Plasmid transformation of Mycoplasma mycoides subspecies mycoides is promoted by high concentrations of polyethylene glycol

The recent isolation and characterization of two plasmids from Mycoplasma mycoides subspecies mycoides has opened up new possibilities for studying mycoplasmal genetics. In order to facilitate the development of a genetic system in M. mycoides subsp. mycoides, parameters of polyethylene glycol (PEG)-mediated transformation were examined, as existing protocols prove very inefficient in this organism. The effects of PEG concentration, DNA concentration, presence of Ca 2+ ions, and choice of buffers on the transformation of the Tn 916-containing plasmid pAM120 into M. mycoides subsp. mycoides were examined. The stability of Tn 916 in the M. mycoides subsp. mycoides chromosome was also evaluated. The optimal PEG concentration (53–62% ( w v )) in the transformation mixture was substantially higher than the PEG concentration reported to be optimal for transformation of other mycoplasmas (36% ( w v )). The PEG concentrations used here were also higher than the concentration used to promote transformation or fusion of gram-positive bacterial protoplasts. A necessity for the presence of Ca 2+ ions for optimal transformation was shown, as was the possible involvement of cell culture growth stage. Our results demonstrate the need for expanding current transformation techniques for mycoplasmas. Studies also indicate that once Tn 916 inserts into the M. mycoides subsp. mycoides chromosome, it can transpose to other sites at a relatively high frequency.

Effects of repeated stress on turgor pressure and cell elasticity changes in black spruce seedlings

One-year-old black spruce (Piceamariana (Mill.) B.S.P.) seedlings were preconditioned by exposing them to either one or two dehydration–rehydration cycles by using the osmoticum polyethylene glycol 3350. Preconditioned and unconditioned seedlings were then subjected to a more severe osmotic (water) stress by exposing them to a higher concentration of polyethylene glycol. Effects of repeated dehydration–rehydration cycles on cell-water relations were studied after 3, 7, and 13 days of stress relief using pressure–volume curve analysis. Repeated dehydration–rehydration cycles caused a cumulative increase in turgor potentials at full saturation. In these preconditioned plants there was also a progressive lowering of osmotic potentials and relative water contents at zero turgor, which increased over time with stress relief. The decline in osmotic potentials at zero turgor in osmotically stressed black spruce was associated with increased cell wall relaxation, followed by increased turgor potentials, in preconditioned but not in unconditioned seedlings. Saturated osmotic potentials were not altered by repeated, short-term conditioning stresses, suggesting that tissue elasticity was more important for turgor regulation than osmotic adjustment.

Reconstitution of Template-dependent in Vitro Transcriptase Activity of a Yeast Double-stranded RNA Virus

Isolated mature L-A viral particles from yeast have a transcriptase activity that uses endogenous L-A double-stranded RNA (dsRNA) as template. We have previously demonstrated that empty particles derived from mature L-A viral particles have replicase activity capable of synthesizing minus strand single-stranded RNA (ssRNA) on an added plus strand ssRNA template to form dsRNA. We report here that empty particles also have transcriptase activity that uses added viral dsRNA as template. The newly synthesized ssRNA was the plus strand, and some of these transcripts were converted to the dsRNA form by the replicase activity associated with the empty particles. This transcriptase activity, however, required a much higher concentration of polyethylene glycol than that used previously for the replicase activity. The mode of transcription was conservative. The enzyme transcribed ssRNA from L-A, M1, or X (a deletion mutant of L-A) dsRNAs but not from other yeast dsRNAs (L-BC, T, or W), bacteriophage Phi6 dsRNAs, or animal rotavirus dsRNAs, indicating the same template specificity as that expected for the in vivo reaction. This assay system, and the replicase assay system, will allow us to study in vitro all the enzymatic reactions essential for the viral replication cycle.

Effect of polyethylene glycol on protein extraction and enzyme activities in potato cell cultures

Polyethylene glycol (PEG) is often used to produce water stress in plant cell suspension cultures. The amount of soluble protein extracted from potato cell suspension cultures treated with PEG-6000 (10% w/v) decreased to 50%. In addition, the activities of glucose-6-P dehydrogenase, glutamate dehydrogenase and pyrroline-5-carboxylate reductase in these extracts were differentially reduced. High concentrations of PEG ( > 5%) in the enzyme assay systems were required to significantly affect the activities of the three enzymes extracted from PEG untreated cells. PEG must be removed from cells before proteins are extracted or enzymes assayed. A rapid procedure to harvest cells and subsequently to remove PEG from cells stressed with this compound is described.

High concentrations of PEG as a possible uncoupler of the proton motive force: ?-Amylase production with Bacillus amyloliquefaciens in aqueous two-phase systems and PEG solutions

α-Amylase production with Bacillus amyloliquefaciens was investigated in two different aqueous two-phase systems and in polyethylene glycol (PEG) 600 solutions of different concentrations. The cells did not partition totally to the bottom phases of the aqueous two-phase systems, and the enzyme production was repressed in both systems as well as in PEG 600 solutions. Concomitantly, the cultivation time was prolonged, indicating an increased maintenance metabolism. The surface properties of cells grown in 200 g/kg PEG 600 were investigated by phase partitioning and compared to the surface properties of Bacillus subtilis, which under these conditions showed increased α-amylase production. The cells of B. amyloliquefaciens partitioned to the top phase in a PEG-dextran system, whereas the cells of B. subtilis partitioned to the bottom phase. The results are discussed in relation to water activity, oxygen transfer rate and PEG-induced changes of the surface properties of the cells. The possible role of PEG as an uncoupler of the proton motive force at high concentrations is also discussed.

Structure-function relationship of mitochondrial malate dehydrogenase at high dilution and in multicomponent systems.

The structure-function relationship of mitochondrial malate dehydrogenase was investigated at low enzyme concentration, as well as in the presence of polyethylene glycol (PEG 6000) and structure making ions. Previous reports claimed the dimeric enzyme to undergo dissociation in dilute solution, and PEG-induced pairing of dimers in the crystalline state. Sedimentation analysis and gel filtration in 0.1 M sodium phosphate pH 7.6 plus 1 mM EDTA and 1 mM dithioerythritol prove the enzyme to be a stable dimer at c greater than or equal to 0.2 microgram/ml (5 nM). In the presence of 8-20% (w/v) PEG 6000, association of the dimer to tetramers and higher aggregates is observed. At 20% (w/v) polyethylene glycol, ultracentrifugal analysis yields up to 50% tetramers; chemical cross-linking by glutaraldehyde confirms the association in a qualitative way. The enzymatic properties of mMDH (specific activity, Km for oxaloacetate and NADH) in the absence and in the presence of PEG 6000 are indistinguishable. At high polyethylene glycol concentrations (greater than or equal to 20%), the thermal stability of the enzyme is found to be increased. The fluorescence emission, as well as the far-UV and near-UV circular dichroism remain unaffected. Accumulated evidence from equilibrium experiments at low enzyme concentration and reconstitution kinetics (after dissociation at acid pH) proves the active species of mMDH to be the dimer.

Macromolecular crowding accelerates the cohesion of DNA fragments with complementary termini.

Macromolecular crowding increases the rate of nonenzymatic cohesion of the complementary ends of lambda DNA. Both lambda DNA and DNA fragments bearing the cohesive ends of lambda DNA are similarly affected. High concentrations of plasma albumin or Ficoll 70 increase the rate of cohesion by ca. 100-fold whereas high concentrations of polyethylene glycol 8000 cause greater than 2000-fold stimulation in this rate. These results have implications for the mechanism of polymer-stimulated enzymatic ligation of DNA or RNA. In addition, these crowding effects may help to explain the rapid cohesion of lambda DNA observed in vivo. An improved procedure for the recovery of DNA fragments separated by agarose gel electrophoresis is also described.

Elimination of artifactual acetaldehyde in the measurement of human blood acetaldehyde by the use of polyethylene glycol and sodium azide: normal blood acetaldehyde levels in the dog and human after ethanol.

A new procedure is described for the preparation of human blood samples for analysis of acetaldehyde and ethanol by head space gas chromatography. High concentrations of polyethylene glycol were used to remove the hemoglobin and approximately 50% of the plasma protein. Artifactual formation of acetaldehyde from ethanol was inhibited by sodium azide. Using this method, no artifactual acetaldehyde was detectable in human, dog, sheep, and rat blood when spiked with ethanol in final concentrations of 65 mM. The recovery of added acetaldehyde was approximately 80% for human dog, and sheep blood, whereas it was only 30% for rat blood. Following ethanol administration, acetaldehyde levels were determined in blood taken from the pulmonary artery and descending aorta of the dog and human, and also from the hepatic vein of the latter. The relative blood acetaldehyde concentrations at these sites were hepatic vein greater than pulmonary artery greater than descending aorta.