Genetic variation in the 5q31 cytokine gene cluster confers susceptibility to Crohn disease

Linkage disequilibrium (LD) mapping provides a powerful method for fine-structure localization of rare disease genes, but has not yet been widely applied to common disease. We sought to design a systematic approach for LD mapping and apply it to the localization of a gene (IBD5) conferring susceptibility to Crohn disease. The key issues are: (i) to detect a significant LD signal (ii) to rigorously bound the critical region and (iii) to identify the causal genetic variant within this region. We previously mapped the IBD5 locus to a large region spanning 18 cM of chromosome 5q31 (P<10(-4)). Using dense genetic maps of microsatellite markers and single-nucleotide polymorphisms (SNPs) across the entire region, we found strong evidence of LD. We bound the region to a common haplotype spanning 250 kb that shows strong association with the disease (P< 2 x 10(-7)) and contains the cytokine gene cluster. This finding provides overwhelming evidence that a specific common haplotype of the cytokine region in 5q31 confers susceptibility to Crohn disease. However, genetic evidence alone is not sufficient to identify the causal mutation within this region, as strong LD across the region results in multiple SNPs having equivalent genetic evidence-each consistent with the expected properties of the IBD5 locus. These results have important implications for Crohn disease in particular and LD mapping in general.

Genomewide search in Canadian families with inflammatory bowel disease reveals two novel susceptibility loci

The chronic inflammatory bowel diseases (IBDs)-Crohn disease (CD) and ulcerative colitis (UC)-are idiopathic, inflammatory disorders of the gastrointestinal tract. These conditions have a peak incidence in early adulthood and a combined prevalence of approximately 100-200/100,000. Although the etiology of IBD is multifactorial, a significant genetic contribution to disease susceptibility is implied by epidemiological data revealing a sibling risk of approximately 35-fold for CD and approximately 15-fold for UC. To elucidate the genetic basis for these disorders, we undertook a genomewide scan in 158 Canadian sib-pair families and identified three regions of suggestive linkage (3p, 5q31-33, and 6p) and one region of significant linkage to 19p13 (LOD score 4.6). Higher-density mapping in the 5q31-q33 region revealed a locus of genomewide significance (LOD score 3.9) that contributes to CD susceptibility in families with early-onset disease. Both of these genomic regions contain numerous genes that are important to the immune and inflammatory systems and that provide good targets for future candidate-gene studies.

Characterization of the peptidergic afferent innervation of the stomach in the rat, mouse and guinea-pig

Retrograde tracing of the fluorescent marker, True Blue, has been used together with immunohistochemistry employing antibodies to substance P, calcitonin gene-related peptide, somatostatin, vasoactive intestinal polypeptide and morphine-modulating peptide to study the afferent innervation of the stomach in rat, mouse and guinea-pig. Up to 85% of spinal afferents to the stomach in all three species contained immunoreactive calcitonin gene-related peptide, and up to 50% contained substance P. In all three species less than 10% of vagal afferents to the stomach reacted with antibodies to calcitonin gene-related peptide, or substance P. Cacitonin gene-related peptide-immunoreactive fibres were found in the myenteric plexus, circular muscle and around submucosal blood vessels in the stomach. In the rat, removal of the coeliac ganglion, splanchnic nerve section, or capsaicin treatment virtually abolished calcitonin gene-related peptide immunoreactivity in the stomach. Capsaicin and splanchnic section also abolished the staining of immunoreactive calcitonin gene-related peptide fibres in the coeliac ganglion. The same treatments abolished substance P staining of fibres around submucosal blood vessels, but in the myenteric plexus and circular smooth muscle there were still abundant immunoreactive fibres, presumably arising from intrinsic cell bodies. No somatostatin-containing visceral afferents could be found, although somatostatin was localized to cell bodies in rat dorsal root ganglia. Immunoreactive vasoactive intestinal polypeptide-containing dorsal root ganglia neurons were not found; although antibodies to morphine-modulatory peptide revealed immunoreactive nerve cell bodies, we were unable to exclude the possibility that this result is attributable to cross reactivity with calcitonin gene-related peptide. These results provide direct evidence that calcitonin gene-related peptide is a marker for a major subset of visceral primary afferent neurons and suggest that this population of spinal afferents makes a major contribution to the total gastric content of calcitonin gene-related peptide.

The metabolism and disposition of hexachloro-1:3-butadiene in the rat and its relevance to nephrotoxicity

Following po administration of a nephrotoxic dose (200 mg/kg) of hexachloro-1:3-butadiene (HCBD) to male rats, the principal route of excretion was biliary, 17-20% of the dose being eliminated on each of the first 2 days. Fecal excretion over this period was less than 5% of the dose per day, suggesting enterohepatic recirculation of biliary metabolites. Urinary excretion was small, not exceeding 3.5% of the dose during any 24-hr period. The major biliary metabolite was a direct conjugate between glutathione and HCBD itself. The cysteinylglycine conjugate of HCBD has also been found in bile. Evidence was obtained to show that biliary metabolites of HCBD are reabsorbed and excreted via the kidneys. The glutathione conjugate, its mercapturic acid derivative, and bile containing HCBD metabolites were all nephrotoxic when dosed orally to rats. In common with HCBD, these metabolites caused localized damage to the kidney with minimal effects in the liver. Rats fitted with a biliary cannula were completely protected from kidney damage when dosed with HCBD, demonstrating that hepatic metabolites were solely responsible for the nephrotoxicity of this compound. It is proposed that the hepatic glutathione conjugate of HCBD was degraded to its equivalent cysteine conjugate which was cleaved by the renal cytosolic enzyme beta-lyase to give a toxic thiol which caused localized kidney damage. A urinary sulphenic acid metabolite of HCBD has been identified which is consistent with this hypothesis. The mode of activation of HCBD conjugates in the kidney is believed to be analogous to that proposed for S-(1,2-dichlorovinyl)-L-cysteine.

Recognition, clinical diagnosis and management of patients with primary antibody deficiencies: a systematic review

The primary purpose of this systematic review was to produce an evidence-based review of the literature as a means of informing current clinical practice in the recognition, diagnosis and management of patients with suspected primary antibody deficiency. Randomized controlled trials (RCTs) were identified from a search of MEDLINE, EMBASE, The Cochrane Library, DARE (CRD website) and CINAHL by combining the search strategies with The Cochrane Collaboration's validated RCT filter. In addition, other types of studies were identified in a separate search of MEDLINE and EMBASE. Patients at any age with recurrent infections, especially in the upper and lower respiratory tracts, should be investigated for possible antibody deficiency. Replacement therapy with immunoglobulin in primary antibody deficiencies increases life expectancy and reduces infection frequency and severity. Higher doses of immunoglobulin are associated with reduced infection frequency. Late diagnosis and delayed institution of immunoglobulin replacement therapy results in increased morbidity and mortality. A wide variety of organ-specific complications can occur in primary antibody deficiency syndromes, including respiratory, gastroenterological, hepatic, haematological, neurological, rheumatological and cutaneous. There is an increased risk of malignancy. Some of these complications appear to be related to diagnostic delay and inadequate therapy. High-quality controlled trial data on the therapy of these complications is generally lacking. The present study has identified a number of key areas for further research, but RCT data, while desirable, is not always obtained easily for rare conditions. Few data from registries or large case-series have been published in the past 5 years and a greater focus on international collaboration and pooling of data is needed.

Structure/activity studies of the nephrotoxic and mutagenic action of cysteine conjugates of chloro- and fluoroalkenes

The cysteine conjugates of the nephrotoxins hexachlorobutadiene (HCBD), tetrafluoroethylene (TFE) and hexafluoropropene (HFP), together with those of trichloroethylene and perchloroethylene, have been chemically synthesized and a relationship determined between their structures and their nephrotoxicity and mutagenicity in vitro. All of the conjugates had a marked effect on the uptake of both the organic anion p-aminohippuric acid (PAH) and the cation tetraethylammonium bromide (TEA) into rat kidney slices, suggesting activation of the conjugates in the slices to a toxic species which interferes with ion transport. This observation is consistent with the known nephrotoxicity of HCBD, TFE and HFP in vivo. Each of the conjugates was found to be metabolised by rat kidney slices and by semi-purified rat kidney beta-lyase to pyruvate, ammonia and an unidentified reactive metabolite. When semi-purified beta-lyase was used stoichiometric amounts of pyruvate and ammonia were produced. Although all of the conjugates were activated by beta-lyase and had a similar effect on ion transport their mutagenicity differed markedly. The conjugates of HCBD, trichloroethylene and perchloroethylene were mutagenic in the Ames bacterial mutation assay when activated by rat kidney S9. Metabolic cofactors were not required suggesting that activation was due to the enzyme beta-lyase. In the same assay the conjugates of TFE and HFP were not mutagenic either in the presence or absence of rat kidney S9 and cofactors. With a limited number of cysteine conjugates a clear distinction has been identified between the conjugates of chloroalkenes which were were similarly nephrotoxic but were not mutagenic. The mutagenicity of the cysteine conjugate of HCBD is consistent with the known renal carcinogenicity of this chemical.

Calcitonin gene-related peptide and substance P in afferents to the upper gastrointestinal tract in the rat

Combined immunohistochemistry and retrograde tracing was used to investigate the origin of the sensory calcitonin gene-related peptide (CGRP) innervation of the rat stomach. Up to 85% of spinal gastric afferents (T6-L1) contained CGRP immunoreactivity compared with less than 6% of vagal gastric afferents. By comparison substance P immunoreactivity occurred in about 50% of spinal gastric afferents and less than 2% of vagal afferents. The vagal afferents to the oesophagus were 14 and 26% substance P- and CGRP-immunoreactive respectively. The results suggest an important role for CGRP in gastric spinal afferents.

Evidence that human class Theta glutathione S-transferase T1-1 can catalyse the activation of dichloromethane, a liver and lung carcinogen in the mouse. Comparison of the tissue distribution of GST T1-1 with that of classes Alpha, Mu and Pi GST in human

The cDNA encoding human glutathione S-transferase (GST) T1 has been expressed as two recombinant forms in Escherichia coli that could be purified by affinity chromatography on either IgG-Sepharose or nickel-agarose; one form of the transferase was synthesized from the pALP 1 expression vector as a Staphylococcus aureus protein A fusion, whereas the other form was synthesized from the pET-20b expression vector as a C-terminal polyhistidine-tagged recombinant. The yields of the two purified recombinant proteins from E. coli cultures were approx. 15 mg/l for the protein A fusion and 25 mg/l for the C-terminal polyhistidine-tagged GST T1-1. The purified recombinant proteins were catalytically active, although the protein A fusion was typically only 5-30% as active as the histidine-tagged GST. Both recombinant forms could catalyse the conjugation of glutathione with the model substrates 1,2-epoxy-3-(4'-nitrophenoxy)propane,4-nitrobenzyl chloride and 4-nitrophenethyl bromide but were inactive towards 1-chloro-2,4-dinitrobenzene, ethacrynic acid and 1-menaphthyl sulphate. Recombinant human GST T1-1 was found to exhibit glutathione peroxidase activity and could catalyse the reduction of cumene hydroperoxide. In addition, recombinant human GST T1-1 was found to conjugate glutathione with dichloromethane, a pulmonary and hepatic carcinogen in the mouse. Immunoblotting with antibodies raised against different transferase isoenzymes showed that GST T1-1 is expressed in a large number of human organs in a tissue-specific fashion that differs from the pattern of expression of classes Alpha, Mu and Pi GST. Most significantly, GST T1-1 was found in only low levels in human pulmonary soluble extract of cells, suggesting that in man the lung has little capacity to activate the volatile dichloromethane.

Species differences in response to trichloroethylene. II. Biotransformation in rats and mice

Detailed analysis of urine from two strains of rats and mice dosed po with trichloroethylene at four doses from 10 to 2000 mg/kg failed to detect any major species or strain differences in the metabolism of trichloroethylene. Although a greater proportion of the dose was metabolized in mice than in rats, the relative proportions of the major metabolites were very similar in both strains and were unaffected by the dose amount. Analysis of the same urine samples for minor metabolites failed to establish a major species difference. Small amounts of dichloroacetic acid (less than 1% of the dose) were present in both rat and mouse urine and were not considered significant. Monochloroacetic acid accounted for less than 0.1% of the dose. Daily dosing of trichloroethylene (1000 mg/kg po) for 180 days did not induce the overall metabolism of trichloroethylene but did double the urinary excretion of trichloroacetic acid. This finding was accompanied by an equivalent percentage decrease in the concentration of trichloroethanol. CO2 has been shown to be a major metabolite of trichloroacetic acid, suggesting that this is the source of trichloroethylene-derived CO2. Trichloroacetic acid was also excreted in bile in both rats and mice suggesting possible conjugation of this metabolite in the liver. Very little evidence was found for the formation of chemically reactive species from trichloroethylene in either rats or mice and none that could be the basis of a major species difference. The increased rate of metabolism in the mouse, the resulting high blood concentrations of trichloroacetic acid, and stimulation of hepatic peroxisome proliferation in this species appears to be the major species difference possibly related to tumor formation in the liver. The conjugation of trichloroacetic acid and its metabolism to CO2 may be related to peroxisome proliferation.

Species differences in response to trichloroethylene. I. Pharmacokinetics in rats and mice

The elimination of radioactivity in two strains of rats and mice following a single po dose of trichloro[14C]ethylene at dose levels from 10 to 2000 mg/kg has shown a marked dose dependence in rats but not in mice. The metabolism of trichloroethylene in the mouse was linear over the range of doses used, whereas in the rat it became constant and independent of dose at 1000 mg/kg and above. At the 10-mg/kg dosage, both species metabolized trichloroethylene almost completely, 60% of the dose being excreted in urine with only 1 to 4% being eliminated unchanged in expired air in the first 24 hr. At 2000 mg/kg, 78% of the dose was eliminated unchanged in the rat, but only 14% in the mouse. Consequently at high dosages, the mouse was exposed to significantly higher concentrations of trichloroethylene metabolites than the rat. Blood level kinetics of trichloroethylene and its metabolites confirmed a faster rate of metabolism in the mouse than in the rat. Peak concentrations of the metabolites were reached within 2 hr of dosing in the mouse compared to 10 to 12 hr in the rat. The concentrations of both trichloroethanol (4X) and trichloroacetic acid (7X) were significantly higher in the mouse than in the rat. Whereas trichloroethanol was rapidly eliminated from blood, the higher concentrations of trichloroacetic acid were maintained for over 30 hr. The high blood quantities of trichloroethylene-derived trichloroacetic acid are known to induce hepatic peroxisome proliferation in mice but are insufficient to induce this response in rats. These data suggest that trichloroacetic acid blood amounts, peroxisome proliferation, and the link between peroxisomes and liver cancer are the basis of species difference in response to trichloroethylene.

A susceptibility locus for asthma-related traits on chromosome 7 revealed by genome-wide scan in a founder population

The genetics of asthma and atopy have been difficult to determine because these diseases are genetically heterogeneous and modified by environment. The pedigrees in our study (n=86) originate in eastern central Finland (Kainuu province). According to census records, this region had only 200 households (2,000 inhabitants) in the mid sixteenth to mid seventeenth centuries. The current population of 100,000 represents the expansion of these founders within the past 400 years. Because this population is relatively homogeneous, we hypothesized that the molecular genetic mechanisms underlying asthma might also have reduced heterogeneity and therefore be easier to dissect than in mixed populations. A recent twin family study supported a strong genetic component for asthma in Finland. We carried out a genome-wide scan for susceptibility loci in asthma in the Kainuu subpopulation. We identified two regions of suggestive linkage and studied them further with higher-density mapping. We obtained evidence for linkage in a 20-cM region of chromosome 7p14-p15 for three phenotypes: asthma, a high level of immunoglobulin E (IgE; atopy) and the combination of the phenotypes. The strongest linkage was seen for high serum IgE (non-parametric linkage (NPL) score 3.9, P=0.0001), exceeding the threshold for genome-wide significance based on simulations. We also observed linkage between this locus and asthma or atopy in two independent data sets.

Identification of amino acid residues that control functional behavior in GluR5 and GluR6 kainate receptors

GluR5 and GluR6 kainate receptors differ in their responses to a variety of agonists, despite their relatively high primary sequence homology. We carried out a structure-function study to identify amino acids underlying these divergent responses. Patch clamp analysis of chimeric GluR5-GluR6 receptors indicated that several functionally dominant sites were localized to the C-terminal side of M1. All nonconserved amino acids in the region between M3 and M4 of GluR6 were then individually mutated to their GluR5 counterparts. We found that a single amino acid (N721 in GluR6) controls both AMPA sensitivity and domoate deactivation rates. Additionally, mutation of A689 in GluR6 slowed kainate desensitization. These functional effects were accompanied by alterations in binding affinities. These results support a critical role for these residues in receptor binding and gating activity.

Interactions of vinyl chloride with rat-liver DNA in vivo

9beta-D-2'-Deoxyribofuranosyl-imidazo-[2,1-i]purine ("etheno-deoxyadenosine") and 1beta-D-2'-deoxyribofuranosyl-1,2-dihydro-2-oxo-imidazo-[1,2-c]pyrimidine ("etheno-deoxycytidine") are identified in the enzyme hydrolysates obtained (i) from calf-thymus DNA which had been modified by chemical reaction with chloroacetaldehyde and (ii) from liver DNA prepared from rats which had been exposed orally to vinyl chloride in their drinking water (250 ppm) for approx. 2 years. Thus, vinyl chloride-derived chloroethylene oxide and/or chloroacetaldehyde behaves as a bifunctional alkylating agent towards deoxyadenosine and deoxycytidine residues of DNA. The separation of deoxyribonucleosides and the two etheno-deoxyribosyl-nucleosides by liquid chromatography, and the mass spectra of etheno-deoxyadenosine and etheno-deoxycytidine and of their O-bis-(trimethylsilyl) derivatives are described. In the animal experiment (ii), the resulting proportion of etheno-deoxyadenosine is small compared with that of etheno-deoxycytidine. Imidazo-[2,1-i]purine (etheno-adenine) is identified: (a) in the supernatant after sedimentation of the modified DNA in the model experiment (i), and (b) in the product resulting from the reaction between chloroacetaldehyde and deoxyadenosine. The effect on the structure of DNA of the imidazo-cyclization of deoxyadenosine and deoxycytidine residues and of the depurination of etheno-deoxyadenosine residues is discussed in relation to vinyl chloride oncogenicity.

The metabolism and nephrotoxicity of tetrafluoroethylene in the rat

Exposure of rats to 6000 ppm tetrafluoroethylene for 6 hr produced marked damage to the proximal tubule of the kidney with no effect on the liver. The toxicity was characterized by very high concentrations of urinary glucose and by marked increases in the concentrations of several urinary enzymes. The no observed effect level for a 6-hr exposure was 2000 ppm. Tetrafluoroethylene was metabolized to S-(1,1,2,2-tetrafluoroethyl)glutathione by rat liver fractions in vitro; the reaction was catalyzed by both microsomal and cytosolic glutathione S-transferases. The rate with microsomes was four times that with cytosol fractions. Evidence for this metabolic pathway in vivo has been obtained by the identification of the cysteinylglycine and cysteine conjugates of tetrafluoroethylene in rat bile. Cytochrome P-450 oxidation, a common metabolic route for haloalkenes, does not appear to occur in the metabolism of tetrafluoroethylene. When administered po to rats, the synthetic cysteine conjugate of tetrafluoroethylene causes renal damage identical to that caused by tetrafluoroethylene itself. The conjugate was metabolized by renal slices in vitro giving pyruvate, ammonia, and a reactive species which caused marked inhibition of organic ion transport into slices. Purified renal beta-lyase also cleaved this conjugate giving stoichiometric amounts of pyruvate and ammonia. The nephrotoxicity of tetrafluoroethylene is believed to derive from the hepatic glutathione conjugate of this compound. Following excretion and degradation of this conjugate in bile, the cysteine conjugate is reabsorbed and further metabolized in the kidney by the enzyme beta-lyase to a cytotoxic species.

The biological fate in rats of vinyl chloride in relation to its oncogenicity

The main eliminative route for [14C]vinyl chloride after oral, i.v. or i.p. administration to rats is pulmonary; both unchanged vinyl chloride and vinyl chloride-related CO2 are excreted by that route and the other [14C] metabolites via the kidneys. After intragastric administration, pulmonary output of unchanged vinyl chloride is proportional to the logarithm of reciprocal dose. Excretion patterns after i.v. and i.p. injections are predictable from the characteristics of excretion following oral administration. Pulmonary excretion of unchanged vinyl chloride after oral dosing is complete within 3-4 h, but pulmonary elimination of CO2 and renal excretion of metabolites occupies 3 days. In comparison, 99% of a small i.v. dose is excreted unchanged within 1 h of injection; 80% within 2 min. The rate of elimination of a single oral doses of [14C]vinyl chloride is uninfluenced by up to 60 days' chronic dosing with the unlabelled substance. The distribution volume of vinyl chloride as displayed by whole-animal autoradiography agrees with deductions from excretion data. Small localization of 14C in the para-auricular region of appropriate sections occurs in sectioned tubules, belonging possibly to the Zymbal glands. Biotransformation of vinyl chloride into S-(2-chloroethyl) cysteine and N-acetyl-S-(2-chloroethyl) cysteine occurs through addition of cysteine, and biotransformation into: (i) chloroacetic acid, thiodiglycollic acid and glutamic acid, and (ii) into formaldehyde (methionine, serine), CO2 and urea is explicable in terms of an associative reaction with molecular O2 involving a singlet oxygen bonded transition state in dynamic equilibrium with a cyclic peroxide ground state. There is no evidence for chloroethylene oxide formation. Thiodiglycollic acid is the major metabolite of chloroacetic acid in rats; more than 60% of the dose. The interaction of vinyl chloride and of its primary metabolites with the intermediates of mammalian metabolism is discussed in relation to the oncogenicity of that substance.

Expression of recombinant homo-oligomeric 5-hydroxytryptamine3 receptors provides new insights into their maturation and structure

A recombinant baculovirus containing a mouse 5-hydroxytryptamine3 (5-HT3) receptor subunit cDNA under the control of the polyhedrin promoter was shown to direct the production of large amounts of functional 5-HT3 receptor in insect cells, as assayed by Western blotting and ligand binding. After solubilization, the receptor was purified to homogeneity by affinity chromatography and characterized pharmacologically. The ligand binding characteristics of the recombinant receptor were essentially identical to those of the native receptor, both before and after purification. Only fully glycosylated receptors bound to the ligand affinity resin, although subsequent removal of the sugar did not affect ligand binding. Visualization of the purified receptor using electron microscopy showed that the receptor preparation contained a homogeneous population of pentameric doughnut-shaped particles. The general appearance of the recombinant homo-oligomeric channels was indistinguishable from that of native 5-HT3 receptors. Yields of purified receptors were of the order of 200 micrograms/3 liters of original culture. The amount and homogeneity of the purified receptor are sufficient to begin preliminary crystallization trials.

Perchloroethylene-induced rat kidney tumors: an investigation of the mechanisms involved and their relevance to humans

Lifetime exposure to perchloroethylene by inhalation has been shown to cause a low incidence of renal tumors in male rats. The mechanisms responsible for the induction of these tumors have been investigated following exposure of rats to perchloroethylene by oral gavage (1500 mg/kg for up to 42 days) or by inhalation (400 ppm for 28 days). Comparisons have been made between rats and mice in vivo and between rats, mice, and humans in vitro. High doses of perchloroethylene given by gavage have been shown to be toxic to the rat kidney, causing increases in urinary markers of kidney damage. A marked accumulation of protein droplets (alpha-2u-globulin) was seen in the P2 segment of the kidney proximal tubules. This response were not seen after inhalation exposure to 400 ppm perchloroethylene for 28 days and hence may not be associated with the tumors seen at this dose level. Protein droplet formation was seen after exposure to 1000 ppm perchloroethylene, suggesting that 400 ppm is below the threshold dose required to induce this response. Perchloroethylene has been shown to be metabolized by glutathione conjugation in the liver, resulting in the formation of a mutagenic cysteine conjugate which is activated by the kidney enzyme beta-lyase. Levels of the mercapturic acid of perchloroethylene have been compared in rat and mouse urine. The enzyme kinetics of hepatic glutathione conjugation and renal beta-lyase activation have been compared in rat, mouse, and human tissues in vitro. Results of these studies are consistent with the rat being the species susceptible to kidney tumors. Although human kidney was shown to contain beta-lyase, glutathione conjugation of perchloroethylene could not be detected in human liver. Perchloroethylene-induced male rat kidney tumors may be a result of chronic toxicity, protein droplet nephropathy, and genotoxicity from the beta-lyase pathway. These mechanisms appear to have little relevance to humans.

Effect of experimenter-delivered and self-administered cocaine on extracellular beta-endorphin levels in the nucleus accumbens

Beta-endorphin is an endogenous opioid peptide that has been hypothesized to be involved in the behavioral effects of drugs of abuse including psychostimulants. Using microdialysis, we studied the effect of cocaine on extracellular levels of beta-endorphin in the nucleus accumbens, a brain region involved in the reinforcing effects of psychostimulant drugs. Experimenter-delivered cocaine (2 mg/kg, i.v.) increased extracellular beta-endorphin immunoreactive levels in the nucleus accumbens, an effect attenuated by 6-hydroxy-dopamine lesions or systemic administration of the D1-like receptor antagonist, SCH-23390 (0.25 mg/kg, i.p.). The effect of cocaine on beta-endorphin release in the nucleus accumbens was mimicked by a local perfusion of dopamine (5 microm) and was blocked by coadministration of SCH-23390 (10 microm). Self-administered cocaine (1 mg/kg/infusion, i.v.) also increased extracellular beta-endorphin levels in the nucleus accumbens. In addition, using functional magnetic resonance imaging, we found that cocaine (1 mg/kg, i.v.) increases regional brain activity in the nucleus accumbens and arcuate nucleus. We demonstrate an increase in beta-endorphin release in the nucleus accumbens following experimenter-delivered and self-administered cocaine mediated by the local dopaminergic system. These findings suggest that activation of the beta-endorphin neurons within the arcuate nucleus-nucleus accumbens pathway may be important in the neurobiological mechanisms underlying the behavioral effects of cocaine.

Familial eosinophilia maps to the cytokine gene cluster on human chromosomal region 5q31-q33

Familial eosinophilia (FE) is an autosomal dominant disorder characterized by peripheral hypereosinophilia of unidentifiable cause with or without other organ involvement. To localize the gene for FE, we performed a genomewide search in a large U.S. kindred, using 312 different polymorphic markers. Seventeen affected subjects, 28 unaffected bloodline relatives, and 8 spouses were genotyped. The initial linkage results from the genome scan provided evidence for linkage on chromosome 5q31-q33. Additional genotyping of genetic markers located in this specific region demonstrated significant evidence that the FE locus is situated between the chromosome 5q markers D5S642 and D5S816 (multipoint LOD score of 6.49). Notably, this region contains the cytokine gene cluster, which includes three genes-namely, those for interleukin (IL)-3, IL-5, and granulocyte/macrophage colony-stimulating factor (GM-CSF)-whose products play important roles in the development and proliferation of eosinophils. These three cytokine genes were screened for potential disease-specific mutations by resequencing of a subgroup of individuals from the present kindred. No functional sequence polymorphisms were found within the promoter, the exons, or the introns of any of these genes or within the IL-3/GM-CSF enhancer, suggesting that the primary defect in FE is not caused by a mutation in any one of these genes but, rather, is caused by another gene in the area.

Lawson Criterion for Ignition Exceeded in an Inertial Fusion Experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion.

Direct effects of metabotropic glutamate receptor compounds on native and recombinant N-methyl-D-aspartate receptors

The actions of glutamate in the central nervous system are mediated through interaction with fast activating ionotropic receptors and G protein-coupled metabotropic glutamate receptors (mGluRs). Studies of these receptors have relied on the availability of agonists and antagonists selective for each receptor class. Compounds that were thought to be selective for mGluRs have been extensively used to study the role of these receptors in the brain. Their use has implicated mGluRs in a wide range of physiological and pathological processes including the modulation of N-methyl-D-aspartate (NMDA) receptors and NMDA receptor-dependent processes. We report that some of the most commonly used mGluR compounds act as antagonists on NMDA receptors at concentrations commonly used to activate or block mGluRs. In addition, several of the drugs also act as agonists at higher concentrations due at least in part to high levels of contaminant amino acids. Our results indicate that caution should be used when using these drugs to study the roles of mGluRs in various NMDA-dependent processes. The antagonist effects were dependent on the concentration of the NMDA receptor coagonists, preventing reappraisal of previously published work.

Increased bioactivation of dihaloalkanes in rat liver due to induction of class theta glutathione S-transferase T1-1

A characteristic feature of the class Theta glutathione S-transferase (GST) T1-1 is its ability to activate dichloromethane and dibromoethane by catalysing the formation of mutagenic conjugates. The level of the GSTT1 subunit within tissues is an important determinant of susceptibility to the carcinogenic effects of these dihaloalkanes. In the present study it is demonstrated that hepatic GST activity towards these compounds can be elevated significantly in female and male Fischer-344 rats by feeding these animals on diets supplemented with cancer chemopreventive agents. Immunoblotting experiments showed that increased activity towards the dihaloalkanes is associated with elevated levels of the GSTT1 subunit in rat liver. Sex-specific effects were observed in the induction of GSTT1 protein. Amongst the chemopreventive agents tested, indole-3-carbinol proved to be the most potent inducer of hepatic GSTT1 in male rats (6.2-fold), whereas coumarin was the most potent inducer of this subunit in the livers of female rats (3. 5-fold). Phenobarbital showed significant induction of GSTT1 only in male rat liver and had little effect in female rat liver. Western blotting showed that class Alpha, Mu and Pi GST subunits are not co-ordinately induced with GSTT1, indicating that the expression of GSTT1 is determined, at least in part, by mechanisms distinct from those that regulate levels of other transferases. The increase in amount of hepatic GSTT1 protein was also reflected by an increase in the steady-state level of mRNA in response to treatment with chemopreventive agents and model inducers. Immunohistochemical detection of GSTT1 in rat liver supported the Western blotting data, but showed, in addition to cytoplasmic staining, significant nuclear localization of the enzyme in hepatocytes from some treated animals, including those fed on an oltipraz-containing diet. Significantly, the hepatic level of cytochrome P-450 2E1, an enzyme which offers a detoxification pathway for dihaloalkanes, was unchanged by the various inducing agents studied. It is concluded that the induction of GSTT1 by dietary components and its localization within cells are important factors that should be considered when assessing the risk dihaloalkanes pose to human health.

Evaluation of the potential carcinogenicity and genetic toxicity to humans of the herbicide acetochlor

Comprehensive toxicological studies of the herbicide acetochlor are presented and discussed. Although it gave a negative profile of responses in the many toxicity tests conducted there were some findings that prompted further investigation. First, although non-mutagenic in the Salmonella assay, acetochlor was clastogenic to mammalian cells treated in vitro. This clastogenic potential was not expressed in vivo in four rodent cytogenetic assays (bone marrow and germ cells). Second, although acetochlor gave a negative response in rat liver UDS assays when tested at the acute MTD, gavage administration of a single, supra-MTD dose (2000 mg/kg) gave a weak positive assay response. This dose-level (2000 mg/kg) was necrotic to the liver, depressed hepatic glutathione levels by up to approximately 80%, altered the metabolism of acetochlor, and was associated with up to 33% lethality. In contrast, reference liver genotoxins such as DMN, DMH and 2AAF were shown to elicit UDS in the absence of such effects, and at approximately 400 x lower dose-levels. Finally, microscopic nasal polypoid adenomas were induced in the rat when acetochlor was administered for two years at the maximum tolerated dose (MTD). The tumours were not life-threatening, they did not metastasize, and no DNA damage was induced in the nasal cells of rats maintained on a diet containing the MTD of acetochlor for either 1 or 18 weeks (comet assay). In order to probe the mechanism of action of these high dose toxicities a series of chemical and genetic toxicity studies was conducted on acetochlor and a range of structural analogues. These revealed the chloroacetyl substructure to be the clastogenic species in vitro. Although relatively inert, this substituent is preferentially reactive to sulphydryl groupings, most evidently, to glutathione (GSH). Similar chemical reactivity and clastogenicity in vitro was observed for two related chemicals bearing a chloroacetyl group, both of which have been defined as non-carcinogens in studies reported by the US.NTP. These collective observations indicate that the source of the clastogenicity of acetochlor in vitro is also the source of its rapid detoxification in the rat in vivo, via reaction with GSH. Metabolic studies of acetochlor are described which reveal the formation of a series of GSH-associated biliary metabolites in the rat that were not produced in the mouse. The metabolism of acetochlor in the rat changes with increasing dose-levels, probably because of depletion of hepatic GSH. It is most likely that a rat-specific metabolite is responsible for the rat nasal tumours observed uniquely at elevated dose-levels. The absence of genetic toxicity to the nasal epithelium of rats exposed acutely or subchronically to acetochlor favours a non-genotoxic mechanism for the induction of these adenomas. The observation of a time- and dose-related increase in S-phase cells in the nasal epithelium is consistent with this conclusion. Despite some confusion caused by the early use of perilethal gavage administrations of acetochlor to rodents, and supra-MTD dietary concentrations in some of the chronic studies, the available MTD data are consistent with acetochlor not posing a genetic or carcinogenic hazard to humans.