Determination of trovafloxacin,a new quinolone antibiotic,in biological samples by reversed-phase high-performance liquid chromatography

A simple, accurate and precise high-performance liquid chromatographic method was developed and validated for the determination of trovafloxacin, a new quinolone antibiotic, in serum and urine. Following solid-phase extraction, chromatographic separation was accomplished using a C₁₈ column with a mobile phase consisting of 0.04 M H₃PO₄-acetonitrile-tetrabutylammonium hydroxide-0.005 M dibutyl amine phosphate (D-4) reagent (83:16.85:0.05:0.1, v/v), pH 3. Trovafloxacin and the internal standard (a methyl derivative of trovafloxacin) were detected by ultraviolet absorbance at 275 nm. The lower limit of quantification for trovafloxacin was 0.1 μg/ml and the calibration curves were linear over a concentration range of 0.1 to 20..0 μg/ml (r² = 0.9997). The average recoveries were greater than 70% for both trovafloxacin and internal standard. The intra-day and inter-day coefficients of variation were generally less than 5% in urine and serum over the concentration range of 0.1 to 20.0 μg/ml. Human serum samples could be stored for up to 12 months at −20°C and urine samples could be stored up to 18 months at −80°C.     

Simultaneous determination of primidone and its three major metabolites in rat urine by high-performance liquid chromatography using solid-phase extraction

A new high-performance liquid chromatographic method for simultaneous determination of primidone (PRM) and of its three major metabolites, phenobarbital (PB), p-hydroxyphenobarbital (p-HO-PB) and phenylethylmalonamide (PEMA), in rat urine, was developed. After acid hydrolysis, these compounds were extracted from urine by means of a Bond Elut Certify LRC column with good clean-up. The extracts were chromatographed on a C₁₈ reversed-phase column using isocratic elution at 40°C, with UV detection at 227 nm. The limit of detection was 0.5 mg/ml for the four compounds. Good linearity (r²>0.99) was observed within the calibration ranges studied: 37.4–299.3 μg/ml for PRM, 26.4–211.2 μg/ml for PB, 12.5–100.2 μg/ml for p-HO-PB and 12.1–97.0 μg/ml for PEMA. Repeatability was in the range 3.1–6.8%. This method constitutes a useful tool for studies on the influence of various parameters on primidone metabolism.     

Efficient high-performance liquid chromatographic assay for the simultaneous determination of metoprolol and two main metabolites in human urine by solid-phase extraction and fluorescence detection

An improved, more efficient method for the determination of metoprolol and its two metabolites in human urine is reported. The simultaneous analysis of the zwitterionic metoprolol acidic metabolite (III, H117/04) with the basic metabolites α-hydroxymetoprolol (II, H119/66), metoprolol (I) and guanoxan (IV, internal standard) was achieved employing solid-phase extraction and isocratic reversed-phase HPLC. The analytes were extracted from urine (100 μl) using C₁₈ solid-phase extraction cartridges (100 mg), and eluted with aqueous acetic acid (0.1%, v/v)–methanol mixture (40:60, v/v, 1.2 ml). The eluents were concentrated (250 μl) under vacuum, and aliquots (100 μl) were analysed by HPLC with fluorescence detection at 229 nm (excitation) and 309 nm (emission) using simple isocratic reversed-phase HPLC (Novapak C₁₈ radial compression cartridge, 4 μm, 100×5 mm I.D.). Acetonitrile–methanol–TEA/phosphate buffer pH 3.0 (9:1:90, v/v) was employed as the eluent (1.4 ml/min). All components were fully resolved within 18 min, and the calibration curves for the individual analytes were linear (r²≥0.996) within the concentration range of 0.25–40.0 mg/ml. Recoveries for all four analytes were greater than 76% (n=4). The assay method was validated with intra-day and inter-day variations less than 2.5%.     

Gas chromatographic–tandem mass spectrometric determination of acetylsalicylic acid in human plasma after oral administration of low-dose aspirin and guaimesal

A fully validated gas chromatographic–tandem mass spectrometric (GC–MS–MS) method is described for the accurate determination of acetylsalicylic acid (ASA) in human plasma after a single low-dose oral administration of aspirin or guaimesal, an ASA releasing prodrug. ASA and the newly prepared O-[²H₃]-acetylsalicylic acid (d3-ASA) used as internal standard were determined in 100-μl aliquots of plasma by extractive pentafluorobenzyl (PFB) esterification using PFB bromide and tetrabutylammoniumhydrogen sulphate as the esterifying and ion-pairing agent, respectively, and by GC–MS–MS analysis in the negative-ion chemical ionization mode. The overall relative standard deviations were below 8% for ASA levels in the range 0–1 μg/ml plasma. Mean accuracy was 3.8% for ASA levels within the range 0–100 ng/ml. The limit of quantitation of the method was determined as 200 pg/ml ASA at an accuracy of 5.5% and a precision of 15.2%. The limit of detection was determined as 546 amol of ASA at a signal-to-noise ratio of 10:1.     

New high-performance liquid chromatographic method for amphotericin B analysis using an internal standard

A simple and reproducible HPLC method for the analysis of amphotericin B (AmB) in serum, lung and liver using natamycin as the internal standard was developed. AmB and natamycin were extracted from serum, lung and liver and were separated using an isocratic elution from a C₁₈ reversed-phase column. The mobile phase consisted of acetonitrile-10 mM acetate buffer pH 4.0 (37:63, v/v). The HPLC system had two detectors in series. One was set at 303 nm and the other at 383 nm for the detection of natamycin and AmB, respectively. The retention times of AmB and natamycin were 15 and 6 min, respectively. The recovery efficiency was 96-70%. The limit of quantification was 0.1 μg/ml. The assay was reproducible, the within-day coefficient of variation (n=6) was <8% for serum, lungs and liver. The between-day variability (n=6) was <7.7% for serum, liver and lungs at 1 μg/ml or 1 μg/g tissue concentration. The assay was linear within the range 1–40 μg/ml (r²=0.999).     

Enantioselective determination of sotalol enantiomers in biological fluids using high-performance liquid chromatography

A simple and sensitive high-performance liquid chromatograhic (HPLC) method for the determination of (+)-(S)-sotalol and (−)-(R)-sotalol in biological fluids was established. Following extraction with isopropyl alcohol from biological samples on a Sep-Pak C₁₈ cartridge, the eluent was derivatized with 2,3,4,6-tetra-O-acetyl-β-d-glucopyranosol isothiocyanate (GITC). The diastereoisomeric derivatives are resolved by HPLC with UV detection at 225 nm. Calibration was linear from 0.022 to 4.41 μg/ml in human plasma and from 0.22 to 88.2 μg/ml in human urine for both (+)-(S)- and (−)-(R)-sotalol. The lower limit of determination was 0.022 μg/ml for plasma and 0.22 μg/ml for urine. The within-day and day-to-day coefficients of variation were less than 7.5% for each enantiomer at 0.09 and 1.8 μg/ml in plasma and at 0.44 and 4.4 μg/ml in urine. The method is also applicable to other biological specimens such as rat, mouse and rabbit plasma.     

High tyrosine-specific protein kinase activity in normal human peripheral blood lymphocytes

Tyrosine-specific protein kinase (ATP: protein phosphotransferase, EC 2.7.1.37) activity was measured in normal human nonadherent peripheral blood lymphocytes using synthetic peptide substrates having sequence homologies with either pp60^src or c-myc. A high level of tyrosine-specific protein kinase activity was found associated with the cell particulate fraction (100 000 × g pellet). High-pressure liquid chromatography and phosphoamino acid analysis of the synthetic peptide substrates substantiated the phosphorylation of tyrosine residues by the particulate fraction enzyme. The human enzyme was also capable of phosphorylating a synthetic random polymer of 80% glutamic acid and 20% tyrosine. Enzyme activity was half-maximal with 22 μM Mg·ATP and had apparent K_m values for the synthetic peptides from 1.9 to 7.1 mM. The enzyme preferred Mg²⁺ to Mn²⁺ for optimal activity and was stimulated 2–5-fold by low levels (0.05%) of some ionic as well as non-ionic detergents including deoxycholate, Nonidet P-40 and Triton X-100. The enzyme activity was not stimulated by N⁶;O^2′-dibutyryl cyclic AMP (100 μM), N⁶;O^2′-dibutyryl cyclic GMP (100 μM), Ca²⁺ (200 μM), insulin (1 μg/ml) or homogeneous human T-cell growth factor (3 μg/ml) under the conditions used. Alkaline-resistant phosphorylation of particulate proteins in vitro revealed protein bands with M_r 59 000 and 54 000 suggesting that there are endogenous substrates for the human lymphocyte tyrosine protein kinase.     

Synthesis of α3 phage DNA in replication mutants of Escherichia coli

Host functions for DNA replication of bacteriophage α3, a representative of group A microvirid phages, were studied using dna and rep mutants of Escherichia coli. In dna⁺ cells, conversion of phage α3 single-stranded DNA (SS) into the double-stranded replicative form (RF) was insensitive to 30–150 μg/ml of chloramphenicol, 200 μg/ml of rifampicin, 50 μg/ml of nalidixic acid, or 200 μg/ml of novobiocin. At 43°C, synthesis of the parental RF was inhibited in dnaG and dnaZ mutants, but not in dnaE and rep strains. Replication of phage α3 progeny RF was prevented by 50 μg/ml of mitomycin C (in hcr⁺ bacteria), 50 μg/ml of nalidixic acid or 200 μg/ml of novoviocin, but neither by 30 μg/ml of chloramphenicol nor by 200 μg/ml of rifampicin. Besides dnaG and dnaZ gene products, dnaE and rep functions were essential for the progeny RF synthesis. Host factor dependence of α3 was relatively simple and, in contrast with phages øX174 and G4, α3 did not require dnaB and dnaC(D) activities.     

Leb-active glycolipid in human plasma: Measurement by radioimmunoassay

A radioimmunoassay that measures Le^b-active glycolipids in human plasma has been developed using antiserum from a goat immunized with a Le^b blood group hapten, lacto-N-difucohexaose I, conjugated to polylysine. Binding by the antiserum of lacto-N-difucohexaose I conjugated to ¹²⁵I-labeled bovine serum albumin is specifically inhibited by Le^b-active ceramide hexasaccharide. Plasma levels of the glycolipid are quantitated by comparing the inhibitory activity of plasma with that of the purified Le^b-active glycolipid. Plasma samples from 35 blood group O Le(a ? b +) individuals contain Le^b-active ceramide hexasaccharide at an average concentration of 0.9 μg/ml (range: 0.2 to 2.5 μg/ml); no Le^b-active glycolipid (less than 0.02 μg/ml) could be detected in plasma from blood group O Le(a + b?) or O Le(a? b?) individuals. Plasma from A₁ Le(a ? b+) individuals contains less Le^b-active glycolipid than plasma from A₂ Le(a? b+) individuals: its level in 19 samples of A, Le(a? b+) plasma averages 0.2 μg/ml (range: 0.1 to 0.45 μg/ml), and its level in 9 samples of A₂ Le(a? b+) plasma averages 1.1 μg/ml (range 0.8 to 1.3 μg/ml). About one-third of the total Le^b-active glycolipid in whole blood is associated with erythrocytes and the rest is found in plasma.     

Ultrafiltration-light absorption spectrophotometric determination of silicon in blood

An ultrafiltration-light absorption spectrometric method for soluble molybdate-reactive silicon was assessed and applied to bovine and ovine blood plasma and sera, giving precise analytical results. Interfering protein above molecular weight 10,000–25,000 was removed by ultrafiltration, and silicon in ultrafiltrates was quantitated by measuring light absorption at 810 nm of the 1,2,4-aminonaphthol sulfonic acid/ascorbic acid-reduced silicomolybdate. Chemical interferences on the color-forming reaction of remaining blood components were tested by measuring recoveries of silicon added to real blood plasma samples and to synthetic blood plasma solutions, the latter containing typical levels of the major ions Na⁺, K⁺, Ca²⁺, HCO₃^?, and Cl^?, together with varying quantities of the potential interferants (amount per analytical reaction): phosphate (0–0.5 mg P), ferric ion (0–3 mg), fluoride (0–1.25 mg), vanadate (0–0.5 mg V), arsenate (0–10 μg As), and germanate (0–0.5 μg Ge). The mean recovery of added 0.8–9 μg silicon/g of bovine and ovine plasma was 97.7% (SE = 1.0, n = 17); the mean recovery of 1 and 5 μg silicon from synthetic blood plasma solutions with interferant levels up to 50-fold that in normal plasma was 99.2% (SE = 0.3, n = 47). Silicon concentrations found in bovine and ovine blood plasma and sera were typically around 7 μg/ml with procedural reagent blanks consistently low at a mean of 0.12 μg/test (SD = 0.011, n = 20). The silicon level in Center for Disease Control bovine serum (reference specimen Lot R-2274) was found to be (mean ± SE, n = 10) 1.147 ± 0.013 μg/g or 1.172 ± 0.013 μg/ml (25°C). The method detectivity (detection limit) was estimated at 0.03 μg.     

Development and Validation of HPLC Method for Determination of Sodium Copper Chlorophyllin – A Food Colorant and Its Application in Pharmacokinetic Study

A simple, accurate, and precise bioanalytical method was developed and validated for the determination of pharmacokinetic parameters of sodium copper chlorophyllin, a USFDA approved food additive and colorant in rat plasma. The column used was Luna^® C₁₈ 250×4.6 mm, 100 Å, having particle size 4.5 μm, and the mobile phase used was methanol (MeOH), and 10 mM ammonium acetate buffer in the ratio of 90 : 10, the flow rate was 1 ml/min, and the injection volume of 20 μL. The retention time of sodium copper chlorophyllin was obtained at 9 min. The method was found to be linear at the range of 0.50–8.00 μg mL^?1.     

Determination of N-(trans-4-isopropylcyclohexylcarbonyl)-d-phenylalanine in human plasma by solid-phase extraction and column-switching high-performance liquid chromatography with ultraviolet detection

A column-switching high-performance liquid chromatography method with ultraviolet detection at 210 nm has been developed for the determination of N-(trans-4-isopropylcyclohexylcarbonyl)-d-phenylalanine (AY4166, I) in human plasma. Plasma samples were prepared by solid-phase extraction with Sep-Pak Light tC₁₈, followed by HPLC. The calibration graph for I was linear in the range 0.1–20 μg/ml. The limit of quantitation of I, in plasma, was 0.05 μg/ml. The recovery of spiked I (0.5 μg/ml) to drug-free plasma was over 92% and the relative standard deviation of spiked I (0.5 μg/ml) compared to drug-free plasma was 4.3% (n = 8).     

Action of two juvenile hormone antagonists on lepidopteran epidermis

The juvenile hormone antagonist ETB (ethyl-4-2(t-butylcarbonyloxy)-butoxybenzoate) caused formation of precocious larval-pupal intermediates after the 4th (penultimate)-larval instar of the tobacco hornworm, Manduca sexta, when 50 μg were applied to any 3rd stage larvae or to 4th stage larvae within 12 hr after ecdysis. This dose was most effective within 12 hr after ecdysis to the 3rd stage. In the black mutant larval assay for juvenile hormone, ETB had activity, 0.75 μg per larva giving half-maximal score. In vitro ETB acted as a juvenile hormone to prevent the ecdysteroid-induced change in commitment at concentrations above 0.1 μg/ml with an ED₅₀ at 2.8 μg/ml and as a partial juvenile hormone antagonist to 0.1 μg/ml juvenile hormone I at concentrations between 10^?3 and 10^?2 μg/ml. By contrast, EMD (ethyl-E-3-methyl-2-dodecenoate) had little juvenile hormone-like activity in vitro up to its limits of solubility (100 μg/ml) and exhibited sporadic partial juvenile hormone antagonistic activity in vitro at concentrations between 1 and 100 μg/ml. Since these concentrations were 10–1000 times that of juvenile hormone I in the medium, EMD apparently is not an efficient competitor.     

Stimulation of HCO3− secretion by the prostaglandin E2 analog enprostil: Studies in human stomach and rat duodenum

This study investigated the action of enprostil, a synthetic analog of PGE₂, on gastric HCO₃⁻ secretion in humans and on duodenal HCO₃⁻ secretion in the anesthetized rat. A previously validated 2-component model was used to calculate gastric HCO₃⁻ and H⁺ secretion in 10 human subjects. Compared to placebo, a single 70 μg oral dose of enprostil increased basal gastric HCO₃⁻ secretion from 1810 +- 340 to 3190 ± 890 μmol/hr (P < 0.05). In addition, enprostil reduced basal gastric H⁺ secretion from 5240 ± 1140 to 1680 ± 530 μmol/hr (P < 0.02). Enprostil also increased HCO₃⁻ and reduced H⁺ secretion during intravenous pentagastrin infusion. In the rat, duodenal HCO₃⁻ secretion was measured by direct titration in situ using perfused segments of duodenum just distal to the Brunner gland area dn devoid of pancreatic and biliary secretions. Addition of enprostil(10 μg/ml) to the duodenal bathing solution increased duodenal HOC₃⁻ secretion from 6.3 ± 1.3 to 15.1 ± 2.0 μmol/cm·hr (P < 0.01, n = 6). The stimulatory action of enprostil on duodenal HCO₃⁻ secretion at 10 μg/ml was comparable in magnitude and duration to that of 10 μg/ml natural PGE₂. In summary, the PGE₂ analog enprostil stimulated gastroduodenal HCO₃⁻ secretion, effects which may be beneficial in protection of the gastroduodenal mucosa against luminal acid.     

Direct analysis of salicylic acid,salicyl acyl glucuronide,salicyluric acid and gentisic acid in human plasma and urine by high-performance liquid chromatography

A method for the simultaneous direct determination of salicylate (SA), its labile, reactive metabolite, salicyl acyl glucuronide (SAG), and two other major metabolites, salicyluric acid and gentisic acid in plasma and urine is described. Isocratic reversed-phase high performance liquid chromatography (HPLC) employed a 15-cm C₁₈ column using methanol-acetonitrile-25 mM acetic acid as the mobile phase, resulting in HPLC analysis time of less than 20 min. Ultraviolet detection at 310 nm permitted analysis of SAG in plasma, but did not provide sensitivity for measurement of salicyl phenol glucuronide. Plasma or urine samples are stabilized immediately upon collection by adjustment of pH to 3–4 to prevent degradation of the labile acyl glucuronide metabolite. Plasma is then deproteinated with acetonitrile, dried and reconstituted for injection, whereas urine samples are simply diluted prior to injection on HPLC. m-Hydroxybenzoic acid served as the internal standard. Recoveries from plasma were greater than 85% for all four compounds over a range of 0.2–20 μg/ml and linearity was observed from 0.1–200 μg/ml and 5–2000 μg/ml for SA in plasma and urine, respectively. The method was validated to 0.2 μg/ml, thus allowing accurate measurement of SA, and three major metabolites in plasma and urine of subjects and small animals administered salicylates. The method is unique by allowing quantitation of reactive SAG in plasma at levels well below 1% that of the parent compound, SA, as is observed in patients administered salicylates.     

The determination of allopurinol and oxipurinol in human plasma and urine

A method is described for allopurinol and oxipurinol assay within human plasma and urine in the range expected during therapy. The method is based on high-performance ion-exchange chromatography following an efficient sample purification step using Chelex-100 resin in the Cu²⁺ form. Linear calibration curves are produced for allopurinol over the range 0.05–10 μmole/1 (0.068–1.36 μg/ml) in plasma and 0.005–1 mmole/1 (0.68–136 μg/ml) in urine and for oxipurinol 0.5–100 μmole/1 (0.076–15.2μg/ml) in plasma and 0.1–2 mmole/1 (15.2–304 μg/ml) in urine.     

Development of a gradient elution high-performance liquid chromatography assay with ultraviolet detection for the determination in plasma of the anticancer peptide [Arg6, d-Trp7,9, mePhe8]-substance P (6–11) (antagonist G), its major metabolites and a C-terminal pyrene-labelled conjugate

[Arg⁶, d-Trp^7,9, mePhe⁸]-substance P (6–11), code-named antagonist G, is a novel peptide currently undergoing early clinical trials as an anticancer drug. A sensitive, high efficiency high-performance liquid chromatography (HPLC) method is described for the determination in human plasma of antagonist G and its three major metabolites, deamidated-G (M1), G-minus Met¹¹ (M2) and G[Met¹¹(O)] (M3). Gradient elution was employed using 40 mM ammonium acetate in 0.15% trifluoroacetic acid as buffer A and acetonitrile as solvent B, with a linear gradient increasing from 30 to 100% B over 15 min, together with a microbore analytical column (μBondapak C₁₈, 30 cm×2 mm I.D.). Detection was by UV at 280 nm and the column was maintained at 40°C. Retention times varied by <1% throughout the day and were as follows: G, 13.0 min; M1, 12.2 min; M2, 11.2 min; M3, 10.8 min, and 18.1 min for a pyrene conjugate of G (G–P). The limit of detection on column (LOD) was 2.5 ng for antagonist G, M1–3 and G–P and the limit of quantitation (LOQ) was 20 ng/ml for G and 100 ng/ml for M1–3. Sample clean-up by solid-phase extraction using C₂-bonded 40 μm silica particles (Bond Elut, 1 ml reservoirs) resulted in elimination of interference from plasma constituents. Within-day and between-day precision and accuracy over a broad range of concentrations (100 ng/ml–100 μg/ml) normally varied by <10%, although at the highest concentrations of M1 and M2 studied (50 μg/ml), increased variability and reduced recovery were observed. The new assay will aid in the clinical development of antagonist G.     

Identification and determination of pirlimycin residue in bovine milk and liver by high-performance liquid chromatography-thermospray mass spectrometry

Determinative and confirmatory methods of analysis for pirlimycin (I) residue in bovine milk and liver have been developed based on HPLC-thermospray (TSP) MS. Milk sample preparation consisted of precipitating the milk proteins with acidified acetonitrile followed by a solvent partitioning with a mixture of n-butyl chloride and hexane, extraction of I from the aqueous phase into methylene chloride (MC), and solid-phase extraction clean-up. For liver, samples (2 g) were extracted with 0.25% trifluoroacetic acid in acetonitrile. The aqueous component was released from the organic solvent with n-butyl chloride. The aqueous solution was reduced in volume by evaporation, basified with ammonium hydroxide, then extracted with MC. The MC was evaporated to dryness and the dried residue reconstituted in 2.0 ml of 0.1 M ammonium acetate for analysis. A chromatographically resolved stereoisomer of I with TSP-MS response characteristics identical to I was used as an internal standard (I.S.) for quantitative analysis based on the ratio of peak areas of I to I.S. in the protonated molecular-ion chromatogram at m/z 411.2.The method for milk was validated by the analysis of control milk samples spiked with I at concentrations from 0.05 to 0.8 μg/ml. The overall recovery of pirlimycin across this concentration range was 95.4% ± 8.7%. The limit of quantitation (LOQ) and limit of confirmation (LOC) of the method were validated to be 0.05 μg/ml and 0.10 μg/ml, respectively.The method for liver was validated by the analysis of control liver samples spiked with I at concentrations ranging from 0.025 to 1.0 μg/g. The overall recovery of pirlimycin was 97.6% ± 5.1% in this concentration range. The validated limit of quantitation (LOQ) and limit of confirmation (LOC) of the method were 0.025 μg/g and 0.10 μg/g, respectively.Four diagnostic ions for I were monitored for confirmation: the pseudo-molecular ions (M + H)⁺ at m/z 411.2 (³⁵Cl) and m/z 413.2 (³⁷Cl), and fragment ions at m/z 375.2 and 158.1. Confirmatory criteria were defined for these assays.     

Binding of lipopolysaccharide and complexes of lipopolysaccharide to serum low density lipoproteins to liver macrophages

Binding of [³H]-lipopolysaccharide toxin (LPS) and complexes of LPS with serum [¹²⁵I]-labeled low density lipoproteins (LDL) to primary culture of rat liver macrophages (Kupffer cells) has been studied. Total, specific and nonspecific binding was determined. The receptor interaction was shown to dominate for both LPS and LDL-LPS complexes, representing 70–77% and 80–85%, respectively. The Scatchard plot was essentially non-linear for LPS binding but linear for the LDL-LPS complexes. At the Scatchard graph of LPS binding, however, two regions approximately fitting the linear regression could be identified. These regions correspond to two different types of specific binding sites: the first is for lower toxin concentrations of 0.25–0.50 μg/ml with K _d = 0.75 μg/ml; while the second is for higher LPS concentrations of 7.5–15 μg/ml with K _d = 5.39 μg/ml. For LDL-LPS complexes only K _d of 2.80 μg/ml was obtained. The LDL-LPS complexes significantly blocked the LPS binding (?40%) while acetylated or oxidized LDLs exerted a less pronounced effect. LPS inhibited binding of LDL-LPS complexes (?60%), while acetylated or oxidized LDLs suppressed interaction of LDL-LPS complexes with Kupffer cells insignificantly. It is suggested that, while binding to the Kupffer cell surface, a substantial portion of both LPS and LDL-LPS complexes share the same scavenger receptors with which, however, modified LDLs interact weakly. The LDL-LPS complexes can interact, apart from receptors common with LPS, with other receptors exhibiting similar binding parameters, with the apo-B/E receptors playing an inessential role.     

Effect of cycloheximide on protein and DNA synthesis and on the yields of chromosomal aberrations induced by DEB and ENU in vicia faba

Incubation of root tips in cycloheximide (CHM) at concentrations of 0.3–50 μg/ml inhibits the incorporation of [¹⁴C]leucine by 40–100% within 2 h. A depression in the incorporation of [³C]thymidine was observed after a 2-h incubation in CHM solution at 1 μg/ml.In root tips exposed for 2 h to CHM at 1 μ/ml the mitotic activity of cells was severely depressed within 15 h of recovery. Metaphases appearing after 20 h carried infrequent aberrations of the chromatid type. CHM at this concentration had no effect on the yield of aberrations induced by the alkylating agents diepoxybutane (DEB) and N-ethyl-N-nitrosourea (ENU) when applied as post-treatment.