Persistent Hepatitis E virus infection across England and Wales 2009-2017: Demography, virology and outcomes

The first clinical case of persistent HEV infection in England was reported in 2009. We describe the demography, virology and outcomes of patients identified with persistent HEV infection in England and Wales between 2009 and 2017. A series of 94 patients with persistent HEV infection, defined by HEV viraemia of more than 12 weeks, was identified through routine reference laboratory testing. Virology, serology and clinical data were recorded through an approved PHE Enhanced Surveillance System. Sixty-six cases (70.2%) were transplant recipients, 16 (17.0%) had an underlying haematological malignancy without stem cell transplantation, six (6.4%) had advanced HIV infection, five (5.3%) were otherwise immunosuppressed, and one patient (1.1%) had no identified immunosuppression. Retrospective analysis of 46 patients demonstrated a median 38 weeks of viraemia before diagnostic HEV testing. At initial diagnosis, 16 patients (17.0%) had no detectable anti-HEV serological response. Of 65 patients treated with ribavirin monotherapy, 11 (16.9%) suffered virological relapse despite undetectable RNA in plasma or stool at treatment cessation. Persistent HEV infection remains a rare diagnosis, but we demonstrate that a broad range of immunocompromised patients are susceptible. Both lack of awareness and the pauci-symptomatic nature of persistent HEV infection likely contribute to significant delays in diagnosis. Diagnosis should rely on molecular testing since anti-HEV serology is insufficient to exclude persistent HEV infection. Finally, despite treatment with ribavirin, relapses occur even after cessation of detectable faecal shedding of HEV RNA, further emphasising the requirement to demonstrate sustained virological responses to treatment.

Thrombolysis for Acute Myocardial Infarction in a District General Hospital

We report our experience in establishing thrombolysis as a routine part of the management of patients with acute myocardial infarction in our hospital; with particular reference to the effectiveness of the policy, safety and delays in administration.

Review article: hepatitis E-a concise review of virology, epidemiology, clinical presentation and therapy

BACKGROUND

Hepatitis E virus (HEV) is a leading cause of acute icteric hepatitis and acute liver failure in the developing world. During the last decade, there has been increasing recognition of autochthonous (locally acquired) HEV infection in developed countries. Chronic HEV infection is now recognised, and in transplant recipients this may lead to cirrhosis and organ failure.

AIM

To detail current understanding of the molecular biology of HEV, diagnostic and therapeutic strategies and propose future directions for basic science and clinical research.

METHODS

PubMed was searched for English language articles using the key words "hepatitis E", "viral hepatitis", "autochthonous infection", "antiviral therapy", "liver transplantation", "acute", "chronic", "HEV", "genotype", "transmission" "food-borne", "transfusion". Additional relevant publications were identified from article reference lists.

RESULTS

There has been increasing recognition of autochthonous HEV infection in Western countries, mainly associated with genotype 3. Chronic HEV infection has been recognised since 2008, and in transplant recipients this may lead to cirrhosis and organ failure. Modes of transmission include food-borne transmission, transfusion of blood products and solid organ transplantation. Ribavirin therapy is used to treat patients with chronic HEV infection, but new therapies are required as there have been reports of treatment failure with ribavirin.

CONCLUSIONS

Autochthonous HEV infection is a clinical issue with increasing burden. Future work should focus on increasing awareness of HEV infection in the developed world, emphasising the need for clinicians to have a low threshold for HEV testing, particularly in immunosuppressed patients. Patients at potential risk of chronic HEV infection must also be educated and given advice regarding prevention of infection.

The histology of acute autochthonous hepatitis E virus infection

AIM

To document the histological appearances of liver biopsies in autochthonous hepatitis E virus (HEV) infection.

METHODS AND RESULTS

Four patients were serologically positive for HEV; three had no traditional risk factors, the fourth had recently returned from China. All four consumed meat products. Liver histology of the three autochthonous (locally acquired) cases showed portal tracts expanded by a severe mixed polymorph and lymphocytic inflammatory infiltrate, with a geographical distribution of polymorphs at the interface and lymphocytes centrally. Moderate to severe interface hepatitis and cholangiolitis were present. There was a striking acinar mixed inflammatory infiltrate made up of polymorphs, lymphocytes and macrophages; frequent apoptotic hepatocytes, focal necrosis, cholestatic rosettes and zone 3 canalicular and cytoplasmic bilirubinostasis were noted. Significant steatosis, megamitochondria and Mallory bodies were not present. There was no evidence of iron, copper or alpha(1)-antitrypsin accumulation. By contrast, the histology of the imported case of HEV infection showed less intense portal and acinar inflammation, no cholangiolitis and no geographical distribution of the portal inflammatory infiltrate.

CONCLUSION

The histological appearances of autochthonous HEV infection are sufficiently distinctive to consider the diagnosis in an acute setting and possibly to differentiate it from the endemic form of the disease.

Human and porcine hepatitis E virus strains, United Kingdom

We describe a case of acquired infection of a strain of hepatitis E virus (HEV)with a 100% amino acid identity to the analogous region in strains of HEV circulating in a United Kingdom pig herd. This case further supports the theory that autochthonous HEV infection in industrialized countries is zoonotic.

The "jaundice hotline" for the rapid assessment of patients with jaundice

PROBLEM

Patients with jaundice require rapid diagnosis and treatment, yet such patients are often subject to delay.

DESIGN

An open referral, rapid access jaundice clinic was established by reorganisation of existing services and without the need for significant extra resources.

BACKGROUND AND SETTING

A large general hospital in a largely rural and geographically isolated area.

KEY MEASURES FOR IMPROVEMENT

Waiting times for referral, consultation, diagnosis, and treatment, length of stay in hospital, and general practitioners' and patients' satisfaction with the service. STRATEGIES OF CHANGE: Referrals were made through a 24 hour telephone answering machine and fax line. Initial assessment of patients was carried out by junior staff as part of their working week. Dedicated ultrasonography appointments were made available.

EFFECTS OF CHANGE

Of 107 patients seen in the first year of the service, 62 had biliary obstruction. The mean time between referral and consultation was 2.5 days. Patients who went on to endoscopic retrograde cholangiopancreatography waited 5.7 days on average. The mean length of stay in hospital in the 69 patients who were admitted was 6.1 days, compared with 11.5 days in 1996, as shown by audit data. Nearly all the 36 general practices (95%) and the 30 consecutive patients (97%) that were surveyed rated the service as above average or excellent.

LESSONS LEARNT

An open referral, rapid access service for patients with jaundice can shorten time to diagnosis and treatment and length of stay in hospital. These improvements can occur through the reorganisation of existing services and with minimal extra cost.

New antigenic regions of streptokinase are identified by affinity-directed mass spectrometry

Streptokinase (SK) is a bacterial protein used for the treatment of myocardial infarction, which is immunogenic in humans. Here we report the use of an affinity-directed MS approach to determine the minimal epitopes involved in the binding between SK and patient antibodies. Using this method we have identified two novel epitopes and mapped these to the minimal recognition regions formed by the amino acids D96-E99 and F323-D328. We have also located three previously identified antigenic regions and have now mapped them and shown that they can be defined more precisely as residues P4-L8, P171-P177 and K334-N338.

Global conformational changes control the reactivity of methane monooxygenase

We present here X-ray scattering data that yield new structural information on the multicomponent enzyme methane monooxygenase and its components: a hydroxylase dimer, and two copies each of a reductase and regulatory protein B. Upon formation of the enzyme complex, the hydroxylase undergoes a dramatic conformational change that is observed in the scattering data as a fundamental change in shape of the scattering particle such that one dimension is narrowed (by 25% or 24 A) while the longest dimension increases (by 20% or 25 A). These changes also are reflected in a 13% increase in radius of gyration upon complex formation. Both the reductase and protein B are required for inducing the conformational change. We have modeled the scattering data for the complex by systematically modifying the crystal structure of the hydroxylase and using ellipsoids to represent the reductase and protein B components. Our model indicates that protein B plays a role in optimizing the interaction between the active centers of the reductase and hydroxylase components, thus, facilitating electron transfer between them. In addition, the model suggests reasons why the hydroxylase exists as a dimer and that a possible role for the outlying gamma-subunit may be to stabilize the complex through its interaction with the other components. We further show that proteolysis of protein B to form the inactive B' results in a conformational change and B' does not bind to the hydroxylase. The truncation thus could represent a regulatory mechanism for controlling the enzyme activity.

Heterologous expression of soluble methane monooxygenase genes in methanotrophs containing only particulate methane monooxygenase

The methanotrophs Methylococcus capsulatus (Bath) and Methylosinus trichosporium OB3b contain particulate methane monooxygenase (pMMO) and soluble methane monooxygenase (sMMO) genes. Other methanotrophs such as Methylomicrobium album BG8 and Methylocystis parvus OBBP contain only pMMO genes. Although molecular genetic techniques are poorly developed in methanotrophs, sMMO genes were expressed in methanotrophs normally containing only pMMO genes. This was achieved by conjugation using broad-host-range plasmids containing the native promoter and sMMO genes from Mc. capsulatus (Bath) and Ms. trichosporium OB3b. sMMO genes derived from Ms. trichosporium OB3b were expressed in an active form in Mcy. parvus OBBP and in Mm. album BG8. Therefore, all of the genes required for active sMMO synthesis were contained on the broad-host-range plasmids and were expressed in the heterologous hosts. Constitutive synthesis of pMMO was observed in Mm. album BG8 when grown at high and low copper-to-biomass ratios, while transcription of the recombinant sMMO genes was only observed under growth conditions of low copper-to-biomass ratios. Therefore, the regulatory protein(s) for sMMO synthesis was also present on the plasmid used, or the heterologous host contained a regulatory system for sMMO. Expression of sMMO genes in methanotrophs containing only pMMO will assist further investigations on the expression and regulation of MMO genes in methanotrophs.

Electron transfer reactions in the alkene mono-oxygenase complex from Nocardia corallina B-276

Nocardia corallina B-276 possesses a multi-component enzyme, alkene mono-oxygenase (AMO), that catalyses the stereoselective epoxygenation of alkenes. The reductase component of this system has been shown by EPR and fluorescence spectroscopy to contain two prosthetic groups, an FAD centre and a [2Fe-2S] cluster. The role of these centres in the epoxygenation reaction was determined by midpoint potential measurements and electron transfer kinetics. The order of potentials of the prosthetic groups of the reductase were FAD/FAD.=-216 mV, [2Fe-2S]/[2Fe-2S].=-160 mV and FAD./FAD.=-134 mV. Combined, these data implied that the reductase component supplied the energy required for the epoxygenation reaction and allowed a prediction of the mechanism of electron transfer within the AMO complex. The FAD moiety was reduced by bound NADH in a two-electron reaction. The electrons were then transported to the [2Fe-2S] centre one at a time, which in turn reduced the di-iron centre of the epoxygenase. Reduction of the di-iron centre is required for oxygen binding and substrate oxidation.

Heterologous expression of alkene monooxygenase from Rhodococcus rhodochrous B-276

Alkene monooxygenase (AMO) from Rhodococcus rhodochrous (formerly Nocardia corallina) B-276 is a three-component enzyme system encoded by the four-gene operon amoABCD. AMO catalyses the stereoselective epoxygenation of aliphatic alkenes, yielding primarily R enantiomers. The presumed site of alkene oxygenation is a dinuclear iron centre similar to that in the soluble methane monooxygenases of methanotrophic bacteria, to which AMO exhibits a significant degree of amino acid sequence identity. The AMO complex was not expressed in Escherichia coli, at least partly because that host did not produce all of the AMO polypeptides. Expression of AMO was achieved in Streptomyces lividans by cloning the AMO genes into the thiostrepton-inducible expression plasmid pIJ6021. No background of AMO activity was detected in S. lividans cells without amoABCD and expression of AMO activity, at a level comparable to that from wild-type R. rhodochrous B-276, coincided with appearance of the AMO subunits. Recombinant AMO activity in cell-free extracts of S. lividans was stimulated by the addition of NADH and produced R-epoxypropane with comparable enantiomeric excess to AMO purified from the original organism. Although the whole AMO complex could not be expressed in E. coli, the functional coupling protein (AmoB) and reductase (AmoD) were expressed individually in E. coli as fusions with glutathione S-transferase. The expression systems described here now allow structure/function studies on AMO to be carried out by site-directed mutagenesis.

Instillation of calf lung surfactant extract (calfactant) is beneficial in pediatric acute hypoxemic respiratory failure. Members of the Mid-Atlantic Pediatric Critical Care Network

OBJECTIVE

Prospective study of the efficacy of calf lung surfactant extract in pediatric respiratory failure.

DESIGN

Multi-institutional, prospective, randomized, controlled, unblinded trial.

SETTING

Eight pediatric intensive care units (ICU) of tertiary medical centers.

PATIENTS

Forty-two children with acute hypoxemic respiratory failure characterized by diffuse, bilateral pulmonary infiltrates, need for ventilatory support, and an oxygenation index of >7.

INTERVENTION

Instillation of intratracheal surfactant (80 mL/m2).

MEASUREMENTS AND MAIN RESULTS

Ventilator parameters, arterial blood gases, and derived oxygenation and ventilation indices were recorded before and at intervals after surfactant administration. Complications and outcome measures, including mortality, duration of mechanical ventilation, and length of pediatric ICU and hospital stay, were also examined. Patients who received surfactant demonstrated rapid improvement in oxygenation and, on average, were extubated 4.2 days (32%) sooner and spent 5 fewer days (30%) in pediatric intensive care than control patients. There was no difference in mortality or overall hospital stay. Surfactant administration was associated with no serious adverse effects.

CONCLUSIONS

Administration of calf lung surfactant extract, calfactant, appears to be safe and is associated with rapid improvement in oxygenation, earlier extubation, and decreased requirement for intensive care in children with acute hypoxemic respiratory failure. Further study is needed, however, before widespread use in pediatric respiratory failure can be recommended.

Rapid analysis of epitope-paratope interactions between HIV-1 and a 17-amino-acid neutralizing microantibody by electrospray ionization mass spectrometry

Progress in therapeutic or prophylactic immune intervention in HIV-1 infections may only come about with a detailed understanding at the molecular/atomic level of how antibodies neutralize (inactivate) virus infectivity. Currently information on the molecular aspects of antibody-virus interaction comes predominantly from X-ray crystallography, a process that is dependent on the production of suitable crystals. NMR can also be valuable but is complex and time consuming, while mass spectrometry has been limited to matrix-assisted laser-desorption ionization (MALDI) analysis of peptides eluted from the cognate antibody. Here, we have used electrospray ionization mass spectrometry (ESI-MS) to detect directly the interactions of a novel 17-amino-acid microantibody (MicroAb) that has HIV-1-inhibitory activity, and peptides representing the V3 regions of primary HIV-1 strains isolated from Brazil (clade B) and Africa (clade A). The MicroAb is based on the third complementarity-determining region of the heavy chain (CDR-H3) of a murine monoclonal IGGI (F58) specific for the V3 loop of the gp120 envelope glycoprotein of HIV-1. ESI-MS proved to be rapid (taking < 3 h for the entire analysis), sensitive (analytes at 2 mmol/ml), and accurate (RMM estimation to 0.01-0.1%). With it, we showed that the MicroAb forms complexes with the V3 peptides, implying that its antiviral activity is mediated by binding directly to the virus particle. In addition, through controlled protease digestion of the V3 peptides, we concluded that the CDR-H3 MicroAb bound to RKXXXIGPGR, a region similar to the epitope of the whole IgG as determined by ELISA. We believe that the approach exemplified here will be applicable generally to the identification of groups involved in receptor-ligand interactions.

Sequence-alignment modelling and molecular docking studies of the epoxygenase component of alkene monooxygenase from Nocardia corallina B-276

Whole cells of Nocardia corallina B-276 catalyse the stereoselective epoxygenation of alkenes to chiral epoxides. The bacterium expresses an enzyme, alkene monooxygenase, which catalyses the epoxygenation reaction stereoselectively. The enzyme consists of a terminal oxygenase (epoxygenase), an NADH-dependent reductase (reductase) and a regulatory component (coupling protein). The epoxygenase component contains a bridged diiron centre similar to that found in the hydroxylase component of soluble methane monooxygenase. Sequence-alignment modelling, supported by chemical modification and fluorescence probing, identified a hydrophobic oxygen/substrate binding site within the epoxygenase. The diiron centre was coordinated by the two His and two Glu residues from two conserved Glu-Xaa-Xaa-His sequences and by two further Glu residues. Molecular docking of substrates and products into the proposed active-site model of the epoxygenase suggested that Ala91 and Ala185 were responsible for the stereoselectivity exerted by AMO. It is proposed that these residues clamped the intermediate and/or product of the reaction, thereby controlling the configuration of the epoxide produced. In soluble methane monooxygenase these residues are replaced by two Gly residues which do not provide sufficient steric hindrance to prevent rotation of the intermediate in the active site and, therefore, the product of the reaction catalysed by this enzyme is achiral.

The hydroxylase component of soluble methane monooxygenase from Methylococcus capsulatus (Bath) exists in several forms as shown by electrospray-ionisation mass spectrometry

The hydroxylase of the soluble methane monooxygenase from the bacterium Methylococcus capsulatus (Bath) has been investigated by means of electrospray-ionisation mass spectrometry (ESI-MS) and liquid chromatography ESI-MS (LC/ESI-MS). The hydroxylase is a non-heme diiron protein consisting of three pairs of non-identical subunits (alpha approximately 60 kDa, beta approximately 45 kDa and gamma approximately 20 kDa). Liquid chromatographic separation of the hydroxylase subunits was required before MS analysis in order to detect the alpha-subunit. The masses measured for the three subunits were found to disagree with those calculated from their gene sequences. Experiments involving the use of CNBr and trypsin cleavage followed by LC/ESI-MS and MS/MS analyses permitted the location and correction of errors in the sequences deduced from the use of cDNA. The ESI-MS results also showed that the alpha-subunit of the hydroxylase exists in multiple forms which result from cleavage of the protein. This observation explains a number of enigmatic features of the protein previously reported in the literature and illustrates the pivotal role of ESI-MS in complementing data obtained from molecular biology for the characterisation of the primary sequence of proteins.

Inactivation of the regulatory protein B of soluble methane monooxygenase from Methylococcus capsulatus (Bath) by proteolysis can be overcome by a Gly to Gln modification

The regulatory protein B of soluble methane monooxygenase (sMMO) from Methylococcus capsulatus (Bath), exists as a mixture of the full-length active form and truncated forms, B' and B". Electrospray ionisation mass spectrometry (ESI-MS) was used to identify a cleavage site between Met12 and Gly13, such that 12 amino acids were lost from the N-terminus of protein B. This truncate was designated B' and molecular masses were assigned to proteins B and B' of 15,852.6+/-0.4 Da and 14,629.5+/-0.3 Da, respectively. A cleavage site between Gln29 and Val30 was also identified such that 29 amino acids were lost from the N-terminus of protein B. This truncate was designated B" and had a molecular mass of 12,709.93+/-0.02 Da. Proteins B' and B" were found to be inactive in the sMMO system. Addition of protease inhibitors or the heterologous expression of protein B in various strains of lon-deficient or ompT-deficient Escherichia coli, did not inhibit B' formation. Expression of protein B as a glutathione S-transferase fusion protein and subsequent purification of protein B from E. coli using affinity chromatography resulted in preparations of protein B with higher enzyme activities than that of wild-type protein B. However, ESI-MS confirmed that protein B' was still present. Alteration of the Met12-Gly13 cleavage site to Met12-Gln13 revealed that the stability of G13Q at 20 degrees C and 37 degrees C was higher than that of wild-type preparations. ESI-MS indicated that protein B' was absent and could only be identified after prolonged incubation at room temperature. The amount of active protein B present in the cell may be controlled by protein B cleavage, thereby regulating electron transfer. Alternatively, it may allow protein B to maintain a certain conformation necessary for enzyme activity and this may control the activity of sMMO in response to the supply of methane to the cell.

Alkene monooxygenase from Nocardia corallina B-276 is a member of the class of dinuclear iron proteins capable of stereospecific epoxygenation reactions

Nocardia corallina B-276 possesses a constitutive multi-component alkene monooxygenase which catalyses the epoxidation of terminal and sub-terminal alkenes. The epoxygenase component of this system has been purified with an overall yield of 35%. The electron paramagnetic resonance spectrum of the oxidised protein has a weak signal at g = 4.3, which we ascribe to rhombic iron and a free radical signal at g(ave) = 2.01. Upon partial reduction with dithionite using methyl viologen as a mediator, a signal at g(ave) = 1.9 appeared. Upon further reduction with excess dithionite a signal at g = 15 appeared with the concomitant disappearance of the g(ave) = 1.9 signal. These results indicate that the epoxygenase contains a bridged dinuclear iron centre similar to that found in a variety of proteins involved in oxygen transport and activation as well as desaturation of fatty acids. Analysis of the products of the reaction indicates that AMO is capable of stereospecific epoxidation of alkenes producing the R-enantiomer in high yield, a reaction catalysed by very few oxygenase enzymes. Whole cells gave lower enantiomeric excess values for the epoxide and a stereospecific epoxidase enzyme has been proposed to account for this difference. Although alkene monooxygenase was not inhibited by ethyne, a potent inhibitor of soluble methane monooxygenase with which alkene monooxygenase shares many common features, it was weakly inhibited by propyne with an apparent Km value of 340 microM. The mechanistic implications of these physicochemical features of the enzyme are discussed.

Direct electrochemistry of the hydroxylase of soluble methane monooxygenase from Methylococcus capsulatus (Bath)

The redox properties of the hydroxylase component of soluble methane monooxygenase from Methylococcus capsulatus (Bath) have been thoroughly investigated. Previous studies used redox indicator titrations and spectroscopic methods for the determination of the concentrations of reduced species. Herein we report, for the first time, direct electrochemistry (i.e. without the use of mediators) of the diiron centers of the hydroxylase from M. capsulatus (Bath) at a modified gold electrode giving rise to two waves at 4(+/- 10) mV and -386(+/- 14) mV versus saturated calomel electrode (SCE). In addition, the effects of proteins B and B' on the redox reactions were determined. The redox potentials of the complex with protein B are -25(+/- 14) mV and -433(+/- 8) mV versus SCE whereas protein B' had no effect though it did alter the effect of protein B on the redox potentials.

Calf's lung surfactant extract in acute hypoxemic respiratory failure in children

OBJECTIVE

Open-label trial of the safety and short-term efficacy of calf's lung surfactant in pediatric respiratory failure.

DESIGN

Multi-institutional, uncontrolled, observational trial.

SETTING

Six pediatric intensive care units of tertiary medical centers.

PATIENTS

Twenty-nine children with acute hypoxemic respiratory failure, characterized by diffuse, bilateral, pulmonary infiltrates, need for ventilator support, and an oxygenation index of > or = 7.

INTERVENTIONS

Up to four doses of intratracheal surfactant (80 mL/m2).

MEASUREMENTS AND MAIN RESULTS

Ventilator parameters, arterial blood gases, and derived oxygenation and ventilation indices were recorded before, and at intervals after, surfactant administration. Complications and outcome measures were also noted. There was immediate improvement in oxygenation and moderation of ventilator support associated with surfactant administration in 24 of 29 patients. A modest but statistically insignificant effect was seen with subsequent doses. The only complications occurred in three patients who developed airleaks, two of which were coincident with surfactant administration. The overall mortality rate was 14%, which compares favorably with other published series.

CONCLUSIONS

Administration of calf's lung surfactant appears to be safe and is associated with rapid improvement in oxygenation and moderation of ventilator support in children with acute hypoxemic respiratory failure. These results set the stage for a randomized, controlled study.

Perianal condylomata acuminata

Anal and perianal condylomata acuminata are warts caused by infection with the human papillomavirus (HPV). The annual incidence of genital warts seems to have increased during the past few decades. Approximately 1.5 million consultations per year take place in the United States with this condition (1). Papillomavirus is a sexually transmitted disease, and is associated with several other venereal infections as well as with intraepithelial neoplasia and invasive squamous carcinoma. Only certain genotypes of HPV are carcinogenic, and can be precisely identified by in situ hybridisation techniques. There are many therapeutic alternatives, possibly reflecting the wide variability in treatment response.

Heat-tolerant methanotrophic bacteria from the hot water effluent of a natural gas field

Methanotrophic bacteria were isolated from a natural environment potentially favorable to heat-tolerant methanotrophs. An improved colony plate assay was developed and used to identify putative methanotrophic colonies with high confidence. Fourteen new isolates were purified and partially characterized. These new isolates exhibit a DNA sequence homology of up to 97% with the conserved regions in the mmoX and mmoC genes of the soluble methane monooxygenase (MMO)-coding gene cluster of Methylococcus capsulatus Bath. The copper regulation of soluble MMO expression in the same isolates, however, differs from that of M. capsulatus Bath, as the new isolates can tolerate up to 0.8 microM copper without loss of MMO activity while a drastic reduction of MMO activity occurs already at 0.1 microM copper in M. capsulatus Bath. The isolates can be cultivated and utilized at elevated temperatures, and their copper- and heat-tolerant MMO activity makes these bacteria ideal candidates for future biotechnological use.

Transformation of follicular lymphoma. Expression of p53 and bcl-2 oncoprotein, apoptosis and cell proliferation

Transformation in follicular lymphoma represents an abrupt transition in tumor biology. The protein product of the bcl-2 oncogene is overexpressed in most follicular lymphomas and inhibits apoptosis. The protein product of the p53 oncogene prevents cell proliferation and induces apoptosis and is overexpressed in the dysfunctional (mutated) form. We studied 15 transformed lymphomas (large cell type), 7 follicular lymphomas before transformation and 2 control groups of follicular center cell lymphomas with no evidence of transformation (9 small cleaved cell and 10 de novo large cell lymphomas). High p53 expression (> or = 45% cells) was detected by immunostaining in 9/15 transformed lymphomas as compared with 0/10 de novo large cell lymphomas and 1/7 follicular lymphomas. Overexpression of bcl-2 (> or = 50% cells) was similar in transformed (11/15) and de novo large cell lymphomas (6/10). The apoptotic index was high (> or = 2%) in all transformed and large cell lymphomas and low in all follicular lymphomas and in the control group of small cleaved cell lymphomas. The apoptotic index in the transformed lymphomas appeared to be independent of bcl-2 expression and was sometimes paradoxically high in the presence of both p53 and bcl-2 overexpression. The apoptotic index was weakly associated with bcl-2 expression in de novo large cell lymphomas. Expression of p53 did not correlate with proliferation index. Our results indicate that p53 overexpression is a specific step associated with transformation and may occur shortly before it. This is not seen in de novo large cell lymphoma. Furthermore, the high apoptotic index in transformed lymphomas often occurs despite overexpression of bcl-2 and p53, implying that other factors may induce apoptosis in these tumors.

Further evidence for multiple pathways in soluble methane-monooxygenase-catalysed oxidations from the measurement of deuterium kinetic isotope effects

The data from the deuterium isotope experiments in this study show that the primary kinetic isotope effect for methane oxidation catalysed by soluble methane monooxygenase from Methylococcus capsulatus (Bath) is very small, < 2. In contrast, the primary kinetic isotope effect for -CH3 group oxidation in toluene is large, > 7. A mechanistic pathway in which a substrate radical is formed from hydrogen atom abstraction by a ferryl species is believed to operate for CH4, the toluene -CH3 group and similar alkanes. Direct oxygen atom addition, rather than H atom abstraction, is indicated for aromatic ring oxidations in benzene and toluene and for styrene oxide formation from styrene. Thus, more than one mechanistic pathway appears to operate in soluble methane-monooxygenase-catalysed reactions and, in some cases, the pathway chosen may be dictated by the substrate. In the soluble methane-monooxygenase-catalysed oxidation of toluene the rates of: (a) substrate dissociation from the enzyme-substrate complex, (b) product formation and (c) product release (benzyl alcohol and p-cresol) from the enzyme-product complex are comparable in magnitude. Therefore all three of these steps are partially rate-determining in the soluble methane monooxygenase catalytic cycle for toluene oxidation.

Extracorporeal membrane oxygenation for pediatric respiratory failure: five-year experience at the University of Pittsburgh

OBJECTIVES

To describe the etiology, respiratory severity of illness, and outcome in patients with pediatric respiratory failure who were treated with extracorporeal membrane oxygenation (ECMO). To identify predictors of death, and to compare our morbidity and mortality rates with those rates of a previously reported series of patients with pediatric respiratory failure managed conventionally.

DESIGN

Survey, case series.

SETTING

Intensive care unit in a tertiary care pediatric hospital.

PATIENTS

Twenty-eight pediatric patients (3 wks to 20 yrs of age) who underwent ECMO for pediatric respiratory failure between 1985 and 1991.

MEASUREMENTS AND MAIN RESULTS

Thirteen (46%) of the 28 patients survived. The most common diagnoses were adult respiratory distress syndrome and nonspecific pneumonitis. Multiple organ system failure occurred in only four (14%) patients; most patients died of respiratory failure. The occurrence of persistent airleak during ECMO was significantly greater in nonsurvivors than in survivors. Furthermore, nonsurvivors had significantly less response to lung reexpansion maneuvers compared with survivors, as measured by a calculated compliance index (effective tidal volume/mean airway pressure x 100). The mortality rate was comparable with those rates of other published studies of conventionally managed and ECMO-treated patients with pediatric respiratory failure. Moreover, our patients appeared to exhibit more severe respiratory failure at the start of ECMO than those patients in other studies.

CONCLUSIONS

ECMO appears to be a rational therapy for patients with pediatric respiratory failure who are likely to die with continued conventional management. Recovery of lung function by the end of the first week of ECMO may be a favorable prognostic indicator. Persistent airleak may be a nonfavorable prognostic indicator.

Chemical modification of the hydroxylase of soluble methane monooxygenase gives one form of the protein with significantly increased thermostability and another that functions well in organic solvents

Proteolysis of the hydroxylase component of soluble methane monooxygenase (MMO) with trypsin yielded a protein which retained 50% activity in a standard MMO assay. In an H2O2-driven assay, in which H2O2 replaced two of the protein components, NADH and O2 used in the standard assay, the proteolysed hydroxylase retained full activity for ethane, propane and propene, but had a 2-3-fold increase with methane as substrate. Several crosslinking reagents have been tested for their ability to stabilise the proteolysed form of the hydroxylase. Using polyoxyethylene bis(imidazolyl carbonyl) (M(r) 3350) as the crosslinking agent, increased thermostability of the hydroxylase was observed. Activated methoxypolyethylene glycol (M(r) 5000) was used to modify the hydroxylase which was now soluble in organic solvents as well as water and could be activated by H2O2. The glycol-modified hydroxylase functioned well in organic solvents in the catalysis of propene oxidation.

Abduction of iron(III) from the soluble methane monooxygenase hydroxylase and reconstitution of the binuclear site with iron and manganese

The apo-form of the soluble methane monooxygenase hydroxylase from Methylococcus capsulatus (Bath) was prepared via chelation of iron(III) with 3,4-dihydroxybenzaldehyde. The apohydroxylase was reconstituted by the anaerobic addition of Fe(II) followed by air oxidation. The enzyme thus prepared regained 85-90% of its original catalytic activity. The incorporation of two manganese(II) ions/mol of apohydroxylase was monitored by EPR spectroscopy. The Mn(II) ions occupy the native diiron active site and remain in the +2 oxidation state. The EPR data suggest strong coupling between the two Mn(II) ions and retention of the mu-hydroxo (alkoxo) bridge. The results of this study indicate that the M. capsulatus (Bath) hydroxylase contains a single diiron site.

Pharmacokinetics and serum bactericidal titers of ciprofloxacin and ofloxacin following multiple oral doses in healthy volunteers

Fourteen adult males participated in a randomized three-way crossover study to compare the pharmacokinetics and serum bactericidal titers (SBTs) of 500 mg of ciprofloxacin (regimen A), 750 mg of ciprofloxacin (regimen B), and 400 mg of ofloxacin (regimen C) administered every 12 h for seven doses. Mean steady-state peak concentrations in serum for regimens A, B, and C were 3.0, 4.4, and 6.5 micrograms/ml, respectively (P < 0.01, all comparisons) and mean half-lives were 4.5, 4.3, and 6.5 h, respectively (P < 0.05, C versus A and B). Mean steady-state areas under the concentration-time curve were 14.1, 21.1, and 48.1 micrograms/h/ml for regimens A, B, and C, respectively (P < 0.05, all comparisons). SBTs were determined at different times postdose for three isolates each of Streptococcus pneumoniae, Staphylococcus aureus, Escherichia coli, Enterobacter cloacae, and Pseudomonas aeruginosa. Mean steady-state peak SBTs for regimens A, B, and C, respectively, were as follows: S. pneumoniae, < 1:2, 1:8, 1:8, S. aureus, 1:16, 1:16, 1:16; E. coli, 1: > or = 128, 1: > or = 128, 1:64; E. cloacae, 1: > or = 128, 1: > or = 128, 1:64; P. aeruginosa, 1:8, 1:8, 1:2. These differences in SBTs within each genus were statistically significant. The majority of predicted SBTs were within one dilution of measured SBTs. Areas under the serum bactericidal time curves for E. coli, E. cloacae, and P. aeruginosa were significantly higher for ciprofloxacin; areas under the serum bactericidal time curves for S. pneumoniae and S. aureus were significantly greater for ofloxacin. Ofloxacin achieved higher concentrations in serum than ciprofloxacin, but differences in in vitro activity were a more important determinant of SBTs.

19F NMR study of the interaction of fluoride ion with ribonucleotide reductase and methane monooxygenase

The relaxation rates of fluoride, determined by 19F NMR spectroscopy, were greatly increased in the presence of protein Mn-A, the manganese form of the hydroxylase component of methane monooxygenase. This demonstrates that F- interacts with the manganese center of protein Mn-A. On the contrary, protein Mn-R2, the manganese form of the small subunit of ribonucleotide reductase, had no effect on the relaxation rate of F-. This reflects differences between the two proteins in terms of the accessibility of the metal ion sites, despite the strong similarities of these sites.