Asbestos exposure of building maintenance personnel

The exposures of building maintenance personnel and occupants to airborne asbestos fibers, and the effects of operations and maintenance programs on those exposures, continue to be an important public health issue. The subject of this investigation was a large metropolitan county with numerous public buildings which routinely conducted air sampling for asbestos. A total of 302 personal air samples in nine task categories collected during maintenance worker activities in proximity to asbestos-containing materials were analyzed; 102 environmental air samples in four task categories were also analyzed. The arithmetic means of the 8-hr time weighted average exposures for personal sampling for each task category were all below the Occupational Safety and Health Administration permissible exposure level of 0.1 fibers (f)/cc > 5 microm. The highest mean 8-hr time weighted average exposure was 0.030 f/cc > 5 microm for ceiling tile replacement. The maximum asbestos concentration during sample collection for environmental samples was 0.027 f/cc > 5 microm. All asbestos-related maintenance work was done within the framework of an Operations and Maintenance Program (OMP) which utilized both personal protective equipment and controls against fiber release/dispersion. Results are presented in association with specific OMP procedures or controls. These results support the effectiveness of using Operations and Maintenance Programs to manage asbestos in buildings without incurring unacceptable risk to maintenance workers performing maintenance tasks.

2.0 A resolution structure of a ternary complex of pig muscle phosphoglycerate kinase containing 3-phospho-D-glycerate and the nucleotide Mn adenylylimidodiphosphate

The crystal structure of a ternary complex of pig muscle phosphoglycerate kinase (PGK) containing 3-phosphoglycerate (3-PG) and manganese adenylylimidodiphosphate (Mn AMP-PNP) has been determined and refined at 2.0 A resolution. The complex differs from the true substrate ternary complex only in the presence of an imido- rather than an oxylink between beta- and gamma-phosphates of the bound nucleotide. The 3-PG is bound in a similar manner to that observed in binary complexes. The nucleotide is bound in a similar manner to Mg ADP except that the metal ion is coordinated by all three alpha-, beta-, and gamma-phosphates, but not by the protein. The gamma-phosphate, which is transferred in the reaction, is not bound by the protein. One further characteristic of the ternary complex is that Arg-38 moves to a position where its guanidinium group makes a triple interaction with the N-terminal domain, the C-terminal domain, and the 1-carboxyl group of the bound 3-PG. Although a hinge-bending conformation change is seen in the ternary complex, it is no larger than that observed in the 3-PG binary complex. To reduce that distance between two bound substrates to a value consistent with the direct in-line transfer known to occur in PGK, we modeled the closure of a pronounced cleft in the protein structure situated between the bound substrates. This closure suggested a mechanism of catalysis that involves the "capture" of the gamma-phosphate by Arg-38 and the N-terminus of helix-14, which has a conserved Gly-Gly-Gly phosphate binding motif. We propose that nucleophilic attack by the 1-carboxyl group of the 3-PG on the gamma-phosphorus follows the capture of the gamma-phosphate, leading to a pentacoordinate transition state that may be stabilized by hydrogen bonds donated by the NH groups in the N-terminus of helix 14 and the guanidinium group of Arg-38. During the course of the reaction the metal ion is proposed to migrate to a position coordinating the alpha- and beta-phosphates and the carboxyl group of Asp-374. The mechanism is consistent with the structural information from binary and ternary substrate complexes and much solution data, and gives a major catalytic role to Arg-38, as indicated by site-directed mutagenesis.

Granulocyte-macrophage colony-stimulating factor and interferon-gamma prevent dexamethasone-induced immunosuppression of antifungal monocyte activity against Aspergillus fumigatus hyphae

Treatment with corticosteroids is an important risk factor for development of invasive aspergillosis. We evaluated the effect of dexamethasone (DEX) on superoxide anion (O2-) release and damage caused by elutriated human monocytes (EHM) on unopsonized hyphae of Aspergillus fumigatus. In addition, we studied the effects of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interferon-gamma (IFN-gamma) on these functions of DEX-treated EHM. Treatment of EHM with concentrations of DEX ranging from 5 to 500 nM (1.4-140 ng ml-1) for 48 h suppressed O2- release in response to phorbol myristate acetate in a dose-dependent fashion. Similarly, DEX significantly suppressed hyphal damage caused by EHM as measured by colorimetric MTT assay. Both GM-CSF (5 ng ml-1) and IFN-gamma (1.2 ng ml-1) added at day 0 to the EHM together with DEX (500 nM) significantly enhanced O2- release and percentage hyphal damage, preventing the DEX-induced suppression of EHM function. Thus, GM-CSF and IFN-gamma prevented the deleterious effects of DEX on antifungal activity of EHM against Aspergillus suggesting a potential therapeutic role in patients at risk for or suffering from invasive aspergillosis.

Effects of macrophage colony-stimulating factor on antifungal activity of mononuclear phagocytes against Aspergillus fumigatus

The effects of recombinant human macrophage colony-stimulating factor (M-CSF) on antifungal activity of human monocytes (MNC), MNC-derived macrophages (MDM), and rabbit pulmonary alveolar macrophages (PAM) against Aspergillus fumigatus were studied. MNC-induced hyphal damage was augmented by incubation with M-CSF (P = .027); PAM-induced hyphal damage was moderately enhanced by M-CSF (P = .046). Phagocytosis of Aspergillus conidia by MDM and PAM was strongly enhanced by M-CSF (P < .01). MNC pretreated with M-CSF exhibited enhanced superoxide anion production in response to PMA (P = .026). This effect was not associated with increased levels of mRNA transcripts of the components of NADPH oxidase, the enzyme responsible for superoxide anion production. M-CSF augments antifungal activity of mononuclear phagocytes against both conidia and hyphae of Aspergillus fumigatus partly by enhancement of oxidation-dependent mechanisms and may have an important immunomodulatory role in prevention and treatment of invasive aspergillosis in leukopenic patients.

Effects of granulocyte colony-stimulating factor and interferon-gamma on antifungal activity of human polymorphonuclear neutrophils against pseudohyphae of different medically important Candida species

Polymorphonuclear neutrophils (PMNs) are the major host defense against pseudohyphae, the invasive form of Candida species. We studied the effects of granulocyte colony-stimulating factor (G-CSF) and interferon-gamma (IFN-gamma) on the PMN-induced damage of pseudo-hyphae of Candida albicans, Candida tropicalis, and Candida parapsilosis in vitro by using two antifungal assays: a modified limiting dilution assay and a colorimetric metabolic 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. PMNs from healthy volunteers were incubated with either G-CSF (100-10,000 U/ml) or IFN-gamma (10-5000 U/ml) or buffer at 37 degrees C for 90 min and their capacity to damage nonopsonized pseudohyphae was then measured. C. tropicalis appeared to be the most susceptible species, whereas C. parapsilosis showed the highest rate of resistance to PMN damage. G-CSF (500-10,000 U/ml) and IFN-gamma (100-1000 U/ml) enhanced the antifungal activity of PMNs against C. albicans pseudo-hyphae (P < .01 and P < .05). Among the others, G-CSF enhanced PMN-induced damage of C. parapsilosis at concentrations 500-10,000 U/ml (P < .05), whereas it enhanced damage of C. tropicalis only at 10,000 U/ml (P < .01). IFN-gamma (100-1000 U/ml)-primed PMNs also caused augmented damage of C. parapsilosis (P < .05) but not of C. tropicalis at the same concentrations. Species-dependent differences exist in the responses of PMNs to Candida pseudohyphae and G-CSF as well as IFN-gamma are important immunomodulators of phagocytic host defenses against them.

The refined structure of the quinoprotein methanol dehydrogenase from Methylobacterium extorquens at 1.94 A

BACKGROUND

Methanol dehydrogenase (MDH) is a bacterial periplasmic quinoprotein; it has pyrrolo-quinoline quinone (PQQ) as its prosthetic group, requires Ca2+ for activity and uses cytochrome cL as its electron acceptor. Low-resolution structures of MDH have already been determined.

RESULTS

The structure of the alpha 2 beta 2 tetramer of MDH from Methylobacterium extorquens has now been determined at 1.94 A with an R-factor of 19.85%.

CONCLUSIONS

The alpha-subunit of MDH has an eight-fold radial symmetry, with its eight beta-sheets stabilized by a novel tryptophan docking motif. The PQQ in the active site is held in place by a coplanar tryptophan and by a novel disulphide ring formed between adjacent cysteines which are bonded by an unusual non-planar trans peptide bond. One of the carbonyl oxygens of PQQ is bonded to the Ca2+, probably facilitating attack on the substrate, and the other carbonyl oxygen is out of the plane of the ring, confirming the presence of the predicted free-radical semiquinone form of the prosthetic group.

Antifungal activity of elutriated human monocytes against Aspergillus fumigatus hyphae: enhancement by granulocyte-macrophage colony-stimulating factor and interferon-gamma

Human monocytes are important effector cells in host defenses against Aspergillus hyphae, and as elutriated monocytes (EHM) they may be transfused in large quantities to leukopenic patients with invasive aspergillosis. The antifungal activity of EHM against Aspergillus hyphae was compared with that of polymorphonuclear leukocytes (PMNL). The effects of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interferon-gamma (IFN-gamma) on superoxide anion (O2-) release and on hyphal damage caused by EHM against unopsonized A. fumigatus hyphae was investigated. EHM had antihyphal activity comparable to that of PMNL. GM-CSF significantly augmented O2- release by EHM in response to PMA. Also, both GM-CSF and IFN-gamma significantly enhanced the antifungal activity of EHM compared with untreated controls. Thus, EHM have demonstrable antifungal activity against Aspergillus hyphae that may be increased by GM-CSF and IFN-gamma, suggesting their potential therapeutic role in immune reconstitution of effector cells.

Prostaglandin synthase. At the heart of the matter

The structure of prostaglandin synthase, the target of aspirin therapy in cardiovascular disease, reveals a remarkable integration of the enzyme's catalytic and membrane-binding properties.

Protective wear and instrument sterilisation/disinfection in UK general dental practice

The 18,000 United Kingdom general dental practitioners registered for National Health Service (NHS) practice were surveyed in July 1991 to assess their current use of protective gloves, eyewear and masks, and instrument sterilisation. Nearly 7,000 (6,588) valid responses were obtained immediately; of these, 70% of practitioners wore gloves routinely for clinical work, but only 14.5% donned new gloves for each patient. About 60% wore protective eyewear routinely or all the time but 12% never wore eye protection, and only 36% of practitioners used masks. Autoclaves or chemical solutions were the most popular methods to disinfect handpieces, but less than half the respondents stated that handpieces were sterilised or disinfected after each patient use. Most respondents (81%) routinely used autoclaves for sterilisation of other instruments. Although the response rate to the questionnaire was low, the results indicate that, despite the risks of, and publicity about, cross-infection, a substantial number of NHS dental practitioners may not adequately disinfect or sterilise their equipment between patients.

Defective antifungal activity of monocyte-derived macrophages from human immunodeficiency virus-infected children against Aspergillus fumigatus

Invasive aspergillosis recently has been encountered in adults and children with human immunodeficiency virus (HIV) infection even without known risk factors, such as neutropenia or corticosteroid therapy. Macrophages play a significant role in the host defenses against Aspergillus organisms by ingesting conidia and preventing their germination to hyphae. The antifungal activity of peripheral blood monocyte-derived macrophages (MDM) from 19 HIV-infected children was compared with that of 16 normal controls. The phagocytic activity of patients' MDM, measured as percentage of phagocytosis, was significantly decreased compared with normal donors (P = .014). In addition, the inhibitory activity of MDM on germination of intracellular A. fumigatus conidia was significantly impaired in patients compared with normal controls (P = .016). There was no significant difference in the defects between patients with lower or higher CD4 lymphocyte counts. Impairment of antifungal activity of macrophages may contribute to the susceptibility of HIV-infected patients to aspergillosis.

Management of variceal bleeding in the 1990s

BACKGROUND

Variceal bleeding is a common and serious problem.

OBJECTIVE

To review the current management of patients with variceal bleeding.

SUMMARY

Therapeutic options now include pharmacologic reduction of portal hypertension, endoscopic obliteration of varices, placement of decompressive shunts (both surgical and percutaneous), and liver transplantation. Each of these options may be required in different settings. A nonselective beta blocker can prophylactically reduce the risk of an initial bleed. Acute variceal bleeding is best managed by endoscopic sclerosis. Selection of therapy to prevent recurrent bleeding should be based on a full evaluation of the risk of bleeding and of liver failure.

CONCLUSIONS

Successful management requires a multidisciplinary team, full patient evaluation, and selection of appropriate therapy.

Impairment of neutrophil antifungal activity against hyphae of Aspergillus fumigatus in children infected with human immunodeficiency virus

Human immunodeficiency virus (HIV)-infected patients may acquire invasive aspergillosis without previously recognized risk factors, such as neutropenia or corticosteroid therapy. Because neutrophils (PMNL) are an important component of host defense in aspergillosis, the antifungal activity of PMNL against hyphae of Aspergillus fumigatus in 31 HIV-infected children was assessed. Hyphal damage was unaffected in 15 HIV-infected children with age-adjusted CD4 cell counts > or = 25% of the normal median value; it was decreased in 16 with CD4 cell counts < 25% (both vs. 20 healthy controls, P = .001. Incubation with sera from 12 of 14 HIV-infected children but not with the recombinant HIV proteins gp120, gp41, and p24 suppressed antifungal activity of normal PMNL compared with normal serum (P = .002). Pretreatment of defective PMNL from 5 patients with granulocyte colony-stimulating factor (G-CSF) partially corrected the defect (P = .002). These findings suggest that impaired serum-mediated antifungal activity against Aspergillus hyphae exists in PMNL of HIV-infected patients with low CD4 cell counts; G-CSF may improve this activity.

The control of cross-infection in UK clinical dentistry in the 1990s: immunisation against hepatitis B

Thirty thousand dentists and clinical ancillary staff in the UK were surveyed in July 1991 to assess the current state of immunisation against hepatitis B virus (HBV). About 11,000 responded immediately and nearly 94% of these had been, or were being, immunised against HBV. Nearly all dentists and therapists (94% in each group), 95% of hygienists, and 96% of dental surgery assistants had been immunised. However, one half of the respondents were at or approaching 5 years post-immunisation, the time when booster immunisation is recommended. About 53% of most responding clinical dental staff had been vaccinated 4 to 5 years before the survey, but, of these, nearly 81% had not had booster immunisation. Booster immunisation will now be indicated for most dental clinical personnel.

Synthesis and antitumor activity of 9-[(carbamoyloxy)alkyl]anthracyclines: a novel class of anthracycline derivatives

A number of 4-demethoxyanthracyclines having hydroxylalkyl functions at the 9-position have previously been synthesized and shown to have potent antitumor activity. A series of carbamate derivatives of these (hydroxyalkyl)anthracyclines have now been prepared, many of which possess considerably greater efficacy in an L-1210 leukemia test system than do the parent alcohols or the known anthracyclines daunorubicin (1), doxorubicin (2), and 4-demethoxydaunorubicin (3). Phenylcarbamate 8a was more active than methyl analogue 8b, while the 4'-deoxy and 4'-epi phenylcarbamates 17 and 18 showed particularly high efficacy at optimal dose levels similar to that of doxorubicin. Secondary carbamates were more potent, with the 13R isomer 23 having significantly higher efficacy than 13S analogue 24.

Synthesis and antitumor activity of novel 4-demethoxyanthracyclines

A versatile and efficient synthetic route to 4-demethoxyanthracyclinones has been utilized in the preparation of a number of aglycons having 9-alkyl, 9-(hydroxylalkyl), or 9-carbamoyl substituents. Silver trifluoromethanesulfonate catalyzed coupling of these aglycons with various daunosamine derivatives has yielded a series of novel anthracyclines which have been evaluated as antitumor agents. 9-Alkylanthracyclines 22, 23, 33, and 34 have higher efficacy vs L-1210 leukemia than the parent 4-demethoxydaunorubicin (21), or the natural anthracyclines daunorubicin (1) and doxorubicin (2). 9-(Hydroxyalkyl) derivatives have in most cases high efficacy but are slightly less potent than 21. 9-Methyl analogue 22 has higher efficacy vs P388 leukemia than other anthracyclines tested, while 9-(hydroxymethyl) derivative 37 retains similar efficacy to anthracyclines 1, 2, and 21 but is considerably more potent. The N-substituted 9-carbamoylanthracyclines are devoid of antitumor activity.

Simultaneous enzyme immunoassay of two thyroid hormones

We describe an enzyme immunoassay in which the two thyroid hormones, triiodothyronine and thyroxin, are measured simultaneously in a single tube. The method involves labeling the two with separate enzymes (beta-galactosidase and alkaline phosphatase, respectively), whose catalyzed reactions can easily be distinguished from each other by absorption spectrophotometry, with o-nitrophenyl-beta-galactoside and phenolphthalein monophosphate as substrates. Performance of this dual assay method compares well with that of conventional single-hapten enzyme-labeled assays, and results compare well with those by two single-hapten radioimmunoassays. The dual assay has certain advantages over single-hapten methods: smaller sample volume, lower reagent cost, and shorter overall assay time. As presented here, the use of enzyme labels to measure two (or more) haptens simultaneously represents a significant advance in the use of immunoassay techniques.

Simultaneous enzyme immunoassay of two thyroid hormones

We describe an enzyme immunoassay in which the two thyroid hormones, triiodothyronine and thyroxin, are measured simultaneously in a single tube. The method involves labeling the two with separate enzymes (beta-galactosidase and alkaline phosphatase, respectively), whose catalyzed reactions can easily be distinguished from each other by absorption spectrophotometry, with o-nitrophenyl-beta-galactoside and phenolphthalein monophosphate as substrates. Performance of this dual assay method compares well with that of conventional single-hapten enzyme-labeled assays, and results compare well with those by two single-hapten radioimmunoassays. The dual assay has certain advantages over single-hapten methods: smaller sample volume, lower reagent cost, and shorter overall assay time. As presented here, the use of enzyme labels to measure two (or more) haptens simultaneously represents a significant advance in the use of immunoassay techniques.

Effects of lucanthone on the sedimentation properties of DNA from HeLa cells

Exposure of HeLa cells to lucanthone (3 microgram/ml) caused dissociation of a fast-sedimenting duplex DNA complex, as judged by lysis and sedimentation in alkaline sucrose gradients. The effect of lucanthone on the DNA complex resembled that of actinomycin D and ionizing radiation. Protein synthesis inhibitors such as cycloheximide or inhibitors of DNA synthesis such as hydroxyurea did not lead to dissociation of the complex. Lucanthone was more active than were hycanthone and five other closely related thiaxanthenones tested. Lucanthone promoted X-ray-induced denaturation of DNA in intact cells, as judged by their nuclear immunoreactivity to antinucleoside antibodies. Lucanthone did not inhibit repair of X-ray-induced DNA single-strand breaks.