Receptor-mediated activation of heterotrimeric G-proteins in living cells

Receptor-mediated activation of heterotrimeric GTP-binding proteins (G-proteins) was visualized in living Dictyostelium discoideum cells by monitoring fluorescence resonance energy transfer (FRET) between alpha- and beta- subunits fused to cyan and yellow fluorescent proteins. The G-protein heterotrimer rapidly dissociated and reassociated upon addition and removal of chemoattractant. During continuous stimulation, G-protein activation reached a dose-dependent steady-state level. Even though physiological responses subsided, the activation did not decline. Thus, adaptation occurs at another point in the signaling pathway, and occupied receptors, whether or not they are phosphorylated, catalyze the G-protein cycle. Construction of similar energy-transfer pairs of mammalian G-proteins should enable direct in situ mechanistic studies and applications such as drug screening and identifying ligands of newly found G-protein-coupled receptors.

Localization of the G protein betagamma complex in living cells during chemotaxis

Gradients of chemoattractants elicit signaling events at the leading edge of a cell even though chemoattractant receptors are uniformly distributed on the cell surface. In highly polarized Dictyostelium discoideum amoebas, membrane-associated betagamma subunits of heterotrimeric guanine nucleotide-binding proteins (G proteins) were localized in a shallow anterior-posterior gradient. A uniformly applied chemoattractant generated binding sites for pleckstrin homology (PH) domains on the inner surface of the membrane in a pattern similar to that of the Gbetagamma subunits. Loss of cell polarity resulted in uniform distribution of both the Gbetagamma subunits and the sensitivity of PH domain recruitment. These observations indicate that Gbetagamma subunits are not sufficiently localized to restrict signaling events to the leading edge but that their distribution may determine the relative chemotactic sensitivity of polarized cells.

Receptor-mediated hydrolysis of plasma membrane messenger PIP2 leads to K+-current desensitization

Phosphatidylinositol bisphosphate (PIP2) directly regulates functions as diverse as the organization of the cytoskeleton, vesicular transport and ion channel activity. It is not known, however, whether dynamic changes in PIP2 levels have a regulatory role of physiological importance in such functions. Here, we show in both native cardiac cells and heterologous expression systems that receptor-regulated PIP2 hydrolysis results in desensitization of a GTP-binding protein-stimulated potassium current. Two receptor-regulated pathways in the plasma membrane cross-talk at the level of these channels to modulate potassium currents. One pathway signals through the betagamma subunits of G proteins, which bind directly to the channel. Gbetagamma subunits stabilize interactions with PIP2 and lead to persistent channel activation. The second pathway activates phospholipase C (PLC) which hydrolyses PIP2 and limits Gbetagamma-stimulated activity. Our results provide evidence that PIP2 itself is a receptor-regulated second messenger, downregulation of which accounts for a new form of desensitization.

The WNT signalling pathway and diabetes mellitus

The WNT signalling pathway is involved in many physiological and pathophysiological activities. WNT ligands bind to Frizzled receptors and co-receptors (LDL receptor-related protein 5/6), triggering a cascade of signalling events. The major effector of the canonical WNT signalling pathway is the bipartite transcription factor beta-catenin/T cell transcription factor (beta-cat/TCF), formed by free beta-cat and one of the four TCFs. The WNT pathway is involved in lipid metabolism and glucose homeostasis, and mutations in LRP5 may lead to the development of diabetes and obesity. beta-Cat/TCF is also involved in the production of the incretin hormone glucagon-like peptide-1 in the intestinal endocrine L cells. More recently, genome-wide association studies have identified TCF7L2 as a diabetes susceptibility gene, and individuals carrying certain TCF7L2 single nucleotide polymorphisms could be more susceptible to the development of type 2 diabetes. Furthermore, beta-cat is able to interact with forkhead box transcription factor subgroup O (FOXO) proteins. Since FOXO and TCF proteins compete for a limited pool of beta-cat, enhanced FOXO activity during ageing and oxidative stress may attenuate WNT-mediated activities. These observations shed new light on the pathogenesis of type 2 diabetes as an age-dependent disease.

Profound analgesic effects of beta-endorphin in man

Profound and long-lasting analgesia (mean duration of pain relief 33.4 h, range 22.5--73.5 h) was produced by intrathecal administration of 3 mg synthetic beta-endorphin in all of 14 patients with intractable pain due to disseminated cancer. No respiratory depression, hypotension, hypothermia, or catatonia was observed.

Oltipraz upregulates the nuclear factor (erythroid-derived 2)-like 2 [corrected](NRF2) antioxidant system and prevents insulin resistance and obesity induced by a high-fat diet in C57BL/6J mice

AIMS/HYPOTHESIS

We investigated whether oltipraz, a nuclear respiratory factor 2 alpha subunit (NRF2) activator, improves insulin sensitivity and prevents the development of obesity in mice.

METHODS

C57BL/6J mice were fed with a low-fat diet (10% of energy as fat), a high-fat diet (HFD) (45% of energy as fat) or a HFD with oltipraz for 28 weeks. The effects of oltipraz on body weight, fat content, glucose disposal, insulin signalling, metabolic profiles and endogenous NRF2 functional status in the three groups of mice were investigated.

RESULTS

Oltipraz prevented or significantly attenuated the effect of HFD on glucose disposal, body weight and fat gain. Impairment of protein kinase B/Akt phosphorylation in this HFD-fed mouse model in response to intraperitoneal insulin injection was observed in adipose tissue, but not in the muscles, accompanied by inhibition of AMP-activated protein kinase signalling and activation of p70S6 kinase, as well as reduced GLUT4 content. These defects were attenuated by oltipraz administration. Nuclear content of NRF2 in adipose tissue was reduced by HFD feeding, associated with increased Keap1 mRNA expression and reduced production of haem oxygenase-1 and superoxide dismutase, increased protein oxidation, decreased plasma reduced:oxidised glutathione ratio and the appearance of macrophage marker F4/80. These defects were also restored by oltipraz. Finally, oltipraz attenuated HFD-induced inducible nitric oxide synthase overproduction.

CONCLUSIONS/INTERPRETATION

Impairment of the endogenous redox system is important in the development of obesity and insulin resistance in chronic HFD feeding. NRF2 activation represents a potential novel approach in the treatment and prevention of obesity and diabetes.

The chaperone protein BiP binds to a mutant prion protein and mediates its degradation by the proteasome

Familial prion diseases are thought to result from a change in structure of the mutant prion protein (PrP), which takes a pathogenic conformation. We have examined the role of molecular chaperones in the folding of normal and mutant PrP Q217R (PrP(217)) in transfected neuroblastoma cells. In a previous report we showed that, although most of the PrP(217) forms escape the endoplasmic reticulum quality control system and aggregate in post-Golgi compartments, a significant proportion of PrP(217) retains the C-terminal glycosylphosphatidyl inositol signal peptide (PrP32), and does not exit the endoplasmic reticulum (Singh, N., Zanusso, G., Chen, S. G., Fujioka, H., Richardson, S., Gambetti, P., and Petersen, R. B. (1997) J. Biol. Chem. 272, 28461-28470). We have now studied the folding and turnover of PrP32 to understand the mechanism by which abnormal PrP forms cause cellular toxicity in our cell culture model and in the human brain carrying the Gerstmann-Sträussler-Scheinker disease Q217R mutation. In this report, we show that PrP32 remains associated with the chaperone BiP for an abnormally prolonged period of time and is degraded by the proteasomal pathway. This study is the first demonstration that BiP is chaperoning the folding of PrP and plays a role in maintaining the quality control in the PrP maturation pathway. Our data provide new insight into the diverse pathways of mutant PrP metabolism and neurotoxicity.

Lanthanide Coordination with α-Amino Acids under Near Physiological pH Conditions: Polymetallic Complexes Containing the Cubane-Like [Ln4(μ3-OH)4]8+ Cluster Core

Tetranuclear lanthanide-hydroxo complexes of the general formula [Ln(4)(mu(3)-OH)(4)(AA)(x)(H(2)O)(y)](8+) (1, Ln = Sm, AA = Gly, x = 5, y = 11; 2, Ln = Nd, AA = Ala, x = 6, y = 10; 3, Ln = Er, AA = Val, x = 5, y = 10) have been prepared by alpha-amino acid controlled hydrolysis of lanthanide ions under near physiological pH conditions (pH 6-7). The core component of these compounds is a cationic cluster [Ln(4)(mu(3)-OH)(4)](8+) whose constituent lanthanide ions and triply bridging hydroxo groups occupy the alternate vertexes of a distorted cube. The amino acid ligands coordinate the lanthanide ions via bridging carboxylate groups. Utilizing L-glutamic acid as the supporting ligand, a cationic cluster complex (4) formulated as [Er(4)(mu(3)-OH)(4)(Glu)(3)(H(2)O)(8)](5+) has been obtained. Its extended solid-state structure is composed of the cubane-like [Er(4)(mu(3)-OH)(4)](8+) cluster building units interlinked by the carboxylate groups of the glutamate ligands. All compounds are characterized by using a combination of spectroscopic techniques and microanalysis (CHN and metal). Infrared spectra of the complexes suggest the coordinated amino acids to be zwitterionic. The presence of mass (MALDI-TOF) envelopes corresponding to the [Ln(4)(mu(3)-OH)(4)](8+) (Ln = trivalent Sm, Nd, or Er) core containing fragments manifests the integrity of the cubane-like cluster unit. Magnetic studies using Evans' method suggest that exchange interactions between the lanthanide ions are insignificant at ambient temperature. The structural identities of all four compounds have been established crystallographically. The tetranuclear cluster core has been demonstrated to be a common structural motif in these complexes. A mechanism responsible for its self-assembly is postulated.

Proteasomal degradation and N-terminal protease resistance of the codon 145 mutant prion protein

An amber mutation at codon 145 (Y145stop) of the prion protein gene results in a variant of an inherited human prion disease named Gerstmann-Sträussler-Scheinker syndrome. The characteristic features of this disorder include amyloid deposits of prion protein in cerebral parenchyma and vessels. We have studied the biosynthesis and processing of the prion protein containing the Y145stop mutation (PrP(145)) in transfected human neuroblastoma cells in an attempt to clarify the effect of the mutation on the metabolism of PrP(145) and to gain insight into the underlying pathogenetic mechanism. Our results demonstrate that 1) a significant proportion of PrP(145) is not processed post-translationally and retains the N-terminal signal peptide, 2) most PrP(145) is degraded very rapidly by the proteasome-mediated pathway, 3) blockage of proteasomal degradation results in intracellular accumulation of PrP(145), 4) most of the accumulated PrP(145) is detergent-insoluble, and both the detergent-soluble and -insoluble fractions are resistant to mild proteinase K (PK) treatment, suggesting that PK resistance is not simply because of aggregation. The present study demonstrates for the first time that a mutant prion protein is degraded through the proteasomal pathway and acquires PK-resistance if degradation is impaired.

G protein beta subunit-null mutants are impaired in phagocytosis and chemotaxis due to inappropriate regulation of the actin cytoskeleton

Chemotaxis and phagocytosis are basically similar in cells of the immune system and in Dictyostelium amebae. Deletion of the unique G protein beta subunit in D. discoideum impaired phagocytosis but had little effect on fluid-phase endocytosis, cytokinesis, or random motility. Constitutive expression of wild-type beta subunit restored phagocytosis and normal development. Chemoattractants released by cells or bacteria trigger typical transient actin polymerization responses in wild-type cells. In beta subunit-null cells, and in a series of beta subunit point mutants, these responses were impaired to a degree that correlated with the defect in phagocytosis. Image analysis of green fluorescent protein-actin transfected cells showed that beta subunit- null cells were defective in reshaping the actin network into a phagocytic cup, and eventually a phagosome, in response to particle attachment. Our results indicate that signaling through heterotrimeric G proteins is required for regulating the actin cytoskeleton during phagocytic uptake, as previously shown for chemotaxis. Inhibitors of phospholipase C and intracellular Ca2+ mobilization inhibited phagocytosis, suggesting the possible involvement of these effectors in the process.

Activation of proglucagon gene transcription through a novel promoter element by the caudal-related homeodomain protein cdx-2/3

The proglucagon gene is expressed in a highly restricted tissue-specific manner in the A cells of the pancreatic islet and the L cells of the small and large intestines. The results of previous experiments indicate that cell-specific expression of the proglucagon gene is mediated by proteins that interact with the proximal G1 promoter element. We show here that the G1 element contains several AT-rich subdomains that bind proteins present in islet and enteroendocrine cell extracts. Electrophoretic mobility shift assay experiments using specific antisera identified the homeobox protein cdx-2/3 (which designates the same homeobox protein called cdx-2 for mice and cdx-3 for hamsters) as a major component of the G1-Gc2 complex in islet and intestinal cells. Mutations of the Gc element that decreased cdx-2/3 binding also resulted in decreased proglucagon promoter activity in islet and intestinal cell lines. The finding that cdx-2/3 mediates activation of the proglucagon promoter in both islet and enteroendocrine cells is consistent with the common endodermal lineage of these tissues and provides new insight into the coordinate regulation of genes expressed in both pancreatic and intestinal endocrine cell types.

Cadmium-induced apoptosis and changes in expression of p53, c-jun and MT-I genes in testes and ventral prostate of rats

Apoptosis and a change in the expression of p53, c-jun and MT-I genes occurred in rats exposed to cadmium in a way known to cause carcinogenesis in testes and ventral prostate. In situ end labelling (ISEL), DNA electrophoresis, and RT-PCR methods were used in present study. Adult male Wistar rats were given a single (s.c.) injection of 0, 5, 10, or 20 micromol/kg CdCl2. Then 12, 48 or 96 h after administration of cadmium, animals were sacrificed. It was observed that cadmium markedly induced apoptosis in the testes at the dose of 5 micromol/kg while 10 and 20 micromol/kg cadmium caused more necrosis than apoptosis. Apoptosis in the ventral prostate was markedly induced by all the doses of cadmium and there was an obvious time- and dose-dependent relationship between apoptotic index (AI) and cadmium treatment. Far fewer apoptotic cells appeared in liver, compared to the testes and ventral prostate. p53 mRNA expression was clearly enhanced in the ventral prostate but clearly suppressed in the testes by cadmium exposure, and the time- and dose-effect was very clear. The expression level of p53 in the liver was not affected by cadmium treatment. Cadmium-induced overexpression of c-jun gene appeared at 12 h in the liver, but not until 96 h in the testes and ventral prostate. Although the MT-I gene was found to be expressed in all tissues, marked induction by cadmium of the expression of MT-I gene was only observed in the liver. These results indicate: (1) that apoptosis is an early mechanism of acute tissue damage by cadmium in the testes and ventral prostate; (2) that p53 and c-jun genes may be involved in cadmium-induced cytotoxicity (apoptosis) and related carcinogenicity in male reproductive tissues; and (3) that the enhanced expression of MT-I in the liver could protect this organ from cadmium-induced cytotoxicity (apoptosis) and carcinogenicity.

Activation of proglucagon gene transcription by protein kinase-A in a novel mouse enteroendocrine cell line

The gene encoding proglucagon is expressed predominantly in the pancreas and intestine. The physiological importance of glucagon secreted from the islets of Langerhans has engendered considerable interest in the molecular control of proglucagon gene transcription in the endocrine pancreas. In contrast, little is known about the molecular control of proglucagon gene expression in the intestine. The recent demonstration that glucagon-like peptide-1 (GLP-1) secreted from the intestine is a potent regulator of insulin secretion and glucose homeostasis has stimulated renewed interest in the factors that control GLP-1 synthesis in the intestinal L-cell. To develop a model for the analysis of intestinal proglucagon gene expression, we have targeted expression of a proglucagon gene-simian virus-40 large T-antigen fusion gene to enteroendocrine cells in transgenic mice. These mice develop intestinal tumors that were used to derive a novel cell line, designated GLUTag, that expresses the proglucagon gene and secretes immunoreactive GLP-1 in vitro. GLUTag cells demonstrate morphological characteristics of enteroendocrine cells by electron microscopy and are plurihormonal, as shown by immunocytochemistry and RNA analyses. GLUTag cells express the proglucagon and cholecystokinin genes, consistent with the pattern of lineage-specific enteroendocrine differentiation described for mouse intestine. Proglucagon gene expression was induced by activators of the protein kinase-A pathway, and a combination of messenger RNA half-life and nuclear run-on experiments demonstrated that the protein kinase-A-induction is mediated by an increase in proglucagon gene transcription. In contrast, activators of protein kinase-C stimulated secretion, but not biosynthesis of the PGDPs in GLUTag cell cultures. Analysis of proglucagon processing in GLUTag cells demonstrated the liberation of glucagon, oxyntomodulin, glicentin, and multiple forms of GLP-1. These observations provide evidence for the direct induction of proglucagon gene transcription by a cAMP-dependent pathway and suggest that the GLUTag cell line represents a useful model for the analysis of the molecular determinants of enteroendocrine gene expression.

Integrated analysis of transcriptomics and metabonomics profiles in aflatoxin B1-induced hepatotoxicity in rat

The aim of this work was to identify mechanisms and potential biomarkers for predicting the development and progression of aflatoxin B1 (AFB1)-induced acute hepatotoxicity. In this study, microarray analysis and metabolites profiles were used to identify shifts in gene expression and metabolite levels associated with the affected physiological processes of rats treated with AFB1. Histopathological examinations and serum biochemical analysis were simultaneously performed; the results indicated that hepatotoxicity occurred in higher dosage groups. However, gene expression analysis and metabolite profiles are more sensitive than general toxicity studies for detecting AFB1-induced acute hepatotoxicity as the patterns of low-dose AFB1-treated rats in these two technique platforms were more similar to the rats in higher dosage groups than to the control rats. Integrated analysis of the results from general toxicity studies, transcriptomics and metabonomics profiles suggested that p53 signaling pathway induced by oxidative damage was the crucial step in AFB1-induced acute hepatotoxicity, whereas gluconeogenesis and lipid metabolism disorder were found to be the major metabolic effects after acute AFB1 exposure. The genes and metabolites significantly affected in common in rat liver or serum of three doses AFB1 treatments served as potential biomarkers for detecting AFB1-induced acute hepatotoxicity.

Occurrence of ammonia-oxidizing Archaea in activated sludges of a laboratory scale reactor and two wastewater treatment plants

AIMS

Characterization of the ammonia-oxidizing archaea (AOA) community in activated sludge from a nitrogen removal bioreactor and wastewater treatment plants (WWTPs).

METHODS AND RESULTS

Three primer sets specific for ammonia mono-oxygenase alpha-subunit (amoA) were used to construct clone libraries for activated sludge sample from a nitrogen removal bioreactor. One primer set resulted in strong nonspecific PCR products. The other two clone libraries retrieved both shared and unique AOA amoA sequences. One primer set was chosen to study the AOA communities of activated sludge samples from Shatin and Stanley WWTPs. In total, 18 AOA amoA sequences were recovered and compared to the previous reported sequences. A phylogenetic analysis indicated that sequences found in this study fell into three clusters.

CONCLUSIONS

Different primers resulted in varied AOA communities from the same sample. The AOA found from Hong Kong WWTPs were closely similar to those from sediment and soil, but distinct from those from activated sludge in other places. A comparison of clone libraries between Shatin WWTP and bioreactor indicated the AOA community significantly shifted only after 30-day enrichment.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study confirmed the occurrence of AOA in a laboratory scale nitrogen removal bioreactor and Hong Kong WWTPs treating saline or freshwater wastewater. AOA communities found in this study were significantly different from those found in other places. To retrieve diverse AOA communities from environmental samples, a combination of different primers for the amoA gene is needed.

Inactivation of Salmonella in liquid egg albumen by antimicrobial bottle coatings infused with allyl isothiocyanate, nisin and zinc oxide nanoparticles

AIMS

To develop an antimicrobial bottle coating effective at inhibiting the growth of Salmonella in liquid egg albumen (egg white) and reduce the risk of human Salmonellosis.

METHODS AND RESULTS

Four-ounce glass jars were coated with a mixture of polylactic acid (PLA) polymer and antimicrobial compounds containing 100-500 μl allyl isothiocyanate (AIT), 250 mg nisin, 250 mg zinc oxide nanoparticles per jar or their combinations. The coated jars contained 100 ml of liquid egg white (LEW) inoculated with a three-strain Salmonella enterica ssp. enterica cocktail at populations of 10(3) or 10(7) CFU ml(-1) and stored at 10°C for 28 days. The PLA coating with 500 μl AIT completely inactivated 3 and 7 log CFU ml(-1) of Salmonella after 7 and 21 days of storage, respectively. The PLA coating with 200 μl AIT in combination with 250 mg nisin reduced Salmonella populations to an undetectable level (<10 CFU ml(-1) ) after 21 days of storage.

CONCLUSIONS

PLA coatings containing AIT alone or in combination with nisin effectively inactivated salmonellae in LEW.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study demonstrated the commercial potential of applying the antimicrobial bottle coating method to liquid eggs and possibly other fluid food products.

Examination of POU homeobox gene expression in human breast cancer cells

Abnormal expression of homeobox genes may lead to the development of leukemias, lymphomas, and solid tumors. Expression of homeobox genes in mammary glands, however, has not been studied actively until recently. We have examined the expression of POU homeobox genes in human breast cancer cell lines and human breast tissue samples. Using a pair of degenerate primers for reverse transcription-polymerase chain reaction (RT-PCR) followed by DNA sequencing, we found that the human breast cancer cell line, MCF7, expresses at least 4 POU gene products: OCT1, OCT2, OCT3 and OCT11 (Skn-1a/i, Epoc-1). The expression of OCT1 and OCT2 in other human breast epithelial cell lines was further determined by Western blot analyses and electrophoretic mobility shift assay. We were unable to detect OCT11 in human breast cancer cell lines using the anti rat Skn-1a/i antibody, although the expression of this gene in both human breast cancer cell lines and human primary breast tumors was detected by RT-PCR. OCT3 is an embryonic transcription factor. We found that this gene is also expressed in human breast cancer cell lines and all human primary breast carcinomas examined, but not in normal human breast tissue. Taken together, we have shown that several POU genes are expressed in human breast epithelial cells. As OCT3 expression was detected only in the breast cancerous cells, this embryonic transcription factor could play an important role in mammary gland carcinogenesis.

Biomarkers of cadmium and arsenic interactions

Advances in proteomics have led to the identification of sensitive urinary biomarkers of renal dysfunction that are increasingly used in toxicology and epidemiology. Recent animal data show that combined exposure to inorganic arsenic (As) and cadmium (Cd) gives rise to more pronounced renal toxicity than exposure to each of the agents alone. In order to examine if similar interaction occurs in humans, renal dysfunction was studied in population groups (619 persons in total) residing in two metal contaminated areas in China: mainly a Cd contaminated area in Zhejiang province (Z-area) and mainly a As contaminated area in Guizhou province (G-area). Nearby control areas without excessive metal exposure were also included. Measurements of urinary beta(2)-microglobulin (UB2MG), N-acetyl-beta-glucosaminidase (UNAG), retinol binding protein (URBP) and albumin (UALB) were used as markers of renal dysfunction. Urinary Cd (UCd) and total As (UTAs) were analyzed by graphite-furnace atomic absorption spectrometry. Urinary inorganic As and its mono- and di-methylated metabolites (UIAs) were determined by Hydride generation. Results. As expected, the highest UCd values occurred in Z-area (Geometric mean, GM 11.6 microg/g crea) while the highest UTAs values occurred in G-area (GM = 288 microg/g crea). Statistically significant increases compared to the respective control area were present both for UTAs, UCd and for UB2MG, UNAG and UALB in Z-area as well as in G-area. UIAs was determined only in Z area. In G-area, there was a clear dose-response pattern both in relation to UTAs and UCd for each of the biomarkers of renal dysfunction. An interaction effect between As and Cd was demonstrated at higher levels of a combined exposure to As and Cd enhancing the effect on the kidney. In Z-area an increased prevalence of B2MG-uria, NAG-uria and ALB-uria was found in relation to UCd, but no relationship to UTAs was found. A statistically significant relationship between UIAs and UB2MG was found among women in this area and an interaction between As and Cd was indicated for B2MG. Conclusion. The present studies, which employed sensitive biomarkers of renal dysfunction, give support to the idea that human co-exposure to Cd and inorganic arsenic gives rise to more pronounced renal damage than exposure to each of the elements alone, but further studies are needed to establish and clarify this interaction.

Identification of Neisseria gonorrhoeae in synovial fluid using the polymerase chain reaction

OBJECTIVE

To analyze synovial fluid (SF) for the presence of Neisseria gonorrhoeae DNA using the polymerase chain reaction (PCR).

METHODS

We used a modified, nested PCR to detect the presence of N gonorrhoeae DNA in 41 samples of SF obtained from 10 patients with clinical gonococcal arthritis whose SF samples were sterile by culture and from 27 controls, including 11 patients with Reiter's syndrome. Results obtained using this method were compared with those obtained using the GEN-PROBE system, an RNA-DNA hybridization technique.

RESULTS

With nested PCR, N gonorrhoeae DNA was detected in 11 of 14 SF samples obtained from patients with culture-negative clinical gonococcal arthritis but in none of the 11 SF samples from Reiter's syndrome patients. The specificity of this technique was 96.4%, with a sensitivity of 78.6%. The rate of false-positive results was 3.6%. The GEN-PROBE technique was unable to detect N gonorrhoeae ribosomal RNA in any of the samples.

CONCLUSION

These findings demonstrate the potential utility of the PCR in confirming the clinical diagnosis of gonococcal arthritis as well as providing insight into the pathogenesis of this disorder in patients whose SF are sterile by standard culture techniques. PCR may also prove helpful in differentiating N gonorrhoeae arthritis from acute Reiter's syndrome.