Studies on sperm survival and motility in the presence of cytotoxic sperm antibodies

The effect of cytotoxic sperm antibodies and native complement in the serum and secretions from 40 fertile and 93 infertile couples on in vitro sperm survival and motion characteristics was studied. Sperm survival in vitro was unaffected by sera from fertile and infertile subjects without cytotoxic sperm antibodies and from infertile men with antibodies to control but not to autologous sperm. Sperm survival was reduced (P less than .001) by sera from infertile men with antibodies to autologous sperm or to antologous and control sperm and from women with cytotoxic antibodies to sperm from both. Sera from fertile couples without sperm antibodies enhanced sperm swimming speed and motility index (P less than .0001). Sera from infertile women with or without cytotoxic sperm antibodies did not affect sperm motility. Sperm survival and motility were reduced by seminal plasma from infertile men with cytotoxic antibodies to autologous and/or control sperm. Seminal plasma from fertile men enhanced sperm survival. Cervical mucus from infertile women with antibodies to autoimmune husbands' sperm or to husbands' and control sperm inhibited sperm motion, whereas cervical mucus from infertile women without sperm antibodies and women with antibodies to control sperm failed to have any effect. It is concluded that cytotoxic sperm antibodies developed through exposure to sperm antigens in autoimmune infertile men decrease in vitro sperm survival and/or motility.

The role of intestinal microflora in the formation of the methylthio adduct metabolites of paracetamol. Studies in neomycin-pretreated and germ-free mice

The contribution of the gastrointestinal microflora to the formation of methylthio adducts from paracetamol has been studied by comparing the fate of this drug in conventional mice with that in germ-free and neomycin-treated animals. In both germ-free and neomycin-treated mice there was a highly significant reduction in the urinary excretion of 3-methylthioparacetamol, its glucuronic acid and sulfate conjugates and its sulfoxide, with no other systemic alteration to the overall fate of the drug. These data are consistent with the gut flora playing a major role in the C-S cleavage of paracetamol-3-cysteine, thereby reducing the excretion of the array of methylthio adducts subsequently formed by tissue enzymes from 3-thioparacetamol, the putative product of the C-S cleavage.

The metabolism and disposition of fenofibrate in rat, guinea pig, and dog

The metabolism and disposition of orally administered single doses of [14C]fenofibrate (isopropyl 2-[4-(4-chlorobenzoyl)phenoxy]-2- methylpropionate) have been studied in rat, guinea pig, and dog. In rats, the urinary excretion of 14C in 5 days varied from 11 to 51% of the dose and was markedly dependent upon the dose form given. The interpretation of these data in terms of factors affecting the absorption of fenofibrate from the gut is complicated by the enterohepatic recirculation of metabolites. The tissue distribution of 14C after oral administration of an ethanolic solution of fenofibrate has been studied in the rat. The only tissues in which the concentration of 14C exceeded that in the blood were the organs of absorption and elimination, the gut, liver, and kidneys. Guinea pigs excreted 53% of the dose in the urine in 5 days, with a further 34% in the feces, while in dogs the corresponding figures were 9% and 81%, respectively. In all three species, all the urinary metabolites were products of ester hydrolysis, and the principal excretion product was "reduced fenofibric acid" which arose by subsequent carbonyl reduction. Glucuronidation of fenofibric acid and "reduced fenofibric acid" was a very minor reaction in the rat and guinea pig and was not detected in the dog. In addition, polar unknown metabolite(s) were detected in all three species, but were not investigated further. The results are discussed in terms of the comparative disposition of fenofibrate and other hypolipidemic agents and the contribution of these findings to the safety assessment of such drugs.

Influence of dose size on the disposition of trans-[methoxy-14C]anethole in human volunteers

The influence of dose size on the metabolic fate of the naturally occurring food flavouring trans-anethole has been investigated in human volunteers, using the [methoxy-14C]-labelled compound. The doses chosen were: 1 mg; close to the daily intake in the diet from foods, 50 mg; approximating to the amount present in a normal measure of an anise-flavoured beverage, and 250 mg. The order of administration was randomized. The major routes of elimination of 14C were in the urine (54-69% of the administered dose) and as exhaled 14CO2 (13-17%). Dose size had no systematic effect on either rate or route of excretion. Urinary metabolites were separated by high-pressure liquid chromatography, before and after treatment with beta-glucuronidase, and identified by comparison of their chromatographic mobilities with those of authentic standards. The principal metabolite (greater than 90% of urinary 14C) was 4-methoxyhippuric acid, accompanied by much smaller amounts of 4-methoxybenzoic acid and up to three other compounds, which were not examined further. The pattern of urinary metabolites was unaffected by dose size. These data are discussed with reference to the comparative metabolic disposition of trans-anethole in rats and mice, the species commonly used in toxicity testing and in which its fate exhibits a very marked dose dependence.

Proton-translocating ATPase from bovine kidney medulla: partial purification and reconstitution

The proton-translocating ATPase that is responsible both for urinary and vacuolar acidification was partially purified from bovine kidney medulla microsomes. ATPase activity was purified to a maximum specific activity of 1.7 mumol.min-1.mg prot-1 and was inhibited completely by N-ethylmaleimide. The relative molecular weight (Mr) of the intact protein estimated by high-pressure size-exclusion liquid chromatography was 586,000. Nondenaturing gels of the isolated enzyme revealed two protein bands at MrS of 551,000 and 523,000. Sodium dodecyl sulfate-gel electrophoresis of the isolated H+-ATPase revealed component subunits at MrS of 70,000, 56,000, 45,000, 42,000, 38,000, 31,000, 15,000, 14,000, and 12,000. The properties of the isolated H+-ATPase and of microsomal ATP-dependent proton transport correlated closely. The isolated H+-ATPase was reconstituted into phospholipid liposomes and demonstrated N-ethylmaleimide-inhibitable ATP-dependent potential generation, consistent with electrogenic proton transport. In overall structure, the enzyme appears to be a new type of H+-ATPase with several features of the F0F1 class of ion-translocating ATPases but is immunologically and structurally different from the mitochondrial F1-ATPase.

The metabolic chiral inversion and dispositional enantioselectivity of the 2-arylpropionic acids and their biological consequences

The 2-arylpropionic acids are currently an important group of non-steroidal anti-inflammatory agents. They contain a chiral centre, and in vitro studies on inhibition of prostaglandin synthesis show that their activity resides almost exclusively in the S(+)-isomers. However, this stereoselectivity of action is not manifest in vivo, due to the thus-far-unique unidirectional metabolic inversion of the chiral centre from the inactive R(-)-isomers to the S(+)-antipodes. Available evidence strongly suggests that this reaction proceeds via the formation of the acyl CoA thioesters of the 2-arylpropionates, but the participation of enzyme(s) in the inversion process remains uncertain. Although the chiral inversion is seemingly a general feature of the fate of 2-arylpropionates, there do occur important combinations of acid and species where the reaction is not extant. The stereochemistry of the chiral centre of these acids also influences other aspects of their disposition, including the oxidative metabolism of the aryl/arylakyl moiety, glucuronidation of the -COOH group and plasma protein binding, and the importance of certain of these becomes more evident when renal function is impaired. The biological consequences of the metabolic chiral inversion and enantioselective disposition of the 2-arylpropionates have been summarized in terms of their implications for the development and use of safer and more effective drugs of this class.

High-performance liquid chromatographic assay for theophylline and its major metabolites in human urine

A highly selective automated high-performance liquid chromatographic (HPLC) method has been developed for the assay of theophylline and its major metabolites in urine. The method involves direct injection of urine on to a reversed-phase column, followed by gradient elution and ultraviolet detection. Quantitation is achieved by the peak-height ratio method with reference to an internal standard, 8-chlorotheophylline. The assay is accurate and reproducible, with a sensitivity of 1 microgram/ml in urine. In order to confirm its accuracy, theophylline and its major metabolites in urine were quantified after HPLC separation by both peak-height ratio of ultraviolet absorbance and liquid scintillation spectrometry after oral administration of [14C]theophylline to a human volunteer. The assay was also applied to the analysis of theophylline and its major metabolites in urine following the oral administration of theophylline to three healthy volunteers.

Immunoaffinity purification and characterization of vacuolar H+ATPase from bovine kidney

Vacuolar proton-translocating ATPase from bovine kidney was purified in one step by immunoprecipitation and immunoaffinity chromatography using an immobilized anti-H+ATPase monoclonal antibody. The monoclonal antibody affinity matrix coprecipitated polypeptides with Mr of 70,000, a cluster at 56,000, 45,000, 42,000, 38,000, 33,000, 31,000, 15,000, 14,000, and 12,000 from solubilized bovine kidney microsomal membranes, a pattern that was unaffected by different detergent washing conditions. A nearly identical pattern of polypeptides was observed in H+ATPase partially purified by an entirely independent method. The immunoaffinity purified H+ATPase had reconstitutively active ATP-induced acidification and potential generation that was inhibited by N-ethylamaleimide. The purified enzyme had specific activities as high as 3.1 mumol/min/mg protein, dual pH optima at 6.5 and 7.2, and a Km for ATP of 150 microM. The substrate preference was ATP greater than ITP much greater than UTP greater than GTP greater than CTP. The affinity purified H+ATPase was stimulated by phosphatidyl glycerol greater than phosphatidyl inositol much greater than phosphatidyl choline greater than phosphatidyl serine. The immunoaffinity purified enzyme did not require monovalent anions or cations for activity, and the divalent cation preference for activity was Mn, Mg much greater than Ca greater than Co much greater than Sr, Ba. The enzyme was not inhibited by ouabain, azide, or vanadate, but had kappa 1/2 inhibitory concentrations of 22.2 microM for N-ethylmaleimide, 14.9 microM for NBD-Cl, 4.9 microM for N,N'-dicyclohexylcarbodiimide, 13.8 microM for 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid, and 315 microM for Zn, values close to those for inhibition of proton transport in the native vesicles. The affinity purified kidney enzyme has similarities to but also significant differences in structural and enzymatic properties from those reported for other vacuolar H+ATPase.

Effect of poly rI:rC treatment upon the metabolism of [14C]-paracetamol in the BALB/cJ mouse

The effect of the immunomodulator, poly rI:rC, upon the in vivo metabolism of [14C]-paracetamol has been investigated in male BALB/cJ mice. In both poly rI:rC treated and control groups of mice the major part of the dose was excreted in the 0-24 hr urine and the major urinary metabolites were the glucuronic acid and sulphate conjugates. The urinary excretion of these two conjugates and of free paracetamol was not significantly altered following poly rI:rC treatment. Following enzymic hydrolysis of glucuronides and sulphates, the 3-cysteine, 3-mercapturate, 3-thiomethyl and 3-methylsulphoxide metabolites of paracetamol were all identified in the 0-24 hr urine together with very small amounts of 3-methoxy paracetamol. Although poly rI:rC treatment reduced the proportional urinary excretion of each of the thio adducts the individual differences were not significant. However, total thio adduct excretion, an indirect estimate of the metabolic activation of paracetamol, was significantly lower following poly rI:rC treatment. This depression in the urinary excretion of thio adducts following poly rI:rC treatment is discussed in relation to possible implications for paracetamol toxicity.

Metabolism of estragole in rat and mouse and influence of dose size on excretion of the proximate carcinogen 1'-hydroxyestragole

The major metabolic pathways of estragole have been established in rats and mice, and in both species the relative importance of the different pathways has been shown to be dose related. At low doses, estragole mainly undergoes detoxication reactions, notably O-demethylation and side-chain cleavage, but as the dose is increased, the extent of O-demethylation falls and other pathways, notably l'-hydroxylation, come into prominence. The disproportionate relationship between dose size and the elimination of the proximate carcinogenic metabolite l'-hydroxyestragole may influence the relationship between dose size and tumour incidence. These findings may have important implications for the safety assessment of this food flavouring, since the dose levels used in carcinogenicity studies have been very much larger than the estimated human daily intake. Moreover the percentage of an administered dose of estragole eliminated as 1-hydroxyestragole glucuronide in human urine is much lower than that found with even the lowest doses examined in rats in this study.

The metabolic disposition of [methoxy-14C]-labelled trans-anethole, estragole and p-propylanisole in human volunteers

1. The metabolic fates of the naturally occurring food flavours trans-anethole and estragole, and their synthetic congener p-propylanisole, have been investigated in human volunteers using the [methoxy-14C]-labelled compounds. The doses used were close to those encountered in the diet, 1 mg, 100 micrograms and 100 micrograms respectively. 2. In each case, the major routes of elimination of 14C were in the urine and in the expired air as 14CO2. 3. Urinary metabolites were separated by solvent extraction, t.l.c. and h.p.l.c., and characterized by comparison of chromatographic mobilities with standards and by radioisotope dilution. Nine 14C urinary metabolites were found after trans-anethole administration, four after p-propylanisole and five after estragole. All were products of side chain oxidations. 4. The principal metabolites of p-propylanisole were 4-methoxyhippuric acid (12%) and 1-(4'-methoxyphenyl)propan-1-ol (2%) and -2-ol (8%). 5. The major metabolite of trans-anethole was 4-methoxyhippuric acid (56% of dose), accompanied by much smaller amounts of the two isomers of 1-(4'-methoxyphenyl)propane-1,2-diol (together 3%). 6. After estragole administration, the two volunteers eliminated 0.2 and 0.4% of the dose respectively as 1'-hydroxyestragole. 7. The human metabolic data is discussed with reference to the comparative metabolic disposition of these compounds in the mouse and rat, species commonly used in their safety assessment.

Effect of interferon synthesis upon the metabolism of [carboxyl-14C]-aspirin in the mouse

The effect of stimulation of interferon (IFN) synthesis with the immunomodulators, polyriboinosinic polyribocytidylic acid (poly rI:rC) and Newcastle Disease Virus (NDV) upon the in vivo metabolism of [carboxyl-14C]-aspirin was investigated in male mice of three different strains. Following poly rI:rC administration to DBA/2 mice, the metabolic conjugation of salicylic acid with glycine was significantly increased, glucuronidation was little changed and there was an approximately 10-fold reduction in the excretion of the oxidation product, gentisic acid. Prolongation of hexobarbitone-induced sleeping time confirmed the ability of this agent to depress oxidative metabolism in vivo. Poly rI:rC administration to C57BL/6By and BALB/cBy mice resulted in similar changes in aspirin metabolism in vivo. Treatment of C57BL/6By mice with NDV produced high levels of circulating IFN and produced alterations in aspirin metabolism similar to those seen after poly rI:rC treatment. Comparable studies in BALB/cBy mice, which did not produce detectable levels of IFN in response to NDV challenge, revealed no change in the fate of aspirin metabolism following treatment with this agent. These data indicate that the in vivo oxidation of salicylate, but not its conjugation, can be depressed, at least indirectly, by an interferon-associated mechanism.

Studies on benzyl acetate. III. The percutaneous absorption and disposition of [methylene-14C]benzyl acetate in the rat

[methylene-14C]Benzyl acetate was applied over an area of 6.25, 12 or 18 cm2 to the shaved backs of male Fischer 344 rats under an occlusive dressing at dose levels of 100, 250 and 500 mg/kg. The compound was administered either as the neat substance or as a 50% (v/v) solution in ethanol. After 6 hr the dressing was removed, the shaven area was washed with ethanol and the dressing and washings were counted for 14C. Urine and faeces were collected for 72 hr from the start of treatment and urinary metabolites were assayed by radio-TLC and HPLC. Following administration of the neat compound, a significant proportion of the dose was recovered from the application site (28-48%) and a similar proportion (28-46%) was absorbed and excreted in the 0-24-hr urine. Excretion of 14C in the urine over 0-24 hr accounted for c. 95% of absorbed 14C in all cases, and total recovery of radioactivity was 79-84% with less than 2% of the dose present in the carcass at the end of the experiments. The extent of absorption of benzyl acetate per unit area of skin, as assessed by the recovery of its metabolites in urine, rose with increasing concentration (mg/cm2) of the test compound on the skin. The absorption of topically applied benzyl acetate was essentially the same when the dose was administered in a 50% ethanolic solution. In all cases, the major urinary metabolite was hippuric acid (c. 95% of urinary 14C), together with much smaller amounts of benzoyl glucuronide, benzoic acid and benzylmercapturic acid. The distribution of 14C in the tissues was examined 6 and 24 hr after the topical application of 5 mg [methylene-14C]benzyl acetate/kg as a 1% (v/v) solution in ethanol to rats. Radioactivity in all carcasses was less than 4% of the administered dose and levels in all the organs examined were lower at 24 than at 6 hr.

Studies on the metabolism of arylacetic acids. 6. Comparative metabolic conjugation of 1- and 2-naphthylacetic acids in the guinea pig, mouse, hamster and gerbil

The patterns of metabolic conjugation of the isomeric 1- and 2-naphthylacetic acids have been compared in guinea pig, mouse, hamster and gerbil. Equimolar doses of [carboxy-14C]1- and 2-naphthylacetic acids were given to these species by i.p. injection, their urine collected and urinary metabolites examined by t.l.c. before and after treatment with beta-glucuronidase or mild alkali. 2. Urinary excretion of 14C following administration of 14C-1-naphthylacetic acid was 76-93% of dose in 72 h, the bulk being eliminated in 24 h. Urinary metabolites comprised 1-naphthylacetic-glycine and -glucuronide together with the unchanged acid. 3. Following administration of 14C-2-naphthylacetic acid, some 68-94% of the 14C dose was recovered in the urine in 72 h, with the majority in the 0-24 h urine. All four species excreted 2-naphthylacetyl-glucuronide and -glycine: additionally, 2-naphthylacetyl-taurine was excreted by mouse, gerbil and hamster and the glutamine conjugate was also present in hamster urine.

Studies on the metabolism of arylacetic acids. 7. The influence of varying dose size upon the conjugation pattern of 2-naphthylacetic acid in the guinea pig, mouse and hamster

1. The influence of dose size upon the metabolic conjugation of 2-naphthylacetic acid with various amino acids and glucuronic acid has been studied in the guinea pig, mouse and hamster. 2. Guinea pigs conjugated 2-naphthylacetic acid with glycine and glucuronic acid. 3. Mice conjugated 2-naphthylacetic acid with glycine, taurine and glucuronic acid. Taurine conjugation had the highest capacity, and both this and the glycine mechanism were saturated at doses above 100 mg/kg. 4. Hamsters utilized glutamine, glycine, taurine and glucuronic acid for the conjugation of 2-naphthylacetic acid. No conjugation pathway was saturated by doses up to 200 mg/kg. 5. The thus-far unique ability of 2-naphthylacetic acid to evoke multiple amino acid conjugations, using the taurine and glutamine mechanisms hitherto unknown in these species, appears to be due to its affinity for previously unrecognized enzyme systems, rather than to saturation of 'normal' pathways revealing novel routes at high doses.

Analytical methodology to determine stable isotopically labelled and unlabelled theophylline in human plasma using capillary gas chromatography-mass spectrometry

A method is described for the simultaneous determination of [1,3-15N] theophylline and unlabelled theophylline in human plasma using gas chromatography-mass spectrometry. Plasma samples were subjected to extractive alkylation and the stable isotopically labelled and unlabelled forms of the drug were analysed as their N-pentafluorobenzyl derivatives on an SE-52 fused-silica capillary column. Quantitation was made by selected-ion monitoring employing as the internal standard 3-isobutyl-1-methylxanthine. The method has been used to study the absorption kinetics and bioavailability of a sustained release formulation of the drug when co-administered to human volunteers with a conventional formulation of the drug labelled with the stable isotope.

The bioavailability of phenylbutazone in the horse

[phenyl-14C]-Phenylbutazone was administered to 2 horses p.o. and i.v. on separate occasions. Plasma levels and urinary and faecal elimination of 14C were monitored for up to 7 days after dosing. Phenylbutazone was rapidly and extensively absorbed after oral administration, and its bioavailability was 91% assessed by comparison of plasma AUCs of unchanged drug after p.o. and i.v. administration. The plasma elimination half-life of phenylbutazone was 9.7 h and this was independent of the route of administration. The pattern of elimination of phenylbutazone was independent of the route of administration, with 55% of the dose being found in the urine in 3 days and a further 39% in the faeces in 7 days. These data, which are the first reports of the absolute bioavailability and excretion pathways of phenylbutazone in the horse, are discussed in terms of their significance for the gastrointestinal toxicity of this drug.

Depression of oxidative metabolism of aspirin in mice via an interferon-associated mechanism in relation to Reye's syndrome

Interferon synthesis was induced in inbred strains of mice with either polyriboinosinic-polyribocytidylic acid or Newcastle disease virus. The strains, BALB/cBy and C57BL/6By, respond to Newcastle disease virus by producing 'low' and 'high' levels of serum interferon, respectively. 24 h after interferon induction mice received [carboxyl-14C]-aspirin orally. The metabolic conjugation of aspirin was little changed after either treatment while the urinary excretion of gentisic acid, a minor product of metabolic oxidation, was significantly depressed after polyriboinosinic-polyribocytidylic acid in both strains and in C57BL/6By mice after Newcastle disease virus. The results suggest that such a metabolic impairment in aspirin metabolism would not significantly affect salicylate clearance and hence are unlikely to be directly related to the aetiology of Reye's syndrome which has been associated with both a prodromal viral infection and aspirin therapy.

The role of traditional fertility regulation in Sri Lanka

Among the countries of South Asia, Sri Lanka, with a birth rate of 26 per 1,000, has achieved by far the lowest fertility level. The research reported here shows that at least half of all fertility control there is still practiced by means other than those offered by the national family planning program. This paper reports on an investigation carried out by the Sri Lankan Department of Census and Statistics, employing a micro-approach to demographic research, on the levels of "traditional" methods of family planning and attitudes toward the practice of both modern and traditional contraception. It is shown that knowledge of rhythm was diffused throughout society as the cost of raising children increased during a period when other methods of family planning were not easily accessible. These traditional methods were employed efficiently and their high level of continued use arises from strong cultural resistance to the pill and IUD, based upon local interpretations of how these methods function. Thus, any programmatic effort to reduce dependence on traditional family planning might well result in higher fertility levels. In addition, low fertility among Indian Tamil workers on the Tea Estates, as early as the 1950s, probably resulted from a desire (manifested by lower levels of sexual activity and some abortion) to avoid frequent pregnancies, since pregnancy interrupts work that the female Estate workers cannot afford to miss.

Studies on benzyl acetate. I. Effect of dose size and vehicle on the plasma pharmacokinetics and metabolism of [methylene-14C]benzyl acetate in the rat

Male Fischer 344 rats received [methylene-14C]benzyl acetate by gavage in a dose of 5,250 or 500 mg/kg, as the neat substance, in corn oil or in propylene glycol. Urine and faeces were collected and urinary metabolites were assayed by radio-TLC and HPLC. Other animals were killed at various times and exsanguinated, and plasma levels of 14C in Plasma occurred earliest and were highest when benzyl acetate was given neat. Peak levels were lower and absorption was delayed with the propylene glycol vehicle. The use of corn oil as the dose vehicle at the higher doses (250 and 500 mg/kg) led to the maintenance of plateau plasma levels, at about one half of the peak levels seen with the neat compound, for up to 8 hr after administration. At the 5 mg/kg dose, the plasma levels of 14C were essentially the same whether the dose was given in corn oil or propylene glycol. At the 250- and 500-mg/kg doses, at all time points, the major metabolite in plasma was benzoic acid, accompanied by smaller amounts of hippuric acid. Benzyl alcohol was also detected in some plasma samples. At the 5-mg/kg dose, the major plasma metabolite was hippuric acid, together with a smaller amount of benzoic acid. When propylene glycol was used as the vehicle at this dose level, benzylmercapturic acid was also present in the plasma. The major urinary metabolite was hippuric acid (c. 66% of the dose), with benzoic acid (2%) and benzylmercapturic acid (1%) also present. The elimination of benzoyl glucuronide increased with increasing dose, from c. 3 to 11% of the dose.

Modeling complex molecular interactions involving proteins and DNA

We have presented a perspective of progress in three areas of simulations of complex molecules: the development of force fields for molecular simulation; the application of computer graphics, molecular mechanics and molecular dynamics in simulations of DNA and DNA-drug complexes and the application of computer graphics, molecular mechanics and quantum mechanics in studies of enzyme substrate interactions. It is our perspective that improvements are being made in force fields, and these will allow a more accurate simulation of structures and energies of complex molecules. In the area of DNA molecular mechanics and dynamics, it is clear that the use of computer graphics model building combined with NMR NOE data is a potentially very powerful tool in accurately determining structures of drug-DNA complexes using molecular mechanics and dynamics. Finally, we are in a position to reasonably simulate structures and (qualitatively) energies for complete reaction pathways of enzymes using a combination of computer graphics, molecular mechanics and quantum mechanics. More accurate energies and pathways are sure to follow, using the combined molecular mechanics/quantum mechanics optimization developed by Singh and the free energy perturbation methods pioneered in Groningen and Houston.

The metabolic chiral inversion of 2-phenylpropionic acid in rat, mouse and rabbit

The metabolic chiral inversion of the 2-arylpropionic acids has been investigated in laboratory animals, using the simplest congener, 2-phenylpropionic acid, as a model compound. The chiral inversion was found to occur after administration of the racemate to the rat and rabbit, but not in the mouse. The formation of the ester glucuronide was enantioselective for the S-(-)-isomer in the rat and mouse, but showed no stereoselectivity in the rabbit. [corrected] In the rat, the extent of inversion from R-(-) to S-(+) was greater at a dose of 30 mg/kg than at 150 or 300 mg/kg. The enantiomeric composition of the acid in urine was the same when the racemate was given orally or by i.p. injection. When the R-(-)isomer was given to rats, some 30% of the excreted acid was in the S-(+)-form, but when the S-(+)-isomer was given, the inversion was much less evident. In this case, the S/R ratio of the excreted phenylproprionic acid was ca 9:1. Following the administration of the racemate to rats, the plasma elimination half-life of the R-(-)-form was shorter (3.0 vs 4.8 hr for the S-(-)-isomer); this was due to its considerably greater plasma clearance (65.9 vs 43.6 micrograms/ml hr), since the volumes of distribution of the enantiomers were the same. The S/R ratio of 2-phenylpropionic acid in plasma rose progressively with time, from 1:1 in the dose solution to 2.1:1 at 8 hr.

Studies on benzyl acetate. II. Use of specific metabolic inhibitors to define the pathway leading to the formation of benzylmercapturic acid in the rat

Specific metabolic inhibitors were used to define the route of metabolism of benzyl acetate leading to the formation of benzylmercapturic acid. Male Fischer 344 rats were dosed by gavage with [methylene-14C]benzyl acetate (500 mg/kg) alone or together with pyrazole (200 mg/kg), pentachlorophenol (10 mg/kg) or both pentachlorophenol (10 mg/kg) and pyrazole (200 mg/kg), given in each case ip. Urine and faeces were collected and urinary metabolites were assayed by radio-TLC and HPLC. The excretion of 14C was rapid in all cases, with most of the dose excreted in the urine within 24 hr. Co-administration of pyrazole (an inhibitor of alcohol dehydrogenase) with benzyl acetate caused an 11-fold increase in the excretion of benzylmercapturic acid and halved the percentage of the dose excreted as benzoyl glucuronide. Pretreatment with pentachlorophenol, an inhibitor of sulphotransferase activity in vivo, abolished the excretion of benzylmercapturic acid, while excretion of the mercapturate following treatment with both pyrazole and pentachlorophenol was higher than in control or pentachlorophenol-treated rats, but much lower than in the animals given pyrazole alone. Taken together, these results suggest very strongly that the formation of benzylmercapturic acid involves the sulphate ester of benzyl alcohol as an obligatory intermediate and does not appear to involve a metabolic intermediate with sufficient reactivity to have toxicological relevance.

Absolute oral bioavailability of ciprofloxacin

We evaluated the absolute bioavailability of ciprofloxacin, a new quinoline carboxylic acid, in 12 healthy male volunteers. Doses of 200 mg were given to each of the volunteers in a randomized, crossover manner 1 week apart orally and as a 10-min intravenous infusion. Half-lives (mean +/- standard deviation) for the intravenous and oral administration arms were 4.2 +/- 0.77 and 4.11 +/- 0.74 h, respectively. The serum clearance rate averaged 28.5 +/- 4.7 liters/h per 1.73 m2 for the intravenous administration arm. The renal clearance rate accounted for approximately 60% of the corresponding serum clearance rate and was 16.9 +/- 3.0 liters/h per 1.73 m2 for the intravenous arm and 17.0 +/- 2.86 liters/h per 1.73 m2 for the oral administration arm. Absorption was rapid, with peak concentrations in serum occurring at 0.71 +/- 0.15 h. Bioavailability, defined as the ratio of the area under the curve from 0 h to infinity for the oral to the intravenous dose, was 69 +/- 7%. We conclude that ciprofloxacin is rapidly absorbed and reliably bioavailable in these healthy volunteers. Further studies with ciprofloxacin should be undertaken in target patient populations under actual clinical circumstances.

Theophylline pharmacokinetics after intravenous infusion with ethylenediamine or sodium glycinate

Six healthy volunteers received two theophylline preparations by short intravenous infusion, at weekly intervals in a randomized cross-over design. The solubilizer was ethylenediamine or sodium glycinate. Plasma concentrations of theophylline and ethylenediamine were measured by h.p.l.c. for up to 24 h after dosing. The pharmacokinetics of theophylline did not show any significant intra-subject variation associated with the solubilizing agent used.

Stereospecific induction of rat liver bilirubin UDPglucuronosyltransferase and lauric acid 12-hydroxylation by the isomers of 2-phenylpropionic acid

The inductive effects of racemic 2-phenylpropionic acid and its isomers on rat liver bilirubin UDP-glucuronosyltransferase activity and lauric acid 12-hydroxylation (cytochrome P-452-dependent) were compared. The (S)-(+)-enantiomer and the racemic mixture gave the greatest induction of both enzyme activities, whereas (R)-(-)-2-phenylpropionic acid produced increases of only one-third of those of its antipode. The determination of the enantiomeric composition of the excreted 2-phenylpropionic acid after a single oral dose indicated that the (R)-(-)-enantiomer given as such or in the racemate was inverted to its antipode, which strongly suggests that (S)-(+)-2-phenylpropionic acid is responsible for the inductive effects observed. The demonstration of the same stereospecificity for the induction of bilirubin UDPglucuronosyltransferase and lauric acid 12-hydroxylation further indicates a close mechanistic link between these two processes.

Application of a radial compression column to the high-performance liquid chromatographic separation of the enantiomers of some 2-arylpropionic acids as their diastereoisomeric s-(-)-1-(naphthen-1-yl)ethylamines

The enantiomers of 2-phenylpropionic acid and four congeneric anti-inflammatory drugs were separated as their diastereoisomeric amides with S-(-)-1-(naphthen-1-yl)ethylamine by high-performance liquid chromatography using a silica-packed radial compression cartridge. The order of elution of the diastereoisomeric amides was always R, S or -, S before S,S or +,S. The conditions for the derivatization, using 1-(3-dimethylaminopropyl)-3-ethyl-carbodiimide as coupling agent, were optimized, and it was found that the addition of 1-hydroxybenzotriazole rendered the reaction quantitative. Good calibration curves were obtained for the quantitation and determination of the enantiomeric composition of 2-phenylpropionic acid in urine, and the application of the method to the study of the metabolism of this acid in vivo is described.

Local active gingival immunization by a 3,800-molecular-weight streptococcal antigen in protection against dental caries

Local gingival immunization was attempted in an effort to confine the immune response to the oral cavity and bypass the systemic immune response. A low-molecular-weight (3.8K) streptococcal antigen (SA) I/II was applied 10 times over a period of 1 year to the gingival crevices of rhesus monkeys. The antigen was maintained in situ by means of silicone rubber appliances. Serial examinations over a period of 1 year showed that topical gingival immunization with the 3.8K SA results in a significantly lower incidence of dental caries and colonization of Streptococcus mutans compared with that of the sham-immunized controls. This was associated with an increase in gingival crevicular immunoglobulin G and salivary immunoglobulin A anti-SA I/II antibodies, whereas no change occurred in serum antibodies to SA I/II. The immune mechanism which prevents the colonization of S. mutans and the development of caries may involve antibodies that prevent the adherence of S. mutans to the teeth and facilitate phagocytosis and killing by the local neutrophils. This novel route of local immunization is noninvasive, does not cause side effects, and bypasses systemic immunization.

Medical student teaching in the preclinical years: a national family medicine survey

We surveyed teaching by departments of family medicine at American medical schools during the preclinical period of their programs. Ninety-seven percent of departments responded to our questionnaire. Eighty-five percent participate in at least one required preclinical medical school course. The course title most frequently mentioned was "Introduction to Clinical Medicine," and the most frequent content areas with some department of family medicine responsibility were interviewing, physical diagnosis, and the physician-patient relationship. Departments from schools with a four-year enrollment of less than 300 are more likely to participate in at least one required course, but we found no other differences based on size of medical school enrollment, geographic region, or public v. private status. In conjunction with the current period of national reassessment regarding American medical education, now is a good time to evaluate department of family medicine medical student teaching, fill in gaps, and implement new programs for the next phase of our development as an academic specialty.

The metabolism of aspirin in man: a population study

The metabolism of a 900 mg oral dose of aspirin has been investigated in 129 healthy volunteers. For this purpose, the 0-12 h urine was collected and analysed for the following excretion products: salicylic acid, its acyl and phenolic glucuronides, salicyluric acid, its phenolic glucuronide and gentisic acid. The total excretion of salicylate and metabolites was normally distributed within the population group studied, showing a 2.5-fold variation: a mean of 68.1% of the dose was recovered in 12 h. The excretion of salicylic acid was found to be highly variable within the study panel (1.3-31% of dose in 12 h), and was related to both urine volume and pH. Salicyluric acid was the major metabolite in the majority of the volunteers and its excretion was normally distributed amongst the study panel. The elimination of this metabolite ranged from 19.8 to 65% of the dose and was related to the total recovery of salicylate. The excretion of the two salicyl glucuronides was highly variable, ranging from 0.8 to 42% of the dose. The elimination of the glucuronides was inversely related to that of salicyluric acid. Gentisic acid and salicyluric acid phenolic glucuronide were minor metabolites of salicylate, accounting for 1 and 3% of the dose, respectively. The recovery of gentisic acid was statistically significantly greater in female subjects than in males, whilst the opposite was found for salicyluric acid and total salicylate. However, these differences were small in magnitude.

The influence of conformational factors on the metabolic conjugation of aryloxyacetates

Among p-chlorophenoxyalkanoic acids, the acetate and 2-propionate are essentially inert towards metabolic conjugation, whereas the isobutyrate (clofibric acid) undergoes extensive glucuronidation, as well as amino acid conjugation in carnivores. To try to explain these differences, the conformational behaviour of three model compounds was studied by quantum mechanical calculations (PCILO method). All three compounds prefer syn (folded) conformers, but the isobutyrate, in contrast to its two lower homologues, also has anti (extended) conformers of relatively low energy. Based on these results, a hypothetical topographical model is proposed for the binding site of glucuronyltransferase.

Local passive immunization by monoclonal antibodies against streptococcal antigen I/II in the prevention of dental caries

Local passive immunization with monoclonal antibodies (Mc Ab) to Streptococcus mutans was attempted as an alternative approach to active systemic immunization. We prepared an immunoglobulin G class Mc Ab to the cell surface protein determinant of streptococcal antigen I/II and applied it repeatedly to the teeth of rhesus monkeys. This resulted in decreased colonization by S. mutans in fissures and smooth surfaces of teeth and no dental caries, unlike the results in control animals, which developed caries and showed a high proportion of S. mutans on their teeth. There was no significant difference in serum, salivary, or gingival fluid antibodies to S. mutans between the two groups of animals. Any objections raised over systemic immunization inducing cross-reactive antibodies are therefore overcome by local passive immunization. The mechanism of prevention of colonization has not been established, but we postulate that the Mc Ab which is directed against an important cell surface antigenic determinant of S. mutans (streptococcal antigen I/II) prevents adherence of S. mutans to the acquired pellicle on the tooth surface. S. mutans reacts with the Mc Ab and becomes opsonized, phagocytosed, and killed by the local gingival traffic of neutrophils.

Nifedipine dilates the pulmonary vasculature without producing symptomatic systemic hypotension in upright resting and exercising patients with pulmonary hypertension secondary to chronic obstructive pulmonary disease

Vasodilator therapy may lower pulmonary vascular resistance in patients with chronic air-flow limitation. However, the effects of these agents on left ventricular afterload, cardiac output, and bronchial smooth muscle could lower the calculated pulmonary vascular resistance without specifically affecting pulmonary vascular tone. In addition, systemic hypotension in the upright position and worsening ventilation/perfusion heterogeneity could limit their use. We determined the pulmonary driving pressure (pulmonary arterial-pulmonary arterial wedge pressure) to flow relationship, as well as the transmural pulmonary arterial pressure in 9 patients with severe chronic air-flow limitation with pulmonary hypertension while in a clinically stable condition. Measurements were made at rest and during 3 stages of progressively increasing upright exercise on a bicycle before and after a single 20-mg dose of nifedipine. Nifedipine displaced both the driving pressure to flow and the pulmonary arterial transmural pressure to flow relationships towards higher flows in every subject, suggesting an active vasodilation. In the upright position, PaO2 did not change, and the systemic arterial pressure was only mildly reduced. In patients with pulmonary hypertension from chronic air-flow limitation, acute administration of nifedipine to upright patients causes pulmonary, as well as systemic vasodilation without causing symptomatic hypotension or reducing arterial oxygenation.

Structure-dependent induction of bilirubin glucuronidation and lauric acid 12-hydroxylation by arylcarboxylic acids chemically related to clofibrate

The inductive potency of carboxylic acids, structurally related to clofibrate, on bilirubin UDPglucuronosyltransferase was investigated in the rat. For this purpose, structure-induction relationships were established using ten different arylcarboxylic or chlorophenoxycarboxylic acids. 4'-Chlorophenoxyacetic, -propionic and -isobutyric (clofibric) acids progressively increased hepatic glucuronidation of bilirubin (17%, 43%, 60% greater than controls, respectively) after a 5-day treatment in rat (100 mg/kg per day). 2-Phenylpropionic acid also enhanced bilirubin UDPglucuronosyltransferase activity (50%) in contrast to phenylacetic acid. The other compounds did not, or only slightly, affect this parameter. These results indicate that specific structural features are required for the induction property. Moreover, a good correlation (r = 0.962) was found between the extent of induction and the physiochemical descriptors which characterize the electronic state of the molecules, when analysed by multidimensional regression. Fluorescence polarization revealed that the compounds tested, especially clofibric acid, did not affect, in vivo or in vitro, the anisotropy of two different probes embedded in the microsomal membranes. Finally, since the interaction of the carboxylic acids with the membranes did not modify the latency state of bilirubin UDPglucuronosyltransferase, it was concluded that the increase in enzyme activity was due more to a real induction than to activation of bilirubin UDPglucuronosyltransferase. A close linkage was established between bilirubin UDPglucuronosyltransferase induction and that of cytochrome P-452, as shown by enhanced omega-oxidation of lauric acid. This led to the hypothesis that both processes could be under coordinate regulation and mediated by a molecular interaction depending on the physicochemical properties of the carboxylic acids.

Comparison of serum and cerebrospinal fluid levels of methotrexate in man during high-dose chemotherapy for aggressive non-Hodgkin's lymphoma

The relationship between plasma and cerebrospinal fluid levels of methotrexate was studied in five patients, four with aggressive non-Hodgkin's lymphoma and one with mixed epithelial mesothelial tumour, who were treated with high-dose methotrexate (1.5 g/m2) as part of combination chemotherapy. Cerebrospinal fluid was sampled for 24 h via a permanent indwelling lumbar catheter. No complications were observed with this technique. In two patients with central nervous system involvement adequate "cytotoxic" levels (greater than 10(-6) M) were obtained for greater than 12 h. The remaining three patients, with no direct evidence of central nervous system involvement, never attained adequate cytotoxic methotrexate levels in the cerebrospinal fluid. Serum levels were therapeutic in all patients. These results suggest that patients with central nervous system tumour involvement may receive adequate doses of methotrexate in the cerebrospinal fluid. Patients with occult central nervous system tumour involvement may not attain adequate cerebrospinal fluid levels. A 24-h serum methotrexate level of greater than 10(-5) M may indicate that patients have achieved therapeutic cerebrospinal fluid levels of methotrexate. Cranial irradiation following chemotherapy is still recommended in this tumour group until adequate cytotoxic levels of methotrexate can be obtained in all patients for prolonged periods.

Increases in intrathoracic pressure do not explain the rise in left ventricular end-diastolic pressure that occurs during exercise in patients with chronic obstructive pulmonary disease

During exercise, patients with chronic obstructive pulmonary disease (COPD) increase their pulmonary arterial wedge (Ppaw) and left ventricular (LV) end-diastolic pressures more than normal control subjects. The increase in pressure is commonly attributed to an increase in intrathoracic pressure (Pit). However, mean esophageal pressure (Pes) does not increase with supine exercise in patients with COPD. Because changes in Pes may not represent changes in Pit when recorded in the supine position, we measured Ppaw and Pes during upright exercise in 8 patients with severe air-flow limitation (mean +/- SD) FEV1, 0.88 +/- 0.27 L secondary to COPD and no history or electrocardiographic abnormalities suggesting a previous myocardial infarct, history of angina, evidence of systemic hypertension, or use of cardiac medications. In addition, all patients completed a progressive exercise test to exhaustion without angina or ST segment changes, and all had normal LV function at rest assessed by equilibrium radionuclide ventriculography. The Ppaw increased a mean of 7.2 +/- 4.3 mmHg, whereas Pes increased a mean of only 1.3 +/- 1.6 mmHg. By multiple linear regression analysis, Ppaw was significantly associated with the work level performed (p less than 0.01), but had no significant association with Pes (p greater than 0.1). The change in Ppaw could not be attributed to changes in Pes. If changes in Pes during upright exercise are representative of changes in Pit or juxtacardiac pressure, a rise in Pit does not explain the exercise-induced increase in Ppaw and LV end-diastolic pressure that occurs in patients with COPD.

Comparative pharmacokinetics of theophylline and ethylenediamine following single and repeated doses of a sustained-release aminophylline preparation to volunteers

Plasma concentrations of theophylline and ethylenediamine have been measured by HPLC after a single dose and also after a further four consecutive doses at 12 h intervals of a tablet containing 225 mg aminophylline in a sustained release matrix (Phyllocontin) had been taken by volunteers. A dissolution study of the product showed the release of theophylline to follow zero-order kinetics, to be independent of bath pH, and to be complete in 6.5 h, while the release of ethylenediamine depended upon the pH of the medium and was more extensive in acid solutions. After one tablet, the plasma theophylline concentrations reached a maximum of 4 micrograms ml-1 at 5 h and fell slightly at 7 h. Immediately before the fifth dose. The areas under the plasma level-time curves (AUC) were significantly (P less than 0.001) increased by the chronic regimen, and although the individual values were highly variable, the increase in AUC from the first to the fifth dose was significantly (P less than 0.001) correlated within each subject. Ethylenediamine concentrations after a single dose reached a peak of 0.16 micrograms ml-1 at 1 h, and returned to baseline values in 5-7 h. After the fifth dose, the plasma levels and kinetics were no different from those obtained with the first dose indicating that ethylenediamine did not accumulate as a result of chronic administration of aminophylline in a form designed to give steady-state levels of theophylline.