An investigation of the interaction between halofantrine, CYP2D6 and CYP3A4: studies with human liver microsomes and heterologous enzyme expression systems

1. We have assessed the interaction of the antimalarial halofantrine with cytochrome P450 (CYP) enzymes in vitro, with the use of microsomes from human liver and recombinant cell lines. 2. Rac-halofantrine was a potent inhibitor (IC50 = 1.06 microM, Ki = 4.3 microM) of the 1-hydroxylation of bufuralol, a marker for CYP2D6 activity. Of a group of structurally related antimalarials tested, only quinidine (IC50 = 0.04 microM) was more potent. 3. Microsomes prepared from recombinant CYP2D6 and CYP3A4 cell lines were shown to catalyse halofantrine N-debutylation. 4. The metabolism of halofantrine to its N-desbutyl metabolite by human liver microsomes showed no correlation with CYP2D6 genotypic or phenotypic status and there was no consistent inhibition by quinidine. 5. The rate of halofantrine metabolism showed a significant correlation with both CYP3A4 protein levels (r = 0.88, P = 0.01) and the rate of felodipine metabolism (r = 0.86, P = 0.013), a marker substrate for CYP3A4 activity. Inhibition studies showed that ketoconazole is a potent inhibitor of halofantrine metabolism (IC50 = 1.57 microM). 6. In conclusion, we have demonstrated that halofantrine is a potent inhibitor of CYP2D6 in vitro and can also be metabolised by the enzyme. However, in human liver microsomes it appears to be metabolised largely by CYP3A4.

Pharmacogenetics of cocaine: a critical review

The development of genetic models to help explain individual differences in sensitivity to and susceptibility to misuse certain CNS active substances, like ethanol and psychostimulants, spans a brief, thirty-plus years. The first animal models involved inbred strains and selected lines of mice and rats and predicted genetic-based differential sensitivity to ethanol and its misuse in humans found a few years later. With drugs like cocaine, tracking genetic differences in sensitivity and misuse liability in humans is difficult because of legal problems. Genetically-defined animals, however, have shown most if not all of cocaine-related behavioural, neurophysiological and toxicological effects to evince wide variation with most effects being influenced by several genes. Thus, we argue that animal and human studies of individual differences in drug sensitivity be studied from both quantitative and molecular genetic approaches. For the former, new techniques involving recombinant inbred strains of rodents, genetic correlational analysis and quantitative trait loci analysis are particularly useful, especially as genetic synteny between rodents and humans becomes better described. Also, because drug effects are highly labile to environmental conditions as well as genetic-based individual differences, multivariate, systems level studies should be developed to provide more complete descriptive and mechanistic views of a multifaceted problem.

Synthesis, absolute configuration, and enantioselectivity of antiretroviral effect of (R)-(-)- and (S)-(+)-cytallene. Lipase-catalyzed enantioselective acylations of (+/-)-N4-acylcytallenes

Enantioselectivity of acylations of (+/-)-cytallene (1b), (+/-)-N4-acetylcytallene (11a), (+/-)-N4-benzoylcytallene (11b), and (+/-)-N4-(9-fluorenylmethoxycarbonyl)cytallene (11c) using vinyl butyrate or acetate catalyzed by lipases in organic solvents was investigated. Reactions with 1b, 11a, and adenallene (1a) did not display a high enantioselectivity but all resulted in a predominant acylation of the (-)-enantiomers. Application of the Lowe-Brewster rule led to a tentative assignment of the R-configuration to all acylated products. Studies of the time course of acylation of (+/-)-N4-benzoylcytallene (11b) in chloroform, tetrahydrofuran (THF), tetrahydropyran (THP), tetrahydrothiophene (THT), and dioxane with lipase PS30 and/or AK showed that the reaction in THF catalyzed by lipase AK was the most promising for resolution of 11b. Indeed, a large-scale acylation afforded, after separation and deprotection of intermediates 3e and 10d, (+)- and (-)-cytallene (3c and 2b) in high yield and enantioselectivity. Acylation of 11c in THF led also to formation of 3c and 2b in high enantioselectivity. Single crystal X-ray diffraction established the S-configuration of (+)-cytallene (3c), thus confirming the assignment made on the basis of Lowe-Brewster rule. An improved large-scale synthesis of (+/-)-cytallene (1b) is also described. The R-enantiomer 2b inhibited the replication of a primary human immunodeficiency virus (HIV-1) isolate in phytohemagglutinin-activated peripheral blood mononuclear cells (PHA-PBM) with IC50 0.4 and IC90 1.7 microM. (+/-)-Cytallene (1b) exhibited IC50 0.8 and IC90 3.4 microM. Both compounds completely suppressed replication of HIV-1 at 10 microM with no detectable cytotoxicity. The S-enantiomer (3c) was inactive.

Alcohol acceptance, preference, and sensitivity in mice. II. Quantitative trait loci mapping analysis using BXD recombinant inbred strains

Quantitative trait loci (QTL) mapping of complex phenotypes has emerged as an important feature of the recombinant inbred (RI) strain methodology. In this second study of our series on alcohol-related behaviors in mice, we examine alcohol acceptance, preference, and hypnotic dose sensitivity (HDS) to a standard dose of alcohol measured in BXD RI strains to identify candidate QTL regions responsible for their heritability. We detected highly significant marker associations for acceptance on chromosome 12 (Eif4e), for preference on chromosome 1 (D1Rti2) and chromosome 7 (D7Mit7), and for HDS on chromosome 7 (Mpmv1). These are the strongest QTL associations that we detected, but several other candidate QTL regions are reported. Given the limited number of BXD RI strains available, the large number of markers used herein, and the consequent chance of identifying false marker associations, these RI QTL mapping results must be seen as tentative, but an important first step toward identifying QTL for alcohol-related behaviors.

Alcohol acceptance, preference, and sensitivity in mice. I. Quantitative genetic analysis using BXD recombinant inbred strains

Although the recombinant inbred strain method was designed for molecular genetic analysis of linkage, it also provides powerful quantitative genetic analyses of heritability and genetic correlations. Measures of alcohol acceptance, alcohol preference, and hypnotic dose sensitivity (HDS) were assessed in 21 strains of mice from the BXD RI series. Sex differences were found to be significant at a phenotypic level. However, heritability estimates for acceptance, preference, and HDS are similar in males and females. Heritability estimates for the three measures are approximately 0.20 for acceptance and preference, and 0.10 for HDS. Analyses of genetic correlations reveal that acceptance and preference share some degree of genetic influence, although they mostly operate under different genetically mediated mechanisms. HDS did not show a significant genetic relationship to either acceptance or preference. Strong correlations were obtained when acceptance, preference, and HDS strain means were correlated across male and female recombinant inbreds, suggesting substantial genetic similarity across sexes.

Effects of acute and chronic ethanol administration on neurotensinergic systems

A summary of pharmacogenetic studies designed to test the hypothesis that NT receptors might mediate or regulate some of the actions of ethanol is presented. Indeed, there are significant genetic correlations between ethanol-induced locomotor activation and high-affinity NT receptor densities in the FC. The results suggest that further studies are needed to determine the role of NT receptors in the FC and MPFC in regulating locomotor activity. In other studies, chronic ethanol treatment, under conditions that produced tolerance to ethanol and caused NT receptor downregulation in the NA and VMB, caused tolerance to locomotor inhibitory effects of centrally administered NT and blunted the effects of intra-VTA NT on dopamine metabolism in the NA and CP. The results show a relationship between NT receptor densities and pharmacological effects of ethanol.

Inhibition of p-nitrophenol hydroxylase in rat liver microsomes by small aromatic and heterocyclic molecules

The cytochrome P450 isoenzyme P4502E1 is constitutively expressed in human liver and catalyzes the oxidation of many known or suspected carcinogens of low molecular weight. In this structure-metabolism study, the role that heteroatoms in heterocyclic compounds play in determining their affinity for P4502E1 was investigated. The ability of 16 six-membered and 10 five-membered compounds to inhibit the hydroxylation of p-nitrophenol, which is specifically catalyzed by P4502E1, was studied in suspensions of microsomes from rat livers in which P4502E1 had been induced by inclusion of acetone in the drinking water. Apparent Ki values were extrapolated from kinetic models of Dixon or Cornish-Bowden plots for enzyme inhibition. Enzyme inhibition was generally of the non-or uncompetitive type. Pyridine was the most potent and benzene one of the least potent inhibitors, with Ki values of 0.4 microM and 8,400 microM, respectively. Pyridazine was less inhibitory than 1,3,5-triazine, which inhibited P4502E1 to a lesser degree than pyrazine and pyrimidine. Among the unsubstituted unsaturated five-membered ring molecules, pyrrole was a better inhibitor than furan or thiophene. 4-Methylimidazole was a much stronger inhibitor than imidazole or 1-and 2-methylimidazole. The ability of compounds to inhibit P4502E1 seems to depend in the main on the presence of a nitrogen atom in the molecule and on the ability of the nitrogen lone pair of electrons to ligand to the heme.

Comprehensive health care reform: an imperative

A public relations marketing strategy is essential to the consensus building for the enactment of health care reform legislation. As Governor of Kentucky, the author reflects on the complex legislative experience that he went through in his state, while attempting to enact a health care reform bill similar to President Clinton's proposal. This article draws the parallel in the politics of health reform between the political reality of an individual state, as compared to the one operating on the national scene.

Altered monamine metabolism in caudate-putamen of iron-deficient rats

The effect of iron deficiency on brain monoamine metabolism using in vivo microdialysis techniques has not been previously reported. We, therefore, examined the monoamines, dopamine and norepinephrine, and their metabolites at steady state by in vivo microdialysis in rat brain caudate-putamen in 11-week-old iron-deficient anemic (hemoglobin < 7 g/dl) and control rats (Hb > 14 g/dl). Caudate-putamen dopamine (DA), dihydroxyphenyl acetic acid (DOPAC), and homovanillic acid (HVA) concentrations were increased by 53%, 57%, and 30% (p < 0.001), respectively, in iron-deficient rats in samples collected over a 4-h period. While diminished numbers of D2 receptors have been previously reported, the present findings suggest an additional defect in monoamine uptake and catabolism.

Characterization of dopamine transporter and locomotor effects of cocaine, GBR 12909, epidepride, and SCH 23390 in C57BL and DBA mice

C57BL/6 and DBA/2 mice were used to examine genetic differences in locomotor activating effects of acute cocaine administration and to determine whether differences were mediated by dopaminergic systems. C57BL/6 mice were less activated than DBA/2 mice at 5 and 10 min after 10 and 15 mg/kg cocaine. HPLC analysis showed equivalent brain cocaine concentrations in the two strains at 5 and 10 min after 10, 15, or 20 mg/kg doses. The selective dopamine uptake inhibitor, GBR 12909, at 5 and 7.5 mg/kg, produced greater locomotor activation in DBA/2 mice than in C57BL/6 mice. However, binding studies with the selective dopamine uptake ligand [3H]GBR 12935, revealed no between-strain difference in Kd or Bmax in caudate putamen (CP) or nucleus accumbens (NA) membranes. Competition assays using unlabeled dopamine to compete for [3H]GBR 12935 binding in CP or NA membranes showed no between-strain difference by brain region. The specific D1 or D2 antagonists, SCH 23390 or epidepride, respectively, produced dose-dependent decreases in locomotor activity but there were no between-strain differences. However, epidepride, at a dose of 0.003 mg/kg, completely reversed cocaine-induced (15 mg/kg) activation in both strains. These findings show that C57BL/6 and DBA/2 mice differ in dopamine-related behaviors and suggest that dopaminergic processes may mediate genetic differences in cocaine sensitivity.

Effects of sulfite on the uptake and binding of benzo[a]pyrene diol epoxide in cultured murine respiratory epithelial cells

Sulfur dioxide (SO2) may act as a cocarcinogen with benzo[a]pyrene (BaP) in the respiratory tract. We have modeled this effect by examining the interactions of 7r,8t-dihydroxy-9t,10t-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BPDE) with sulfite, the physiological form of SO2, in a murine respiratory epithelial cell line (C10). We exposed C10 cells to [3H]-anti-BPDE and determined the effects of 1 and 10 mM sulfite on the uptake and subcellular localization of labeled products. Autoradiographic analysis showed that sulfite doubled the nuclear localization of anti-BPDE-derived materials after a 4-hr incubation period. The net nuclear localization of anti-BPDE-derived materials was not affected by sulfite during the first 60 min, but nuclear localization continued to increase in the sulfite-containing incubations throughout the 4-hr incubation period. Little increase in nuclear localization of anti-BPDE-derived material was noted in the incubations without sulfite after 60 min. Subcellular fractionation was performed to determine the amount of label associated with cytosolic and nuclear fractions and to determine covalent binding to protein and DNA. Sulfite produced a modest increase in the amount of [3H]-anti-BPDE-derived products bound to protein; however, binding to nuclear DNA increased by more than 200% with 10 mM sulfite. Analysis of the supernatants from the cytosolic and nuclear fractions of cells exposed to anti-BPDE and sulfite demonstrated the presence of 7r,8t,9t-trihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene-10c-su lfonate (BPT-10-sulfonate). [3H]-BPT-10-sulfonate was unable to enter C10 cells, suggesting that it is formed intracellularly.(ABSTRACT TRUNCATED AT 250 WORDS)

Synovial sarcoma: MR imaging findings in 34 patients

OBJECTIVE

MR imaging is considered the procedure of choice for detecting and staging soft-tissue tumors. Its ability to show differences between benign and malignant soft-tissue tumors and its usefulness in suggesting a specific histologic diagnosis remain controversial. We studied the MR features of synovial sarcoma in 34 patients to determine if these tumors have specific MR findings that can be used to suggest the diagnosis.

MATERIALS AND METHODS

MR imaging studies of 34 patients with synovial sarcoma were collected from two institutions and studied to determine the following characteristics of the tumor: size, shape, location, signal intensity and homogeneity, margin definition, presence of hemorrhage, and relationships to adjacent structures. These findings were then correlated with pathologic findings.

RESULTS

The tumors tended to be deep, large (85% were > or = 5 cm in diameter), and located in the extremities with epicenters close to joints (63% within 7 cm of a joint). The lesions were usually inhomogeneous on T2-weighted images (82%) and clearly delineated from surrounding tissues (91%). Forty-four percent had high signal consistent with hemorrhage on both T1- and T2-weighted images. Fluid-fluid levels, best visualized on T2-weighted images, were present in 18% of patients. Thirty-five percent of the lesions had areas that were hyper-, iso-, and hypointense relative to fat on T2-weighted images, constituting a triple signal intensity. The tumors frequently involved adjacent bone, with 71% invading, eroding, or touching bone. No association of pathologic subtypes with specific imaging findings was noted.

CONCLUSION

Our results show a spectrum of MR imaging findings in synovial sarcoma. Nevertheless, the results suggest that synovial sarcoma should be considered when MR images show a relatively well-defined but inhomogeneous hemorrhagic lesion near a joint and in contact with bone. Fluid-fluid levels and areas hyper-, hypo-, and isointense relative to fat (triple signal) on T2-weighted sequences support the diagnosis.

Strain and housing affect cocaine self-selection and open-field locomotor activity in mice

We recently conducted an experiment to investigate the possible cooperation between genetic makeup and differential housing on cocaine self-administration in male and female C57BL/6J and DBA/2J mice. Cocaine self-selection was measured in a two-choice test with one choice being cocaine-HCl solution of 40 mg% in tap water and the other choice being plain tap water. Housing conditions began at weaning (21-23 days of age) and consisted of group housed (GH) with 2-3 mice per cage, and isolated housed (IH) with 1 mouse per cage. The results of this study revealed overall strain, sex and housing differences, with C57BL/6Js consuming more cocaine solution than DBA/2J subjects, females consuming more cocaine solution than males, and group housed consuming more than isolate housed subjects. In a second study, the effect of differential housing on open-field locomotor activity was investigated. Testing was conducted on two consecutive days, with subjects receiving an IP injection of saline on day 1, and 15 mg/kg cocaine HCl on day 2. Four behaviors were recorded, including: total distance, nosepokes, stereotypy, and margin time. Overall, the results revealed significant strain differences for stereotypy and nosepokes, and males were found to be more activated by cocaine than females. Additionally, DBA males tended to be differentially affected by housing condition, with IH showing suppressed locomotor activity as compared to GH subjects. Last, significant strain by housing interactions occurred in nosepokes and stereotypy time.

Pharmacogenetics of cocaine: I. Locomotor activity and self-selection

We investigated the effects of cocaine on multiple activity measures and cocaine self-selection in C57BL/6Ibg and DBA/2Ibg mice. Male mice were tested in an automated activity monitor at three doses of cocaine, 5, 15 and 30 mg kg-1. Activity measures included locomotion, rearings, stereotyped movements and wall-seeking. Testing was conducted on 2 days with saline injection, i.p. on day one and cocaine i.p. injected on day two. We also tested other mice of both strains for cocaine ingestion in a two-choice test, pairing tap water with 40 mg% cocaine HCl in tap water. Two separate groups of mice received 15 or 30 mg kg-1 of cocaine i.p., killed at 5 min and brain cocaine levels were determined by HPLC. Cocaine produced dose-related increases in locomotion in both strains, with a delay in initial activation noticed at 30 mg kg-1 in C57s but not in DBAs. In DBAs, cocaine suppressed rearings and increased stereotyped movements while having no consistent effect on either behaviour in C57s. At all doses, cocaine produced moderate increases in proximity to the wall in DBAs and 30 mg kg-1 produced pronounced wall-seeking in C57s. At 15 and 30 mg kg-1 DBAs tended to have higher levels of cocaine in whole brain than did C57s. Finally, C57s consumed significantly more cocaine than did the DBAs.

Pharmacogenetics of cocaine: II. Mesocorticolimbic and striatal dopamine and cocaine receptors in C57BL and DBA mice

Studies were conducted to determine whether genetic differences in behavioural effects of cocaine in C57BL/6 and DBA/2 mice might be mediated by strain differences in dopamine and serotonin transporters and dopamine D1 and D2 receptors in specific brain regions. Binding characteristics of [3H]CFT, a cocaine analogue, in the presence of either GBR12909, a dopamine uptake blocker or fluoxetine, a serotonin uptake blocker and binding of [3H]-paroxetine, a specific serotonin uptake receptor antagonist, were evaluated. We observed regional differences in [3H]CFT binding parameters in the presence of GBR12909 or fluoxetine, but no strain differences by brain region were observed. There were no differences in [3H]paroxetine binding characteristics between corresponding brain regions from C57BL and DBA/2 mice. The D1 antagonist, [3H]SCH23390 and the D2 ligands [3H]sulpiride or [125I]epidepride were used to determine dopamine receptor characteristics. Regional differences were found in [3H]SCH23390 and [3H]sulpiride, with higher affinities and lower densities in frontal cortex compared to striatum; with no differences in [3H]SCH23390 binding in corresponding tissues from C57BL and DBA/2 brains. There were strain-related differences in [3H]sulpiride and in [3H]epidepride binding in striatal membranes with higher densities in C57BL than in DBA/2. Our findings suggest striatal D2 receptor differences are possibly involved in genetic differences in cocaine-related behaviours.

Brain iron: location and function

This review has a focus on the distribution and function of iron in human brain and appropriate animal models. Data are presented on the consequences of abnormalities of iron status with regard to neural development, neurotransmitter metabolism, and cognition.

Genetic-based differences in neurotensin levels and receptors in brains of LS x SS mice

Levels of endogenous neurotensin (NT-IR) in the LS x SS RI strains differed by 3.0-, 4.7-, 5.4-, and 6.9-fold in the ventral midbrain (VMB), hypothalamus (HY), nucleus accumbens (NA), and caudate putamen (CP), respectively. Frequency distributions and estimates of the number of genes indicate that differences in NT-IR are polygenically influenced. The NT-IR levels in NA and CP were significantly correlated, but levels in the VMB did not correlate with those in the NA or CP. Specific binding to either low (NTL)- or high (NTH)-affinity receptors as measured in the absence or presence of levocabastine differed significantly in brain regions from among LS X SS mouse strains. Results indicate a polygenic influence mediating the differences in receptor densities and suggest differences in genetic regulation of NTL and NTH receptors.

Iron in the brain

The location and function of iron in the central nervous system are reviewed with particular emphasis on human biology. Iron is distributed to different cell types in the brain in a heterogeneous fashion through the action of transferrin, transferrin receptors, and the metabolic needs of those cells. The function of this iron and its storage is documented in states of growth and development as well as during pathological states associated with aging. The information relating this biology to current observations of attention deficits in iron-deficient humans is also reviewed.

Inhibitor-induced conformational change in cytochrome P-450CAM

The X-ray crystal structures of cytochrome P-450CAM complexed with both enantiomers of a chiral, multifunctional inhibitor have been refined to R-factors of 21.0% [(+)-enantiomer] and 19.6% [(-)-enantiomer] at approximately 2.1-A resolution. Binding of either enantiomer, both considerably larger than the natural substrate camphor, results in similar, dramatic structural changes in the enzyme. In contrast to all previous P-450CAM crystallographic structures, the Tyr96 side chain is not pointing "down" toward the heme but is rather directed "up" into the proposed substrate access channel. This conformational change is accompanied by the displacement of the Phe193 side chain out into the solvent at the enzyme surface. These changes are consistent with the assignment of this region of the enzyme as the access channel [Poulos et al. (1986) Biochemistry 25, 5314-5322] and suggest that several aromatic residues lining the channel may be involved in substrate recognition and channeling to the active site. The cation usually observed coordinated to the Tyr96 carbonyl oxygen is missing in the presence of the (+)-enantiomer but is present with the (-)-enantiomer. The Phe87 side chain, located near the inhibitor binding site, adopts different orientations depending upon which enantiomer is bound. Finally, electron density reveals that although the inhibitor enantiomers were dichlorinated as provided, when bound to P-450CAM the chlorine atoms are present at only 0-20% occupancy, probably reflecting selective binding of impurities in the samples. Coordinates of these inhibited P-450CAM complexes have been deposited in the Brookhaven Protein Data Bank [Bernstein et al. (1977) J. Mol. Biol. 112, 535-542].

Genetic correlations among ethanol-related behaviors and neurotensin receptors in long sleep (LS) x short sleep (SS) recombinant inbred strains of mice

Studies were designed to examine the hypothesis that genetic based differences in sensitivity to several behavioral effects of ethanol are mediated, in part, by shared genes and that some of ethanol's actions are mediated by brain neurotensinergic processes. In these studies we have used recombinant inbred (RI) strains of mice derived from Long Sleep (LS/Ibg) and Short Sleep (SS/Ibg) lines of mice. The LS and SS mice were selectively bred to differ in hypnotic sensitivity but also differ in hypothermia and locomotor effects of ethanol. Therefore LS x SS RI strains were used to answer the question whether there are shared genetic influences on these diverse ethanol actions. Moreover, since the LS and SS mice were found to differ in neurotensin (NT) receptor densities in various brain regions, the LS x SS RI strains were used to determine associations between NT receptor densities and ethanol actions. The results showed a significant genetic correlation (r = .38) between hypnotic sensitivity and low-dose locomotor effects of ethanol and indicated multigenetic influences, with estimates of seven, four and three genes being responsible for mediating differences in hypnotic, hypothermic, and locomotor effects of ethanol, respectively. The findings are consistent with one or more genes having pleiotropic effects on these ethanol actions.

Hepatocyte ultrastructure following exposure to aroclors and pure polychlorinated biphenyls

Three agriculturally important minor species, the goat, rabbit, and duck, were exposed to various subclinical levels of pure polychlorinated biphenyls (PCBs) and/or PCB mixtures (Aroclors) for short periods of time. Upon sacrifice, liver samples were prepared for ultrastructural observation. Regardless of species, hepatocytes displayed qualitatively similar morphological responses to PCB exposure. At lower exposure levels, cellular changes included increased density of mitochondrial matrix and proliferation of endoplasmic reticulum. At higher exposure levels, degradative changes such as cytoplasmic loss and peripheralization of cytoplasm and organelles became more obvious. When compared quantitatively, it was obvious that goats were much more sensitive to PCB exposure than either rabbits or ducks. Goats showed extensive hepatocyte degradation (cytoplasmic and nucleoplasmic leaching) at exposures of 2 mg/kg body weight of Aroclor 1254. Such species-related differences in response to chlorinated biphenyls cautions against the use of single species animal models in xenobiotic exposure studies.

Speculations on the substrate structure-activity relationship (SSAR) of cytochrome P450 enzymes

This brief review attempts to define the SSAR of two families of cytochrome P450. With P4502D catalytic competence is achieved by tight ionic binding which gives the enzyme high regioselectivity. In contrast P4503A achieves catalytic competence by a flexible binding site relying on hydrophobic forces that allow chemically vulnerable sites to be the principal sites of metabolism. In general, the different binding mechanism should be reflected in the enzyme, such that substrates of P4502D should have lower Km values than substrates of P4503A. Thus, routes of metabolism catalysed by P4502D may be saturated at substrate concentrations lower than routes catalysed by P4503A. The apparent differences between P4502D and P4503A in terms of substrate specificity bring into question what relationships govern other families of cytochrome P450. Our analysis of data suggests that the other principal form involved, generally, in the metabolism of pharmaceuticals in humans is P4502C9 (possibly 2C8 and 2C10). The enzyme is responsible for the metabolism of phenytoin, tolbutamide, tienilic acid [4], naproxen, ibuprofen, diclofenac [38], the 7-hydroxylation of S-warfarin [39] and the 7-hydroxylation of delta 1-tetrahydrocannabinol [40]. These compounds all have areas of strong hydrogen bond [4] forming potential (Fig. 8), all distanced 5-10A from the site of metabolism. Moreover the carboxylic acid function of naproxen, ibuprofen and diclofenac (pKa 4.5) and the sulfonylurea of tolbutamide (pKa 5.4) render the compounds ionized at physiological pH. The ionised group is positioned 7-11A from the site of metabolism. It is likely, therefore, that hydrogen bonding and possibly ion-pair interactions play a major role in determining the SSAR of the P4502C isoenzymes. These interactions would suggest that the P4502C enzymes are analogous to P4502D rather than P4503A. In this regard it is noteworthy that P4502C9 is selectively and potently inhibited by sulfaphenazole (IC50 of 0.6 microM), a compound that is structurally related (Fig. 8) to the substrates in terms of potential hydrogen bonding regions [4, 41]. Simplistically we suggest that the SSAR of the various P450 enzymes ranges from the highly selective enzymes dealing with endogenous substrates, through the enzymes metabolising exogenous substrates with narrow substrate structure requirements such as P4502D to P4503A with its broad substrate structure range. It would seem logical that animals and humans would evolve such combinations of isoenzymes to deal with the vast array of exogenous xenobiotics.

Chronic ethanol consumption produces genotype-dependent tolerance to ethanol in LS/Ibg and SS/Ibg mice

It is well known that chronic ethanol administration produces tolerance to the sedative-hypnotic and hypothermic effects as well as low-dose locomotor inhibitory effects of ethanol. We report herein characterization of a convenient method of producing genotype-dependent functional tolerance to ethanol-induced locomotor inhibition. Mice, LS/Ibg (LS) and SS/Ibg (SS), which differ markedly in acute effects of ethanol on locomotor activity, hypothermia, and hypnotic sensitivity, were required to consume solutions of ethanol in water as the sole source of liquid. Mice were provided lab chow ad lib. and the following regimen of ethanol in water, v/v: 10% for 4 days, 15% for 4 days, 20% for 7 days, followed by 15% for periods longer than 2 weeks. Control animals received water only or were pair-fed sucrose (isocaloric with ethanol) solutions plus lab chow; both control and ethanol-consuming (15 g ethanol/kg/24 h) mice maintained similar body weights for up to 4 weeks. Blood ethanol concentrations from 10-200 mg% were obtained during a 12 L:12 D cycle. At 6 h following withdrawal, LS and SS mice showed differential dose-dependent tolerance to locomotor inhibitory effects of ethanol. However, low-dose locomotor activation was unaltered in either line of mice, and results indicate that an apparent sensitization in SS mice is secondary to development of tolerance to locomotor inhibition. Maximum tolerance to locomotor inhibition was observed after 2 weeks of chronic ethanol consumption, with responses returning to control values within 1-2 weeks after withdrawal. Rates of acquisition of tolerance were similar in LS and SS mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Paradoxical effects of nitrous oxide on human memory

Using the method of adjusted learning, subjects learned number-noun pairs while breathing either placebo or 30% nitrous oxide. Subjects breathing nitrous oxide required more acquisition trials to attain a learning criterion than did subjects breathing placebo. Two weeks later, half of the subjects from each group were administered either placebo or nitrous oxide and were asked to recall the noun that had accompanied each number cue. Results showed that: 1) nitrous oxide inhalation can decrease the accessibility of to-be-recalled material and 2) nitrous oxide administered during the acquisition of material can paradoxically improved the recall of that material 2 weeks later. The additional number of acquisition trials subjects received during nitrous oxide inhalation could potentially account for this paradoxical enhancement of delayed recall; however, correlational analyses suggest this was not the case. No evidence for any state-dependent effects of nitrous oxide on cued recall were found.

Cocaine actions, brain levels and receptors in selected lines of mice

The effects of cocaine (15 mg/kg IP) versus IP saline on open-field behaviors were evaluated using a crossover design in long-sleep (LS) and short-sleep (SS) mice. Under treatment order 1, mice received saline injection on day 1 followed 24 h later by cocaine (saline-cocaine, S-C). Under treatment order 2, animals received cocaine on day 1 and saline on day 2 (cocaine-saline, C-S). Immediately following injection, animals were placed into an automated open-field apparatus with behavioral samples taken at 5-min intervals for 30 min. The behaviors measured were distance traveled, stereotypy and time spent in proximity to the margins of the test apparatus (thigmotaxis). Cocaine increased locomotor activity in both lines of mice, with S-C producing more pronounced initial activation than C-S in LS mice. Compared to S-C, C-S also increased thigmotaxis, an effect more pronounced in SS mice. In a separate experiment, brain cocaine levels were measured in brains of adapted and nonadapted LS and SS mice 5 min following injection of 15 mg/kg cocaine. Regardless of order, SS mice had significantly higher brain cocaine levels than did LS mice. Mazindol and cocaine binding studies in the forebrain indicated higher Bmax values for both ligands in LS compared to SS mice. The results of this study indicate that genetically based differences in cocaine receptors as well as treatment order contribute to behavioral actions of cocaine.

Regional characterization of brain neurotensin receptor subtypes in LS and SS mice

Neurotensin (NT) receptor subtypes were investigated in nine brain regions from long sleep (LS) and short sleep (SS) mice that were selectively bred for differences in sensitivity to ethanol. Differences in NT receptor densities may mediate, in part, genetically selected differences in ethanol sensitivity between the two lines of mice. The use of [3H] NT at concentrations from 0.02 to 20 nM yielded biphasic binding isotherms as revealed by Scatchard analysis. Membranes from LS ventral midbrain yielded dissociation constants (KD values) of 0.34 and 3.85 nM for the high (NTH) and low (NTL) affinity components, respectively. SS membranes displayed similar KD values, however the maximum number of binding sites (Bmax) for both receptor subtypes were significantly greater in SS than in LS membranes (46.7 vs. 71.5 fmol/mg protein for NTH and 170.2 vs. 208.2 fmol/mg protein for NTL). Using levocabastine, and H1 antagonist with selectivity for NTL, characterization of NTH and NTL binding in nine brain regions was performed. In general, membranes from each brain region of SS mice had higher densities than LS for both receptor subtypes. Significant differences for the total density of receptors and NTL were found in entorhinal cortex, nucleus accumbens, hippocampus, and ventral midbrain. The only region to differ in NTH was the ventral midbrain. Competition experiments using various NT fragments to compete for NTH binding showed the C-terminal amino acids to be essential for binding. The order of potency was NT1-13 = NT8-13 greater than Neuromedin N greater than NT1-8 = NT1-11.

Expression of the glucocorticoid receptor and K-ras genes in urethan-induced mouse lung tumors and transformed cell lines

Glucocorticoids influence cell proliferation and differentiation in the lung. We examined the expression of the glucocorticoid receptor (GR) gene in urethan-induced mouse lung tumors and transformed lung cell lines to determine whether any altered responsiveness to these steroids is involved in the neoplastic development of some lung tumors. We find that a GR mRNA of similar size and amount is expressed in both normal lung and urethan-induced lung tumors. The K-ras gene is activated in urethan-induced lung adenomas and transformed lung cell lines. Both alveolar and papillary lung adenomas express slightly elevated levels of K-ras mRNA and similar levels of H-ras mRNA, but variable levels of c-myc mRNA, GR and K-ras mRNAs are concurrently expressed in a cyclic manner during the proliferation of nontransformed C10 and transformed A5 lung cell lines. Treatment of the C10 cells with dexamethasone (Dex) results in the inhibition of cell proliferation and the down-regulation of both the GR and K-ras mRNA. Dex treatment also down-regulated GR mRNA levels in A5 and LM2 cells, but no inhibitory effect was observed on K-ras mRNA levels or cell proliferation. These results suggest that glucocorticoids can inhibit K-ras expression in nontransformed lung cells. Although transformed lung cells respond to the steroid by down-regulation of the GR, the presence of an activated K-ras allele may override the inhibitory effects of these hormones on cell proliferation.

Metabolism in the rat of a model xenobiotic plant metabolite S-benzyl-N-malonyl-L-cysteine

1. The metabolism of a model xenobiotic plant metabolite S-benzyl-N-malonyl-L-cysteine (BMC) administered to rat at 10 mg/kg has been studied using a combination of radio-t.l.c. and h.p.l.c. 2. The major route of excretion for the administered 14C was via the urine (79% in 3 days). 3. The major metabolite was hippuric acid. The extent of biotransformation of BMC indicated the lability of the N-malonyl bond whose hydrolytic removal initiated a metabolic sequence which involved the action of C-S lyase to produce benzyl thiol. 4. A comparison of the findings from this study with those from experiments with N-acetyl-S-benzyl-L-cysteine and S-benzyl-L-cysteine is made to support the metabolic pathway proposed.

Further characterization of LSxSS recombinant inbred strains of mice: activating and hypothermic effects of ethanol

Lines of mice selected for differential initial sensitivity to the anesthetic effects of ethanol also differ in their locomotor responses to lower doses of ethanol. Sixteen recombinant inbred strains of mice derived from long-sleep (LS) and short-sleep (SS) selected lines as well as inbred LS and SS mice were used in a genetic correlational study to investigate possible associations between high-dose and low-dose indices of initial sensitivity to ethanol. Measurements of high-dose (4.1 g/kg) effects of ethanol were hypothermia, sleep time, and blood ethanol content at regaining of righting response, and the index of low-dose (1.875 g/kg) sensitivity was distance traveled during a 5-min period immediately following intraperitoneal injection with ethanol. The results indicated wide genetic variation in hypothermia and ethanol-induced locomotor activation in a manner consistent with polygenic influence. Furthermore, correlations between low-dose locomotor activity and hypnotic dose effects tended to be low and nonsignificant, indicating independence of inherited mechanisms underlying high- and low-dose ethanol sensitivity.

Low doses of ethanol reduce neurotensin levels in discrete brain regions from LS/Ibg and SS/Ibg mice

Studies were designed to examine the previously proposed hypothesis that some of the pharmacological actions of ethanol are mediated by neurotensinergic processes. Neurotensin-immunoreactivity (NT-ir) was extracted from various brain regions and shown by high performance liquid chromatography to possess the same retention time as authentic bovine NT1-13. The highest levels of NT-ir were observed in the hypothalamus with intermediate levels in the midbrain and striatum and lowest levels in the frontal cortex. Levels of NT-ir were higher in hypothalamus and midbrain from long-sleep (LS) than from short-sleep (SS) mice. Ethanol, in vivo, produced a dose-dependent decrease in NT-ir in several brain regions; low doses, 1.5 to 3.0 g/kg, but not high doses, 4.1 g/kg, of ethanol significantly decreased NT-ir in hypothalamus, midbrain, and striatum of LS and SS mice. Levels of NT-ir in the frontal cortex were not altered by ethanol administration. Ethanol-induced decreases in NT-ir were of rapid onset with a maximum decrease in 5 min after intraperitoneal (i.p.) injection, and they were of long duration with levels remaining depressed for 4 hr. These findings show that subhypnotic, intoxicating doses of ethanol enhance NT release, in vivo, and support the hypothesis that some of ethanol's actions are mediated by neurotensinergic systems.

Isolate housing alters ethanol sensitivity in long-sleep and short-sleep mice

Beginning at 45 days of age, male long-sleep (LS) and short-sleep (SS) mice were placed into individual cages for 21-22 days. Control animals were group-housed for the same amount of time. At 65-66 days of age, animals were given anesthetic doses of ethanol, IP. Measures taken were sleep time, body temperature at 30 and 60 minutes postinjection and blood ethanol content (BEC) at regain of righting response. Compared to the same measures in group-housed animals, sleep times and hypothermia were attenuated in isolate-housed LS and SS mice. Isolate housing resulted in a 15% increase, compared to levels observed in group-housed animals, in BEC at regain of righting in LS; there was no significant difference in BEC in SS mice. The results indicated an isolation-related decrease in sensitivity to the anesthetic effects of ethanol in LS; the effect of isolation in SS may be an increased clearance rate of ethanol.

Synthesis and biological evaluation of some phosphate triester derivatives of the anti-cancer drug araC

A number of novel phosphate triester derivatives of the anti-cancer nucleoside analogue araC have been prepared by a rapid 2-step procedure, not necessitating prior sugar protection. Spectroscopic and lipophilicity data have been collected on these compounds. An in vitro assay indicated inhibition of thymidine incorporation by mammalian epithelial cells, by each of these compounds, in the range 3-300 microM. Moreover, the degree of inhibition showed a close correlation to chemical structure; in particular, there was a clear relationship between inhibition of thymidine incorporation and log(P). These results are consistent with cellular penetration by the intact phosphate triesters and intracellular action by an unspecified mechanism. Triethyl phosphate is inactive under the conditions of the test.

Comparison of neurotensin levels, receptors and actions in LS/Ibg and SS/Ibg mice

Neurotensin (NT), injected centrally, markedly enhances sensitivity to ethanol-induced anesthesia in SS but not in LS mice (4). Since LS and SS mice were bred selectively for differential sensitivity to ethanol, these findings suggest that neurotensinergic neuronal processes mediate some of ethanol's actions and that LS and SS mice might differ genetically in neurotensinergic systems. Indeed, in biochemical studies it was shown that LS and SS mice differ in NT-like immunoreactivity in specific brain regions, i.e., hypothalamus, and in NT receptor densities (Bmax) in frontal cortex and striatum. In other experiments LS and SS mice differed in behavioral responses to centrally administered NT. Intracerebroventricular (ICV) administration of NT produced dose-dependent changes in motor activity, hypothermia, and analgesia in both LS and SS mice. SS mice appeared to be more sensitive than LS to NT-induced analgesia but not hypothermia. Neurotensin increased or decreased locomotor activity in both SS and LS mice following intraventral tegmental area or ICV administration, respectively. The results indicate that LS and SS mice, which were selectively bred for differences in ethanol sensitivity, differ genetically in NT concentrations, receptor densities in specific brain regions, and in some receptor-mediated behavioral responses to NT.

Central muscarinic cholinergic influences on ethanol sensitivity in long-sleep and short-sleep mice

Sensitivity to the hypnotic effects of ethanol was increased selectively by central administration of muscarinic agonists. Carbachol or oxotremorine, but not nicotine, i.c.v., enhanced hypnotic sensitivity to ethanol markedly, as measured by blood ethanol concentration at loss or righting response, in short-sleep (SS) but not long-sleep (LS) mice. Likewise, the acetylcholinesterase inhibitor, neostigmine, i.c.v., differentially enhanced hypnotic sensitivity to ethanol in these mouse lines. LS and SS mice were equally sensitive to the hypothermic effects of carbachol, neostigmine or oxotremorine i.c.v. The muscarinic antagonists, atropine or pirenzepine, i.c.v., were without effect on ethanol sensitivity, but these compounds antagonized muscarinic agonist-enhanced ethanol sensitivity in SS mice effectively. Pirenzepine, and M1 selective antagonist, produced a parallel shift in the oxotremorine dose-response curve, indicating that the enhanced hypnotic sensitivity to ethanol may be due to interaction of oxotremorine with M1 muscarinic receptors. This possibility was supported by the finding that atropine and pirenzepine which are known to have comparable affinities for M1 but not M2 receptors, had comparable potencies in antagonizing the action of oxotremorine or neostigmine. The results suggest that LS and SS mice differ genetically in neuronal processes activated by specific muscarinic agonists and are consistent with the hypotheses that ethanol acts in part via membrane receptor coupling to intracellular processes known to mobilize intracellular Ca++.

A comparison of the metabolic fate of phenol, phenyl glucoside and phenyl 6-O-malonyl-glucoside in the rat

The metabolic fates of 14C-phenol and its model plant conjugates 14C-phenyl glucoside and 14C-phenyl 6-O-malonyl-glucoside have been compared following equimolar oral dosing to rats (1.2 mg phenol/kg). Rapid excretion of radioactivity in the urine (at least 80% within 24 h) was observed with each compound. Phenol was eliminated as expected mainly as phenyl sulphate (68%) and partly as phenyl glucuronide (12%). The excretion profile for phenyl malonyl-glucoside was very similar to that of phenol, with the exception that small amounts of phenyl glucoside and phenyl malonyl-glucoside were excreted. In contrast, a major part of the dose of phenyl glucoside was eliminated unchanged. The value of metabolism studies in the assessment of the toxicology of xenobiotic metabolites derived from plants is discussed.

Differential immune response in two handled inbred strains of mice

C57BL/10J and BALB/cJ mice, outfostered at birth to C3H/2Ibg dams were subjected to handling on days 1 through 20 of life. Their plaque forming cell (PFC) response to sheep red blood cells as adults on day 5 post-immunization was compared to the PFC response in non-handled control mice. The PFC response of handled C57BL/10J mice was significantly suppressed compared to the PFC response in non-handled mice while the response of the handled and non-handled BALB/cJ mice was not significantly different.

Spontaneous hemothorax in a patient with Osler-Weber-Rendu disease

We have reported a case of spontaneous hemothorax as a rare complication of Osler-Weber-Rendu disease (hereditary hemorrhagic telangiectasia). Because of the possibility of confusion with pulmonary infarction and its attendant treatment with anticoagulants, physicians should be aware of possible hemothorax in Osler-Weber-Rendu disease.

A pharmacogenetic analysis of the effects of tetrahydrocannabinol (delta 9THC) on brain gamma glutamyl transpeptidase

The effects of oral administration of (-)delta 9 Trans-Tetrahydrocannabinol (THC) on the membrane bound enzyme, gamma-glutamyl transpeptidase (gamma-GTP) was studied. Adult male mice were given an oral dose of THC on each of 5 consecutive days in a vehicle of sesame oil, coconut oil and tween. The dosage ranged from 2.5 to 10 mg/kg. The animals were decapitated and the brains dissected into eight regions. Each brain region was homogenized in Tris buffered saline and assayed for protein and gamma-GTP activity. The higher doses of THC produced higher levels of gamma-GTP activity in the brain regions studied.

The influence of infantile handling, age and strain on alcohol selection in mice

Male mice from three inbred strains (C57B1/10J, BALB/cJ and C3H/2lbg) were assigned to infantile handling or control conditions. In a cross-sectional developmental design, handled and control mice were tested for two-choice selection of 10% (v/v) ethanol vs. tap water at 60, 90 or 120 days of age. The volume of fluid consumed from both tubes was recorded for fifteen days. In 60 day old mice, handling produced a trend toward increased total fluid consumption in the C57 mice and a trend toward increased ethanol selection in the BALBs. In 90 day old mice, there were trends noted toward handling-related decreased fluid consumption in BALBs. Also noted was a trend toward handling related increased ethanol selection in C57 mice. In 120 day old mice, a handling-related increase in alcohol selection was noted in the C3H strain.

Effects of the maternal consumption of alcohol on alcohol selection in rats

The present study was undertaken to determine the effects of the maternal administration of alcohol on alcohol selection in the adult offspring. Female Wistar rats were pair-fed liquid diets containing either alcohol (6.7% or 4% v/v) or isocaloric carbohydrates starting on day 1 of gestation. The litters were culled to 6 and the pups placed with non-alcohol treated surrogate mothers until they were weaned. At 45 days of age all rats were tested for two-choice selection of 10% (v/v) ethanol vs. water. Consumption from both drinking tubes was recorded for 30 days and selection ratios for alcohol per total fluid volume were calculated. In all conditions a significant increase in alcohol selection was observed across the 30 day test period. These data indicate that prenatal exposure to alcohol may play a part in subsequent selection of alcohol, at least initially. However, the mother's alcohol treatment did not significantly influence the offspring's selection of alcohol over the 30 day test period. Alcohol selection by an individual may be, at least in part, determined by the mother's consumption of alcohol during gestation.

Stability of cefazolin sodium admixtures in plastic bags after thawing by microwave radiation

The effect on antibiotic stability of thawing, with microwave radiation, cefazolin sodium admixtures frozen in polyvinyl chloride minibags was studied. Two brands of cefazolin sodium (Ancef and Kefzol) were reconstituted and placed in 50-, 100- and 250-ml polyvinyl chloride minibags of 5% dextrose in water or 0.9% sodium chloride. The resulting solutions were assayed for antibiotic stability, using an agar disk diffusion technique, and for pH. The solutions were then stored at -20 degrees C for 48 hours, thawed to room temperature in a microwave oven, and kept at room temperature for four hours, after which they were reassayed for potency and pH. The results indicated that after the freeze-thaw process, the cefazolin sodium minibag admixtures retained at least 90% of their initial antimicrobial activity. The minimal pH changes could not be related to changes in antimicrobial activity, and no color changes could be detected visually. Using a microwave oven can greatly reduce thawing time of antibiotic admixtures. To maintain solution stability and prevent accidents, it is important to calibrate the oven, avoid solution overheating, and observe full precautions in oven operation.

Enhanced megakaryocyte repopulating ability of stem cells surviving 5-fluorouracil treatment

The effect of 5-fluorouracil treatment of donor mice on the capacity of transplanted bone marrow to produce megakaryocytes in the spleens of lethally irradiated recipients has been examined. At both 10 and 13 days after transplantation, the spleens of recipients of 5-fluorouracil treated bone marrow had significantly more megakarocytes per unit area of spleen section than recipients injected with an equivalent number of spleen colony forming units from normal bone marrow. It is suggested that such treatment may provide a sensitive in vivo system for the investigation of endogenous factors influencing megakaryocyte progenitor proliferation. The results are consistent with the concept of stem cells being heterogeneous with respect to self-renewal capacity.

Morphometric changes in an elasmobranch (Squalus acanthias) after preservation

Length, weight, and volume of eggs, embryos, and postembryonic spiny dogfish (Squalus acanthias) up to 83 cm long were differentially affected when frozen or kept in 5% formaldehyde solutions of different salinities. Deviations from measurements in the unpreserved condition were greater with longer periods of storage and larger fish size. Morphometric changes were similar to those for teleosts at small sizes, but less at larger sizes.

The interaction of delta9-tetrahydrocannabinol with cholinomimetic drugs in an agonist-antagonist paradigm

In rabbits, i.v. delta9-tetrahydrocannabinol (delta9-THC) at 0.5 mg/kg was challenged with i.v. arecoline (0.025 mg/kg), nicotine (0.02 mg/kg) or physostigmine (PHYSO, 0.05 mg/kg), and observations were made on quantified EEG and behavior. The cholinomimetics effectively reversed the cortical and hippocampal EEG alterations induced by delta9-THC. Arecoline and PHYSO temporarily reversed the behavioral-sedative effects of delta9-THC whereas the combination of delta9-THC with nicotine produced behavioral collapse preceded by behavioral disturbance.

Acute effects of morphine and chlorpromazine on the acquisition of shuttle box conditioned avoidance response

Morphine sulfate, 0.25-24.0 mg/kg, or chlorpromazine hydrochloride, 0.0625-4.0mg/kg were administered subcutaneously to naive rats 30 min prior to the start of massed-trials conditioned avoidance response (CAR) testing. The graded doses of both drugs were applied in each of three CAR task difficulty levels created by manipulation of the duration of conditioned and unconditioned stimuli, intertrial interval and shock intensity. Chlorpromazine, in a dose-related manner, caused a decrement in CAR acquisition in all tasks. Morphine, in comparison, produced a biphasic dose response. For a given task difficulty, low doses of morphine enhanced acquisition, whereas higher doses inhibited acquisition. With increasing task difficulty, relatively larger doses of morphine were required to inhibit or facilitate acquisition of CAR. These results emphasize the need to consider not only drug dosage levels, but also the interaction of task difficulty in the application of drugs in learning paradigms.