Providing Public Engagement Training to Build Connections Between the Community and Research Ethics Professionals: A Pilot Project

There is growing interest for research ethics professionals to engage with members of the public, yet they often lack the training needed to engage effectively. The STEM Ambassador Program provides a promising framework for training research ethics professionals to form authentic community connections and carry out effective engagement activities based on shared interests and values. The experiences of ten research administrators who participated in a pilot of the STEM Ambassador training for research ethics professionals are presented. Post-training surveys of the research administrators indicate that they valued the training and the skills obtained, and intend to continue with public engagement activities with support of their leadership.

Using single IRB consultations to meet the educational needs of investigative teams

Single IRB (SIRB) consultation resources were established by the Utah Trial Innovation Center to assist and educate investigative teams prior to the submission of funding applications for multisite, cooperative research. Qualitative analysis of the written consultation materials and meeting minutes revealed the most common areas of education needed by investigative teams, including (a) the differences and relationships between the IRB and a Human Research Protection Program (HRPP); (b) the main phases of the SIRB process; and (c) the use of technology platforms for documentation of SIRB review processes. For investigative teams who are inexperienced with using a SIRB, such consultation in the pre-award period is likely to fill in knowledge gaps and improve the study start-up process.

Disseminated Tuberculosis in a Nigerian Adolescent with Linear IgA Bullous Dermatosis: A Case Report and Review of Literature

Linear IgA bullous dermatosis (LABD) is an auto-immune disease affecting young children and adults, characterized by the linear deposition of IgA at the basement membrane zone with resultant complement activation and a cascade of immune reactions. There is a loss of adhesion at the dermo-epidermal junction and subsequent blister formation. It is a rare disease that has a good prognosis with adequate therapy. However, the underlying depressed immunity associated with the disease may expose them to such infections as tuberculosis. We report the case of an 11-years-old Nigerian female adolescent with LABD, diagnosed at the age of four years but defaulted on follow-up, who developed disseminated tuberculosis (pulmonary, lymph nodes, abdominal and pericardial effusion) seven years after the appearance of the initial blistering skin lesions. She commenced anti-tuberculosis drugs, steroids, and a tube pericardiostomy for the pericardial effusion. Dapsone was initiated for the LABD during the continuation phase of anti-tuberculosis therapy, with subsequent disappearance of the skin rash within two weeks.

Key lessons and strategies for implementing single IRB review in the Trial Innovation Network

The Trial Innovation Network has established an infrastructure for single IRB review in response to federal policies. The Network's single IRB (sIRBs) have successfully supported over 70 multisite studies via more than 800 reliance arrangements. This has generated several lessons learned that can benefit the national clinical research enterprise, as we work to improve the conduct of clinical trials. These lessons include distinguishing the roles of the single IRB from institutional Human Research Protections programs, establishing a consistent sIRB review model, standardizing collection of local context and supplemental, study-specific information, and educating and empowering lead study teams to support their sites.

An Approach to Reviewing Local Context for Exception from Informed Consent Trials Using a Single IRB

In the context of emergency research, researchers can ask the institutional review board (IRB) to waive the regulatory requirement that individuals provide informed consent when enrolling in research studies. A requirement of the waiver of informed consent is that the reviewing IRB must review and approve a community consultation and public disclosure plan. It is critical that an IRB serving as the single IRB (sIRB) for multisite research be thoroughly versed in the local context concerns for each participating site to determine whether the site's community is being adequately consulted about the research in which individuals will be enrolled under an exception to the informed consent requirement. We designed an sIRB review model for evaluating site-specific community consultation plans that included a local evaluation and feedback step, and we piloted the model with a four-site, pediatric exception from informed consent (EFIC) clinical trial. We identified three key roles for the model: the sIRB, the investigators, and the representative of the institution's human research protection program (HRPP). We successfully collected the information and local input needed to evaluate each site's community consultation plan and applied the information to a thorough IRB review, despite the geographic distance between the study site and the sIRB.

Implementing a Central IRB Model in a Multicenter Research Network

Implementing the National Institutes of Health's (NIH's) new single institutional review board (IRB) policy has caused a paradigm shift in IRB review across the country. IRBs and human research protection programs are looking more closely at their processes for ceding review and developing procedures to handle local review when relying on a single IRB. This article describes an NIH-funded network that proactively instituted a central IRB (CIRB) in 2012, anticipating the NIH future mandate. Lessons learned are described. There was a steep learning curve for IRBs and participating sites. IRB submission workload burden shifted from study teams to the data coordinating center, which created new workflow challenges, especially preparing hundreds of consent documents centrally. Despite difficulties encountered with CIRB review, this network is now fully functioning under a CIRB model. Further review and experience are needed to determine whether this shift in IRB review has eliminated duplicative review or regulatory burden from study teams.

Evaluation of emissions and exposures at workplaces using desktop 3-dimensional printer

There is a paucity of data on additive manufacturing process emissions and personal exposures in real-world workplaces. Hence, we evaluated atmospheres in four workplaces utilizing desktop "3-dimensional" (3-d) printers [fused filament fabrication (FFF) and sheer] for production, prototyping, or research. Airborne particle diameter and number concentration and total volatile organic compound concentrations were measured using real-time instruments. Airborne particles and volatile organic compounds were collected using time-integrated sampling techniques for off-line analysis. Personal exposures for metals and volatile organic compounds were measured in the breathing zone of operators. All 3-d printers that were monitored released ultrafine and fine particles and organic vapors into workplace air. Particle number-based emission rates (#/min) ranged from 9.4 × 109 to 4.4 × 1011 (n = 9samples) for FFF3-d printers and from 1.9 to 3.8 × 109 (n = 2 samples) for a sheer 3-d printer. The large variability in emission rate values reflected variability from the printers as well as differences in printer design, operating conditions, and feedstock materials among printers. A custom-built ventilated enclosure evaluated at one facility was capable of reducing particle number and total organic chemical concentrations by 99.7% and 53.2%, respectively. Carbonyl compounds were detected in room air; however, none were specifically attributed to the 3-d printing process. Personal exposure to metals (aluminum, iron) and 12 different organic chemicals were all below applicable NIOSH Recommended Exposure Limit values, but results are not reflective of all possible exposure scenarios. More research is needed to understand 3-d printer emissions, exposures, and efficacy of engineering controls in occupational settings.

Tightly locked optical frequency comb from a semiconductor disk laser

Ultrafast semiconductor disk lasers (SDLs) passively modelocked using semiconductor saturable absorbers mirrors (SESAMs) generate optical frequency combs (OFCs) with gigahertz line spacings - a regime where solid-state and fiber lasers struggle with geometrical and Q-switching limitations. We stabilized both the frequency comb spacing and the offset without any additional external optical amplification or pulse compression. The overall noise performance is competitive with other gigahertz OFCs. A SESAM-modelocked vertical external-cavity surface-emitting laser (VECSEL) at a center wavelength around 1 µm generates 122-fs pulses with 160 mW average output power and we only needed 17-pJ pulse energy coupled into a silicon nitride (Si₃N₄) waveguide for supercontinuum generation (SCG) and OFC offset stabilization.

Frequency comb offset detection using supercontinuum generation in silicon nitride waveguides

We present the first direct carrier-envelope-offset (CEO) frequency detection of a modelocked laser based on supercontinuum generation (SCG) in a CMOS-compatible silicon nitride (Si(3)N(4)) waveguide. With a coherent supercontinuum spanning more than 1.5 octaves from visible to beyond telecommunication wavelengths, we achieve self-referencing of SESAM modelocked diode-pumped Yb:CALGO lasers using standard f-to-2f interferometry. We directly obtain without amplification strong CEO beat signals for both a 100-MHz and 1-GHz pulse repetition rate laser. High signal-to-noise ratios (SNR) of > 25 dB and even > 30 dB have been generated with only 30 pJ and 36 pJ of coupled pulse energy from the megahertz and gigahertz laser respectively. We compare these results to self-referencing using a commercial photonic crystal fiber and find that the required peak power for CEO beat detection with a comparable SNR is lowered by more than an order of magnitude when using a Si(3)N(4) waveguide.

The reaction of methyl sterculate and malvalate with silver nitrate-silica gel and its use as a basis for the estimation of cyclopropene fatty acids

When in contact with silver nitratesilica gel, methyl esters of cyclopropene fatty acids undergo ring opening to yield pairs of isomers with methylene, hydroxymethyl, or nitratomethyl side-chains at the original ring positions. Thus the main products from methyl sterculate were the methyl 9 (or 10)-methylene octadec-10 (or 8)-enoates, and, in lesser quantities, the methyl 9 (or 10)-(nitratomethyl)-octadec-9-enoates and the methyl 9 (or 10)-(hydroxymethyl)-octadec-9-enoates. Hydrogenation quantitatively converted this mixture of isomeric pairs to a mixture of methyl 9- and methyl 10-methyloctadecanoates.Chromatography on silver nitrate-silica gel, followed by gas chromatography of the hydrogenated products, has been used as the basis of a new method for estimating individual cyclopropene and cyclopropane acids in lipids.

Inhibition by cyclopropene fatty acids of the desaturation of stearic acid in hen liver

The mechanism of the hardening of body fats of animals by dietary lipids which contain cyclopropene fatty acids has been studied. Dietary methyl sterculate increased the stearic acid content of egg yolk lipid and decreased the activity of the stearic acid desaturase system of hen liver. The cyclopropene fatty acids were specific inhibitors of the stearic acid desaturase system of hen livers since other fatty acids, including two possible metabolites of sterculic acid, failed to inhibit the system at equivalent concentrations. Sterculic acid was a more effective inhibitor of the system than malvalic acid. Kinetic studies have shown that the inhibition is irreversible. Apparent kinetic constants were determined for the system.The results support the hypotheses that cyclopropene fatty acids inactivate an essential component of the desaturase system, probably by combination with-SH groups, and that this inhibition causes many of the effects of dietary cyclopropene fatty acids, including permeability disorders of eggs.

Surveillance of Australian workplace Based Respiratory Events (SABRE) in New South Wales

BACKGROUND

The Surveillance of Australian workplace Based Respiratory Events (SABRE) New South Wales (NSW) scheme is a voluntary notification scheme established to determine the incidence of occupational lung diseases in NSW Australia.

AIMS

Data presented in this paper summarize the last 7 years of reporting to SABRE (June 2001 to December 2008).

METHODS

Every 2 months, participating occupational physicians, respiratory physicians and general practitioners (accredited by the NSW WorkCover Authority) reported new cases of occupational lung disease seen in their practices. Data collected include gender, age, causal agent and the occupations and industries believed responsible. Estimated incidence was calculated for each disease.

RESULTS

Three thousand six hundred and fifty-four cases were notified to the scheme, consisting of 3856 diagnoses. Most of the cases were males (76%). Pleural plaques [1218 (28%)] were the most frequently reported condition, followed by mesothelioma [919 (24%)]. Silicosis [90 (2%)] and occupational asthma [OA; 89 (2%)] were the most frequently reported non-asbestos-related diseases. Estimated rates for mesothelioma, diffuse pleural thickening (DPT) and OA were 83, 83 and 5 cases per million employed males per year, respectively. Trades such as carpenters and electricians associated with the building industry, electricity supply and asbestos product manufacture were the most common occupations and industries reported.

CONCLUSIONS

Asbestos-related diseases are the most frequently reported conditions to SABRE NSW. The very low incidence of OA for NSW most likely reflects under-diagnosis as well as under-reporting. Occupational lung disease is still occurring in NSW despite current preventative strategies. The SABRE scheme currently provides the only available information in this area.

On the origin of selective nitrous oxide N-N bond cleavage by three-coordinate molybdenum(III) complexes

Reaction of Mo(N[R]Ar)(3) (R = (t)Bu or C(CD(3))(2)CH(3)) with N(2)O gives rise exclusively to a 1:1 mixture of nitride NMo(N[R]Ar)(3) and nitrosyl ONMo(N[R]Ar)(3), rather than the known oxo complex OMo(N[R]Ar)(3) and dinitrogen. Solution calorimetry measurements were used to determine the heat of reaction of Mo(N[R]Ar)(3) with N(2)O and, independently, the heat of reaction of Mo(N[R]Ar)(3) with NO. Derived from the latter measurements is an estimate (155.3 +/- 3.3 kcal.mol(-1)) of the molybdenum-nitrogen bond dissociation enthalpy for the terminal nitrido complex, NMo(N[R]Ar)(3). Comparison of the new calorimetry data with those obtained previously for oxo transfer to Mo(N[R]Ar)(3) shows that the nitrous oxide N-N bond cleavage reaction is under kinetic control. Stopped-flow kinetic measurements revealed the reaction to be first order in both Mo(N[R]Ar)(3) and N(2)O, consistent with a mechanism featuring post-rate-determining dinuclear N-N bond scission, but also consistent with cleavage of the N-N bond at a single metal center in a mechanism requiring the intermediacy of nitric oxide. The new 2-adamantyl-substituted molybdenum complex Mo(N[2-Ad]Ar)(3) was synthesized and found also to split N(2)O, resulting in a 1:1 mixture of nitrosyl and nitride products; the reaction exhibited first-order kinetics and was found to be ca. 6 times slower than that for the tert-butyl-substituted derivative. Discussed in conjunction with studies of the 2-adamantyl derivative Mo(N[2-Ad]Ar)(3) is the role of ligand-imposed steric constraints on small-molecule, e.g. N(2) and N(2)O, activation reactivity. Bradley's chromium complex Cr(N(i)Pr(2))(3) was found to be competitive with Mo(N[R]Ar)(3) for NO binding, while on its own exhibiting no reaction with N(2)O. Competition experiments permitted determination of ratios of second-order rate constants for NO binding by the two molybdenum complexes and the chromium complex. Analysis of the product mixtures resulting from carrying out the N(2)O cleavage reactions with Cr(N(i)Pr(2))(3) present as an in situ NO scavenger rules out as dominant any mechanism involving the intermediacy of NO. Simplest and consistent with all the available data is a post-rate-determining bimetallic N-N scission process. Kinetic funneling of the reaction as indicated is taken to be governed by the properties of nitrous oxide as a ligand, coupled with the azophilic nature of three-coordinate molybdenum(III) complexes.

Slow-binding inhibition of human prostaglandin endoperoxide synthase-2 with darbufelone, an isoform-selective antiinflammatory di-tert-butyl phenol

The antiinflammatory agent darbufelone, ((Z)-5-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl] methylene]-2-imino-4-thiazolidinone, methanesulfonate salt), was discovered as a dual inhibitor of cellular prostaglandin and leukotriene production. To study the mechanism of action of this drug, we expressed human prostaglandin endoperoxide synthase-1 (PGHS-1) and PGHS-2 and purified the recombinant enzymes using buffers that contain octylglucoside. In cyclooxygenase assays following a 15-min incubation of enzyme with inhibitor, darbufelone potently inhibits PGHS-2 (IC(50) = 0.19 microM) but is much less potent with PGHS-1 (IC(50) = 20 microM). Interestingly, when the assay buffer contains traces of Tween 20 (0.0001%), darbufelone appears inactive with PGHS-2 due to a detergent interaction that is detectable by absorption spectroscopy. We therefore used octylglucoside, which does not affect darbufelone in this way, in place of Tween 20 in our PGHS buffers. Inhibition of PGHS-2 with darbufelone is time dependent: with no preincubation, darbufelone is a weak inhibitor (IC(50) = 14 microM), but after a 30-min incubation it is 20-fold more potent. Plots of PGHS-2 activity vs preincubation time at various darbufelone concentrations reach a plateau. This finding is inconsistent with irreversible or one-step slow-binding inhibition. A two-step slow-binding inhibition model is proposed in which the E.I complex (K(i) = 6.2 +/- 1.9 to 14 +/- 1 microM) slowly transforms (k(5) = 0.015-0.030 s(-)(1)) to a tightly bound E.I form with K(i) = 0.63 +/- 0.07 microM and k(6) = 0.0034 s(-)(1). In steady-state kinetics inhibition experiments performed with no preincubation, we find that darbufelone is a noncompetitive inhibitor of PGHS-2 (K(i) = 10 +/- 5 microM). Darbufelone quenches the fluorescence of PGHS-2 at 325 nm (lambda(ex) = 280 nm) with K(d) = 0.98 +/- 0.03 microM. The PGHS substrate, arachidonate, and various cyclooxygenase inhibitors do not alter this binding affinity of darbufelone but a structural analogue of darbufelone competes directly for binding to PGHS-2. Di-tert-butyl phenols such as darbufelone may inhibit PGHS-2 by exploiting a previously unrecognized binding site on the enzyme.

Synthesis of homochiral tris(2-alkyl-2-aminoethyl)amine derivatives from chiral alpha-amino aldehydes and their application in the synthesis of water soluble chelators

A novel synthesis of 3-fold symmetric, homochiral tris(2-alkyl-2-aminoethyl)amine (TREN) derivatives is presented. The synthesis is general in scope, starting from readily prepared chiral alpha-amino aldehydes. The optical purity of the N-BOC protected derivatives of tris(2-methyl-2-aminoethyl)amine and tris(2-hydroxymethyl-2-aminoethyl)amine has been ascertained by polarimetry and chiral NMR chemical shift experiments. An X-ray diffraction study of the L-alanine derivative (tris(2-methyl-2-aminoethyl)amine.3 HCl, L-Ala(3)-TREN) is presented: crystals grown from ether diffusion into methanol are cubic, space group P2(1)3 with unit cell dimensions a = 11.4807(2) A, V = 1513.23(4) A(3), and Z = 4. Attachment of the triserine derived backbone tris(2-hydroxymethyl-2-aminoethyl)amine (L-Ser(3)-TREN) to three 3-hydroxy-1-methyl-2(1H)-pyridinonate (3,2-HOPO) moieties, followed by complexation with Gd(III) gives the complex Gd(L-Ser(3)-TREN-Me-3,2-HOPO)(H(2)O)(2), which is more water soluble than the parent Gd(TREN-Me-3,2-HOPO)(H(2)O)(2) and a promising candidate for magnetic resonance imaging (MRI) applications. Crystals of the chiral ferric complex Fe(L-Ser(3)-TREN-Me-3,2-HOPO) grown from ether/methanol are orthorhombic, space group P2(1)2(1)2(1), with unit cell dimensions a = 13.6290(2) A, b = 18.6117(3) A, c = 30.6789(3) A, V = 7782.0(2) A(3), and Z = 8. The solution conformation of the ferric complex has been investigated by circular dichroism spectroscopy. The coordination chemistry of this new ligand and its iron(III) and gadolinium(III) complexes has been studied by potentiometric and spectrophotometric methods. Compared to the protonation constants of previously studied polydentate 3,2-HOPO-4-carboxamide ligands, the sum of protonation constants (log beta(014)) of L-Ser(3)-TREN-Me-3,2-HOPO (24.78) is more acidic by 1.13 log units than the parent TREN-Me-3,2-HOPO. The formation constants for the iron(III) and gadolinium(III) complexes have been evaluated by spectrophotometric pH titration to be (log K) 26.3(1) and 17.2(2), respectively.

Occupational asthma in adults in six Canadian communities

We examined the prevalence, population attributable risk (PAR), and clinical characteristics of occupational asthma (OA) in a randomly selected population in six communities in Canada. Our study followed the European Community Respiratory Health Survey protocol. A randomly selected population of 18,701 (87% response rate) persons from the study communities, ranging in age from 20 to 44 yr, completed an initial questionnaire, of whom 2,974 (39% response rate) attended the laboratory and completed supplementary questionnaires. Of these latter individuals, 383 had asthma. Asthma was defined as physician-diagnosed asthma, and adult-onset asthma was defined as a first attack at age 15 yr or older. We used several methods for estimating OA as follows: (1) reporting of a high-risk job (occupation and industry) for OA at the time of asthma onset (Probable OA); (2) reporting of exposure to a substance that may cause OA (Possible OA) while not in a high-risk job at the time of asthma onset; and (3) combination of the PAR for high-risk jobs and exposures. The prevalence (95% confidence interval [CI]) of Probable OA and Possible OA combined was 36.1% (31.3 to 41.0%) among subjects with adult-onset asthma. The occupations most commonly reported in association with OA were nursing in the Probable OA group and clerical and food preparation in the Possible OA group. The clinical characteristics and exposures reported by both groups were similar. The PAR for adult-onset asthma in high-risk jobs and exposures was 18.2%. The assessment of occupation and industry alone, rather than of exposures, may underestimate the contribution of occupational exposures to asthma prevalence.

Spinal nerve segmentation in the chick embryo: analysis of distinct axon-repulsive systems

In higher vertebrates, the segmental organization of peripheral spinal nerves is established by a repulsive mechanism whereby sensory and motor axons are excluded from the posterior half-somite. A number of candidate axon repellents have been suggested to mediate this barrier to axon growth, including Sema3A, Ephrin-B, and peanut agglutinin (PNA)-binding proteins. We have tested the candidacy of these factors in vitro by examining their contribution to the growth cone collapse-inducing activity of somite-derived protein extracts on sensory, motor, and retinal axons. We find that Sema3A is unlikely to play a role in the segmentation of sensory or motor axons and that Ephrin-B may contribute to motor but not sensory axon segmentation. We also provide evidence that the only candidate molecule(s) that induces the growth cone collapse of both sensory and motor axons binds to PNA and is not Sema3A or Ephrin-B. By grafting primary sensory, motor, and quail retinal neurons into the chick trunk in vivo, we provide further evidence that the posterior half-somite represents a universal barrier to growing axons. Taken together, these results suggest that the mechanisms of peripheral nerve segmentation should be considered in terms of repellent molecules in addition to the identified molecules.

Synthesis of a ligand based upon a new entry into the 3-hydroxy-N-alkyl-2(1H)-pyridinone ring system and thermodynamic evaluation of its gadolinium complex

The synthesis of a new, more water soluble derivative of TREN-Me-3,2-HOPO (tris[(3-hydroxy-1-methyl-2-oxo-1,2- didehydropyridine-4-carboxamido)ethyl]amine) is presented. The synthesis starts with the condensation reaction of (N-methoxyethylamino)acetonitrile hydrochloride and oxalyl chloride to give 3,5-dichloro-N-(methoxyethyl)-2(1H)-pyrazinone. The 3-position is readily substituted with a benzyloxy group, and the pyrazinone is converted to ethyl 3-(benzyloxy)-N-(methoxyethyl)-2(1H)-pyridinone-4-carboxylate by a Diels-Alder cycloaddition with ethyl propiolate. Basic deprotection of the ester followed by activation, coupling to tren, and acidic deprotection of the benzyl groups gives the ligand TREN-MOE-3,2-HOPO (tris[(3-hydroxy-1-(methoxyethyl)- 2-oxo-1,2-didehydropyridine-4-carboxamido)ethyl]amine). The gadolinium complex of TREN-MOE-3,2-HOPO was prepared by metathesis, starting from gadolinium chloride. The solubility of the new metal complex is significantly enhanced. The four protonation constants (determined by potentiometry) for TREN-MOE-3,2-HOPO (log Ka1 = 8.08, log Ka2 = 6.85, log Ka3 = 5.81, log Ka4 = 4.98) are virtually identical to those reported for the parent ligand. The stability constants for the gadolinium complex of TREN-MOE-3,2-HOPO determined by potentiometry (log beta 110 = 19.69(2), log beta 111 = 22.80(2)) and by spectrophotometry (log beta 110 = 19.80(1), log beta 111 = 22.88(1), log beta 112 = 25.88(1)) differ slightly from those for the parent ligand; this follows from a change in the complexation model in which a new diprotonated species, [Gd(TREN-MOE-3,2-HOPO)(H)2]2+, was included. The presence of this extra species was demonstrated by factor analysis, comparison of spectral data, and nonlinear least-squares refinement. Significant formation of this species is observed between pH 3 and pH 1.5.

A rationalization of the acidic pH dependence for stromelysin-1 (Matrix metalloproteinase-3) catalysis and inhibition

The pH dependence of matrix metalloproteinase (MMP) catalysis is described by a broad bell-shaped curve, indicating the involvement of two unspecified ionizable groups in proteolysis. Stromelysin-1 has a third pK(a) near 6, resulting in a uniquely sharp acidic catalytic optimum, which has recently been attributed to His(224). This suggests the presence of a critical, but unidentified, S1' substructure. Integrating biochemical characterizations of inhibitor-enzyme interactions with active site topography from corresponding crystal structures, we isolated contributions to the pH dependence of catalysis and inhibition of active site residues Glu(202) and His(224). The acidic pK(a) 5.6 is attributed to the Glu(202).zinc.H(2)O complex, consistent with a role for the invariant active site Glu as a general base in MMP catalysis. The His(224)-dependent substructure is identified as a tripeptide (Pro(221)-Leu(222)-Tyr(223)) that forms the substrate cleft lower wall. Substrate binding induces a beta-conformation in this sequence, which extends and anchors the larger beta-sheet of the enzyme. substrate complex and appears to be essential for productive substrate binding. Because the PXY tripeptide is strictly conserved among MMPs, this "beta-anchor" may represent a common motif required for macromolecular substrate hydrolysis. The striking acidic profile of stromelysin-1 defined by the combined ionization of Glu(202) and His(224) allows the design of highly selective inhibitors.

Catalytic activities and substrate specificity of the human membrane type 4 matrix metalloproteinase catalytic domain

Membrane type (MT) matrix metalloproteinases (MMPs) are recently recognized members of the family of Zn(2+)- and Ca(2+)-dependent MMPs. To investigate the proteolytic capabilities of human MT4-MMP (i.e. MMP-17), we have cloned DNA encoding its catalytic domain (CD) from a breast carcinoma cDNA library. Human membrane type 4 MMP CD (MT4-MMPCD) protein, expressed as inclusion bodies in Escherichia coli, was purified to homogeneity and refolded in the presence of Zn(2+) and Ca(2+). While MT4-MMPCD cleaved synthetic MMP substrates Ac-PLG-[2-mercapto-4-methylpentanoyl]-LG-OEt and Mca-PLGL-Dpa-AR-NH(2) with modest efficiency, it catalyzed with much higher efficiency the hydrolysis of a pro-tumor necrosis factor-alpha converting enzyme synthetic substrate, Mca-PLAQAV-Dpa-RSSSR-NH(2). Catalytic efficiency with the pro-tumor necrosis factor-alpha converting enzyme substrate was maximal at pH 7.4 and was modulated by three ionizable enzyme groups (pK(a3) = 6.2, pK(a2) = 8.3, and pK(a1) = 10.6). MT4-MMPCD cleaved gelatin but was inactive toward type I collagen, type IV collagen, fibronectin, and laminin. Like all known MT-MMPs, MT4-MMPCD was also able to activate 72-kDa progelatinase A to its 68-kDa form. EDTA, 1,10-phenanthroline, reference hydroxamic acid MMP inhibitors, tissue inhibitor of metalloproteinases-1, and tissue inhibitor of metalloproteinases-2 all potently blocked MT4-MMPCD enzymatic activity. MT4-MMP is, therefore, a competent Zn(2+)-dependent MMP with unique specificity among synthetic substrates and the capability to both degrade gelatin and activate progelatinase A.

Embryonic lens repels retinal ganglion cell axons

During development of the vertebrate visual system, retinal ganglion cell (RGC) axons follow a precise path toward their midbrain targets. Although much is known about the cues that direct RGC axons once they have left the optic disc, less is known about the guidance of axons at earlier stages, when RGCs first send out their axons to navigate within the developing retina. Using collagen gel coculture experiments, we find that the embryonic lens produces a powerful diffusible repulsive activity for RGC axons. We also find that this activity is localized to the lens epithelium and not the lens fiber layer, while the pigmented epithelium and vitreous humour are devoid of activity. The further observation that the lens also chemorepels primary sensory axons, but does not repel olfactory bulb axons, shows that this activity is specific for subsets of axons. Our experiments have excluded two candidate repellents for RGC axons (collapsin-1/sema III and chondroitin sulfate proteoglycans). These results implicate the lens in the earliest stages of RGC axon guidance. One function of the lens repellent may be to prevent aberrant targeting toward the lens, and it may also be involved in the directional guidance of RGC axons toward the optic disc.

Neurotoxicity in single photon emission computed tomography brain scans of patients reporting chemical sensitivities

The subset of patients reporting chemical sensitivity with neurocognitive complaints usually exhibits specific abnormalities of brain metabolism consistent with neurotoxicity, on imaging with single photon emission computed tomography (SPECT). These recurrent neurotoxic patterns are characterized by a mismatch in tracer uptake between early- and late-phase imaging, multiple hot and cold foci throughout the cortex, temporal asymmetry and increased tracer uptake into the soft tissues and, sometimes, the basal ganglia. Previous studies confirm these neurotoxic findings in patients with neurotoxic chemical exposures and breast implants. Affective processes such as depression do not, alone, show this pattern. These abnormalities in SPECT images correlate with documented neurocognitive impairment. Controlled challenges to ambient chemicals can induce profound neurotoxic changes seen on SPECT imaging in chemically sensitive patients. Detoxification treatment techniques frequently produce significant improvement on brain SPECT brain imaging in these patients. Neurotoxicity appears to be characteristic in many cases of chemical sensitivity.

Investigation of a catalytic zinc binding site in Escherichia coli L-threonine dehydrogenase by site-directed mutagenesis of cysteine-38

L-Threonine dehydrogenase catalyzes the NAD+-dependent oxidation of threonine forming 2-amino-3-ketobutyrate. Chemical modification of Cys-38 of Escherichia coli threonine dehydrogenase, whose residue aligns with the catalytic zinc-binding residue, Cys-46, of related alcohol/polyol dehydrogenases, inactivates the enzyme [B. R. Epperly and E. E. Dekker (1991) J. Biol. Chem. 266, 6086-6092; A. R. Johnson and E. E. Dekker (1996) Protein Sci., 382-390]. To probe its function, Cys-38 was changed to Ser, Asp, and Glu by site-directed mutagenesis. Mutants C38S and C38D were purified to homogeneity and found to be, like the wild-type enzyme, homotetrameric proteins containing one Zn2+ atom per subunit. The circular dichroism spectra of these mutants were essentially identical to that of the wild-type enzyme. Mutant C38S was catalytically inactive but mutant C38D had a specific activity of 0.2 unit/mg, a level approximately 1% that of the wild-type enzyme. After it was incubated with 1 mM Zn2+ and then assayed in the presence of 15 mM Zn2+, mutant C38S showed only a trace of enzymatic activity (i.e., 0.013 unit/mg). Preincubation of mutant C38D with 5 mM Zn2+, Co2+, or Cd2+ increased its activity 57-, 6-, or 3-fold, respectively; 1 mM Mn2+ halved and 0.5 mM Hg2+ abolished activity. Zn2+-stimulated mutant C38D showed these properties: apparent substrate activation at low threonine concentrations, a maximum activity of 27 units/mg with 20 mM threonine, and inhibition by high levels of substrate; an activation Kd = 3 mM Zn2+; and a pH optimum of 8.4 (in contrast to pH 10.3 for the wild-type enzyme). Without added Zn2+, mutant C38D is equally active with threonine and 2-amino-3-hydroxypentanoate, but Zn2+-activated mutant C38D is 10-fold more reactive with threonine than with 2-amino-3-hydroxypentanoate. In the absence of added metal ions, wild-type enzyme similarly uses substrates other than threonine and shows a dramatic increase in activity with only threonine when stimulated by either Cd2+ or Mn2+; added Zn2+ has no effect on activity with threonine. Cys-38 of threonine dehydrogenase, therefore, is located in an activating divalent metal ion-binding site. Having a negatively charged residue like Asp in this position allows the binding of a catalytic Zn2+ ion which enhances activity with threonine and reduces activity with substrate analogs. Whether Cys-38 of wild-type threonine dehydrogenase binds a catalytic metal ion (possibly Zn2+) in vivo remains to be established.

Pattern formation in a patch occupancy metapopulation model: a cellular automata approach

The explicit consideration of space in ecological research is of paramount importance to understand the structure and functioning of ecological systems. In this paper we develop a simple spatially explicit metapopulation model in which colonization is constant and independent of the number of occupied patches (i.e. propagule-rain effect, Gotelli, 1991). Extinction, on the other hand, is modelled as a stochastic process whose intensity depends on the number of occupied patches in the neighborhood of each focal patch. Our model is the CA counterpart of two classical patch occupancy metapopulation models. We analytically prove this by showing that our CA converges to the differential equation in the mean-field approximation. The asymptotic behaviour of the system, expressed as the proportion of occupied patches, agrees with the equilibrium proportion of patches derived by using ODEs. In both models, the existence of a rescue-effect increases the range of extinction and colonization parameters over which the system attains complete occupancy of patches. However, in our model this result is strongly influenced by the degree of coupling among patches and is apparent only for local interactions. With local interactions and particular parameter values of colonization and extinction, self-organized spatio-temporal patterns emerge with a fractal-like clustering, even though the environment is spatially homogeneous. Our results point out that the importance of being spatial and discrete (Durrett & Levin, 1994a) in our model is a result of local interactions.

Biocatalytic sulfur removal from fuels: applicability for producing low sulfur gasoline

Environmental regulations are driving R&D efforts to produce low sulfur fuels, including diesel fuel and gasoline for motor vehicles. Biocatalytic sulfur removal from fuels has potential applicability for producing low sulfur gasoline. Microbial biocatalysts have been identified that can biotransform sulfur compounds found in fuels, including ones that selectively remove sulfur from dibenzothiophene heterocyclic compounds. Most attention is give to the 4S pathway of Rhodococcus, which can remove sulfur from substituted and unsubstituted dibenzothiophenes, including sulfur compounds that hinder chemical catalysis and that resist removal by mild hydrotreatment. Various bioreactor and bioprocess designs are being tested for use with biocatalysts, including recombinant biocatalysts, for use in removing sulfur from fuels and feedstocks within the petroleum refinery stream. With bioprocess improvements that enhance biocatalyst stability, achieve faster kinetics, improve mass transfer limitations, temperature and solvent tolerance, as well as broaden substrate specificity to attack a greater range of heterocyclic compounds, biocatalysis may be a cost-effective approach to achieve the production of low sulfur gasoline. The challenge will be to accomplish these improvements by the time the regulations for low sulfur gasoline and other vehicle fuels go into effect in order to be competitive with emerging nonbiological desulfurization technologies.

Site-directed mutagenesis of histidine-90 in Escherichia coli L-threonine dehydrogenase alters its substrate specificity

Escherichia coli L-threonine dehydrogenase is a member of the Zn(2+)-containing alcohol/polyol dehydrogenase family. Methylation of His-90 of L-threonine dehydrogenase was recently found to cause total inactivation (J. P. Marcus and E. E. Dekker, 1995 Arch. Biochem. Biophys. 316, 413-420). Since His-90 is not conserved among the related dehydrogenases, this residue was changed to arginine, asparagine, and alanine by site-directed mutagenesis in order to probe its role. All three purified, homogeneous mutants, like wild-type enzyme, contained one Zn2+ atom/subunit and exhibited a sequential catalytic mechanism; the kcat value for each, however, was reduced approximately 10-fold. The K(m) value for threonine was elevated from 3 mM for wild-type enzyme to 31, 328, and 417 mM, respectively, for mutants H90R, H90N, and H90A. The activation energy of catalysis for mutant H90A was increased by 6.6 kcal/mol, suggesting that in the wild-type enzyme His-90 forms at least one crucial hydrogen bond in the transition state. Whereas wild-type enzyme catalyzed the oxidation of threonine amide (0.75 M) about twice as fast as this same concentration of threonine or 0.375 M L-2-amino-3-hydroxypentanoate, the reaction rate of mutant H90A with 0.75 M threonine amide or threonine methyl ester was 33- to 35-fold higher than with this level of threonine. Similarly, mutant H90N used 0.75 M threonine methyl ester or threonine amide as substrate 9- to 13-fold better than it used this concentration of threonine. Mutants H90A and H90N were more reactive with 0.225 M L-threonine hydroxamate than with 0.75 M threonine, but mutant H90A did not oxidize L-2-amino-3-hydroxypentanoate (0.375 M) and mutant H90N used this substrate poorly. The best substrates for mutant H90R were threonine methyl ester, threonine, and threonine amide (all tested at 0.75 M); 0.375 M L-2-amino-3-hydroxypentanoate was a poor substrate. The isolation and characterization of these first His-90 mutants of E. coli L-threonine dehydrogenase confirm the importance of this residue in catalysis and suggest that His-90 is an active-site residue which modulates the substrate specificity of L-threonine dehydrogenase.

Surround repulsion of spinal sensory axons in higher vertebrate embryos

We have tested whether the orientation of axons sprouting from bipolar dorsal root ganglion neurons is influenced by diffusible cues from surrounding tissues. Surface ectoderm, dermomyotome, and notochord exert strong chemorepulsion on axons growing in collagen gels, operating at separations beyond those found in vivo and active in cocultures of chick and mouse tissues. Basal and alar plates of the neural tube are devoid of activity, as is the posterior-half-sclerotome, which repels in a contact-dependent manner. When ganglia are sandwiched between dermomyotome and notochord placed at a distance, axon growth is channeled in a bipolar trajectory. These results show that gradients of diffusible repulsion molecules flanking axon pathways can generate linear patterns of axon growth. We suggest that such "surround repulsion" may function generally, in concert with contact-dependent guidance mechanisms, to guide axons in the developing nervous system.

Evoked-potential thresholds and cubic distortion product otoacoustic emissions in the chinchilla following carboplatin treatment and noise exposure

Twenty-two chinchillas were given either a single intraperitoneal (i.p.) or intravenous (i.v.) injection (50 or 75 mg/kg) of Paraplatin, an asymptotic threshold shift-producing noise or a combination of the drug and noise in series. Auditory evoked potential (pure-tone) audiograms and cubic distortion product otoacoustic emissions were obtained on each animal before and after treatment, and the sensory epithelium of the cochlea was evaluated using the surface preparation method. Anatomical analysis indicated that the carboplatin alone caused relatively severe but scattered losses of inner hair cells throughout most of the cochlea which were dependent on dose and administration route. The outer sensory cell population remained essentially intact. In animals that had up to 40% scattered losses of only inner hair cells, evoked potential thresholds were near normal and the emission functions either were normal or showed an enhanced output. The severe losses of inner hair cells produced by the drug had no effect on the threshold shift dynamics produced by a five-day uninterrupted noise exposure. In general, there was not a consistent relation between the emission data and both the permanent threshold shift and outer hair cell losses.

Differential expression of the urokinase receptor in fibroblasts from normal and fibrotic human lungs

Binding of urokinase-type plasminogen activator (uPA) to a specific receptor (uPAR) on human lung fibroblasts enables it to regulate cellular proteolysis and remodeling of the extracellular matrix. Binding studies with radiolabeled uPA indicated that both normal and fibrotic lung fibroblasts express the receptor, but cells from fibrotic tissues bound significantly more uPA (P < 0.001). Phorbol myristate acetate, lipopolysaccharide, transforming growth factor-beta (TGF-beta), and tumor necrosis factor-alpha (TNF-alpha) increased uPA binding and plasminogen activation at the cell surface, with a greater maximal effect on fibrotic than on normal fibroblasts. Excess unlabeled uPA, specific antibody, or antisense oligonucleotides inhibited uPA binding. Ribonuclease (RNase) protection assays showed higher levels of uPAR messenger ribonuleic acid (mRNA) in each of the five fibrotic cell lines than in normal fibroblasts. uPA was mitogenic for normal as well as fibrotic fibroblasts, indicating that receptor binding concurrently localizes cellular proteolytic activity and stimulates mitogenesis. Morphometry and immunohistochemical analysis showed that uPAR, as well as uPA, was increased in fibroblasts in fibrotic lung tissue. Increased expression of uPAR by fibrotic lung fibroblasts and enhanced urokinase binding induced by proinflammatory cytokines suggest a novel mechanism by which fibroblast-mediated matrix remodeling and proliferation may be regulated in interstitial lung diseases.

Fibrinogen promotes adhesion of monocytic to human mesothelioma cells

Adhesion between monocytic and mesothelioma or pleural mesothelial cells influences stromal remodeling in pleural neoplasia. We found that cultured monocytic cells (U937) adhere to either human pleural mesothelioma (MS-1) or mesothelial (MeT5A) cells in vitro. 125I-fibrinogen bound specifically and saturably to either cell line, and specific fibrinogen binding increased upon stimulation of these cells with proinflammatory agents such as phorbol myristate (PMA), lipopolysaccharide (LPS) or tumor necrosis factor (TNF-alpha). We purified the fibrinogen receptor protein from a membrane fraction of MS-1 cells and identified it by immunoprecipitation as intercellular adhesion molecule (ICAM-1). Anti-ICAM-1 antibody or antisense oligonucleotides inhibited fibrinogen-mediated cell adhesion and binding of 125I-fibrinogen to mesothelioma or mesothelial cells. Cultured monocytic cells adhere to either mesothelioma or mesothelial cells, and the interaction is promoted by fibrinogen binding ICAM-1 at the cell surface. ICAM-1 is expressed by mesothelioma cells and CD 11b by macrophages in the fibrinous mesothelioma tumor stroma. The data suggest a common mechanism by which monocytic cells could adhere to either malignant mesothelioma cells or the mesothelial surface in pleural neoplasia.

Woodward's reagent K inactivation of Escherichia coli L-threonine dehydrogenase: increased absorbance at 340-350 nm is due to modification of cysteine and histidine residues, not aspartate or glutamate carboxyl groups

L-Threonine dehydrogenase (TDH) from Escherichia coli is rapidly inactivated and develops a new absorbance peak at 347 nm when incubated with N-ethyl-5-phenylisoxazolium-3'-sulfonate (Woodward's reagent K, WRK). The cofactors, NAD+ or NADH (1.5 mM), provide complete protection against inactivation; L-threonine (60 mM) is approximately 50% as effective. Tryptic digestion of WRK-modified TDH followed by HPLC fractionation (pH 6.2) yields four 340-nm-absorbing peptides, two of which are absent from enzyme incubated with WRK and NAD+. Peptide I has the sequence TAICGTDVH (TDH residues 35-43), whereas peptide II is TAICGTDVHIY (residues 35-45). Peptides not protected are TMLDTMNHGGR (III, residues 248-258) and NCRGGRTHLCR (IV, residues 98-108). Absorbance spectra of these WRK-peptides were compared with WRK adducts of imidazole, 2-hydroxyethanethiolate, and acetate. Peptides III and IV have pH-dependent lambda max values (340-350 nm), consistent with histidine modification. Peptide I has pH-independent lambda max (350 nm) indicating that a thiol is modified. WRK, therefore, does not react specifically with carboxyl groups in this enzyme, but rather modifies Cys-38 in the active site of TDH; modification of His-105 and His-255 does not affect enzyme activity. These results are the first definitive proof of WRK modifying cysteine and histidine residues of a protein and show that enzyme inactivation by WRK associated with the appearance of new absorptivity at 340-350 nm does not establish modification of aspartate or glutamate residues, as has been assumed in numerous earlier reports.

Inhibition of factor Xa-mediated procoagulant activity of human lung fibroblasts and pleural mesothelial cells

Extravascular fibrin deposition characterizes diverse forms of lung and pleural injury. Fibrin formation in these compartments is locally potentiated by the assembly and expression of the prothrombinase procoagulant complex (factors Xa, Va and II) at the surface of human lung fibroblasts and pleural mesothelial cells. We sought to identify structural domains on factor Xa that mediate expression of prothrombinase activity by these cells. In order to accomplish this objective, we used panels of monoclonal antibodies (MoAbs) to factor X to block prothrombinase assembly and function on the surface of cultured human lung fibroblasts and pleural mesothelial cells. Of 30 factor X MoAbs that recognized native factors X and Xa, 10 completely inhibited factor Xa function (prothrombin activation), and five others neutralized Xa function without affecting cell-binding, presumably by blocking the prothrombin binding site. Western blots showed that these inhibitory MoAbs reacted with the Xa heavy-chain. One MoAb that recognized the factor Xa light-chain blocked prothrombin activation at the factor Va binding site. Our results indicate that prothrombinase activity at the surface of lung parachymal or pleural cells can be blocked by MoAbs that interact with either the heavy- or light-chain of factors X. Antibodies that neutralize cell surface-expressed prothrombin activation offer a potential means to arrest pericellular fibrin formation in the lung and pleural space.

Regulation of fibrin deposition by malignant mesothelioma

Malignant mesothelioma (MM) is a locally aggressive tumor that spreads by poorly understood mechanisms. Because neoplastic spread has been linked to altered fibrin turnover, we used immunohistochemistry of nine MM and three fibrous tumors of the pleura to confirm in vivo fibrin deposition and expression of selected coagulation and fibrinolytic reactants in MM. Tumor-associated fibrin was readily detectable at site of tissue invasion. Little fibrin was distributed within the tumor, but tissue factor and tissue factor pathway inhibitor, urokinase, urokinase receptor, and plasminogen activator inhibitors 1 and 2 were all detected in either epithelioid or sarcomatous areas of MM. We used the MS-1 human pleural mesothelioma cell line to determine how expression of these reactants is regulated. Fibrinolytic activity of MS-1 is mainly due to urokinase and is responsive to cytokine stimulation. Functional extrinsic activation and prothrombinase complexes assemble at the cell surface. MM express procoagulants as well as fibrinolytic reactants in vivo and in vitro that promote local fibrin formation and remodeling. Fibrin deposition occurs primarily at areas of tissue invasion and could promote local extension of this neoplasm. Sparsity of fibrin within the central portions of the tumor stroma suggests that local resorption of transitional fibrin occurs at sites of established MM.

An analysis of astrocytic cell lines with different abilities to promote axon growth

The adult mammalian central nervous system (CNS) lacks the capacity to support axonal regeneration. There is increasing evidence to suggest that astrocytes, the major glial population in the CNS, may possess both axon-growth promoting and axon-growth inhibitory properties and the latter may contribute to the poor regenerative capacity of the CNS. In order to examine the molecular differences between axon-growth permissive and axon-growth inhibitory astrocytes, a panel of astrocyte cell lines exhibiting a range of axon-growth promoting properties was generated and analysed. No clear correlation was found between the axon-growth promoting properties of these astrocyte cell lines with: (i) the expression of known neurite-outgrowth promoting molecules such as laminin, fibronectin and N-cadherin; (ii) the expression of known inhibitory molecules such tenascin and chondroitin sulphate proteoglycan; (iii) plasminogen activator and plasminogen activator inhibitor activity; and (iv) growth cone collapsing activity. EM studies on aggregates formed from astrocyte cell lines, however, revealed the presence of an abundance of extracellular matrix material associated with the more inhibitory astrocyte cell lines. When matrix deposited by astrocyte cell lines was assessed for axon-growth promoting activity, matrix from permissive lines was found to be a good substrate, whereas matrix from the inhibitory astrocyte lines was a poor substrate for neuritic growth. Our findings, taken together, suggest that the functional differences between the permissive and the inhibitory astrocyte cell lines reside largely with the ECM.

A simple method for preparing modified TES and Tris yolk buffer that is optically clear and membrane filterable

OBJECTIVES

To determine whether modified TES and Tris (TEST) yolk buffer (TYB) made using a commercially available egg yolk extract would exhibit lab performance characteristics equal to the existing preparation made with whole egg yolk and to define the phospholipid content of the new modified TYB formulation.

DESIGN

Divided ejaculates from 21 normozoospermic and 7 oligozoospermic males presenting for pre-IVF evaluation were stored at 0 to 4 degrees C for 42 hours using commercially available or modified TYB before analysis in the optimized sperm penetration assay (SPA).

SETTING

A commercial tissue culture manufacturer and a clinical fertility reference laboratory.

MAIN OUTCOME MEASURES

Sperm swim-up recoveries and average penetrations per ovum, determined by the SPA, were used as measures of sperm function. High-pressure liquid chromatography (HPLC) was used to profile the egg yolk extract.

RESULTS

No significant differences in either sperm swim-up recovery rates or SPA results were found in normal or poor quality semen that was treated with modified or commercial TYB. The major constituent in commercial egg yolk extract is lecithin.

CONCLUSIONS

Commercially available egg yolk extract passes easily through a 0.2-microns filter, is a rich source of lecithin, and can be substituted effectively for whole egg yolk in preparing TYB.

A beta-linked mannan inhibits adherence of Pseudomonas aeruginosa to human lung epithelial cells

Adherence through carbohydrate-binding adhesins is an early step in colonization of the lung by gram-negative organisms, and because published data indicate that binding involves mannose groups, we tested the ability of a beta-linked acetyl-mannan (acemannan) to inhibit adherence of Pseudomonas aeruginosa to cultures of human lung epithelial cells. Adherence of radiolabelled P.aeruginosa to A549 cells (a type II-like pneumocyte line) increased linearly with the duration of the incubation. Acemannan inhibited adherence of bacteria, and the extent of inhibition was related to the concentration of the mannan. Inhibition required continued contact between acemannan and the target epithelial cells; cells washed free of acemannan no longer discouraged bacterial binding. Comparison of binding between seven different strains of P.aeruginosa indicated that fewer mucoid than non-mucoid bacteria adhered, but binding of either phenotype was inhibited by acemannan. Mannose, methyl alpha-D-mannopyranoside, methyl beta-D-mannopyranoside and dextran did not affect adherence of any of the non-mucoid strains. Mannose inhibited adherence by one mucoid strain, but not the other, indicating differences between strains of the same phenotype. Since prior treatment of epithelial cells with concanavalin A did not affect acemannan-induced inhibition of bacterial adherence, we concluded that the inhibitory effect of acemannan probably does not involve mannose-containing receptors.

Regulation of mesothelial cell mitogenesis by antisense oligonucleotides for the urokinase receptor

The association of urokinase-type plasminogen activator (uPA) with its receptor (uPAR) influences various biologic functions, including cell migration, angiogenesis, differentiation, and wound healing. Expression of uPAR at the mesothelial surface could, therefore, influence cellular responses in the pleural space. We found that a line of cultured human mesothelial cells (MeT5A) expressed specific and saturable binding sites for uPA that increased on stimulation with PMA. Ligand blotting studies showed that the mesothelial receptor is a 50 kD protein similar to that in other cell lines. Binding of active and intact, but not amino terminal or low molecular weight fragment, uPA to mesothelial cells enhanced DNA synthesis and cell proliferation, and antibodies against either the active site of uPA or uPAR abrogated this effect. We reasoned that regulation of uPAR expression could control uPA-induced mitogenesis and tested this hypothesis with antisense oligonucleotides complementary to uPAR mRNA. Phosphorothioate-modified antisense oligonucleotides inhibited uPA-mediated mesothelial cell proliferation in a concentration-dependent manner. These effects were associated with decreased binding of 125I-uPA and reduced expression of the uPAR gene product. The results indicate that uPAR is involved in signal transduction pathways that control uPA-mediated mesothelial cell proliferation, a process implicated in the pathogenesis of mesothelial inflammation and pleural neoplasia. Antisense oligonucleotides to uPAR suppress mesothelial cell mitogenesis in vitro and offer a potential means of regulating the process in vivo.

Effects of TGF-beta and TNF-alpha on procoagulant and fibrinolytic pathways of human tracheal epithelial cells

The epithelial lining of the airways is subject to injury through several processes, including infections, bronchiolitis, and fume exposures. Because airway fibrin deposition influences the course of local injury, we examined how two inflammatory cytokines influenced fibrin formation and clearance in human tracheal epithelial cells (TEC). TEC were treated with transforming growth factor-beta (TGF-beta) and tumor necrosis factor-alpha (TNF-alpha). TNF-alpha increased release of tissue factor (TF)-related procoagulant activity that, through generation of factor Xa, promotes assembly of the prothrombinase complex at the cell surface. Fibrinolytic activity was plasminogen dependent and due to both urokinase (uPA) and tissue plasminogen activator (tPA). The cells expressed plasminogen activator inhibitor 1 (PAI-1), but relatively little PAI-2. Depression of fibrinolysis by TGF-beta correlated with increased PAI-1. Conversely, TNF-alpha increased plasminogen activator (PA) activity due to increased uPA. Fibrinolytic activity was inhibited by actinomycin D and cyclohexamide, but changes in mRNAs for uPA, tPA, PAI-1, and TF by either cytokine were not appreciable. PAI-2 mRNA was not found. The data indicate that TGF-beta decreases the fibrinolytic capacity of TEC, suggesting that this cytokine promotes fibrin retention. TNF-alpha increases expression of both procoagulant and fibrinolytic activities; this differential regulation could favor both pericellular fibrin formation and dissolution.

Single photon emission computed tomography of the brain in patients with chemical sensitivities

Chemical sensitivities display a recurrent pattern on scintigraphic examinations of the brain. The pattern can include mismatching between early and late imaging, multiple hot and cold foci distributed throughout the cortex without regard to lobar distribution (salt and pepper pattern), temporal asymmetries, and sometimes increased activity in the basal ganglia. This study used Desert Shield/Desert Storm veterans who present with abnormal neurological and psychological symptoms as a model to exhibit abnormalities by brain scintigraphy. These are typical of those seen in patients with documented exposure to neurotoxic compounds who develop a clinical syndrome that has been termed "chemical sensitivity." Exposure to cocaine, alcohol, and other substances of abuse can result in abnormal scintigrams of the brain using tracers such as [technetium-99m]hexamethylpropyleneoxime. This study used techniques combining regional cerebral blood flow data with delayed distributional data after the intracellular conversion of the tracer into a hydrophilic molecule. In addition to delayed image abnormalities, a mismatch occurs in the regional activity between the two image sets of the veterans. This degree of mismatch was not seen in control subjects who were screened for avoidance of neurotoxic agents. Patterns identified from examinations performed on patients with known exposure to petroleum distillates, pesticides and other materials linked with neurotoxicity were identified in some veterans of the Desert Shield/Desert Storm operation. A single case of repeated examinations on a veteran showed a reversion of these patterns toward normal after therapy. This reversion followed independent assessments of clinical improvement.

Growth factors for human pleural mesothelial cells in soluble products from formed clots

Fibrin deposition within the pleural space may influence repair following pleural injury. Although the mesothelial surface can organize fibrin, the contribution of pleural mesothelial cells to pleural repair is unknown. During coagulation thrombin cleaves Fibrinopeptide A (FPA, A alpha 1-16) and fibrinopeptide B (FPB) from the A alpha and B beta chains of fibrinogen to generate fibrin monomer. Since these peptides are mitogenic for human fibroblasts, we considered that they might stimulate replication of human pleural mesothelial cells (HPMC). Application of fluid expressed from fibrin clots significantly increased cell number and stimulated uptake of 3H-thymidine by HPMC compared with untreated cells. The mitogenic response of subconfluent HPMC to dilutions of clot fluid (30-150 micrograms/ml protein) was comparable to that of 0.1 nM TGF-beta. Fibrinopeptide A (7.5-30 microM) stimulated 3H-thymidine uptake in HPMC, but FPB had only a slight effect at 30 microM. Antibody to FPA antibody significantly attenuated the mitogenic effect of clot fluid, indicating that a major component is FPA. Our study suggests that fibrinopeptides released during fibrin formation in vivo may stimulate local mesothelial regeneration following pleural injury.

Expression and assembly of procoagulant complexes by human pleural mesothelial cells

Many pleural diseases involve fibrin deposition within the pleural cavity, an event that necessarily involves the mesothelium. This study of human pleural mesothelial cells (HPMC) was designed to determine how the mesothelium initiates and sustains the coagulation process. We used functional assays for activation of both factor X and prothrombin to examine expression and assembly of procoagulant activity by human pleural mesothelial cells in culture. The rates of factor Xa and thrombin formation were calcium-dependent. The rate of factor Xa formation in the presence of added factor VII increased in a concentration-dependent manner, suggesting that tissue factor is the primary procoagulant associated with HPMC. The fact that direct binding of radioiodinated factor VIIa to HPMC was specific, concentration-dependent and saturable confirms that tissue factor is expressed on the cell surface. The rate of thrombin formation increased with factor Xa concentration, and the rate was 5-, 6-fold higher in presence of added factor Va indicating that HPMC support expression of prothrombinase activity. Further, direct binding of radioiodinated factor Xa to HPMC was specific, concentration-dependent and saturable, confirming that the cells support the assembly of the prothrombinase complex.

Interleukin-1-mediated release of interleukin-8 by asbestos-stimulated human pleural mesothelial cells

The pleuropulmonary response to inhaled asbestos frequently involves inflammation and release of various cytokines from lung cells. Among these, interleukin-8 (IL-8) released from the mesothelium could augment inflammation of the pleura by attracting neutrophils to the pleural space. We used cultures of human pleural mesothelial cells (HPMC) to examine the mechanism of IL-8 production by asbestos and cytokines. Suspensions of amosite, chrysotile, or crocidolite asbestos in concentrations as low as 5 micrograms/ml enhanced release of IL-8 from HPMC during 6 h of incubation at 37 degrees C. Electron microscopy of asbestos-treated HPMC showed that the cells avidly engulfed each of the different types of asbestos fibers. Two proinflammatory cytokines, interleukin-1 alpha (IL-1 alpha) and tumor necrosis factor-alpha, enhanced IL-8 release within 2 h and had an even greater effect after 6 h. Release of IL-8 was measured by an enzyme-linked immunosorbent assay, and functional activity of the cytokine was assessed by chemotaxis of human neutrophils. Identity of IL-8 in HPMC supernatants was established by absorption with an antibody to IL-8. Preincubation of HPMC with IL-1 receptor antagonist (IL-1ra) significantly decreased release of IL-8 after stimulation with amosite or crocidolite asbestos. We conclude that HPMC release IL-8 in response to asbestos stimulation and that the response is, in part, mediated by IL-1, mainly in the form of IL-1 alpha.

Contact inhibition in the failure of mammalian CNS axonal regeneration

Anamniote animals, such as fish and amphibians, are able to regenerate damaged CNS nerves following injury, but regeneration in the mammalian CNS tracts, such as the optic nerve, does not occur. However, severed adult mammalian retinal axons can regenerate into peripheral nerve segments grafted into the brain and this finding has emphasized the importance of the environment in explaining regenerative failure in the adult mammalian CNS. Following lesions, regenerating axons encounter the glial cells, oligodendrocytes and astrocytes, and their derivatives, respectively myelin and the astrocytic scar. Experiments to investigate the influence of these components on axon growth in culture have revealed cell-surface and extracellular matrix molecules that inhibit axon extension and growth cone motility. Structural and functional characterization of these ligands and their receptors is underway, and may solve the interesting neurobiological conundrum posed by the failure of mammalian CNS regeneration. Simultaneously, this might allow new possibilities for treatment of the severe clinical disabilities resulting from injury to the brain and spinal cord.

Site-directed mutagenesis of glutathione S-transferase YaYa. Mapping the glutathione-binding site

Previous studies from our laboratory have shown that aspartic acid 101 plays an important role in glutathione interaction to rat glutathione S-transferase YaYa, while tyrosine 9 is directly involved in catalysis. Based on the available structural information, site-directed mutagenesis was conducted to examine the function of arginine, lysine, glutamine, and proline residues surrounding the GSH binding pocket. Arginine mutants R13K, R15K, R20K, and R20I retained partial enzymatic activities, while R13I and R15I lost most of their activities. Kinetic studies showed a marked increase in Km toward GSH for R15I suggesting that arginine 15 contributes significantly to the binding of GSH in the active site of glutathione S-transferase YaYa. A drastic decrease in enzymatic activities for R13I suggested the importance of the charged group of arginine 13 either in maintaining the structural integrity of the enzyme or in serving a vital role in enzymatic function. Replacement of glutamine 54 and 67 with glutamic acid or asparagine resulted in decreased enzymatic activities. Moreover, an 11-, 17-, and 9-fold increase in Km values toward GSH for mutant Q54E, Q54N, and Q67N was observed, respectively. These results suggested that glutamine 54 and 67 also contributed significantly to the binding of GSH. Proline at position 56 appears to be important for maintaining the structural integrity of the enzyme since mutants P56A and P56F were much less active and extremely less stable than that of the wild type enzyme. Both lysine mutants, K45R and K45I, exhibited substantially higher catalytic efficiencies toward both 1-chloro-2,4-dinitrobenzene and GSH than the wild type enzyme. Our data clearly show that lysine 45 is not an essential residue for catalysis nor for GSH binding in glutathione S-transferase YaYa.

A bacterial protease perturbs the paracellular barrier function of transporting epithelial monolayers in culture

Tight junctions between cells and adhesion to the substratum maintain the barrier function of epithelia throughout the body. Damage to the epithelial barrier by microbial products allows penetration of bacteria and promotion of infection. We studied the effects of Pseudomonas elastase (PE) on the barrier function of epithelia by using Madin-Darby canine kidney (MDCK) epithelial cells; these cells form tight junctions (zonula occludens [ZO]) in vitro. PE decreased electrical resistance across the monolayers in a concentration- and time-dependent manner. Immunostaining of selected proteins of the ZO and zonula adherens was used to explore the effects of PE on junctional proteins. PE-treated monolayers of MDCK cells had markedly decreased immunostaining of ZO-1, a protein of the ZO, but light microscopy of PE-treated cells revealed no obvious morphologic changes. A chromium release assay indicated that, even with marked changes in transmonolayer electrical resistance, the permeability defect was not due to membrane disruption. Fluorescence staining of F-actin indicated diminution of cellular microfilaments in PE-treated cells, but E cadherin (uvomorulin), a protein of the zonula adherens, was unaffected by the enzyme. Elastases from porcine pancreas and human leukocytes with similar enzymatic activity (6 U/ml) did not decrease transmonolayer electrical resistance or degrade ZO-1. These results suggest that PE disturbs the barrier function of epithelial monolayers, in part, by changing the cell architecture and altering at least one protein of the ZO.

Up-regulation of neutral endopeptidase (CALLA) in human neutrophils by granulocyte-macrophage colony-stimulating factor

Neutral endopeptidase 24.11 (NEP/CALLA/CD10), an enzyme expressed on early lymphoid progenitors, neutrophils, and various other cell types, inactivates many biologically active peptides, including the bacterial chemotactic peptide N-formylmethionyl-leucyl-phenylalanine (fMLP). Inhibition of CD10/NEP on the surface of human neutrophils (PMNs) in vitro inhibits migration toward this chemotaxin, suggesting that enzymatic inactivation by NEP regulates the neutrophil response to fMLP. Because PMNs in inflammatory sites are exposed to various cytokines, we evaluated the effects of selected cytokines on CD10/NEP activity in vitro. Of five cytokines tested--interleukin-1 (IL-1), IL-6, and IL-8, granulocyte colony-stimulating factor, and granulocyte-macrophage colony-stimulating factor (GM-CSF)--GM-CSF provided the most consistent increase in surface NEP activity. Low concentrations (10(-9)-10(-7) M) of GM-CSF increased NEP activity in a time- and concentration-dependent manner to more than 225% that of control (phosphate-buffered saline-treated) cells. Cytofluorometry of cells stained with a fluorescent antibody to CD10 indicated that GM-CSF increased expression of surface CD10/NEP antigen in a similar manner. The effect of GM-CSF on NEP activity was enhanced still further by simultaneous exposure to IL-1, suggesting that combinations of cytokines may direct and regulate the neutrophil response within an inflammatory site. Rapid upregulation of CD10/NEP underscores the importance of this enzyme for control of peptide mediators of inflammation.

Mechanisms of fibrin formation and lysis by human lung fibroblasts: influence of TGF-beta and TNF-alpha

Fibrin gels form within the alveolar and interstitial compartments of the injured lung, and fibroblasts invade and facilitate organization of these transitional gels. We studied the effects of transforming growth factor-beta (TGF-beta) and tumor necrosis factor-alpha (TNF-alpha) on fibrinolytic and procoagulant activities of human lung fibroblasts (HLF) to determine their capacity to regulate pulmonary fibrin deposition. Fibrinolytic activity of cell lysates and media (n = 6 HLF cultures) were uniformly depressed by TGF-beta or TNF-alpha. In dose and time-course studies, HLF plasminogen activator inhibitor-1 (PAI-1) was increased by TGF-beta, whereas TNF-alpha induced release of PAI-1 into the media. HLF and media urokinase concentrations were depressed by TGF-beta, whereas urokinase was unchanged or increased by TNF-alpha. Tissue plasminogen activator was mainly cell associated and unchanged by TGF-beta or TNF-alpha. HLF antiplasmin activity was not detected. Plasma recalcification times of HLF media were decreased by TNF-alpha but unchanged by TGF-beta. These studies suggest that TGF-beta and TNF-alpha impair the ability of HLF to degrade fibrin by disturbing the balance of HLF plasminogen activators and PAI and that these cytokines concurrently leave unchanged or increase the capacity of HLF to initiate fibrin formation. Cytokines likely to occur in the injured lung induce abnormalities of fibrinolysis in HLF from adults; such abnormalities favor extravascular fibrin deposition, a characteristic feature of alveolitis.

Pathways of fibrin turnover of human pleural mesothelial cells in vitro

The mesothelium contains both procoagulant and fibrinolytic activities. An imbalance between these activities could account for the abnormal fibrin turnover and pleural fibrin deposition that is characteristic of pleural inflammation. Procoagulant activity of human pleural mesothelial cells (HPMC) is in part due to tissue factor, and the prothrombinase complex can also assemble at the HPMC surface. HPMC express tissue plasminogen activator (tPA) but no detectable fibrinolytic activity in a fibrin plate assay. Inhibition of HPMC fibrinolytic activity is due, in part, to elaboration of plasminogen activator inhibitors-1 and -2 (PAI-1 and PAI-2) as well as antiplasmins. Synthesis of PAI-1 and PAI-2 is inhibited by actinomycin D and cyclohexamide. HPMC PAI-1 is increased by transforming growth factor-beta (TGF-beta) and tumor necrosis factor-alpha (TNF-alpha), as is tPA release, while PAI-1 mRNA is unchanged and tPA mRNA is increased. PAI-2 release is induced by TNF-alpha and TGF-beta. Because they are a rich source of PAI-1 and PAI-2, HPMC may contribute to the high levels of these inhibitors in pleural exudates. Stimulation of HPMC by TNF-alpha or TGF-beta in vitro did not alter HPMC procoagulant activity nor the balance of elevated PAI and antiplasmins relative to PA, changes that collectively favor formation and persistence of pericellular fibrin.