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Biomedical subjects

W Slikker

Publications and source records attributed to W Slikker.

At least 163 records · Page 9Linked to original sources
PubMed1985

Mass spectral characterization of doxylamine and its rhesus monkey urinary metabolites.

This study describes the use of mass spectrometry (MS), high-performance liquid chromatography (HPLC) and chemical derivatization techniques for the identification of doxylamine and five rhesus monkey urinary metabolites. The analyses were performed using chemical ionization mass spectrometry with either methane or ammonia as the reagent gas. The confirmation of the structures of two of these urinary metabolites was aided by the synthesis of doxylamine N-oxide and desmethyldoxylamine and by the use of methylation and acetylation derivatization techniques. Doxylamine N-oxide, desmethyldoxylamine, didesmethyldoxylamine, and two metabolites which resulted from the cleavage of the aliphatic tertiary nitrogen side chain to the subsequent 2-[1-phenyl-1-(2-pyridinyl)ethoxy]acetic acid or 2-[1-phenyl-1-(2-pyridinyl)ethoxy]methanol compounds were isolated and identified from rhesus monkey urine. Additional data concerning the mass spectral analysis of derivatization or reaction products from the three chloroformate reactions with doxylamine, and the synthesis and separation techniques which afforded mass spectral identification of the urinary metabolites are also presented.

Animals↗
PubMed1985

Identification of the cellular retinoic acid binding protein (cRABP) within the embryonic mouse (CD-1) limb bud.

Retinoic acid, a physiologically active metabolite of vitamin A, is known animal teratogen. Among other malformations, limb abnormalities are produced and are attributed to a selective inhibition of differentiating prechondrogenic mesenchyme resulting in reduced or absent cartilage elements. Evidence is available that the cellular retinoic acid binding protein (cRABP) may be important in mediating the biological effects of retinoic acid. In this study, the cRABP has been identified by sucrose gradient sedimentation analysis in the gestation day 10 (Theiler stages 16-17) mouse forelimb bud, which contains retinoic-acid-sensitive prechondrogenic mesenchyme. Saturation analysis demonstrated values for the apparent dissociation constant (Kd) of 2.0 and 2.2 X 10(-9)M and for the total specific binding capacity for [3H]-trans-retinoic acid of 24.5 and 25.6 pmoles per mg cytosolic protein. The binding specificity of the forelimb bud cRABP for all-trans-retinoic acid was demonstrated in competition assays using all-trans-retinol, all-trans-retinal, and 13-cis-retinoic acid. In addition, 13-cis-retinoic acid was demonstrated to have a lower affinity for the cRABP than all-trans-retinoic acid, a result which may be related to the lower teratogenic potency of the 13-cis-retinoic acid. Thus, the cRABP was demonstrated in the mouse forelimb bud at a time of susceptibility for the production of limb malformations by retinoic acid. The role of the cRABP in the mechanism of retinoic acid teratogenicity remains to be delineated.

Animals↗
PubMed1984

The role of maternal diet in the developmental toxicology of ethanol.

A commonly observed result of ethanol administration to experimental animals is a reduction in voluntary dietary intake. The purpose of this investigation was to examine the role of this reduction in the developmental/reproductive toxicity of ethanol. To achieve this objective, female C3H mice were administered one of the following diets from Day 0 to Day 17 of pregnancy: (1) liquid diet, (2) liquid diet plus 4.1% w/v ethanol, (3) an amount of liquid diet equal to that consumed by the liquid diet plus 4.1% w/v ethanol group, i.e., pair-fed, (4) liquid diet fortified with protein, fats, carbohydrates, vitamins, and minerals, or (5) fortified diet plus 4.1% w/v ethanol. An important aspect of this experiment was the 2 X 2 factorial design, which permitted the analysis of the effects of ethanol consumption, diet intake reduction, and potential interactions between these two factors. After maternal death on Day 17 of gestation, fetuses were examined for evidence of alterations in growth and/or development. Analysis of the results revealed that decreased dietary intake, but not ethanol consumption resulted in a decrease in fertility, maternal pregnancy weight gain, and litter size. In contrast, both decreased dietary intake and ethanol consumption significantly inhibited fetal growth and development. However, no interaction between these two factors was demonstrated, indicating that ethanol's fetotoxic effects occurred, regardless of maternal dietary intake. We conclude that, depending on the endpoint examined, maternal nutrition plays a key role in experimental ethanol fetotoxicity. However, this agent is fetotoxic, even in the well-nourished animal.

Animals↗
PubMed1984

Comparison of the metabolism of cortisol and triamcinolone acetonide in the early, mid, and late gestational age rhesus monkey (Macaca mulatta).

The metabolism of radiolabeled cortisol and triamcinolone acetonide (TAC) was compared in the early, middle, and late gestational age rhesus monkeys. Trace amounts of 14C-cortisol and 10 mg/kg 3H-TAC (Kenalog) were simultaneously administered i.m. to the maternal animal. Whole 30-day embryos or 61- to 137-day fetal organs, amniotic fluid, and placenta were collected from 0.5 to 24 h after dose administration and analyzed by high-performance liquid chromatography (HPLC). Serial blood samples collected from all maternal animals and the late gestational age fetuses were similarly processed. The maternal plasma concentration of total radioactivity derived from TAC 1-60 min after dose administration was significantly less on day 30 of gestation as compared to day 60 at the 5-, 10-, and 60-min time points. At 60 and 130 days of gestation, however, the maternal plasma concentrations of total radioactivity were similar. Concentrations of cortisol-derived radioactivity in the maternal plasma were the same across gestational age. The plasma TAC and cortisol metabolic profiles, as determined by HPLC, were not significantly different throughout pregnancy. In late pregnancy 30 min after dose administration, the fetal to maternal plasma cortisol ratio was 0.34, whereas the same ratio for TAC was 0.96. By 1 h after dose administration, less than 8% of the total 14C radioactivity in fetal tissues was cortisol and over 92% of the 3H was TAC. The extensive fetoplacental metabolism of cortisol to inactive metabolites and the resistance of TAC to metabolic conversion results in greater TAC than cortisol exposure of the developing rhesus monkey conceptus.

Animals↗
PubMed1984

Postnatal toxicity following prenatal reserpine exposure in rats: effects of dose and dosing schedule.

Pregnant CD rats were treated subcutaneously with 0, 0.1, 0.33, or 1.0 mg reserpine/kg/day either on Days 12-15 or on Days 16-19 of gestation. Dams were allowed to deliver and litters (4 +/- 1 of each sex) were weighed weekly and held to 21 days of age. Basal ornithine decarboxylase (ODC) activity and neurochemical determinations were made on hearts and brains, respectively, from pups culled from litters on postnatal Day 1, and from two males and two females/litter at 21 days of age. Following both treatment schedules, the high dose of reserpine resulted in maternal weight loss during dosing, increased stillborn pups, reduced pup weight at birth, retarded postnatal growth, and decreased survival to 21 days of age. Basal cardiac ODC activity was reduced to 33% of control levels only on Postnatal Day 1 in both high-dose groups, while absolute heart weight decreased and relative heart weight increased in these pups. Whole-brain concentrations of two neurotransmitter metabolites, 3-4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindoleacetic acid (5-HIAA), were increased only at Postnatal Day 1 in the high dose group treated on Days 12-15 of gestation. No other changes were found in concentrations of these metabolites or in the transmitters dopamine and serotonin. The only effect found following administration of 0.33 mg/kg reserpine was a reduction in maternal weight gained during both dosing periods. No signs of toxicity were observed following low-dose exposure on either schedule. Most previously reported postnatal functional studies following reserpine exposure have used mid- to late-gestational treatment with 1.0 mg/kg, a dose shown here to result in marked overt maternal and fetal toxicity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Reinstatement of responding maintained by cocaine or thiamylal.

Rhesus monkeys were trained to self-administer one of two reference drugs, either cocaine or thiamylal. The lowest dose of cocaine or thiamylal which maintained responding was determined. Responding extinguished when saline was substituted for a reference drug. Then the effects of a variety of other drugs on saline self-administration were determined. In the cocaine-trained monkeys, the i.m. administration of d-methylamphetamine, cocaine, morphine or codeine during a session reinstated responding for saline infusions; in contrast, naloxone, chlorpromazine, dimethyltryptamine, diazepam and secobarbital did not. Naloxone blocked responding produced by the i.m. administration of morphine. In the thiamylal-trained monkeys, the administration of secobarbital (i.m.), pentobarbital (p.o.), butabarbital (p.o.) and phenobarbital (p.o.) reinstated responding for saline. The onset of behavioral responding was related to the pharmacokinetic properties of the drugs, with phenobarbital greater than pentobarbital = butabarbital. In contrast, cocaine and d-amphetamine i.m. failed to reinstate the responding in monkeys which had been trained to self-administer thiamylal. These data support the hypothesis that drugs producing responding at a rate significantly greater than that produced by vehicle controls share reinforcing properties with the reference drug.

Animals↗
PubMed1983

UDP-glucuronyltransferase activity exhibits two developmental groups in liver from foetal rhesus monkeys.

UDP-glucuronyltransferase was assayed in liver from adult rhesus monkeys and foetuses during late gestation. Activities toward 2-aminophenol, 5-hydroxytryptamine, 1-naphthol and 4-nitrophenol in the foetal liver ranged from 46 to 114% of adult values, whereas activities toward bilirubin, oestradiol and testosterone were less than 5% of adult values. This suggests that in primates UDP-glucuronyltransferase develops differentially in two clusters analogous to that in the rat.

Animals↗
PubMed1983

Ethynylestradiol-17 beta D-ring glucuronide conjugates are potent cholestatic agents in the rat.

17 alpha-Ethynylestradiol-17 beta (beta-D-glucuronide) [EE217 beta (beta G)], a metabolite of 17 alpha-ethynylestradiol (EE2) identified in urine of women taking EE2 in oral contraceptives, and its synthetic anomer, 17 alpha-ethynylestradiol-17 beta (alpha-D-glucuronide), [EE217 beta (alpha G)], were administered intravenously to female rats in order to determine their effects on bile flow. Both agents induced an immediate, profound and dose-dependent decrease in bile flow which returned to control levels within 1-8 hr. The logarithm of the dose vs the cholestatic response curves for the two anomers were not parallel. EE217 beta (alpha G) was significantly more potent than EE217 beta (beta G) such that the doses inhibiting bile flow by 50% were 1.25 and 11 mumol/kg for the alpha-and beta-anomer respectively.

Animals↗
PubMed1983

Characterization of estrogen binding in uterine cytosol from the fetal rhesus monkey.

Cytosol receptor binding of 17 beta-estradiol was demonstrated in the uterus of the late-gestation, fetal rhesus monkey. Sucrose density gradient analysis performed in low-ionic strength buffer indicated a binding component with a sedimentation coefficient of 6-7 S. Under high-ionic strength conditions, the component shifted to a sedimentation coefficient of approximately 4 S. The specificity of the receptor for estrogens was indicated by inhibition of [3H]estradiol binding by both natural and synthetic estrogen competitors, but not by progesterone. Saturation analysis indicated a high degree of nonspecific binding with saturation of specific binding occurring at 2-3 nM. Computer-assisted Scatchard analysis of the data resolved a one-receptor model having a limited number of binding sites and an apparent dissociation constant of 10(-10) M. The interaction of estrogens with the fetal uterus and the cellular mechanisms which permit this interaction are discussed in relation to the development of models for extrapolation to the human.

Animals↗
PubMed1983

Comparative distribution and metabolism of triamcinolone acetonide and cortisol in the rat embryomaternal unit.

Triamcinolone acetonide (TAC) is teratogenic in rats while cortisol has been reported as not teratogenic. The objective of this investigation was to determine whether this difference in teratogenicity could be due to a difference in the metabolism and distribution of the parent compound in the embryomaternal unit. 3H-TAC and 14C-cortisol were administered intramuscularly to pregnant rats on day 12 of gestation. These dams were killed at each of the following time points after injection: 0.5, 1, 3, 6 and 24 hr. Maternal plasma and embryos were analyzed by high performance liquid chromatography (HPLC) and liquid scintillation counting. The plasma concentration of parent TAC was significantly greater than that for parent cortisol at all time points. The plasma elimination half-life for TAC, 86 min, was also calculated to be significantly longer than that for cortisol, 8 min. Furthermore, the percentage of total plasma radioactivity representing HPLC resolved TAC was much higher than that representing cortisol at all time points. The concentration of TAC in the embryos was significantly greater than for cortisol at all time points. The elimination half-life for unchanged TAC in the embryos was 142 min compared to 22 min for cortisol. The percentage of total radioactivity in the embryos representing unchanged TAC was similar to that found in maternal plasma while the percentage of total radioactivity representing unchanged cortisol was much lower than that found in maternal plasma. These findings support the hypothesis that differences in the distribution and metabolism of the parent compound are a critical factor in determining the teratogenicity of that compound.

Animals↗
PubMed1983

Synthesis and characterization of the anomeric pair of 17 beta-glucuronides of ethynylestradiol.

The alpha- and beta-anomers of the 17 beta-D-glucuronide conjugate of ethynylestradiol were synthesized by the SnCl4-promoted reaction between beta-acetoxy GAM and the t-17 beta-hydroxyl group of EE2-3-acetate. The conjugates were resolved by crystallization and HPLC. Positive identification was established by u.v. spectrophotometry, i.r. and mass spectrometry and 1H- and 13C-n.m.r. The structure of the beta-anomer was confirmed by X-ray crystallographic analysis. In addition, the alpha-anomer was refractory to hydrolysis by bovine beta-glucuronidase, establishing a biochemical difference between the conjugate pair.

Chromatography, High Pressure Liquid↗
PubMed1983

Distribution and metabolism of triamcinolone acetonide in the rat embryomaternal unit during a teratogenically sensitive period.

The distribution and metabolism of triamcinolone acetonide (TAC) in the rat embryomaternal unit were investigated during a teratogenically sensitive period. Pregnant rats (Day 12 of gestation) were injected im with 0.125 or 0.5 mg/kg [3H]TAC. Maternal plasma and embryos were collected at selected time points and analyzed by HPLC and liquid scintillation counting. No significant differences in the percentage of total radioactivity representing unchanged TAC, concentration of TAC, or its elimination half-life were detected in either plasma or embryos of the two dose groups. These results provide evidence that the metabolism and distribution of TAC in the rat embryomaternal unit are dose independent over this known teratogenic dose range. To determine whether multiple administration of TAC resulted in any alterations in maternal or embryonal exposure, the same parameters were evaluated following one (Day 12), two (Days 12 and 13), or three (Days 12, 13, and 14) injections of [3H]TAC (0.5 mg/kg, im). The only alterations detected were an increase in the percentage of total radioactivity in maternal plasma representing unchanged TAC at 1 hr following the second or third injection and an increase in the embryonal concentration of TAC at the same time points.

Abnormalities, Drug-Induced↗
PubMed1983

Maternal, fetal, and neonatal elimination of ethanol in nonhuman primates.

Three cynomolgus and 6 rhesus monkeys (106-160 days gestational age) were administered ethanol (0.8-1.5 g/kg i.v.) over a 30-min period. Blood samples were drawn under anesthesia from catheters in the maternal femoral artery, fetal umbilical circulation and/or neonatal umbilical artery. Comparison of maternal/fetal blood sample pairs from 60 to 300 min after initiation of the ethanol infusion revealed a significant correlation of blood ethanol concentration (r = 0.968, p less than 0.001). Thus, during the elimination phase, maternal blood ethanol concentrations are predictive of fetal blood ethanol concentrations. In three studies where the fetus was delivered 2 h after the infusion of ethanol, the neonatal rates of elimination were observed to be approximately 1/4 those of the mother. These data indicate that during the last third of nonhuman primate pregnancy, the maternal component of ethanol elimination appears to be the predominant factor in the overall rate of fetal ethanol elimination.

Animals↗
PubMed1983

Hepatotoxic effects of estradiol-17 beta-D-glucuronide in the rat and monkey.

The steroid D-ring glucuronide conjugate estradiol-17 beta-D-glucuronide (E217G) but not the A-ring conjugate E23-glucuronide (E23G) has been shown to inhibit bile flow in the rat. To determine if primates are also sensitive to E217G-induced cholestasis, a noninvasive approach with the use of indocyanine green (ICG), a dye eliminated primarily by biliary excretion, was first validated in the rat and then applied to the rhesus monkey. ICG (16 mg/kg rat; 4 mg/kg monkey) was administered i.v. 10 min after an i.v. bolus dose of either E217G (5.5 or 11 mumol/kg), E23G (11 mumol/kg) or vehicle alone. In the rat, the elimination T1/2 of ICG was increased by the 11 mumol/kg dose of E217G (P less than .025), whereas E23G produced no significant change from vehicle control values. In the monkey, the 5.5 and 11 mumol/kg doses of E217G increased the T1/2 of ICG in a dose-related manner (P less than .005), whereas E23G was without effect. Plasma levels of total radioactivity demonstrated dose-dependent kinetics after the administration of a tracer dose and 11 mumol/kg of [3H]E217G. A rebound of plasma radioactivity was seen at 11 mumol/kg of [3H] E217G, the time course of which mimicked the time course of E217G-induced cholestasis. High-performance liquid chromatographic analysis of rat bile and plasma after the administration of [3H]E217G revealed primarily E217G and estradiol-3-sulfate-17 beta-D-glucuronide together with small amounts of three unidentified metabolites. In the monkey, only E217G and estradiol-3-sulfate-17 beta-D-glucuronide were observed in the plasma after the administration of [3H]E217G. In contrast to E217G, estradiol-3-sulfate-17 beta-D-glucuronide was choleretic in the bile duct-cannulated rat model. These data indicate that E217G is hepatotoxic in both rodents and nonhuman primates.

Animals↗
PubMed1982

Separation of some natural and synthetic corticosteroids in biological fluids and tissues by high-performance liquid chromatography.

A high-performance liquid chromatography (HPLC) technique was developed for the determination of radiolabeled triamcinolone acetonide (TAC), cortisol and their metabolites in rhesus monkey plasma, urine and tissue samples. After protein precipitation, the parent compounds and metabolites were simultaneously resolved using a single-column reversed-phase HPLC system. TAC was subsequently verified by mass spectrometry and TAC glucuronide was tentatively identified by enzymatic hydrolysis and mass spectrometry of the hydrolysis product. The endogenous hormones, cortisol and cortisone were presumptively identified by cochromatography with authentic standards on two different HPLC systems and positively identified by reverse-isotope recrystallization. Other metabolites of both compounds were detected by selective enzymatic hydrolysis and HPLC. This method is rapid and reproducible with a total recovery greater than 80%.

Adrenal Cortex Hormones↗