Smoking among Buddhist monks in Phnom Penh, Cambodia.
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Buddhism↗
Biomedical subjects
M T Smith
Publications and source records attributed to M T Smith.
Systemic coadministration of chloramphenicol with intravenous but not intracerebroventricular morphine markedly increases morphine antinociception and delays development of antinociceptive tolerance in rats.
Chloramphenicol, an in vitro inhibitor of the glucuronidation of morphine to its putative antianalgesic metabolite, morphine-3-glucuronide (M3G), was coadministered with morphine in adult male Sprague-Dawley rats to determine whether it inhibited the in vivo metabolism of morphine to M3G, thereby enhancing morphine antinociception and/or delaying the development of antinociceptive tolerance. Parenteral chloramphenicol was given acutely (3-h studies) or chronically (48-h studies). Morphine was administered by the i.v. or i.c.v. route. Control rats received chloramphenicol and/or vehicle. Antinociception was quantified using the hotplate latency test. Coadministration of chloramphenicol with i.v. but not i.cv. morphine increased the extent and duration of morphine antinociception by approximately 5.5-fold relative to rats that received i.v. morphine alone. Thus, the mechanism through which chloramphenicol enhances i.v. morphine antinociception in the rat does not directly involve supraspinal opioid receptors. Acutely, parenteral coadministration of chloramphenicol and morphine resulted in an approximately 75% increase in the mean area under the serum morphine concentration-time curve but for chronic dosing there was no significant change in this curve, indicating that factors other than morphine concentrations contribute significantly to antinociception. Antinociceptive tolerance to morphine developed more slowly in rats coadministered chloramphenicol, consistent with our proposal that in vivo inhibition of M3G formation would result in increased antinociception and delayed development of tolerance. However, our data also indicate that chloramphenicol inhibited the biliary secretion of M3G. Whether chloramphenicol altered the passage of M3G and morphine across the blood-brain barrier remains to be investigated.
Analgesics, Opioid↗
Hydroquinone, a benzene metabolite, increases the level of aneusomy of chromosomes 7 and 8 in human CD34-positive blood progenitor cells.
Benzene is an established human carcinogen, producing leukemia, hematotoxicity and perhaps lymphoma. Its carcinogenicity is most likely dependent upon its conversion to phenol and hydroquinone, the latter being oxidized to the highly toxic 1,4-benzoquinone in the bone marrow. Exposure of human lymphocytes and cell lines to hydroquinone has previously been shown to cause various forms of genetic damage, including aneusomy and the loss and gain of chromosomes. However, the target cells for leukemogenesis are the pluripotent stem cells or early progenitor cells which carry the CD34 antigen (CD34(+) cells). In this study, human cord blood, which is particularly rich in CD34(+) cells, was exposed to hydroquinone for 72 h in a medium that favored CD34(+) cell survival and growth. CD34(+) and CD34(-) cells were then isolated. Fluorescence in situ hybridization was employed to determine the level of aneusomy of chromosomes 7 and 8 in both cell types. CD34(+) cells were generally more susceptible to aneusomy induction by hydroquinone than CD34(-) cells. Increased trisomy and monosomy of chromosomes 7 and 8 were observed in CD34(+) cells (P(trend) < 0.001), whereas in CD34(-) cells only an increased level of monosomy 7 was detected (P(trend) = 0.002). Particularly striking effects of hydroquinone were observed in CD34(+) cells on monosomy 7 and trisomy 8, two common clonal aberrations found in myeloid leukemias, suggesting that these aneusomies produced by hydroquinone in CD34(+) cells play a role in benzene-induced leukemogenesis.
Aneuploidy↗
Incomplete, asymmetric, and route-dependent cross-tolerance between oxycodone and morphine in the Dark Agouti rat.
Our previous studies indicate that oxycodone is a putative kappa-opioid agonist, whereas morphine is a well documented micro-opioid agonist. Because there is limited information regarding the development of tolerance to oxycodone, this study was designed to 1) document the development of tolerance to the antinociceptive effects of chronically infused i.v. oxycodone relative to that for i. v. morphine and 2) quantify the degree of antinociceptive cross-tolerance between morphine and oxycodone in adult male Dark Agouti (DA) rats. Antinociceptive testing was performed using the tail-flick latency test. Complete antinociceptive tolerance was achieved in 48 to 84 h after chronic infusion of equi-antinociceptive doses of i.v. oxycodone (2.5 mg/24 h and 5 mg/24 h) and i.v. morphine (10 mg/24 h and 20 mg/24 h, respectively). Dose-response curves for bolus doses of i.v. and i.c.v. morphine and oxycodone were produced in naive, morphine-tolerant, and oxycodone-tolerant rats. Consistent with our previous findings that oxycodone and morphine produce their intrinsic antinociceptive effects through distinctly different opioid receptor populations, there was no discernible cross-tolerance when i.c.v. oxycodone was given to morphine-tolerant rats. Similarly, only a low degree of cross-tolerance (approximately 24%) was observed after i.v. oxycodone administration to morphine-tolerant rats. By contrast, both i.v. and i.c.v. morphine showed a high degree of cross-tolerance (approximately 71% and approximately 54%, respectively) in rats rendered tolerant to oxycodone. Taken together, these findings suggest that, after parenteral but not supraspinal administration, oxycodone is metabolized to a mu-opioid agonist metabolite, thereby explaining asymmetric and incomplete cross-tolerance between oxycodone and morphine.
Analgesics, Opioid↗
Radial capillary array electrophoresis microplate and scanner for high-performance nucleic acid analysis.
The design, fabrication, and operation of a radial capillary array electrophoresis microplate and scanner for high-throughput DNA analysis is presented. The microplate consists of a central common anode reservoir coupled to 96 separate microfabricated separation channels connected to sample injectors on the perimeter of the 10-cm-diameter wafer. Detection is accomplished by a laser-excited rotary confocal scanner with four color detection channels. Loading of 96 samples in parallel is achieved using a pressurized capillary array system. High-quality separations of 96 pBR322 restriction digest samples are achieved in < 120 s with the microplate system. The practical utility and multicolor detection capability is demonstrated by analyzing 96 methylenetetrahydrofolate reductase (MTHFR) alleles in parallel using a noncovalent 2-color staining method. This work establishes the feasibility of performing high-throughput genotyping separations with capillary array electrophoresis microplates.
Electrophoresis, Capillary↗
Polymorphisms in the methylenetetrahydrofolate reductase gene are associated with susceptibility to acute leukemia in adults.
Reduction of 5,10-methylenetetrahydrofolate (methyleneTHF), a donor for methylating dUMP to dTMP in DNA synthesis, to 5-methyltetrahydrofolate (methylTHF), the primary methyl donor for methionine synthesis, is catalyzed by 5,10-methylenetetrahydrofolate reductase (MTHFR). A common 677 C --> T polymorphism in the MTHFR gene results in thermolability and reduced MTHFR activity that decreases the pool of methylTHF and increases the pool of methyleneTHF. Recently, another polymorphism in MTHFR (1298 A --> C) has been identified that also results in diminished enzyme activity. We tested whether carriers of these variant alleles are protected from adult acute leukemia. We analyzed DNA from a case-control study in the United Kingdom of 308 adult acute leukemia patients and 491 age- and sex-matched controls. MTHFR variant alleles were determined by a PCR-restriction fragment length polymorphism assay. The MTHFR 677TT genotype was lower among 71 acute lymphocytic leukemia (ALL) cases compared with 114 controls, conferring a 4.3-fold decrease in risk of ALL [odds ratio (OR = 0.23; 95% CI = 0.06-0.81]. We observed a 3-fold reduction in risk of ALL in individuals with the MTHFR 1298AC polymorphism (OR = 0.33; 95% CI = 0.15-0.73) and a 14-fold decreased risk of ALL in those with the MTHFR 1298CC variant allele (OR = 0.07; 95% CI = 0.00-1.77). In acute myeloid leukemia, no significant difference in MTHFR 677 and 1298 genotype frequencies was observed between 237 cases and 377 controls. Individuals with the MTHFR 677TT, 1298AC, and 1298CC genotypes have a decreased risk of adult ALL, but not acute myeloid leukemia, which suggests that folate inadequacy may play a key role in the development of ALL.
Acute Disease↗
Prevalence of the inactivating 609C-->T polymorphism in the NAD(P)H:quinone oxidoreductase (NQO1) gene in patients with primary and therapy-related myeloid leukemia.
NAD(P)H:quinone oxidoreductase (NQO1) converts benzene-derived quinones to less toxic hydroquinones and has been implicated in benzene-associated hematotoxicity. A point mutation in codon 187 (Pro to Ser) results in complete loss of enzyme activity in homozygous subjects, whereas those with 2 wild-type alleles have normal activity. The frequency of homozygosity for the mutant allele among Caucasians and African Americans is 4% to 5% but is higher in Hispanics and Asians. Using an unambiguous polymerase chain reaction (PCR) method, we assayed nonmalignant lymphoblastoid cell lines derived from 104 patients with myeloid leukemias; 56 had therapy-related acute myeloid leukemia (t-AML), 30 had a primary myelodysplastic syndrome (MDS), 9 had AML de novo, and 9 had chronic myelogenous leukemia (CML). All patients had their leukemia cells karyotyped. Eleven percent of the t-AML patients were homozygous and 41% were heterozygous for the NQO1 polymorphism; these proportions were significantly higher than those expected in a population of the same ethnic mix (P =.036). Of the 45 leukemia patients who had clonal abnormalities of chromosomes 5 and/or 7, 7 (16%) were homozygous for the inactivating polymorphism, 17 (38%) were heterozygous, and 21 (47%) had 2 wild-type alleles for NQO1. Thus, NQO1 mutations were significantly increased compared with the expected proportions: 5%, 34%, and 61%, respectively (P =.002). An abnormal chromosome no. 5 or 7 was observed in 7 of 8 (88%) homozygotes, 17 of 45 (38%) heterozygotes, and 21 of 51 (41%) patients with 2 wild-type alleles. Among 33 patients with balanced translocations [14 involving bands 11q23 or 21q22, 10 with inv(16) or t(15;17), and 9 with t(9;22)], there were no homozygotes, 15 (45%) heterozygotes, and 18 (55%) with 2 wild-type alleles. Whereas fewer than 3 homozygotes were expected among the 56 t-AML patients, 6 were observed; 19 heterozygotes were expected, but 23 were observed. The gene frequency for the inactivating polymorphism (0. 31) was increased approximately 1.4-fold among the 56 t-AML patients. This increase was observed within each of the following overlapping cohorts of t-AML patients: the 43 who had received an alkylating agent, the 27 who had received a topoisomerase II inhibitor, and the 37 who had received any radiotherapy. Thus, the frequency of an inactivating polymorphism in NQO1 appears to be increased in this cohort of myeloid leukemias, especially among those with t-AML or an abnormality of chromosomes 5 and/or 7. Homozygotes and heterozygotes (who are at risk for treatment-induced mutation or loss of the remaining wild-type allele in their hematopoietic stem cells) may be particularly vulnerable to leukemogenic changes induced by carcinogens.
Alleles↗
Benzene, NQO1, and genetic susceptibility to cancer.
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Benzene↗
Site-directed mutants of RTP of Bacillus subtilis and the mechanism of replication fork arrest.
DNA replication fork arrest during the termination phase of chromosome replication in Bacillus subtilis is brought about by the replication terminator protein (RTP) bound to specific DNA terminator sequences (Ter sites) distributed throughout the terminus region. An attractive suggestion by others was that crucial to the functioning of the RTP-Ter complex is a specific interaction between RTP positioned on the DNA and the helicase associated with the approaching replication fork. In support of this was the behaviour of two site-directed mutants of RTP. They appeared to bind Ter DNA normally but were ineffective in fork arrest as ascertained by in vitro Escherichia coli DnaB helicase and replication assays. We describe here a system for assessing the fork-arrest behaviour of RTP mutants in a bona fide in vivo assay in B. subtilis. One of the previously studied mutants, RTP.Y33N, was non-functional in fork arrest in vivo, as predicted. But through extensive analyses, this RTP mutant was shown to be severely defective in binding to Ter DNA, contrary to expectation. Taken in conjunction with recent findings on the other mutant (RTP.E30K), it is concluded that there is as yet no substantive evidence from the behaviour of RTP mutants to support the RTP-helicase interaction model for fork arrest. In an extension of the present work on RTP.Y33N, we determined the dissociation rates of complexes formed by wild-type (wt) RTP and another RTP mutant with various terminator sequences. The functional wtRTP-TerI complex was quite stable (half-life of 182 minutes), reminiscent of the great stability of the E. coli Tus-Ter complex. More significant were the exceptional stabilities of complexes comprising wtRTP and an RTP double-mutant (E39K.R42Q) bound to some particular terminator sequences. From the measurement of in vivo fork-arrest activities of the various complexes, it is concluded that the stability (half-life) of the whole RTP-Ter complex is not the overriding determinant of arrest, and that the RTP-Ter complex must be actively disrupted, or RTP removed, by the action of the approaching replication fork.
Bacillus subtilis↗
Interparenchymal hemorrhagic neurocytoma: an atypical presentation of a rare CNS tumor.
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Brain Neoplasms↗
Achievement of simple mobility milestones after stroke.
OBJECTIVES: To observe the mobility outcomes of an inpatient population of stroke patients grouped according to the Oxfordshire Community Stroke Project classification. STUDY DESIGN: "Mobility milestones," standardized measures of functional movement, were used to examine mobility recovery. PARTICIPANTS: Two hundred thirty-eight stroke patients admitted to the Western General Hospital, Edinburgh. MAIN OUTCOME MEASURES: Times taken to achieve four mobility milestones: 1-minute sitting balance, 10-second standing balance, a 10-step walk, and a 10-meter walk. RESULTS: For all subjects the median times to achieve the milestones were as follows: 1-minute sitting balance, day of stroke; 10-second standing balance, 3 days; 10-step walk, 6 days; and a 10-meter walk, 9 days. Subjects sustaining a partial anterior circulation infarct, lacunar infarct, or posterior circulation infarct achieved the mobility milestones most rapidly and generally had a shorter hospital stay. CONCLUSIONS: A hierarchical pattern of recovery of mobility reflecting variation between subgroups was observed. Predicted timescales for recovery of mobility are suggested.
Achievement↗
Brain region-specific studies of the excitatory behavioral effects of morphine-3-glucuronide.
This study was designed to determine in rats whether morphine-3-glucuronide (M3G) produces its neuro-excitatory effects most potently in the ventral hippocampus (as has been reported previously for subanalgesic doses of opioid peptides). Guide cannulae were implanted into one of seven regions of the rat brain: lateral ventricle; ventral, CA1 and CA2-CA3 regions of the hippocampus; amygdala; striatum or cortex. After a 7 day recovery period, rats received intracerebral injections of (i) M3G (1.1 or 11 nmol) (ii) DADLE ([D-Ala2,D-Leu5]enkephalin), (45 nmol, positive controls) or (iii) vehicle (deionised water), and behavioral excitation was quantified over 80 min. High-dose M3G (11 nmol) evoked behavioral excitation in all brain regions but the onset, severity and duration of these effects varied considerably among brain regions. By contrast, low-dose M3G (1.1 nmol) evoked excitatory behaviors only when administered into the ventral hippocampus and the amygdala, with the most potent effects being observed in the ventral hippocampus. Prior administration of the nonselective opioid antagonists, naloxone and beta-funaltrexamine into the ventral hippocampus, markedly attenuated low-dose M3G's excitatory effects but did not significantly alter levels of excitation evoked by high-dose M3G. Naloxone given 10 min after M3G (1.1 or 11 nmol) did not significantly attenuate behavioral excitation. Thus, M3G's excitatory behavioral effects occur most potently in the ventral hippocampus as reported previously for subanalgesic doses of opioid peptides, and appear to be mediated through at least two mechanisms, one possibly involving excitatory opioid receptors and the other, non-opioid receptors.
Animals↗
Four new species in Lipomyces.
For new species in Lipomyces are described. In terms of nuclear genome comparison the genus Lipomyces comprises three species-clusters. A key to the nine species now assigned to the genus, is given. The delimitation of species by (i) rRNA nucleotide sequence analyses of the 18S and 25S subunits and (II) nDNA homology determinations, do not invariably lead to the recognition of congruent taxa. The family of the Lipomycetaceae, nevertheless provides an illuminative model for phylogenetic studies in terms of more appropriate ribosomal nucleotide sequence analyses of both its teleomorphic and anamorphic members.
Yeasts↗
Modulation of the toxicity and macromolecular binding of benzene metabolites by NAD(P)H:Quinone oxidoreductase in transfected HL-60 cells.
Benzene is oxidized in the liver to produce a series of hydroxylated metabolites, including hydroquinone and 1,2,4-benzenetriol. These metabolites are activated to toxic and genotoxic species in the bone marrow via oxidation by myeloperoxidase (MPO). NAD(P)H:quinone oxidoreductase (NQO1) is an enzyme capable of reducing the oxidized quinone metabolites and thereby potentially reducing their toxicities. We introduced the NQO1 gene into the HL-60 cell line to create a high MPO-, high NQO1-expressing cell line, and tested its response in assays of benzene metabolite toxicity. NQO1 expression reduced a class of hydroquinone- and benzenetriol-induced DNA adducts by 79-86%. The cytotoxicity and apoptosis caused by hydroquinone were modestly reduced, while protein binding was unchanged and the rate of glutathione depletion increased. NQO1's activity in reducing a class of benzene metabolite-induced DNA adducts may be related to its known activities in maintaining membrane-bound endogenous antioxidants in reduced form. Alternatively, NQO1 activity may prevent the formation of adducts which result from polymerized products of the quinones. In either case, this protection by NQO1 may be an important mechanism in the observation that a lack of NQO1 activity affords an increased risk of benzene poisoning in exposed individuals [Rothman, N., et al. (1997) Cancer Res. 57, 2839-2842].
Benzene↗
Enhancement of myeloid cell growth by benzene metabolites via the production of active oxygen species.
In low concentrations, benzene and its metabolite hydroquinone are known to have diverse biological effects on cells, including the synergistic stimulation with GM-CSF of hematopoietic colony formation in vitro, stimulation of granulocytic differentiation in vitro and in vivo, and general suppression of hematopoiesis in vivo. These chemicals are also known to be active in the induction of active oxygen species. We used several assays to determine the effects of benzene metabolites (hydroquinone, benzenetriol, benzoquinone) and active oxygen species (xanthine/xanthine oxidase) on cell growth and cell cycle kinetics of the human myeloid cell line HL-60. HL-60 cells treated with these chemicals for 2 h in PBS showed increased growth over untreated controls in a subsequent 18h growth period in complete media. Incorporation of 3H-thymidine was also increased proportionately by these treatments. Catalase treatment abrogated the increased cell growth of all chemicals, suggesting an oxidative mechanism for the effect of all treatments alike. Cell cycle kinetics assays showed that the growth increase was caused by an increased recruitment of cells from G0/G1 to S-phase for both hydroquinone and active oxygen, rather than a decrease in the length of the cell cycle. Benzene metabolite's enhancement of growth of myeloid cells through an active oxygen mechanism may be involved in a number of aspects of benzene toxicity, including enhanced granulocytic growth and differentiation, stimulation of GM-CSF-induced colony formation, apoptosis inhibition, and stimulation of progenitor cell mitogenesis in the bone marrow. These effects in sum may be involved in the benzene-induced "promotion" of a clonal cell population to the fully leukemic state.
Benzene↗
Intraarticular and periarticular opioid binding in inflamed tissue in experimental canine arthritis.
UNLABELLED: Small-dose (1 mg) intraarticular morphine has been used successfully in many studies to provide long-lasting analgesia after arthroscopic knee surgery. We used radioligand binding to determine whether these effects could be mediated by opioid binding sites in the joint, particularly after the induction of inflammation. Inflammation was induced by the injection of oleyl alcohol (20 microL) in sterile peanut oil (0.25 mL) into the left radiocarpal joint of 27 dogs, and the dogs were euthanized at 12 h. The articular and periarticular tissues from both treated and control joints were collected, and membranes were prepared for equilibrium binding assays. The density of specific opioid binding was markedly enhanced (P < 0.05) in homogenates prepared from the treated relative to those from the control joint. The binding affinities (KD values) for morphine and naloxone (mean +/- SEM) were approximately one one-hundredth (79 +/- 17 nM and 124 +/- 5.5 nM, respectively) that of the corresponding published affinities in brain tissue. However, the binding site densities were approximately one hundred times larger (Bmax = 1032 +/- 265 and 543 +/- 51 fmol/mg of protein) than the respective published values in brain tissue. These findings imply that the opioid binding sites, found in the inflamed articular and periarticular tissues in this study, are similar to those of putative mu 3-opioid binding sites that appear to be present on cultured thymocytes and in the airways of rats and humans. IMPLICATIONS: The high density of opioid binding sites found in inflamed canine joint tissue supports the clinical use of intraarticular opioids in the treatment of postoperative and chronic inflammatory joint pain.
Analgesics, Opioid↗
Malignant peripheral nerve sheath tumor of the prostate: a rare manifestion of neurofibromatosis type 1.
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Adult↗
Red-pigmented Candida albicans in patients with cystic fibrosis.
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Adult↗