Pedro Antonio Rodriguez

d-Limonene-induced male rat specific nephrotoxicity: evaluation of the association between d-limonene and α2u-globulin

d-Limonene is a naturally occurring monoterpene, which when dosed orally, causes a male rat-specific nephrotoxicity manifested acutely as the exacerbation of protein droplets in proximal tubule cells. Experiments were conducted to examine the retention of [14C]d-limonene in male and female rat kidney, to determine whether d-limonene or one or more of its metabolites associates with the male rat-specific protein, alpha 2u-globulin, and if so, to identify the bound material. The results indicated that, 24 hr after oral administration of 3 mmol d-limonene/kg, the renal concentration of d-limonene equivalents was approximately 2.5 times higher in male rats than in female rats. Equilibrium dialysis in the presence or absence of sodium dodecyl sulfate indicated that approximately 40% of the d-limonene equivalents in male rat kidney associated with proteins in a reversible manner, whereas no significant association was observed between d-limonene equivalents and female rat kidney proteins. Association between d-limonene and male rat kidney proteins was characterized by high-performance gel filtration and reverse-phase chromatography. Gel filtration HPLC indicated that d-limonene in male rat kidney is associated with a protein fraction having a molecular weight of approximately 20,000. Separation of alpha 2u-globulin from other kidney proteins by reverse-phase HPLC indicated that d-limonene associated with a protein present only in male rat kidney which was definitively identified as alpha 2u-globulin by amino acid sequencing. The major metabolite associated with alpha 2u-globulin was d-limonene-1,2-oxide. Parent d-limonene was also identified as a minor component in the alpha 2u-globulin fraction. Thus, d-limonene, and more specifically d-limonene-1,2-oxide, associates with alpha 2u-globulin in a reversible manner in male rat kidney. This interaction may be responsible for excessive accumulation of alpha 2u-globulin in kidneys of male rats exposed to d-limonene.

High-efficiency solid scintillation radioactivity detection for high-performance liquid chromatography

Abstract The design and optimization of a detector to monitor 14C radioactivity in the effluent from a high-performance liquid chromatograph is described. The technique of solid scintillation with cerium-impregnated lithium silicate glass scintillating material is employed. The optimized detector provides a counting efficiency for 14C β-radiation greater than 70% which is comparable to counting efficiency typiccally achieved with liquid scintillation techniques. The high counting efficiency was achieved by optimizing the detector electronics and by reducing the particle size of the scintillating glass in the flow cell to more closely approximate the average range of 14c β-radiation in aqueous solution.

Hyaline droplet nephropathy resulting from exposure to 3,5,5-trimethylhexanoyloxybenzene sulfonate

Acute oral dosing of 3,5,5-trimethylhexanoyloxybenzene sulfonate (THBS) to adult male and female rats causes a male rat-specific nephrotoxicity manifested as exacerbation of hyaline droplet formation. This chemical is structurally distinct from the volatile hydrocarbons known to cause male rat-specific kidney lesions. Therefore, to classify THBS as a hyaline droplet-inducing agent, experiments were conducted to determine whether [14C]THBS equivalents bound to alpha 2 mu-globulin and caused the protein to accumulate in male rat kidney cortex. Two-dimensional gel electrophoretic separation of male rat kidney proteins indicated that alpha 2u-globulin levels in kidney increased 24 hr after a single oral dose of THBS (500 mg/kg). Furthermore, a sex-dependent retention THBS was noted as there was approximately 10 times more THBS equivalents in male rat kidney than in female rat kidney. Equilibrium dialysis experiments indicated that 40% of THBS equivalents bound reversibly to male rat kidney proteins, whereas no interaction between THBS and female rat kidney proteins was detected. Specific binding of THBS to alpha 2mu-globulin was determined by anion-exchange HPLC after which metabolites in the alpha 2u-globulin fraction were identified by gas chromatography with parallel radioactivity-mass spectrometry and mass spectrometry-matrix isolation Fourier-transform infrared analysis. Four metabolites of THBS were found in this protein fraction, and the major component (approximately 70%) was identified as the cis gamma-lactone of 3,5,5-trimethylhexanoic acid. Experiments were also conducted in mice to determine whether THBS bound to any mouse kidney proteins, particularly mouse urinary protein. The results indicated that there was no interaction between THBS and mouse urinary protein, a protein which shares significant homology with alpha 2u-globulin. These results indicate that THBS treatment exacerbates hyaline droplet formation in male rat kidneys by binding to alpha 2mu-globulin, thereby causing the protein to accumulate in the renal cortex. The interaction between THBS and alpha 2mu-globulin appears to be unique to this male rat-specific protein as THBS does not interact with a very similar protein found in mice.

Automated quartz injector/trap for fused-silica capillary columns

Abstract An automated quartz injector/trap was developed for a Perkin-Elmer 3920 gas chromatograph. The injector/trap serves to concentrate gaseous or liquid samples without introducing organic contaminants. The concentrated sample is volatilized and transferred to a second trap by cooling a small section of a fused-silica capillary column. Reconcentration in the capillary column preserves band-shape and provides a system which delivers quantitative results on a variety of samples. Liquid samples show relatives standard deviations of 1% and 2%, respectively, for isothermal and temperaure-programmed analyses. A detection limit of less than 1 ppb is expected, with a flame ionization detector, for samples of n-octane in air.

Zinc pyridinethione: Urinary metabolites of zinc pyridinethione in rabbits, rats, monkeys, and dogs after oral dosing

Abstract The metabolites of zinc pyridinethione (ZPT) in the systemic circulation of female rabbits and monkeys and male rats and dogs were studied after 1 mg [ 14 C]ZPT/kg body wt was administered by oral gavage. In all four species, the blood radioactivity concentration showed a complex kinetic pattern. An initial maximum at 1 to 8 hr after dosing coincided with the rapid formation and elimination of several polar metabolites, while a secondary broad peak or plateau paralleled the slow accumulation of a single metabolite. In rats, this latter metabolite was identified as 2-(methylsulfonyl)pyridine (MSP) by spectral and chromatographic comparisons with the synthetic compound. Its concentration in rat serum was proportional to the quantity of ZPT dosed over the range of 0.2 to 10 mg ZPT/kg. its presence as a long-lived circulating metabolite is significant for estimating the systemic load of ZPT. The biotransformations which produce MSP involve a multistep sequence of methylation, oxidation, and reduction. Three minor serum metabolites, 2-(methylthio)pyridine-1-oxide, 2-(methylthio)pyridine, and 2-(methylsulfinyl)pyridine-1-oxide, are apparently the intermediate compounds in the biotransformation of ZPT to MSP. Subchronic feeding of [ 14 C]ZPT produced early signs of hindlimb paralysis in a rat in 6 days; the serum concentration of ZPT-derived metabolites increased linearly over this interval. Since MSP was the only major serum metabolite likely to accumulate, infusion studies were conducted to see if MSP would produce paralysis. Although the duration of infusion and the serum concentrations of MSP attained were greater than those predicted to produce paralysis from the ZPT feeding study, no paralysis was observed.

Improved radioactivity detector for fused-silica capillary columns

Abstract 14 C-labeled and unlabeled organic compounds eluting from fused-silica capillary columns were detected by the parallel combination of a radioactivity detector (RAD) and a flame ionization detector (FID). The RAD consists of a small-volume counter tube and ancillary electronics. It is constructed from readily available parts. For maximum signal-to-noise ratio, the RAD is operated at 70% counting efficiency. The resulting background is less than 5 cpm. The instrumentation delivers high chromatographic efficiency and eliminates combustion artifacts. Radioactive peaks are 12 sec wide, while the detection limit is ca. 440 cpm (0.2 nCi) for peaks with k ′ ⩽ 5. No degradation in column performance is apparent in the FID trace.

Simple and versatile injection system for capillary gas chromatographic columns Performance evaluation of a system including mass spectrometric and light-pipe Fourier-transform infrared detection

Abstract A cryogenic concentrator, a pre-trap, and ancillary systems were developed to facilitate the introduction of large volumes of either gaseous or liquid samples to a capillary GC column. This large-volume injection system, referred to as LVIS, is used in conjunction with the conventional split/splitless injector of a gas Chromatograph. The performance of the split/splitless injector is essentially unchanged by the installation of the cryogenic concentrator; thus, the gas Chromatograph can be operated as usual. Reproducibility, accuracy, and inertness were demonstrated while performing injections of a hydrocarbon mixture (n-C7–C22) and the Grob-programmed test mixture. Liquid samples, up to 100 μl, were conveniently handled by the system. Applicability to gas-phase analyses was demonstrated by sampling perfume components in the headspace of a granular detergent and by sampling pyrolysis products of Kraton 1107. When the LVIS was used with a gas Chromatograph equipped with mass-selective (MSD) and light-pipe Fourier-transform infrared (FT-IR) [IRD] spectrometers, it was possible to achieve identification limits by IRD approaching 1 ppb v/v when analyzing one liter of headspace, and ca. 100 ppb when analyzing 100 μl of a liquid sample. Identification limits with the MSD were lower.

Identification of compounds responsible for an off-odor in wet polyacrylate superabsorbent polymers

Abstract Using dynamic headspace, GC–sniff-port coupled to mass spectrometry (MS) and Fourier transform IR [1] , and two-dimensional GC–MS–matrix isolation Fourier transform IR [2] , we identified the compounds responsible for an off-odor associated with the use of superabsorbent polymers (SAPs) in consumer products. Of those compounds, a C 7 vinyl ketone (5-methylhex-1-en-3-one, isobutyl vinyl ketone) was the best predictor of consumer reaction to the odor. After synthesis, we confirmed this compound as the most offensive odorant in the SAPs. Removing vinyl ketones from the monomer raw material effectively eliminated the product off-odor.

Separation and use of the perdeuterated analogue as an internal standard for the analysis of ethylene dibromide

Separation du dibromo-1,2ethane de son analogue deutere par chromatographie en phase gazeuse sur colonne capillaire a silice fondue

Modification of a commercial pyrolysis probe to improve its temporal and spatial temperature profiles: Performance evaluation using model polymers

Abstract A coiled-filament probe of a commercially available pyrolyzer (Chemical Data Systems, CDS Pyroprobe 120) was modified to change the temporal and spatial temperature profiles delivered by the probe. The modification changes the geometry of the heating filament: it is coiled tightly and a light coating of a ceramic cement is applied to maintain its dimensional stability while minimizing the possibility of developing an electrical short. The modified pyroprobe produced a reproducible and uniform temperature profile over a ∼3-mm long pyrolysis region and had near-perfect emissivity (∼0.95) for monitoring temperature with an optical thermometer. To conduct experiments off-line we also designed a glass housing for the tightly-coiled pyroprobe (TC-pyp). The housing has provisions for making a gas-tight seal with the pyroprobe, for introducing a gas to control the pyrolysis atmosphere and provide a rapid sweep of the pyrolysis region and for interfacing with a pre-trap to collect pyrolysates. To evaluate the results obtained with the TC-pyp we compared mass and temperature dependencies of Kraton D1107P pyrograms with those generated by a Pt ribbon-pyroprobe (PtR-pyp) and an unmodified coil pyroprobe. In addition, we report on the use of the instrumentation for quantitative analyses of model polymers.