Mimicry of Biological Macromolecules by Polyaromatic Anionic Compounds

The preparation, characterization and biological properties of some polyanionic polymers are reported. These polymers are constructed with repeating phenol-based monomers. The anionic groups attached to the aro matic nucleus provide the basis for binding to basic domains of proteins. Scaf fold flexibility permits the polyanionic polymers to adopt low energy conforma tions suitable for interacting with coagulation proteins and an anti-DNA monoclonal antibody. Structure activity relationships (SAR) and comparisons with aurintricarboxylic acid are described. The polymers doubled the clotting time in the APTT assay with value ranging from 10-1000 μg/mL. Binding to an anti-DNA monoclonal antibody occurred with ICso values of 0.3-5.0 μg/mL.

Novel oxazolidinone calcitonin gene-related peptide (CGRP) receptor antagonists for the acute treatment of migraine

In our efforts to develop CGRP receptor antagonists as backups to MK-3207, 2, we employed a scaffold hopping approach to identify a series of novel oxazolidinone-based compounds. The development of a structurally diverse, potent (20, cAMP+HS IC50=0.67 nM), and selective compound (hERG IC50=19 μM) with favorable rodent pharmacokinetics (F=100%, t1/2=7h) is described. Key to this development was identification of a 3-substituted spirotetrahydropyran ring that afforded a substantial gain in potency (10 to 35-fold).

Discovery of MK-3697: a selective orexin 2 receptor antagonist (2-SORA) for the treatment of insomnia

Orexin receptor antagonists have demonstrated clinical utility for the treatment of insomnia. The majority of clinical efforts to date have focused on the development of dual orexin receptor antagonists (DORAs), small molecules that antagonize both the orexin 1 and orexin 2 receptors. Our group has recently disclosed medicinal chemistry efforts to identify highly potent, orally bioavailable selective orexin 2 receptor antagonists (2-SORAs) that possess acceptable profiles for clinical development. Herein we report additional SAR studies within the 'triaryl' amide 2-SORA series focused on improvements in compound stability in acidic media and time-dependent inhibition of CYP3A4. These studies resulted in the discovery of 2,5-disubstituted isonicotinamide 2-SORAs such as compound 24 that demonstrated improved stability and TDI profiles as well as excellent sleep efficacy across species.

Discovery of 5''-chloro-N-[(5,6-dimethoxypyridin-2-yl)methyl]-2,2':5',3''-terpyridine-3'-carboxamide (MK-1064): a selective orexin 2 receptor antagonist (2-SORA) for the treatment of insomnia

The field of small-molecule orexin antagonist research has evolved rapidly in the last 15 years from the discovery of the orexin peptides to clinical proof-of-concept for the treatment of insomnia. Clinical programs have focused on the development of antagonists that reversibly block the action of endogenous peptides at both the orexin 1 and orexin 2 receptors (OX1 R and OX2 R), termed dual orexin receptor antagonists (DORAs), affording late-stage development candidates including Merck's suvorexant (new drug application filed 2012). Full characterization of the pharmacology associated with antagonism of either OX1 R or OX2 R alone has been hampered by the dearth of suitable subtype-selective, orally bioavailable ligands. Herein, we report the development of a selective orexin 2 antagonist (2-SORA) series to afford a potent, orally bioavailable 2-SORA ligand. Several challenging medicinal chemistry issues were identified and overcome during the development of these 2,5-disubstituted nicotinamides, including reversible CYP inhibition, physiochemical properties, P-glycoprotein efflux and bioactivation. This article highlights structural modifications the team utilized to drive compound design, as well as in vivo characterization of our 2-SORA clinical candidate, 5''-chloro-N-[(5,6-dimethoxypyridin-2-yl)methyl]-2,2':5',3''-terpyridine-3'-carboxamide (MK-1064), in mouse, rat, dog, and rhesus sleep models.

Discovery of 2,5-diarylnicotinamides as selective orexin-2 receptor antagonists (2-SORAs)

The orexin (or hypocretin) system has been identified as a novel target for the treatment of insomnia due to the wealth of biological and genetic data discovered over the past decade. Recently, clinical proof-of-concept was achieved for the treatment of primary insomnia using dual (OX1R/OX2R) orexin receptor antagonists. However, elucidation of the pharmacology associated with selective orexin-2 receptor antagonists (2-SORAs) has been hampered by the lack of orally bioavailable, highly selective small molecule probes. Herein, the discovery and optimization of a novel series of 2,5-diarylnicotinamides as potent and orally bioavailable orexin-2 receptor selective antagonists is described. A compound from this series demonstrated potent sleep promotion when dosed orally to EEG telemetrized rats.

[(11)C]MK-4232: The First Positron Emission Tomography Tracer for the Calcitonin Gene-Related Peptide Receptor

Rational modification of the potent calcitonin gene-related peptide (CGRP) receptor antagonist MK-3207 led to a series of analogues with enhanced CNS penetrance and a convenient chemical handle for introduction of a radiolabel. A number of (11)C-tracers were synthesized and evaluated in vivo, leading to the identification of [(11)C]8 ([(11)C]MK-4232), the first positron emission tomography tracer for the CGRP receptor.

MK-8825: a potent and selective CGRP receptor antagonist with good oral activity in rats

Rational modification of the clinically tested CGRP receptor antagonist MK-3207 (3) afforded an analogue with increased unbound fraction in rat plasma and enhanced aqueous solubility, 2-[(8R)-8-(3,5-difluorophenyl)-8-methyl-10-oxo-6,9-diazaspiro[4.5]dec-9-yl]-N-[(6S)-2'-oxo-1',2',5,7-tetrahydrospiro[cyclopenta[b]pyridine-6,3'-pyrrolo[2,3-b]pyridin]-3-yl]acetamide (MK-8825) (6). Compound 6 maintained similar affinity to 3 at the human and rat CGRP receptors but possessed significantly improved in vivo potency in a rat pharmacodynamic model. The overall profile of 6 indicates it should find utility as a rat tool to investigate effects of CGRP receptor blockade in vivo.

Discovery of the dual orexin receptor antagonist [(7R)-4-(5-chloro-1,3-benzoxazol-2-yl)-7-methyl-1,4-diazepan-1-yl][5-methyl-2-(2H-1,2,3-triazol-2-yl)phenyl]methanone (MK-4305) for the treatment of insomnia

Despite increased understanding of the biological basis for sleep control in the brain, few novel mechanisms for the treatment of insomnia have been identified in recent years. One notable exception is inhibition of the excitatory neuropeptides orexins A and B by design of orexin receptor antagonists. Herein, we describe how efforts to understand the origin of poor oral pharmacokinetics in a leading HTS-derived diazepane orexin receptor antagonist led to the identification of compound 10 with a 7-methyl substitution on the diazepane core. Though 10 displayed good potency, improved pharmacokinetics, and excellent in vivo efficacy, it formed reactive metabolites in microsomal incubations. A mechanistic hypothesis coupled with an in vitro assay to assess bioactivation led to replacement of the fluoroquinazoline ring of 10 with a chlorobenzoxazole to provide 3 (MK-4305), a potent dual orexin receptor antagonist that is currently being tested in phase III clinical trials for the treatment of primary insomnia.

Immunomagnetic-Electrochemiluminescent Detection of Bacillus anthracis Spores in Soil Matrices

Rapid (<=1.5-h) detection of anthrax spores in soil suspensions was accomplished by an immunomagnetic electrochemiluminescence method. Strain-dependent detection limits in the range of 10(sup2) to 10(sup5) spores were achieved in buffer. The rank order of sensitivity for the assay in buffer was Sterne > Ames > Vollum 1B. Detection was up to 3 orders of magnitude less sensitive in soil suspensions, and the rank order of sensitivity was altered.

Discovery of a potent, CNS-penetrant orexin receptor antagonist based on an n,n-disubstituted-1,4-diazepane scaffold that promotes sleep in rats

Silent Night: Antagonism of the orexin (or hypocretin) system has recently been identified as a novel mechanism for the treatment of insomnia. Herein, we describe discovery of a dual (OX(1)R/OX(2)R) orexin receptor antagonist featuring a 1,4-diazepane central constraint that blocks orexin signaling in vivo. In telemetry-implanted rats, oral administration of this antagonist produced a decrease in wakefulness, while increasing REM and non-REM sleep.

In vitro antibacterial effects of antilipopolysaccharide DNA aptamer-C1qrs complexes

DNA aptamers were developed against lipopolysaccharide (LPS) from E. coli O111:B4 and shown to bind both LPS and E. coli by a colorimetric enzyme-based microplate assay. The polyclonal aptamers were coupled to human C1qrs protein either directly using a bifunctional linker or indirectly using biotinylated aptamers and a streptavidin-C1qrs complex. Both systems significantly reduced colony counts when applied to E. coli O111:B4 and K12 strains across a series of 10x dilutions of the bacteria in the presence of human serum; it was diluted 1: 10(3) in order to avoid significant bacterial lysis by the competing alternate pathway of complement activation. A number of candidate DNA aptamer sequences were cloned and sequenced from the anti-LPS aptamer library for future screening of antibacterial or "antibiotic" potential and to aid in eventual development of an alternative therapy for antibiotic-resistant bacterial infections.

Antibody-quantum dot conjugates exhibit enhanced antibacterial effect vs. unconjugated quantum dots

The effect of a 20-min exposure to antibody-quantum dot (Ab-QD) conjugates on colony counts of Escherichia coli was assessed by the spread-plate method and compared with exposure to unconjugated QDs having only amine or carboxyl groups on their surfaces. Under these conditions, Ab-QD conjugates generally exhibited >90% reduction in colony-forming units as compared to untreated E. coli and E. coli treated with unconjugated QDs after incubation for as long as 41 h. The antibacterial effect of Ab-QD conjugates vs. unconjugated QDs on Salmonella enterica subsp. enterica serovar Typhimurium was also assessed by means of a disk-diffusion technique which demonstrated greater growth inhibition (approximately 3 mm greater) by Ab-QD conjugate-impregnated disks than by unconjugated-QD-only-impregnated disks at a 10-microg disk load. At a 25-microg disk load, both treatment groups exhibited nearly equal growth inhibition.

Novel immuno-FRET assay method for Bacillus spores and Escherichia coli O157:H7

Novel immunofluorescence resonance energy transfer (immuno-FRET) assays for both Bacillus cereus spores and Escherichia coli O157:H7 are reported. Both assays involve the use of dual (QSY-7 and Oregon Green 514-antibody)-labeled spores or vegetative bacteria, such that Oregon Green 514-labeled antibodies are quenched by proximal QSY-7 molecules that are covalently bound to the dual (Oregon Green 514 and QSY-7)-labeled cells. Upon introduction of unlabeled bacteria or spores, in the respective assays, an increase in fluorescence is observed in proportion to the numbers of unlabeled cells. This is due to migration of Oregon Green 514-labeled antibody from the dual-labeled cells to the unlabeled target cells as verified by fluorescence microscopy. Optimization of the QSY-7 surface density led to a B. cereus spore detection sensitivity of approximately 1.0 x 10(5) to 2.5 x 10(5) spores per milliliter and 3.5 x 10(5) cells per milliliter for E. coli using a conventional cuvette-based spectrofluorometer.

A review of molecular recognition technologies for detection of biological threat agents

The present review summarizes the state of the art in molecular recognition of biowarfare agents and other pathogens and emphasizes the advantages of using particular types of reagents for a given target (e.g. detection of bacteria using antibodies versus nucleic acid probes). It is difficult to draw firm conclusions as to type of biorecognition molecule to use for a given analyte. However, the detection method and reagents are generally target-driven and the user must decide on what level (genetic versus phenotypic) the detection should be performed. In general, nucleic acid-based detection is more specific and sensitive than immunological-based detection, while the latter is faster and more robust. This review also points out the challenges faced by military and civilian defense components in the rapid and accurate detection and identification of harmful agents in the field. Although new and improved sensors will continue to be developed, the more crucial need in any biosensor may be the molecular recognition component (e.g. antibody, aptamer, enzyme, nucleic acid, receptor, etc.). Improvements in the affinity, specificity and mass production of the molecular recognition components may ultimately dictate the success or failure of detection technologies in both a technical and commercial sense. Achieving the ultimate goal of giving the individual soldier on the battlefield or civilian responders to an urban biological attack or epidemic, a miniature, sensitive and accurate biosensor may depend as much on molecular biology and molecular engineering as on hardware engineering. Fortunately, as this review illustrates, a great deal of scientific attention has and is currently being given to the area of molecular recognition components. Highly sensitive and specific detection of pathogenic bacteria and viruses has increased with the proliferation of nucleic acid and immuno-based detection technologies. If recent scientific progress is a fair indicator, the future promises remarkable new developments in molecular recognition elements for use in biosensors with a vast array of applications.

Rapid recovery and identification of anthrax bacteria from the environment

Bacillus anthracis has been recognized as a highly likely biological warfare or terrorist agent. We have designed culture techniques to rapidly isolate and identify "live" anthrax from suspected environmental release. A special medium (3AT medium) allows for discrimination between closely related bacilli and non-pathogenic strains. Nitrate was found to be a primary factor influencing spore formation in Bacillus anthracis. Nitrate reduction in anthrax is not an adaptation to saprophytic environmental existence, but it is a signal to enhance environmental survival upon the death of the anthrax host, which can be mimicked in culture.

Oxidative stress precedes circulatory failure induced by 35-GHz microwave heating

Sustained whole-body exposure of anesthetized rats to 35-GHz radio frequency radiation produces localized hyperthermia and hypotension, leading to circulatory failure and death. The physiological mechanism underlying the induction of circulatory failure by 35-GHz microwave (MW) heating is currently unknown. We hypothesized that oxidative stress may play a role in the pathophysiology of MW-induced circulatory failure and examined this question by probing organs for 3-nitrotyrosine (3-NT), a marker of oxidative stress. Animals exposed to low durations of MW that increased colonic temperature but were insufficient to produce hypotension showed a 5- to 12-fold increase in 3-NT accumulation in lung, liver, and plasma proteins relative to the levels observed in control rats that were not exposed to MW. 3-NT accumulation in rats exposed to MW of sufficient duration to induce circulatory shock returned to low, baseline levels. Leukocytes obtained from peripheral blood showed significant accumulation of 3-NT only at exposure levels associated with circulatory shock. 3-NT was also found in the villus tips and vasculature of intestine and within the distal tubule of the kidney but not in the irradiated skin of rats with MW-induced circulatory failure. The relationship between accumulation in liver, lung, and plasma proteins and exposure duration suggests either that nitro adducts are formed in the first 20 min of exposure and are then cleared or that synthesis of nitro adducts decreases after the first 20 min of exposure. Taken together, these findings suggest that oxidative stress occurs in many organs during MW heating. Because nitration occurs after microwave exposures that are not associated with circulatory collapse, systemic oxidative stress, as evidenced by tissue accumulation of 3-NT, is not correlated with circulatory failure in this model of shock.

Selective cytotoxicity of 3-amino-L-tyrosine correlates with peroxidase activity

In the presence of 3-amino-L-tyrosine (3-AT), abundant brown pigment forms in human HL-60 cells, but not in a variety of other cell lines, which are reported to be lower in mean myeloperoxidase (MPO) content than HL-60. Cells were assessed for peroxidase activity with an ABTS-based colorimetric assay and compared to values obtained with known amounts of human myeloperoxidase. HL-60 cells were estimated to contain the equivalent of 37.1 ng myeloperoxidase/10(6) cells versus 26.1 and 5.0 ng/10(6) cells for human K562 and murine RAW 264.7 cell lines, respectively. HL-60 cells exhibited a nearly 60% inhibition of proliferation and > 70% reduction in cell viability after 4 d of culture in the presence of 100 microg 3-AT per ml. Higher concentrations of 3-AT (up to 400 microg/ml) for 4 d reduced HL-60 proliferation by 80% and decreased viability to 1-3%. Comparable levels of cytotoxicity were achieved in KG-1 cells after 7 d with 200 or 400 microg 3-AT per ml. K562 cells exhibited a 40% reduction in cell number after 7 d with 400 microg 3-AT per ml, but concentrations less than 400 microg/ml did not significantly affect K562 proliferation. K562 viability remained unchanged with doses of 3-AT up to 400 microg/ml. RAW 264.7 cells exhibited unchanged viability and proliferation in the presence of 3-AT at concentrations up to 400 microg 3-AT per ml. K562, KG-1, and RAW 264.7 cells exhibited no evidence of brown pigment formation in the presence of 3-AT and medium containing 10% fetal bovine serum. However, RAW 264.7 cells that were converted to protein-free medium and exposed to 3-AT exhibited intense brown pigment in some cell nuclei. A high percentage of HL-60 cells treated with 3-AT exhibited membrane blebbing, pyknosis, and nuclear fragmentation, which was not observed among other 3-AT-treated cell lines. A mechanism involving toxic intermediates of peroxidase-mediated "aminomelanin" formation is hypothesized.

In vitro selection of DNA aptamers to anthrax spores with electrochemiluminescence detection

Systematic evolution of ligands by exponential enrichment (SELEX) was used to select and PCR amplify DNA sequences (aptamers) capable of binding to and detecting nonpathogenic Sterne strain Bacillus anthracis spores. A simplified affinity separation approach was employed, in which autoclaved anthrax spores were used as the separation matrix. An aptamer-magnetic bead-electrochemiluminescence (AM-ECL) sandwich assay scheme was devised for detecting anthrax spores. Using a low SELEX DNA to spore ratio (154 ng DNA/10(6) spores), at least three distinct populations of single-stranded DNA aptamers, having varied affinities for anthrax spores, were noted by the AM-ECL assay. Results reflect detection of spore components with a dynamic range equivalent to < 10- > 6 x 10(6) anthrax spores. In the low DNA to spore ratio experiments, aptamers could be liberated from spore pellets by heating at 96 degrees C for 5 min after each round of SELEX. When a much higher DNA to spore ratio (10,256 ng DNA/10(6) spores) was used for SELEX development, a higher affinity set of aptamers was selected that could not be heat-eluted even at 99 degrees C for 5 min following round four of SELEX. However, high affinity spore surface bound aptamers were detectable via their 5'-biotinylated tails using labeled avidin and could be eluted in deionized water. Aptamers have potential for use as inexpensive, in vitro-generated receptors for biosensors in biological warfare detection and other areas.

Preliminary electrochemiluminescence studies of metal ion-bacterial diazoluminomelanin (DALM) interactions

Electrochemiluminescence (ECL) studies of the chemiluminescent (CL) polymer diazoluminomelanin (DALM) biosynthesized in nitrate reductase transfected Escherichia coli JM109 bacteria revealed noteworthy anodic ECL and even more intense cathodic ECL. Bacterial DALM (BD) ECL was also assessed in the presence of 100 ppm of 33 different metal and non-metal ions which revealed specific anodic, but not cathodic, enhancements of BD ECL with Ag+, Hg2+ and Ru3+. The precursors and intermediate polymers which comprise DALM, such as luminol, 3-amino-L-tyrosine (3-AT), aminomelanin (AM) and diazomelanin (DM) were screened for ECL enhancement against the same set of elemental ions. Significant anodic ECL enhancements were observed for luminol with Hg2+ in the presence of tripropylamine (TPA), but not for any other DALM component in combination with other elemental ions, either anodically or cathodically. Comparison of BD with luminol in the presence and absence of TPA and Hg2+ revealed very different ECL activity patterns and suggested different mechanisms for BD and luminol ECL.

Preliminary studies of the enhanced electrochemiluminescence of 2,3-diaminonaphthalene in the presence of specific metal ions

Electrochemiluminescence (ECL) of 200 ppm 2,3-diaminonaphthalene (2,3-DAN) was studied alone and in conjunction with 100 ppm of 34 different metal and non-metal ions and revealed three relatively intense ECL responses from interactions of 2,3-DAN with Au+, Fe+3 and V+5. ECL responses from Cr+6 or Ru+3 with 2,3-DAN were less intense, but noteworthy, as was the coloured fluorescent product of the non-metal ion Se+4 interaction with 2,3-DAN. Several intense 2,3-DAN-metal ion ECL reactions were studied in greater detail and revealed various titration curves with ionic detection limits in the low ppm range, using a fixed level (200 ppm) of 2,3-DAN.

A colorimetric inhibition study of single-stranded DNA decamer sequence interactions with dinitrotoluene

A novel colored reaction between 2,4-dinitrotoluene (DNT) and dimethylsulfoxide (DMSO) on carbonate-activated plastic surfaces is described. In a preliminary study of the potential of oligonucleotides to bind nitroaromatic explosives, a random library of 1,040 single stranded (ss) DNA decamers (10 bases) in polystyrene microtitre plates were screened for inhibition of color development. The vast majority (89%) of sequences in the library completely inhibited color formation, suggesting that hydrogen bonding between DNA and the nitro groups of DNT was the predominate attractive force. Of the 114 sequences which allowed some visible color development, absorbance (405 nm) values were negatively correlated with GC content (r = -0.764), suggesting that some specific binding "pocket" structures for DNT may exist in the small library examined. Among the color evolving combinations, differences in amount of DNA were not correlated with absorbance.

In vitro selection of DNA to chloroaromatics using magnetic microbead-based affinity separation and fluorescence detection

In vitro selection (SELEX) of DNA ligands to the chloroaromatics, 4-chloroaniline (4-CA), 2,4,6-trichloroaniline (TCA) and pentachlorophenol (PCP), was performed by a novel method utilizing magnetic beads (MBs) having a linker arm for immobilization. Use of MBs was advantageous in obviating elution and precipitation of DNA as conjugated MBs with surface-captured template DNA could be directly added to PCR mixtures. In addition, a simplified PCR scheme requiring only one type of primer and a rapid fluorescence microscopic method for assessing nucleic acid binding after each round of SELEX were demonstrated.

Further characterization of tunicate and tunichrome electrochemiluminescence

Electrophoresis, size exclusion chromatography, fluorescence, and electrochemiluminescence (ECL) data obtained from the cell-rich perivisceral fluid ('blood') of the tunicate, Molgula occidentalis, suggests that a yellowish protein or protein subunit of < 6.5 kDa is probably responsible for the low level intrinsic ECL reported previously. Variable potential ECL scans and spectrofluorometric analyses directly indicated that chlorophylls from ingested phytoplankton were not significant contaminants of M. occidentalis blood samples. Chlorophylls were also examined indirectly from monocultures of dinoflagellate and diatom species to determine their ECL levels. While ECL was observed in these cultures, high concentrations (10(6) organisms/mL) of dinoflagellates or diatoms were needed to produce ECL levels comparable to those observed for M. occidentalis blood. Additional work with two synthetic tunichrome isomers indicated 10-fold increases in ECL when the '2,3,4-tunichrome' was reacted with Tl+ in 1:1 and 1:2 metal ion to ligand molar ratios. The '3,4,5-tunichrome' isomer exhibited a titration curve with Hg2+ suggestive of the existence of at least two Hg2+ binding sites and a 9- to 10-fold increase in ECL output.

Development of an immunomagnetic assay system for rapid detection of bacteria and leukocytes in body fluids

Immunomagnetic (IM) separation and concentration of specific target ligands or particles, such as bacteria or leukocytes, from complex mixtures, such as bone marrow, blood and other body fluids, is now a widely accepted technique. IM methodologies require high affinity antibodies or other receptors, but are potentially as effective as density gradient separations. Thus, a computer-controlled first-generation immunomagnetic assay system (IMAS) biodetector is being developed for clinical diagnostics. This system is fully automated and affords the advantage of rapid flow-through capture of all types of magnetic beads (MBs) and obviates operator contact with body fluid samples during the collection and analysis phases. In the present work, biotinylated capture antibodies were bound to streptavidin-coated MBs for capture of E. coli O157:H7, T cells and T cell subsets. Samples were automatically vortex mixed with antibody-coated MBs, stained with an acridine dye or fluorescent antibody and collected in a specially designed flow cell containing multiple steel pins, which concentrate external magnetic field lines. IM complexes were rapidly (within minutes), separated from their media in the magnetic field. Magnetically captured particles were automatically rinsed in the flow cell to remove unwanted materials and detection was achieved via a flow-through fluorimeter. Samples can be subsequently captured on a microbiological filter for microscopic visualization and image analysis. Preliminary results demonstrate that rapid detection of target bacteria and leukocytes at low concentrations in body fluids is possible with a total assay time under 1 h. This IM technology has many other potential clinical, industrial and environmental monitoring applications.

Electrochemiluminescence from tunicate, tunichrome-metal complexes and other biological samples

Low level intrinsic electrochemiluminescence (ECL) was induced from body fluids and homogenized tissues of oysters and several species of tunicates. No significant ECL was detected in human blood cell lysates, or bovine haematin, but minor ECL was observed in avian blood cell lysates. Both terrestrial grass and seagrass exhibited ECL, which is probably attributable to chlorophyll, since dead (brown) grass did not demonstrate ECL. It was postulated that organic-metal complexes in marine invertebrates were, at least in part, responsible for the intrinsic ECL, since such animals are known to be rich in organically bound metals. However, alternative biochemical mechanisms for the observed ECL, which do not involve metal chelates, are possible. Various metal ions were added to the invertebrate preparations to determine whether exogenous metals could enhance or inhibit the ECL reactions. Strongly oxidizing metal ions such as Ag+, Au+, Cu2+, Hg2+ and Sb2+ at > or = 100 ppm severely inhibited the intrinsic ECL response. No statistically significant ECL enhancement due to addition of metal ions was noted. ECL "profiles' were generated which demonstrated differences in the ECL responses of individual tunicate preparations to the presence of various exogenous metal ions. Differences in ECL profiles may represent differences in types or levels of endogenous metal chelates or other biochemical constituents. In addition, synthetic tunichromes (tunicate pigments) were analysed for ECL in the presence and absence of various added metal ions. One synthetic tunichrome isomer demonstrated a specific ECL interaction with Hg2+, while the other demonstrated broader ECL activity with several metal ions.

Highly selective acridine and ethidium staining of bacterial DNA and RNA

The acridine dyes acridine orange (AO) and coriphosphine O (CPO) and ethidium bromide (EtBr) were used to stain bacterial digests after electrophoresis in native and denaturing (SDS) polyacrylamide gels and were shown to stain DNA and RNA preferentially over other subcellular components in the gels. Vegetative cell digests of Bacillus subtilis, Escherichia coli, Micrococcus luteus, and Staphylococcus aureus showed intense staining of DNA with AO and CPO near the top of the gel, but little or no staining of other cellular constituents. EtBr stained both DNA and RNA in the gels. Protein standards and non-nucleic acid cellular constituents stained faintly with high concentrations (> or = 100 microM) of AO, lower concentrations (13.9 microM) of CPO, and did not stain with 0.5 microgram/ml EtBr in denaturing gels. The complete set of cellular biochemicals was visualized by silver staining, while the protein subset was detected by Coomassie blue staining. The highest concentrations of AO (120 microM) and CPO (13.9 microM) were shown to detect purified DNA in gels with a sensitivity in the range of 25-50 ng per band. This work demonstrates the specificity of acridine and ethidium dyes for nucleic acids, while illustrating the level of non-nucleic acid-specific interactions with other cellular components by staining of electrophoretically separated cellular components in a gel matrix.

Immunomagnetic-electrochemiluminescent detection of Escherichia coli O157 and Salmonella typhimurium in foods and environmental water samples

Hemorrhagic Escherichia coli O157:H7 strains and other virulent enteric pathogens can pose a serious health threat in tainted meats, poultry, and even drinking water. Traditional culture-based methods for assay of enteric pathogens in foods and water sources are relatively slow, and results can be ambiguous. Immunomagnetic separation (IMS) and detection methods have been investigated and appear promising for rapid bacterial assay of foods and environmental samples. In this work, a commercial sensor which combines IMS with electrochemiluminescence (ECL) detection is evaluated for detection of E. coli O157 and Salmonella typhimurium in foods and fomites. Results indicate that detection limits are in the range of 100 to 1,000 bacteria per ml in pristine buffer for E. coli O157 and S. typhimurium, respectively, or 1,000 to 2,000 bacteria per ml in food samples (depending on the sample) and that total processing and assay time is rapid (< 1 h) even in food samples. An immunologic "hook" or high-antigen-concentration prozone effect was observed above 10(4) and 10(5) bacteria per ml for E. coli O157 and S. typhimurium, respectively. IMS was accomplished in milk, juices, serum, supernatant fluids from ground beef, finely minced chicken, and fish suspensions as well as several freshwater sources and followed by ECL assay. Some samples, especially fish, gave unexpectedly high background ECL. Conversely, low ECL intensity was observed in nonfat and 2% fat milk samples, which appeared to be related to binding or entrapment of the antibody-coated magnetic beads by particulates in the milk, as revealed by microscopy. Results of this evaluation suggest the feasibility of immunomagnetic-ECL methodology for rapid, sensitive, and facile preliminary screening of various foods and fomites for the presence of virulent enteric pathogens.

A color image analysis method for assessment of germination based on differential fluorescence staining of bacterial spores and vegetative cells using acridine orange

Color fluorescence image analysis of acridine orange (AO) stained germinating Bacillus subtilis var. niger bacteria revealed a cell population initially dominated by small green spores followed by the emergence of at least three additional discernible subpopulations in response to stimulation with D-glucose. These subpopulations were small, round or oblong red cells; intermediate to large metachromatic cells; and large red rods. Large green rods were rarely observed. An increase in red emissions (i.e., putative RNA synthesis) was sometimes seen as early as 90 min after exposure to D-glucose and uptake of AO at room temperature. This may represent either metabolic recovery from quiescence or RNA synthesis associated with germination. In the absence of D-glucose, or using autoclaved bacteria in the presence of glucose, no relative increase in the red signal was observed despite hours of observation. Digital image analysis was used for relative measurement of red, green and blue signals and to correlate the size of various subpopulations with their fluorescence color emissions over time. Image analysis demonstrated a trend toward increasing size and red emission in the presence of glucose. The average red emission was found to be a good discriminator of the various subpopulations, while the average green emission was approximately equal among the subpopulations making it a poor discriminator. These data suggest that AO staining might be used for rapid computer-assisted discrimination of spores vs. vegetative cells.

A comparative study of PCR product detection and quantitation by electro-chemiluminescence and fluorescence

Amplification and detection of target DNA sequences are made possible in a polymerase chain reaction (PCR) by using a mixture of biotinylated and ruthenium(II) trisbipyridal (Ru(bpy)3(2+))-end-labelled primers. In this way, biotin for capture and Ru(bpy)3(2+) for detection are directly incorporated into the PCR product obviating subsequent probe hybridization. PCR of a bacterial DNA template from Alteromonas species strain JD6.5 using a cocktail of biotin- and Ru(bpy)3(2+)-labelled primers amplified a 1 kilobase region. Serial dilution of PCR product followed by magnetic separation with Streptavidin (SA)-coated magnetic beads and an electrochemiluminescence (ECL) assay using the semi-automated QPCR System 5000 demonstrated sensitive (pg range) DNA detection. ECL assay of probe hybridization to a human immunodeficiency virus (HIV) sequence also produced pg level sensitivity. Quantitative DNA determination by ECL assay correlated well with visual detection of DNA in electrophoretic gels. However, DNA detection by ECL assay was 10 to 100 times more sensitive than conventional ethidium bromide staining. The combination of DNA-based magnetic separation with ECL assay provides a very sensitive and rapid method of quantitating DNA which, owing to its rapid and facile nature, may have many applications in the research, environmental monitoring, industrial and clinical fields.

Sensitive detection of biotoxoids and bacterial spores using an immunomagnetic electrochemiluminescence sensor

Extremely sensitive detection of various biotoxoids and bacterial spores using the commercial ORIGEN analyzer was achieved by capture on antibody-conjugated micron sized magnetic beads (MBs) followed by binding of ruthenium (II) trisbipyridal chelate (Ru(bpy)2+3-labelled reporter antibodies. Immunomagnetically captured target materials were collected on a magnet. Electrochemiluminescence (ECL) was evoked from the Ru(bpy)3(2+)-tagged reporter antibodies by application of an electrical potential. Femtogram sensitivity levels were obtained for all biotoxoids tested including botulinus A, cholera beta subunit, ricin and staphylococcal enterotoxoid B by this immunomagnetic (IM)-ECL approach. An IM-ECL assay for Bacillus anthracis spores yielded a detection limit of at least 100 spores. The ECL signal was a function of analyte quantity over several orders of magnitude, but the immunological 'hook' effect at high antigen loads made quantitation impossible over a broader range. All assays were performed with a maximum combined incubation and assay time of approximately 40 min. This work demonstrates the extreme sensitivity of the IM-ECL approach for soluble and particulate antigens.

Plant nitrate reductase gene fragments enhance nitrite production in activated murine macrophage cell lines

Nitrate reductase (NR) gene fragments (1.1 kb and 800 bp) from the barley plant were incorporated into pSV2neo and transfected by electroporation into a variety of cell lines of different functionality. Only transfected murine macrophage cell lines demonstrated appreciably enhanced NO2- production (i.e., NR activity) both in the presence and absence of exogenous nitrate (NO3-). Addition of NO3- caused the greatest increase in NO2- production when macrophages were primed with interferon-gamma (INF-gamma) and lipopolysaccharide (LPS). Transfection of RAW 264.7 murine macrophages led to isolation of several novel neomycin-resistant subpopulations designated NR10(1), NR10(2) (both containing the 1.1 kb NR fragment) and NR800(5) (containing the 800 bp NR fragment). Similarly transfected nonleukocytic and leukocytic stem cell lines showed no significant NO2- production. Outside of the macrophage cell lines, only the murine T cell line EL-4 showed evidence of mild nitrite production enhancement. The mechanism of enhanced NO2- formation in NR transfected murine macrophages is unknown. However, study of these novel cells may lead to greater understanding of the expression of a plant NR in mammalian cells and highly controlled production of a cytotoxic molecule (NO2-) in macrophages.

Synthesis of diazoluminomelanin (DALM) in HL-60 cells for possible use as a cellular-level microwave dosimeter

Chemical and bacterial synthesis of a thermochemiluminescent polymer known as diazoluminomelanin (DALM) has been previously reported. This paper focuses on the intracellular synthesis of aminomelanin (AM) in mammalian cell lines and subsequent DALM synthesis from this core molecule. B16 melanoma cells, HL-60 myeloid leukemia cells, and RAW 264.7 macrophages show AM and DALM production. Macroscopic image analysis of HL-60 cell lysates containing DALM using the Quantitative Luminescence Imaging System (QLIS) showed increased chemiluminescence (CL) with increased microwave power input and increased temperature. This work represents a first step toward the goal of microscopic radiofrequency dosimetry of individual DALM-loaded cells using image analysis.

Luminol and diazoluminomelanin as indicators of HL-60 cell differentiation

This paper describes use of a novel substituted melanin which is useful in detection of differentiating leukemia cells and their membranes. Comparisons of luminol-(5-amino-2,3-dihydro-1,4-phthalazinedione) and diazoluminomelanin (DALM)-mediated chemiluminescence (CL) were made with various types of differentiated and undifferentiated HL-60 whole cells, cell lysates, and membrane fractions. Luminol had a greater CL response than DALM with HL-60 promyelocytic stem cells and differentiated macrophage-like or neutrophil-like whole cell and cell lysate preparations. However, DALM showed markedly greater CL than luminol for membrane fractions derived from each cell type. The greatest luminol-dependent CL was observed for cell types high in myeloperoxidase (MPO). The greatest DALM-mediated CL was seen with cell types that are high in MPO or strong producers of superoxide (O2-) anions. In some cases, significant differences in CL could also be distinguished on the basis of inducing agent used [i.e. dimethylsulfoxide, all-trans retinoic acid or 12-o-tetradecanoylphorbol-13-acetate]. Both luminol- and DALM-dependent CL were strongly inhibited by preincubation of cellular preparations with 3-amino-L-tyrosine (a component of DALM). Taken together, these data suggest that the reaction mechanism of luminol favors interaction with cytoplasmic MPO whereas that of DALM favors membrane interactions. Thus, both reagents may be of use in assays to detect differentiating leukocytes or their cellular components.

Influence of cell cycle synchronization on digital image analysis of HL-60 granulopoiesis

Retinoic acid (RA)-treated HL-60 cells subjected to density arrest (DA) and double thymidine block (TB) synchronization demonstrated image feature changes associated with cellular proliferation and differentiation. RA-treated TB cells demonstrated an increased level of morphologic differentiation (assessed by differential counts and quantitation of nuclear shape) and more rapid functional differentiation (assessed by superoxide production and expression of complement receptors) than RA-treated DA cells. By comparison to DA cells, TB cells had less variation in virtually all image features values. A Kruskal-Wallis test of image features ranked total optical density (TOD) of Feulgen-stained cells, nuclear area and shape factor as the top three features regardless of synchronization method. Statistically significant changes in image feature values of RA-treated cells were first noted on day 1. The computer-assisted ability to discriminate RA-treated cells on a given day after induction from paired controls by means of an unsupervised learning algorithm increased over a seven-day period for both DA and TB cells. However, in the dichotomous (RA-treated versus untreated) classification scheme employed, which did not account for continuous levels of morphologic differentiation, there was no advantage in the use of the TB over DA procedure.

Angiotensin converting enzyme inhibitors. 10. Aryl sulfonamide substituted N-[1-carboxy-3-phenylpropyl]-L-alanyl-L-proline derivatives as novel antihypertensives

Compounds 1a-g consisting of enalaprilat covalently bonded to aryl sulfonamides, including several known thiazide diuretics, were synthesized and tested for ACE inhibitory and diuretic and overall antihypertensive effects. All compounds were potent ACE inhibitors in vitro, with IC50 = 6.5-85 nM. At 10 mg/kg iv or ip in the rat, 1a-g inhibited the AI pressor response by 76-100%; inhibition declined significantly upon oral dosing. Compounds 1a and 1f at 100 mg/kg ip in the sodium-depleted, spontaneously hypertensive rats reduced blood pressure 28-35% and 41-42%, respectively. Compounds 1a and 1f elicited natriuresis and kaliuresis without accompanying volume increases in the rat; 1c at 25 mg/kg iv induced delayed diuresis. Compound 1f has been chosen for further development.

Computerized morphometric differentiation of chromatin changes in splenocytes from normal and calorie-restricted mice

Morphometric image analysis of splenocytes obtained from mice fed calorie-restricted diets for periods of up to three weeks revealed slight but significant changes in nuclear size, nuclear texture and total amounts of stainable Feulgen-positive DNA as compared to age-and-sex-matched control cells. The cellular changes were associated with body weight loss and changes in the distribution of splenic T cells and B cells during the three weeks of dietary restriction. The reduced nuclear area and Feulgen-stained DNA may reflect an altered susceptibility of cells from nutrient-restricted sources toward acid hydrolysis. This in turn may be indicative of a temporarily altered synthesis of subcellular components, as these phenomena seem to lessen by the third week of dietary restriction.