A coupled assay for bile acid:CoA ligase

A new assay for the enzyme bile acid:CoA ligase is presented. The new assay is designed to supplant the existing radiometric assays which require radiolabeled bile acids. The new assay couples the formation of bile acid-CoA to its glycination in a reaction catalyzed by bile acid-CoA:glycine N-acyltransferase. The coupling reaction utilizes [14C]glycine and the bile acid-CoA is quantitatively converted to [14C]glycobile acid. The [14C]glycobile acid is isolated by solvent extraction and quantitated by liquid scintillation counting. The method is shown to be accurate, highly sensitive, and applicable to a wide variety of bile acids.

Dopamine and norepinephrine activity in schizophrenia. An integrative perspective

The dopamine (DA) hypothesis of schizophrenia stated that increased DA activity is the primary cause of schizophrenia. Recently, even though increased DA activity is in fact involved in psychotic symptoms and antipsychotic drug response, it has become clear that decreased DA activity is present in remitted and chronic states and may relate to deficit symptoms and cortical lesions. In addition, the norepinephrine (NE) system seems to be involved in symptomatology, antipsychotic drug response, course, and outcome in schizophrenia. This review supports the hypothesis that a disturbance in DA and NE activity regulates schizophrenic behavior. A plethora of DA- and NE-related findings in schizophrenic patients are reviewed in relationship to each other according to basic science data and to presently entertained hypotheses, with emphasis on a neural developmental disturbance interacting with a genetic predisposition shaped by environmental factors.

In vitro methodology for resistance arteries

Two commonly used methods for examining the physiological and pharmacological properties of isolated resistance arteries are the ring-mounted preparation and the cannulated, pressurized vessel. Each technique is discussed and consideration given to limitations and advantages. Also presented are examples of comparative differences between them, and practical experimental schemes for calibrating cannulae and for perfusing resistance arteries. Although both methods are valuable, the cannulated approach may better reflect the in vivo properties of the arteries.

Hypotensive responses to common daily activities in institutionalized elderly. A potential risk for recurrent falls

Transient hypotension may be one of many factors contributing to the high prevalence of falls among elderly people. To determine the frequency and magnitude of hypotensive responses to common daily activities, and their potential relationship to falls in the elderly, we examined blood pressure (BP) and heart rate during a standardized series of activities in 38 institutionalized recurrent fallers (age, 87 +/- 6 years), 20 institutionalized nonfallers (age, 85 +/- 5 years), and 10 healthy young control subjects (age, 24 +/- 3 years). The coefficient of variation for systolic BP during all activities was higher in elderly subjects (fallers, 14% +/- 5%; nonfallers, 12% +/- 3%) than in young control subjects (8% +/- 1%). In contrast, the coefficient of variation for heart rate during all activities was higher in young subjects than in the elderly subjects. Elderly subjects had marked BP reduction following meals and nitroglycerin, which was significantly greater in fallers than in nonfallers, independent of the cause of the fall. Thus, institutionalized elderly have marked BP variability and hypotensive responses to meals and nitroglycerin. A decline in BP during common preload-reducing stresses may predispose some elderly people to falls.

Telephone triage in the office setting

During a six-month period in 1988, two nurse-midwives documented the telephone calls they received in an OB/GYN/CNM practice. Calls were then tallied and categorized for analysis. A discussion of the numbers and types of calls is presented as well as a review of the literature on telephone triage/management.

A test of the tridimensional personality theory: association with diagnosis and platelet imipramine binding in obsessive-compulsive disorder

We administered the Tridimensional Personality Questionnaire (TPQ) to a sample of 25 individuals with obsessive-compulsive disorder (OCD) and 35 normal controls. As predicted, OCD cases scored much higher on the harm avoidance dimension than normal controls. Findings for the novelty seeking and reward dependence dimensions were less dramatic, although compatible with the underlying theory. Despite a theoretical link between the harm avoidance dimension and serotonin-mediated neuropathways, we failed to find an association between this dimension and platelet imipramine binding in either OCD cases or controls.

Effects of cytochrome P-450 monooxygenase inducers on mouse hepatic microsomal metabolism of testosterone and alkoxyresorufins

The effects of treatment with phenobarbital, 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP), pregnenolone-16 alpha-carbonitrile (PCN), 3-methylcholanthrene (3-MC) and isosafrole on the hepatic microsomal formation of nine monohydroxy metabolites of testosterone and the O-dealkylation of the ethyl and pentyl ethers of resourfin were evaluated in adult male C57BL/6J and DBA/2NCR mice. In both strains, phenobarbital, TCPOBOP and PCN induced testosterone 2 beta-, 6 beta-, 15 beta- and 16 beta-hydroxylases up to 5-fold, while phenobarbital and TCPOBOP increased the rate of dealkylation of pentoxyresorufin by approximately 30-fold. However, phenobarbital and TCPOBOP did not exhibit identical patterns of induction for the testosterone oxidation reactions. Hepatic microsomes from C57BL/6J mice treated with TCPOBOP displayed a depression in 6 alpha-testosterone hydroxylase activity, which was also observed in PCN-treated animals, whereas phenobarbital-treated mice exhibited an elevation in this monooxygenase activity. A dose of TCPOBOP (0.5 mumol/kg) previously demonstrated to represent an ED50 for mouse aminopyrine N-demethylase activity was also found to approximate the ED50 for pentoxyresorufin O-dealkylase activity in the C57BL/6J mouse. Isosafrole or 3-MC treatment had little effect on testosterone metabolism or pentoxyresorufin O-dealkylase activity in either strain, while 3-MC induced ethoxyresorufin O-deethylase activity in C57BL/6J but not DBA/2NCR mice. This study confirms that TCPOBOP is a potent cytochrome P-450 inducer which most closely resembles phenobarbital in its mode of action. However, TCPOBOP and phenobarbital do not evoke identical modulations of cytochrome P-450-dependent monooxygenases in mice.

The effects of ions on the conjugation of xenobiotics by the aralkyl-CoA and arylacetyl-CoA N-acyltransferases from bovine liver mitochondria

The aralkyl-CoA:glycine N-acyltransferase and the arylacetyl-CoA:amino acid of N-acyltransferase were purified from bovine liver mitochondria and their response to a variety of ions investigated. The activity of the aralkyl transferase was inhibited by divalent cations with all substrates investigated. For benzoyl-coenzyme A (CoA), K+ was a competitive inhibitor, competing for binding at the benzoyl-CoA binding site. With salicylyl-CoA, K+ did increase the dissociation constant (KD) for acyl-CoA but it was not a competitive inhibitor and in addition, K+ increased the Michaelis constant for glycine (Kglym) tenfold. The data suggest that the increase in Kglym is due to bound K+ forcing reorientation of salicylyl-CoA at the active site so that it impinges on the glycine binding site. Inorganic anions and cations did not affect the extent of product inhibition by hippuric acid with either acyl-CoA and this was because they affected the binding of acyl-CoA and hippuric acid to the same extent. Ions did, however, greatly reduce the extent of product inhibition by CoA. This is critical because under approximate in vivo conditions (2.5 mM CoA), the salt-free enzyme would be almost completely inhibited by CoA. The arylacetyl transferase was activated by inorganic ions when assayed at saturating substrate concentrations. However, at physiologic concentrations of glycine certain salts were modestly inhibitory. The inhibitory effect of KCl was characterized by a large decrease in the affinity of the enzyme for phenylacetyl-CoA, suggesting that the arylacetyl-CoA region of the active site contained an inhibitory ion binding site. At low (physiologic) concentrations of substrate, the arylacetyl transferase was extensively inhibited by CoA and this inhibition was greatly reduced by ions. The 3'-phosphate group on CoA was found to be important for binding to the salt-free enzyme but in the presence of ions its importance was diminished. In the absence of inorganic ions the affinity of the enzyme for phenylacetyl-CoA and naphthylacetyl-CoA was so high that it could not be measured. In the presence of KCl the KD values for phenylacetyl-CoA and naphthylacetyl-CoA were similar, but the Km for glycine was extremely high for 1-naphthylacetyl-CoA conjugation, which accounts for its slow rate of metabolism. Conjugation with glutamine had a high Michaelis constant for glutamine (KGlum) and a low maximum velocity (Vmax) which accounts for the absence of glutamine conjugation in vivo.

Corticotropin-releasing factor immunoreactive neurons persist throughout the brain in Alzheimer's disease

Corticotropin-releasing factor (CRF) immunoreactivity was examined in the hippocampal formation, cerebellum and hypothalamus of normal aged and Alzheimer's disease (AD) brains. Immunoreactive non-pyramidal neurons were located in the polymorphic layer of the dentate gyrus and CA fields. A plexus of CRF terminals was seen in the supragranular layer of the dentate gyrus. In AD, occasional senile plaques contained CRF-immunoreactive fiber terminals but the pattern of staining was otherwise unchanged aside from a suggestion of increased staining intensity. Similarly, the pattern of immunoreactive cerebellar climbing fibers and paraventricular hypothalamic neurons was preserved in AD brains aside from increased perikaryal staining intensity in the hypothalamus.

Direct observation of microtubules with the scanning tunneling microscope

To observe surface topography of microtubules, we have applied scanning tunneling microscopy (STM), which can image metal and semiconductive surfaces with atomic resolution. Isolated microtubules fixed in 0.1% glutaraldehyde in reassembly buffer containing 0.8 M glycerol were imaged in air on a graphite substrate. The presence of microtubules in solution was verified by electron microscopy. At atmospheric pressure and room temperature, STM probing of both freeze-dried and hydrated microtubules reveals structures approximately 25 nm in width, consisting of longitudinal filaments about 4 nm in width. These structures match electron microscopy images of microtubules and their component protofilaments. Microtubules imaged by STM frequently appear buckled and semiflattened. Top-view shaded scans show what appear to be individual tubulin subunits within protofilaments. We believe these results represent the first direct STM observation of protein assemblies in which components can be identified. Although the microtubule image resolution described here is no better than that presently obtainable by other techniques (e.g., electron microscopy with freeze-drying, shadowing, and/or negative staining), it is significant that suitably prepared biomolecules may be sufficiently conductive and stable for STM imaging, which is ultimately capable of atomic resolution. Further development of STM technology, computer-enhanced image processing, and elucidation of optimal STM sample preparation indicate that STM and related applications will offer unique opportunities for the study of biomolecular surfaces.

Radiation enhancement of lung nodule formation in mice is not potentiated by treatment with a perfluorochemical emulsion and carbogen

The ability of intravenously-injected mouse mammary tumor cells to form lung tumors is increased by irradiation of the thorax 24 h previously. We examined the effects of treatment with a perfluorochemical emulsion (Fluosol-DA, 20%) plus carbogen before and during irradiation on the radiation-induced enhancement of lung nodule formation. We found no evidence that treatment with Fluosol plus carbogen altered the development of tumor nodules in irradiated mouse lungs.

Organ-specific effects of long term feeding of 2,3,7,8-tetrachlorodibenzo-p-dioxin and 1,2,3,7,8-pentachlorodibenzo-p-dioxin on I-compounds in hepatic and renal DNA of female Sprague-Dawley rats

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a potent hepatocarcinogen, and 1,2,3,7,8-pentachlorodibenzo-p-dioxin (PCDD) on liver and kidney DNA of female Sprague-Dawley rats were investigated by 32P-post-labeling assay. The compounds were administered by gavage [1 microgram/kg/week in corn oil (5 ml/kg)] to the animals for up to 6 months. No exposure-related 32P-labeled spots indicative of TCDD or PCDD covalent DNA adducts were noted on the chromatograms of kidney or liver DNA nucleotides from the rats exposed to the toxins for 2 and 6 months. Corn-oil treated control animals exhibited the characteristic tissue- and age-specific patterns of 32P-labeled I-spots in liver and kidney DNA which are associated with specific DNA modifications of unknown origin and function. Treatment with either TCDD or PCDD resulted in a substantial reduction of the levels of I-compounds in liver, a target organ for TCDD carcinogenesis. After 6 months of exposure to TCDD the reductions in the amounts of individual hepatic I-compounds ranged from 37 to 77% and decreased levels were also observed after 2 months of treatment. It was apparent that PCDD was not as effective as TCDD in reducing hepatic I-compound levels and this corresponded with the lower aryl hydrocarbon receptor binding activity of the former compound. In contrast, TCDD and PCDD did not cause any significant decrease of I-compounds in the kidney which is not a site of TCDD-mediated carcinogenicity in female Sprague-Dawley rats. Whether I-compound deficiency contributes to TCDD-mediated hepatocarcinogenesis (e.g. by facilitating DNA replication) needs to be investigated.

Preclinical studies of a perfluorochemical emulsion as an adjunct to radiotherapy

Tumor growth and tumor cell survival endpoints were used to examine the effects of a perfluorochemical emulsion, Fluosol-DA, 20%, and carbogen (95% O2/5% CO2) on EMT6 mouse mammary tumors in BALB/c mice. These studies defined the effects of the Fluosol dose on the hematocrit and fluorocrit of the mice and on the radiation response of the tumors. The effect of varying the duration of carbogen breathing before irradiation was examined; times of 5-60 min gave similar enhancements of tumor radiosensitivity. Potentiating effects were not observed when the tumors were irradiated 1-3 days after Fluosol injection, probably reflecting the observed clearance of the perfluorochemicals from the circulating blood. Fluosol injected 30 min-2 days before irradiation did not alter the radiation response of tumors in air-breathing or N2-asphyxiated mice. Together, these studies provided additional support for the hypothesis that the potentiation of tumor radiation response observed after treatment with Fluosol plus carbogen results from changes in O2 delivery to the hypoxic tumor cells by oxygenated perfluorochemical particles. This confirms the conclusion drawn on the basis of the observed changes in the tumor cell survival curve. Studies of tumor cell survival, tumor cell yield, tumor growth, and artificial lung metastasis formation revealed no effects of Fluosol treatment (without irradiation) on tumor progression or metastasis. Studies examining the effects of Fluosol plus carbogen on the growth of tumors irradiated with 5 Gy showed that the changes in tumor radiosensitivity observed using cell survival endpoints also occurred in tumors left in situ after irradiation with a radiation dose similar to those used in some clinical trials.

OKT4+ T cell abnormality in patients with active systemic lupus erythematosus: HLA-DR antigen expressions

The objective of this study was to define immunologic T cell abnormality characteristic of active systemic lupus erythematosus (SLE). Eight of nine patients who had severe clinical and laboratory manifestations of active SLE had a characteristically marked increase in OKT4+ and a decrease in OKT8+ T cells. Using OKIa1 and OKDR monoclonal antibody, we found that, in circulating blood of all patients with active SLE, an increased percentage of Ia+ and DR+ T cells is present compared to inactive SLE. Five of these active SLE patients had Tac+ antigens, an interleukin 2 receptor on OKT4+ and OKT8+ T cell subsets in resting blood. The present study demonstrates that Ia+ and DR+ antigens are selectively expressed on the majority of OKT4+ T cell subsets of all patients with active SLE, whereas Ia+ and DR+ antigens are expressed almost equally on both OKT4+ and OKT8+ T cell subsets in inactive SLE. The elevated percentage of Ia+, DR+, OKT4+ T cells in active SLE was accompanied by a highly depressed proliferative response to T cell mitogens, phytohemagglutinin and concanavalin A. However, OKT8+ T cell subsets in active SLE possessed a normal proliferative response to these T cell mitogens. We conclude that this abnormality of activated OKT4+ T cells bearing HLA-DR antigens may play a role in the development of active SLE.

Interactions between a viral protease and cystatins

The interactions of two cystatins with a viral cysteine protease were studied using several types of assays. Complex formation between the protease and inhibitor was directly demonstrated using a gel retardation assay. It was also shown that the formation of enzyme inhibitor complexes could occur after first binding either the enzyme or the inhibitor to filter paper, and ultimately decorating the complex with antibody and radio-labelled protein A or by preparing one of the protein ligands with an internal radiolabel. The procedure can be adapted to provide a method for screening expression libraries for protease or inhibitor genes. The inhibition of a cysteine protease by a cystatin was shown not to directly involve binding to the active site thiol of the enzyme, but rather to be the result of a steric block in the active site region which prevents large affinity labels and protein substrates from reaching the active site.

Co-induction of cytochrome P-450 isozymes in rat liver by 2,4,5,2',4',5'-hexachlorobiphenyl or 3-methoxy-4-aminoazobenzene

A multitude of xenobiotics have been demonstrated to co-induce either cytochromes P-450c and P-450d or cytochromes P-450b and P-450e in rat hepatic microsomes. Recently, the compounds 2,4,5,2',4',5'-hexachlorobiphenyl (HCB) and 3-methoxy-4-aminoazobenzene (3-MeO-AAB) have been suggested as selective inducers of cytochrome P-450b (Eur. J. Biochem. 151:67 (1985)) and P-450d (Biochem. Biophys. Res. Commun. 133:1072 (1985)), respectively. Since the identification of inducers with such unique characteristics would have implications with regard to the mechanism of induction of all four isozymes, we have examined the induction of cytochromes P-450b and P-450e by HCB and cytochromes P-450c and P-450d by 3-MeO-AAB in liver microsomes from adult male rats. Immunoblot analysis with monoclonal antibodies directed against cytochromes P-450b and P-450e indicate that HCB induces both isozymic species at the three dosage levels examined (10, 90, and 180 mg/kg). Similarly, 3-MeO-AAB does not appear to represent a unique inducer. Immunoblots of hepatic microsomes from animals treated with three different dosage regimens of 3-MeO-AAB demonstrate that, even at the lowest dosage level (50 mg/kg), both cytochromes P-450c and P-450d are induced. Moreover, immunoinhibition of 7-ethoxyresorufin O-deethylase (EROD) activity by monospecific antibody against either cytochrome P-450c or P-450d confirms this result. 3-MeO-AAB increases this enzyme activity 10-fold; approximately one-third of this induced activity is inhibited with monospecific anti-P-450c, while two-thirds is inhibited with monospecific anti-P-450d. This study also demonstrates that hepatic EROD activity is not an accurate estimate of cytochrome P-450c content since the majority of this enzyme activity in control and 3-MeO-AAB-treated rats is inhibited with monospecific anti-P-450d but not with monospecific anti-P-450c.

High-level expression in Escherichia coli of a soluble and fully active recombinant interleukin-1 beta

A complementary DNA sequence encoding monocyte interleukin-1 (IL-1), beta form/pI7, was expressed in Escherichia coli. Recombinant plasmid pDP516 was constructed by cloning and rebuilding the mature IL-1 coding sequence into an E. coli expression vector. Bacteria transformed with pDP516 constitutively produced recombinant IL-1 (r-IL-1) at 15-20% of total E. coli protein. The r-IL-1 was found to be in the soluble fraction of sonicated E. coli Bacterial r-IL-1 (DP516) has been purified to homogeneity by anion exchange and sizing column chromatography, with an apparent molecular weight of 17,500. The identity of the purified r-IL-1 was confirmed by amino acid and DNA sequencing analyses. Purified recombinant IL-1 DP516 exhibits biological activity similar to that of native monocyte IL-1 (3 approximately 4 X 10(7) units/mg). An amino-terminal deletion mutant completely abolishes the biological activity, indicating that the integrity of the IL-1 molecule might be important for its function.

Effects of ovariectomy and estradiol benzoate on high affinity choline uptake, ACh synthesis, and release from rat cerebral cortical synaptosomes

Several presynaptic processes were studied in cerebral cortical synaptosomes prepared from intact adult female rats or from ovariectomized animals that received 3 subcutaneous injections of either estradiol benzoate (10 micrograms/kg) or vehicle. Injections were given 1/day, every other day, and animals were sacrificed 1 h after the last injection. High affinity choline uptake and coupled acetylcholine (ACh) synthesis were reduced by ovariectomy, and restored to control levels by the estradiol benzoate injections. In contrast, low affinity choline uptake and depolarization-induced [3H]ACh release were unaffected by either ovariectomy or estradiol benzoate injections. These results suggest that changes in estradiol levels may alter the high affinity transport process regulating ACh synthesis in this tissue.

The effects of organochlorine pesticides as inducers of testosterone and benzo[a]pyrene hydroxylases

p,p'-DDE, phenobarbital, dieldrin heptachlor, chlordane and toxaphene induced rat liver microsomes exhibited increased formation of the 4,5-dihydrodiol, 3,6-quinone, 9- and 3-hydroxymetabolites of benzo[a]pyrene and the latter three compounds also induced an increase in the rate of formation of the 9,10-dihydrodiol metabolite. Lindane was inactive as an inducer of benzo[a]pyrene hydroxylase. With the exception of lindane, all the organochlorine pesticides and PB induced testosterone 16 alpha- and 16 beta-hydroxylases; in contrast lindane induced testosterone 6 alpha-, 7 alpha- and 6 beta-hydroxylases and PB also induced testosterone 15 beta-hydroxylase and androstenedione formation. Using a battery of monooxygenase enzyme assays it was evident that there were significant differences between PB and several organochlorine pesticides as inducers of rat hepatic cytochrome P-450-dependent monooxygenases.

Interaction of 2,4-dichlorophenoxyacetate (2,4-D) and 2,4,5-trichlorophenoxyacetate (2,4,5-T) with the acyl-CoA: amino acid N-acyltransferase enzymes of bovine liver mitochondria

The amino acid conjugation of the phenoxyherbicides 2,4-dichlorophenoxyacetate (2,4-D) and 2,4,5-trichlorophenoxyacetate (2,4,5-T) by animals was examined at the level of the enzymes catalyzing the reactions. The phenoxyherbicides were not substrates for the bile acid conjugating system but were substrates for the mitochondrial xenobiotic conjugating system. The two mitochondrial xenobiotic-CoA: amino acid N-acyltransferases (benzoyltransferase and phenylacetyltransferase) were separated and tested for activity towards 2,4-D-CoA and 2,4,5-T-CoA. The phenylacetyltransferase showed activity towards phenylacetyl-CoA, phenoxyacetyl-CoA and 2,4-D-CoA, but not 2,4,5-T-CoA. Benzoyltransferase conjugated both 2,4-D-CoA and 2,4,5-T-CoA. The overall rates of conjugation of the phenoxyherbicides were slow relative to the standard substrates with both enzymes. This slow rate was found to be due in both cases to a relatively high Km for glycine, and a very slow catalytic rate constant. Both enzymes did, however, have a very high affinity for 2,4-D-CoA and 2,4,5-T-CoA so these compounds proved to be potent alternate substrate inhibitors of both enzymes. The data show that the inefficient in vivo conjugation of the phenoxyherbicides relative to structurally similar compounds can be understood in terms of the kinetic properties of the mitochondrial N-acyltransferases. Further, the potential for the interference of the phenoxyherbicides with the conjugation of other compounds is revealed.

1,4-Bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP) and related compounds as inducers of hepatic monooxygenases. Structure-activity effects

1,4-Bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP) resembles phenobarbital (PB) in its mode of induction of the hepatic drug-metabolizing enzymes in mice. The structural features of this molecule include: a linear tricyclic aromatic ether ring system, an internal 1,4-disubstituted benzene ring and two 3,5-dichloropyridyloxy substituents. Ten analogs of TCPOBOP have been synthesized and their activities as microsomal enzyme inducers evaluated. Dose-response induction of mice hepatic microsomal cytochrome P-450, aldrin epoxidase and dimethylaminoantipyrine N-demethylase gave ED50 values for TCPOBOP and five homologs. The results illustrate that changes in the structure of the pyridyloxy ring markedly affect enzyme induction activity. The order of activity for the substituents was 3,5-dibromopyridyloxy approximately 3,5-dichloropyridyloxy greater than 5-bromopyridyloxy approximately 5-chloropyridyloxy greater than 3-chloropyridyloxy greater than pyridyloxy. In addition, the effects of altered substitution pattern of the benzene ring and structural alterations of the internal ring moiety were evaluated by measuring hepatic microsomal coumarin hydroxylase activity. The results confirm the microsomal monooxygenase enzyme induction activity of TCPOBOP, and the observed structure-dependent potencies of several related homologs support a receptor-mediated mechanism of action for the process.

Thymidine and methionine syntheses in pregnant rats exposed to nitrous oxide

The dose-dependent effects of nitrous oxide on thymidine and methionine syntheses were investigated in pregnant rats. Female Sprague-Dawley rats were exposed on day 9 of gestation to 0.75%, 7.5%, or 75% nitrous oxide for 24 h. Immediately and 72 h after exposure, a deoxyuridine-suppression test was performed on maternal bone marrow and a methionine synthetase assay was performed on maternal liver to assess thymidine and methionine syntheses, respectively. Inhibition of thymidine synthesis was seen after exposure to 7.5% and 75%, but not after 0.75%, nitrous oxide. Recovery was complete 72 h after exposure. Methionine synthetase activity was abolished at all concentrations of nitrous oxide tested and did not return to control values 72 h after exposure. Fetal weight and gross appearance were not affected by exposure to nitrous oxide; however, the observed decrease in thymidine and methionine syntheses after nitrous oxide exposure may account for its teratogenic effects.

Human monocyte functional heterogeneity: monocyte fractionation by discontinuous albumin gradient centrifugation

Human monocytes subserve many roles in the immune response. It is not clear, however, whether this functional heterogeneity reflects the action of different monocyte subpopulations. We separated human blood monocytes into distinct populations using a discontinuous (15-35%) serum albumin gradient technique. We examined if any of a number of monocyte functions were preferentially expressed by these five monocyte subsets. Monocytes in the 25% and 30% albumin fractions possessed more Fc (IgG) and C3 receptor activity than did monocytes in either of the 15, 20 or 35% fractions. In addition, monocytes isolated in the more dense albumin fractions were enriched for the capacity to support pokeweed mitogen-induced B-cell differentiation. All gradient fractions were equally capable of binding Raji cells and inhibiting Raji cell incorporation of [3H]thymidine. These data indicate that fractionation of monocytes by a discontinuous albumin gradient is an effective method to enrich for those monocytes with certain functional characteristics.

Modulation of the number of ligand binding sites of UDP-glucuronyltransferase by the gel to liquid-crystal phase transition of phosphatidylcholines

The kinetics of a pure, delipidated form of microsomal UDP-glucuronyltransferase is non-Michaelis-Menten when the enzyme is reconstituted into unilamellar vesicles of phosphatidylcholine that are in a gel phase. Double reciprocal plots of velocity as a function of the concentration of UDP-glucuronic acid show a downward curvature under these conditions. Binding studies indicate that the basis for the kinetic pattern is the presence of one high affinity and one low affinity binding site for UDP-glucuronic acid. The two classes of binding sites seem to be generated by the presence of two subunits that bind UDP-glucuronic acid within a single molecule of UDP-glucuronyltransferase. Melting the phospholipids from the gel phase to the liquid-crystal phase is associated with a switch from non-Michaelis-Menten to Michaelis-Menten kinetics for UDP-glucuronyltransferase. Binding studies for interaction of UDP-glucuronic acid with enzyme present in a liquid-crystal lipid phase indicate that the two binding sites for UDP-glucuronic acid do not become identical in this setting. Instead, one of the sites becomes nonfunctional. Binding studies carried out with UDP as ligand lead to similar results. There is a high affinity and a low affinity site for UDP when enzyme is reconstituted into a phospholipid bilayer in a gel phase. There is only one UDP binding site per holoenzyme when enzyme is reconstituted into a phospholipid bilayer in a liquid-crystal phase. Delipidated enzyme or enzyme reconstituted with lysophosphatidylcholine displays Michaelis-Menten kinetics. Binding studies show that these forms have only one binding site for UDP-glucuronic acid per holoenzyme. However, they have two nonidentical binding sites for binding of UDP. Thus, the physical properties of its phospholipid milieu influence the number of functional binding sites of UDP-glucuronyltransferase.

Mutagenicity of experimental inhalational anesthetic agents: sevoflurane, synthane, dioxychlorane, and dioxyflurane

A modification of the Ames bacterial assay system employing two histidine-dependent strains of Salmonella typhimurium, TA1535 and TA100, was used to test the mutagenicity of four experimental, inhalational anesthetic agents: sevoflurane, synthane, dioxychlorane, and dioxyflurane. None of the anesthetics was mutagenic. Increased activity was seen only with vinylidene chloride, the positive control.

Lack of toxicity of enflurane on male reproductive organs in mice

Enflurane has been shown to increase slightly the percentage of abnormal spermatozoa in mice. To examine in more detail possible adverse effects of enflurane on male reproductive organs, 125 Swiss/ICR mice were exposed to 0.3% enflurane for up to 18 months; a control group of 125 mice was exposed concurrently to air. Exposures were for 4 hours/day, 5 days/week. After 12 months of exposure, groups of 25 enflurane-treated and control mice were killed, and chromosomal analysis of spermatogonial cells was performed. After 18 months exposure, remaining mice were killed and epididymal sperm were collected for morphologic examination. In addition, the reproductive organs of all mice dying or killed throughout the study were examined histologically. Approximately 1% of spermatogonial cells from both enflurane-treated and control mice had aberrant chromosomes. The average percentage of morphologically abnormal sperm was 9.4 +/- 1.7 for enflurane-treated mice and 6.5 +/- 1.3 for control mice; the difference was not statistically significant (p = 0.18). Finally, there was no difference between the treated and control mice in histologic appearance of reproductive organs. It was concluded that long-term exposure to enflurane has no adverse effects on male reproductive organs in mice.

Lack of mutagens in urines of operating room personnel

Mutagenic activity of urines obtained from operating room personnel was assayed in the Ames Salmonella/mammalian microsome system using three strains of histidine-dependent S. typhimurium, TA1535, TA1538, and TA100. Two procedures were employed. In the first, 100- and 200-microliter aliquots of urine obtained from 28 subjects working in either scavenged or unscavenged operating rooms were tested. In the second, urine samples obtained from 13 physicians before and after starting an anesthesia residency, as well as 250-fold concentrates of these samples, were assayed. There was no statistically significant difference in urinary mutagenic activities between individuals working in scavenged and those working in unscavenged operating rooms. Furthermore, urines of anesthesiologists collected before and after beginning training had similar mutagenic activities. Only heavy smokers had mutagenic urine. It was concluded that the majority of operating room workers do not excrete mutagens in the urine.

Mutagenicity of inhalation anaesthetics: trichloroethylene, divinyl ether, nitrous oxide and cyclopropane

The mutagenic potential of trichloroethylene, divinyl ether, nitrous oxide and cyclopropane was assessed in vitro by microbial assay employing two histidine-dependent strains of Salmonella typhimurium, TA1535 and TA100. Anaesthetic agents in various concentrations were incubated with bacteria in the presence or absence of an enzyme system prepared from enzyme-induced rat liver. Nitrous oxide and cyclopropane were not mutagenic, whereas divinyl ether gave a strongly positive response. Results for trichloroethylene were equivocal. These and previous studies with the salmonella system, together with mutagenicity studies using different test systems, indicate that modern inhalation anaesthetic agents are unlikely to be mutagenic.

Fluroxene mutagenicity

The commercially available volatile anesthetic fluroxene (2,2,2-trifluoroethyl vinyl ether) which contains the stabilizer N-phenyl-1-napthylamine, was tested for mutagenicity using four strains of S. typhimurium, TA1535, TA1537, TA98 and TA100, and one strain of E. coli, WP2. In addition, purified fluroxene; N-phenyl-1-napthylamine; trifluoroethanol, a major metabolite of fluoroxene; and urine from rats anesthetized with fluroxene were tested. Several procedures were utilized including exposure of bacteria to vapor in desiccators and in liquid suspension. Results indicate that fluroxene, but not its stabilizer, was mutagenic to strains TA1535, TA100 and WP2 only in liquid suspension and only in the presence of a rat-liver enzyme system. Trifluoroethanol and urine from fluroxene-treated rat were not mutagenic to any strain of bacteria. These findings indicate that fluroxene is a promutagen which requires preincubation before it is recognized. Further experiments were performed with enzymes prepared from mouse, hamster and human liver. Fluroxene was mutagenic only in the presence of enzymes prepared from Aroclor 1254 pretreated rodents. Since fluroxene was not mutagenic in the presence of enzymes prepared from three human livers, the significance of these findings to man are unclear.

Mutagenicity of halogenated ether anesthetics

An in vitro microbial assay system employing two histidine-dependent strains of Salmonella typhimurium, TA1535 and TA100, was used to test the mutagenicities of enflurane, methoxyflurane, isoflurane and fluroxene. Enflurane, isoflurane and fluroxene in concentrations ranging from 0.01 to 30 per cent and methoxyflurane in concentrations ranging from 0.01 to 7 per cent were incubated with bacteria in the presence or absence of homogenates of liver prepared from rats pretreated with the enzyme inducer, Aroclor 1254. Enflurane, methoxyflurane, isoflurane, and urines from patients anesthetized with these agents were not mutagenic. Fluroxene, however, was highly mutagenic, and therefore poses a possible hazard for operating room personnel and patients.

Acute sedative properties of SKF 525A in rats: implications for its use as a metabolism inhibitor in the study of psychoactive drugs

SKF 525A was found possess sedative properties in rats at doses of 25 and 50 mg per kg, when injected intraperitoneally. The behavioural effects of the drug were assessed in two ways. Firstly, by "Time Sampling Behavioural Categorisation" of explatory behaviour; and secondly by activity measurements obtained with an ultrasonic motion recorder. The results clearly demonstrate that SKF 525A has sedative properties in rats at doses which are conventionally used to inhibit metabolism of a wide range of drugs. The implications of these results for the use of SKF 5251 in the study of the actions of psychotropic drugs are discussed.