Optimal heat stress metric for modelling heat-related mortality varies from country to country

Combined heat and humidity is frequently described as the main driver of human heat-related mortality, more so than dry-bulb temperature alone. While based on physiological thinking, this assumption has not been robustly supported by epidemiological evidence. By performing the first systematic comparison of eight heat stress metrics (i.e., temperature combined with humidity and other climate variables) with warm-season mortality, in 604 locations over 39 countries, we find that the optimal metric for modelling mortality varies from country to country. Temperature metrics with no or little humidity modification associates best with mortality in ~40% of the studied countries. Apparent temperature (combined temperature, humidity and wind speed) dominates in another 40% of countries. There is no obvious climate grouping in these results. We recommend, where possible, that researchers use the optimal metric for each country. However, dry-bulb temperature performs similarly to humidity-based heat stress metrics in estimating heat-related mortality in present-day climate.

Estimating heat-related mortality in near real time for national heatwave plans

Heatwaves are a serious threat to human life. Public health agencies that are responsible for delivering heat-health action plans need to assess and reduce the mortality impacts of heat. Statistical models developed in epidemiology have previously been used to attribute past observed deaths to high temperatures and project future heat-related deaths. Here, we investigate the novel use of summer temperature-mortality associations established by these models for monitoring heat-related deaths in regions in England in near real time. For four summers in the period 2011-2020, we find that coupling these associations with observed daily mean temperatures results in England-wide heatwave mortality estimates that are consistent with the excess deaths estimated by UK Health Security Agency. However, our results for 2013, 2018 and 2020 highlight that the lagged effects of heat and characteristics of individual summers contribute to disagreement between the two methods. We suggest that our method can be used for heatwave mortality monitoring in England because it has the advantages of including lagged effects and controlling for other risk factors. It could also be employed by health agencies elsewhere for reliably estimating the health burden of heat in near real time and near-term forecasts.

Validation of a Metastatic Assay using biopsies to improve risk stratification in patients with prostate cancer treated with radical radiation therapy

Background

Radiotherapy is an effective treatment of intermediate/high-risk locally advanced prostate cancer, however, >30% of patients relapse within 5 years. Clinicopathological parameters currently fail to identify patients prone to systemic relapse and those whom treatment intensification may be beneficial. The purpose of this study was to independently validate the performance of a 70-gene Metastatic Assay in a cohort of diagnostic biopsies from patients treated with radical radiotherapy and androgen deprivation therapy.

Patients and methods

A bridging cohort of prostate cancer diagnostic biopsy specimens was profiled to enable optimization of the Metastatic Assay threshold before further independent clinical validation in a cohort of diagnostic biopsies from patients treated with radical radiotherapy and androgen deprivation therapy. Multivariable Cox proportional hazard regression analysis was used to assess assay performance in predicting biochemical failure-free survival (BFFS) and metastasis-free survival (MFS).

Results

Gene expression analysis was carried out in 248 patients from the independent validation cohort and the Metastatic Assay applied. Ten-year MFS was 72% for Metastatic Assay positive patients and 94% for Metastatic Assay negative patients [HR = 3.21 (1.35–7.67); P = 0.003]. On multivariable analysis the Metastatic Assay remained predictive for development of distant metastases [HR = 2.71 (1.11–6.63); P = 0.030]. The assay retained independent prognostic performance for MFS when assessed with the Cancer of the Prostate Assessment Score (CAPRA) [HR = 3.23 (1.22–8.59); P = 0.019] whilst CAPRA itself was not significant [HR = 1.88, (0.52–6.77); P = 0.332]. A high concordance [100% (61.5–100)] for the assay result was noted between two separate foci taken from 11 tumours, whilst Gleason score had low concordance.

Conclusions

The Metastatic Assay demonstrated significant prognostic performance in patients treated with radical radiotherapy both alone and independent of standard clinical and pathological variables. The Metastatic Assay could have clinical utility when deciding upon treatment intensification in high-risk patients. Genomic and clinical data are available as a public resource.

A real-time Global Warming Index

We propose a simple real-time index of global human-induced warming and assess its robustness to uncertainties in climate forcing and short-term climate fluctuations. This index provides improved scientific context for temperature stabilisation targets and has the potential to decrease the volatility of climate policy. We quantify uncertainties arising from temperature observations, climate radiative forcings, internal variability and the model response. Our index and the associated rate of human-induced warming is compatible with a range of other more sophisticated methods to estimate the human contribution to observed global temperature change.

Polar vortices on Earth and Mars: A comparative study of the climatology and variability from reanalyses

Polar vortices on Mars provide case-studies to aid understanding of geophysical vortex dynamics and may help to resolve long-standing issues regarding polar vortices on Earth. Due to the recent development of the first publicly available Martian reanalysis dataset (MACDA), for the first time we are able to characterise thoroughly the structure and evolution of the Martian polar vortices, and hence perform a systematic comparison with the polar vortices on Earth. The winter atmospheric circulations of the two planets are compared, with a specific focus on the structure and evolution of the polar vortices. The Martian residual meridional overturning circulation is found to be very similar to the stratospheric residual circulation on Earth during winter. While on Earth this residual circulation is very different from the Eulerian circulation, on Mars it is found to be very similar. Unlike on Earth, it is found that the Martian polar vortices are annular, and that the Northern Hemisphere vortex is far stronger than its southern counterpart. While winter hemisphere differences in vortex strength are also reported on Earth, the contrast is not as large. Distinctions between the two planets are also apparent in terms of the climatological vertical structure of the vortices, in that the Martian polar vortices are observed to decrease in size at higher altitudes, whereas on Earth the opposite is observed. Finally, it is found that the Martian vortices are less variable through the winter than on Earth, especially in terms of the vortex geometry. During one particular major regional dust storm on Mars (Martian year 26), an equatorward displacement of the vortex is observed, sharing some qualitative characteristics of sudden stratospheric warmings on Earth.

Assessing the daily consistency of bladder filling using an ultrasonic Bladderscan device in men receiving radical conformal radiotherapy for prostate cancer

OBJECTIVE

Consistency in target organ and organ at risk position from planning to treatment is an important basic principle of radiotherapy. This study evaluates the effectiveness of bladder-filling instructions in achieving a consistent and reproducible bladder volume at the time of planning CT and daily during the course of radical radiotherapy for prostate cancer. It also assessed the rate of bladder filling before and at the end of radiotherapy.

METHODS

30 men attending for radiation therapy planning for prostate cancer received written and verbal bladder-filling instructions. They had their bladder volume assessed using a bladder ultrasound scanner post-void, immediately prior to planning CT scan and then daily immediately prior to treatment while in the therapy position. The inflow was calculated using the void and full bladder volumes and the time for the bladder to fill.

RESULTS

The mean bladder volume at the time of planning was 282 ml (range 89-608 ml, standard deviation (SD) = 144.5 ml). This fell during treatment, with a mean value for all treatments of 189 ml (range 11-781 ml, SD = 134 ml). During radiotherapy, 76% (828/1090), 53% (579/1090) and 36% (393/1090) of bladder volumes had >50 ml, >100 ml and >150 ml difference, respectively when compared with their volume at the time of planning. Inflow reduced from 4.6 ml min(-1), SD = 2.9 min(-1) at planning to 2.5 min(-1), SD = 1.8 min(-1) after radiotherapy.

CONCLUSION

The Bladderscan device (BVI 6400 Bladderscan, Verathon Medical UK, Sandford, UK) provides an effective means of assessing bladder volume prior to radiotherapy for prostate cancer. The evaluated bladder-filling protocol does not produce consistent, reproducible bladder volumes for radiotherapy.

SENSORY NEURON DEGENERATION IN VITAMIN DEFICIENCY : DEGENERATION OF THE POSTERIOR COLUMNS OF THE SPINAL CORD, PERIPHERAL NERVES, AND DORSAL ROOT GANGLION CELLS IN YOUNG PIGS FED A DIET CONTAINING THIAMIN (B(1)) AND RIBOFLAVIN BUT OTHERWISE DEFICIENT IN VITAMIN B COMPLEX

Young pigs were given an artificial diet presumably adequate in all respects. As they developed, the quantity of yeast was gradually reduced while thiamin (vitamin B₁) and riboflavin were given in its place. The rate of growth decreased, the general condition of the animals became impaired, and marked ataxia without motor weakness developed. Histologically, severe degeneration of the posterior columns of the spinal cord, the dorsal root ganglion cells, and the peripheral nerves was found.

Recto-urethral fistula following brachytherapy for localized prostate cancer

OBJECTIVE

The use of prostate brachytherapy (BT) in the management of prostate cancer is increasing. BT is often chosen because of its perceived lower toxicity when compared with other radical therapy options. Rarely however serious complications can occur. One such complication is recto-urethral fistula (RUF). We report the incidence of RUF following BT at our centre and review the potential factors in fistula development.

METHOD

A prospectively collected database was used to identify cases of RUF among 1455 patients treated with prostate BT at a single UK centre with at least 2 years of follow up. This included patients treated with BT monotherapy, as well as those treated with BT combined with external beam radiotherapy and BT used as salvage as all these groups have a higher incidence of RUF. Implant dose and volume characteristics for those patients, their co-morbidities and history of endoscopic procedures were recorded.

RESULTS

Recto-urethral fistula was identified in three (0.2%) patients, occurring at 19-27 months following BT. All these patients had BT monotherapy. All three patients had rectal symptoms after their BT and had been investigated with endoscopy and low rectal biopsy. Subsequent surgical management with faecal and/or urinary diversion was required. On review of patients' BT details, radiation dose and volume parameters were higher on the postprocedure CT calculations than had been suggested by the preimplant plan. No other predisposing risk factors for RUF were identified.

CONCLUSION

The incidence of RUF in our population is low. RUF following BT has been associated with rectal biopsy in previous series and this is confirmed in our report. Gastrointestinal specialists should not perform biopsy of the anterior rectum in patients who have had BT unless there is a very high clinical suspicion of malignancy.

Interhospital provision of emergency vascular services for a large population: early outcomes and clinical results

Background

In 1999 an emergency vascular service for Bristol and Avon (including Weston-Super-Mare) (population approximately 1 million) was initiated.

Methods

Collaboration between Bristol Royal Infirmary, Frenchay and Southmead Hospitals provides week-on–week-off vascular cover for patients requiring urgent and emergency interventions within 24 h. The rota accommodates National Confidential Enquiry into Perioperative Deaths and Vascular Surgical Society of Great Britain and Ireland recommendations, governance issues, and enhances emergency vascular care for Avon residents. Prospectively collected data for the first year (May 1999 to April 2000) are reviewed.

Results

There were 289 emergency admissions. (In-hospital referrals were not transferred but contributed up to 40 per cent of the extra emergency workload per unit.) Referrals were also accepted from seven Trusts outside the designated catchment area. Caseload included 86 patients with a ruptured or acutely symptomatic aortic aneurysm, of whom 69 underwent operation (30 per cent mortality rate); 17 patients were not operated on. Some 136 patients had critical leg ischaemia (43 acute, 93 chronic); angiography or duplex ultrasonography was performed in 105 cases (77 per cent); 39 patients (29 per cent) had undergone previous intervention for peripheral vascular disease; the mortality rate was 18 (13 per cent) of 136; 18 (13 per cent) of 136 patients required an amputation. Other cases included: upper limb ischaemia, 20 (7 per cent); paediatric emergency, seven (2 per cent); symptomatic carotid disease, five (2 per cent; four endarterectomies with no death or stroke). Some 5 per cent of referrals were inappropriate (venous ulcer, spinal stenosis, etc.). No outcomes were compromised by interhospital transfers. Vascular surgeons operated on nine high-risk patients away from their ‘base’ hospital. A consultant was the principal or assistant operator in more than 95 per cent of operations but, despite trainee rota adjustments, a designated vascular trainee was present in only about 40 per cent of cases.

Conclusion

Interhospital provision of emergency vascular services for a large population is feasible, does not compromise quality of care, and regulates emergency workload. Further attention to training issues is indicated.

Genetic polymorphism of MUC7: allele frequencies and association with asthma

MUC7 encodes a small salivary mucin, previously called MG2, a glycoprotein with a putative role in facilitating the clearance of oral bacteria. The central domain of this glycoprotein was previously shown to comprise five or six tandemly repeated units of 23 amino-acids which carry most of the O-linked glycans. The polymorphism of these two allelic forms (MUC7*5 or MUC7*6) has been confirmed in this study in which we have analysed a large cohort of subjects (n = 375) of various ethnic origins. We have also identified a novel rare allele with eight tandem repeats (MUC7*8). MUC7*6 was the most common allele (0.78-0.95) in all the populations tested. The tandem repeat arrays of 22 MUC7*5 alleles and 34 MUC7*6 alleles were sequenced. No sequence differences were detected in any of the MUC7*6 alleles. Twenty-one MUC7*5 alleles sequenced lacked the 4th tandem repeat (structure TR12356), while one showed the structure TR12127. The structure of the MUC7*8 allele was TR12343456. Because of the known role of MUC7 in bacterial binding, and thus its potential involvement in susceptibility to chest disease we also tested MUC7 in our previously described series of Northern European atopic individuals with and without associated asthma. The MUC7*5 allele was rarer in the atopic asthmatics than in the atopic non-asthmatics (P = 0.014, OR for no asthma in atopic individuals 3.13, CI 1.01-6.10), and the difference in frequency between all asthmatics and all non-asthmatics was statistically significant (P = 0.009) while there was no difference between atopy and non-atopy (P = 0.199). In this study we also report the electrophoretic analysis of the MUC7 glycoprotein in saliva from individuals of different MUC7 genotype.

Nucleosome remodeling at the IL-12 p40 promoter is a TLR-dependent, Rel-independent event

Lipopolysaccharide (LPS) induction of the gene encoding interleukin 12 p40 requires remodeling of a promoter-encompassing nucleosome and the Toll-like receptor (TLR)-mediated activation of a c-Rel-containing complex. Analysis of TLR4-mutant mice revealed that remodeling requires TLR signaling. However, Rel proteins and other proteins required for transcription of an integrated p40 promoter were insufficient for remodeling. c-Rel was also unnecessary for remodeling, as remodeling was observed in c-Rel-/- macrophages, which lack p40 transcripts. These results suggest that remodeling requires TLR signaling pathways that diverge from the c-Rel activation pathways. The factors that stimulate remodeling may represent, therefore, newly identified targets of TLR signaling and of agents that regulate inflammatory responses and TH1 development.

Polymorphism of human mucin genes in chest disease: possible significance of MUC2

Most of the genes that encode epithelial mucins are highly polymorphic due to variations in the length of domains of tandemly repeated (TR) coding sequence, the part of the apomucin that is heavily glycosylated. We report here for the first time a difference in the distribution of MUC TR length alleles in chest disease. We examined the distribution of the length alleles of those MUC genes whose expression we have confirmed in the bronchial tree in an age- and sex-matched series of 50 pairs of atopic patients with and without asthma. There was no significant difference in the distribution of alleles of MUC1, MUC4, MUC5AC, and MUC5B. MUC2, however, showed a highly significant difference in distribution. The atopic, nonasthmatic individuals showed an allele distribution that was very different from all our other patient and control groups, this group showing a longer mean allele length. The observations suggest that longer MUC2 alleles may help protect atopic individuals from developing asthma, though the effect may be due to a linked gene. The biological significance of this variation with respect to susceptibility to asthma will merit further investigation, and it will also be important to substantiate this finding on an independent data set.

Follicular lymphoma can be distinguished from benign follicular hyperplasia by flow cytometry using simultaneous staining of cytoplasmic bcl-2 and cell surface CD20

The distinction between benign follicular hyperplasia (FH) and follicular lymphoma (FL) is sometimes problematic. We wanted to determine whether the expression of bcl-2 of FH was quantitatively different from that of FL, using surface CD20 expression as a discriminator of the various lymphoid compartments. Lymph node cell suspensions from 12 cases of FH and 17 cases of FL were analyzed by flow cytometry using a combined surface CD20 and intracellular bcl-2 staining. CD20- T cells in FH demonstrated the same bcl-2 expression as the CD20+ mantle cells, but the bright CD20+ germinal center cells showed near absence of bcl-2 expression. In contrast, the neoplastic cells of FL showed greater bcl-2 expression than the T cells of the same tumors and all cell populations of FH. This difference was particularly significant between the neoplastic B cells of FL and the germinal center cells of FH. The combined analysis of CD20 and bcl-2 should be useful for the differential diagnosis between FH and FL and particularly applicable to limited samples or when B-cell clonality is in question. Whether the quantitation of bcl-2 expression can be of further discriminatory value in malignant lymphomas remains to be determined.

HIV and tuberculosis co-infection in an inner London hospital--a prospective anonymized seroprevalence study

OBJECTIVES

Since 1987 there has been an increase in tuberculosis notifications in the U.K., with this increase disproportionately affecting London. A recent national survey suggests that co-infection with HIV occurs in less than 5% of tuberculosis patients. This study asked if local co-infection rates in Inner London differed from the national results.

METHODS

157 consecutive patients starting antituberculous chemotherapy were venesected 2 weeks into treatment. Anonymized blood samples were screened for antibodies for HIV-1 and HIV-2 by enzyme-linked immunosorbent assay (ELISA). Epidemiological data were collected on each patient which was also coded before HIV test results were known.

RESULTS

Of 157 patients commencing antituberculous therapy, 39 patients (24.8%) were found to be co-infected with HIV-1. HIV-negative and positive patients were similar in terms of age and sex. When 98 patients giving their country of origin as other than Europe were considered there were 22 co-infected with HIV (22.4%). Of the 39 HIV-positive identified in this study, 37 were also identified by our voluntary HIV testing programme.

CONCLUSIONS

This study has shown that there may be very different rates of co-infection at a local level in the U.K. The local variation may be missed by national surveys and diverse local testing procedures. Anonymous testing identified only two patients with tuberculosis and HIV infection who were not identified by our voluntary HIV testing programme and this suggests that offering HIV tests to patients with tuberculosis is largely taken up by those at risk of HIV infection. Surveillance studies of this type are important in identifying marked local variation from the national pattern of HIV and Mycobacterium tuberculosis infection.

Apoprotein B100 has a prolonged interaction with the translocon during which its lipidation and translocation change from dependence on the microsomal triglyceride transfer protein to independence

When lipid synthesis is limited in HepG2 cells, apoprotein B100 (apoB100) is not secreted but rapidly degraded by the ubiquitin-proteasome pathway. To investigate apoB100 biosynthesis and secretion further, the physical and functional states of apoB100 destined for either degradation or lipoprotein assembly were studied under conditions in which lipid synthesis, proteasomal activity, and microsomal triglyceride transfer protein (MTP) lipid-transfer activity were varied. Cells were pretreated with a proteasomal inhibitor (which remained with the cells throughout the experiment) and radiolabeled for 15 min. During the chase period, labeled apoB100 remained associated with the microsomes. Furthermore, by crosslinking sec61beta to apoB100, we showed that apoB100 remained close to the translocon at the same time apoB100-ubiquitin conjugates could be detected. When lipid synthesis and lipoprotein assembly/secretion were stimulated by adding oleic acid (OA) to the chase medium, apoB100 was deubiquitinated, and its interaction with sec61beta was disrupted, signifying completion of translocation concomitant with the formation of lipoprotein particles. MTP participates in apoB100 translocation and lipoprotein assembly. In the presence of OA, when MTP lipid-transfer activity was inhibited at the end of pulse labeling, apoB100 secretion was abolished. In contrast, when the labeled apoB100 was allowed to accumulate in the cell for 60 min before adding OA and the inhibitor, apoB100 lipidation and secretion were no longer impaired. Overall, the data imply that during most of its association with the endoplasmic reticulum, apoB100 is close to or within the translocon and is accessible to both the ubiquitin-proteasome and lipoprotein-assembly pathways. Furthermore, MTP lipid-transfer activity seems to be necessary only for early translocation and lipidation events.

FT-IR analysis of membranes of Rhodobacter sphaeroides 2.4.3 grown under microaerobic and denitrifying conditions

Fourier transform infrared spectroscopic analysis of CO binding proteins in Rhodobacter sphaeroides reveals the presence of a membrane-bound nitric oxide reductase (Nor). Nor has been clearly distinguished from the cytochrome oxidases by the temperature-dependence of relaxation following photodissociation of the CO complex at cryogenic temperatures. The center frequency and band shape, 1970 cm-1 and 20-30 cm-1 width at half-peak height, are similar to those reported for resonance Raman spectra of purified Paracoccus denitrificans Nor. Additional evidence is presented to indicate this enzyme is part of dissimilatory nitric oxide metabolism and that one of the genes in the nor operon required for production of an active Nor is not required for protein assembly or heme incorporation.

Comparison of the views of junior doctors, consultants and managers on work and training

OBJECTIVE

To determine the views of junior hospital doctors on their working conditions, NHS reforms and training, and to compare their views with those of consultants and managers.

SUBJECTS

A questionnaire was distributed to 52 junior doctors, 19 consultants and 14 middle or senior grade managers in an acute NHS trust.

CONCLUSIONS

Junior doctors had strong feelings about several areas covered in the questionnaire; in particular, more structured training without the requirement to undertake a higher degree would be welcomed. Shift systems are unpopular and the reduction of 'non-medical' tasks with a reduction in work intensity is perceived to be more important than further reductions in hours available for work.

Matrix-assisted laser desorption ionization mass spectrometry of membrane proteins: demonstration of a simple method to determine subunit molecular weights of hydrophobic subunits

Matrix-assisted laser desorption ionization (MALDI) mass spectrometry has been used to obtain accurate molecular weight information for each subunit of several hydrophobic integral membrane proteins: cytochrome bo3 (4 subunits) and cytochrome bd (2 subunits) from E. coli, and the bc1 complex (3 subunits) and the cytochrome c oxidase (3 subunits) from Rhodobacter sphaeroides. The results demonstrate that the MALDI method is a convenient, quick, sensitive and reliable means for obtaining the molecular masses of the subunits of purified multisubunit membrane proteins.

Glutamate 286 in cytochrome aa3 from Rhodobacter sphaeroides is involved in proton uptake during the reaction of the fully-reduced enzyme with dioxygen

The reaction with dioxygen of solubilized fully-reduced wild-type and EQ(I-286) (exchange of glutamate 286 of subunit I for glutamine) mutant cytochrome c oxidase from Rhodobacter sphaeroides has been studied using the flow-flash technique in combination with optical absorption spectroscopy. Proton uptake was measured using a pH-indicator dye. In addition, internal electron-transfer reactions were studied in the absence of oxygen. Glutamate 286 is found in a proton pathway proposed to be used for pumped protons from the crystal structure of cytochrome c oxidase from Paracoccus denitrificans [Iwata et al. (1995) Nature 376, 660-669; E278 in P.d. numbering]. It is the residue closest to the oxygen-binding binuclear center that is clearly a part of the pathway. The results show that the wild-type enzyme becomes fully oxidized in a few milliseconds at pH 7.4 and displays a biphasic proton uptake from the medium. In the EQ(I-286) mutant enzyme, electron transfer after formation of the peroxy intermediate is impaired, CuA remains reduced, and no protons are taken up from the medium. Thus, the results suggest that E(I-286) is necessary for proton uptake after formation of the peroxy intermediate and transfer of the fourth electron to the binuclear center. The results also indicate that the proton uptake associated with formation of the ferryl intermediate controls the electron transfer from CuA to heme a.

Factors determining electron-transfer rates in cytochrome c oxidase: studies of the FQ(I-391) mutant of the Rhodobacter sphaeroides enzyme

The mechanisms of internal electron transfer and oxygen reduction were investigated in cytochrome c oxidase from Rhodobacter sphaeroides (cytochrome aa3) using site-directed mutagenesis in combination with time-resolved optical absorption spectroscopy. Electron-transfer reactions in the absence of O2 were studied after flash photolysis of CO from the partly-reduced enzyme and the reaction of the fully-reduced enzyme with O2 was studied using the so-called flow-flash technique. Results from studies of the wild-type and mutant enzyme in which phenylalanine-391 of subunit I was replaced by glutamine (FQ(I-391)) were compared. The turnover activity of the mutant enzyme was approximately 2% ( approximately 30 s-1) of that of the wild-type enzyme. After flash photolysis of CO from the partly-reduced mutant enzyme approximately 80% of CuA was reduced, which is a much larger fraction than in the wild-type enzyme, and the rate of this electron transfer was 3.2 x 10(3) s-1, which is significantly slower than in the wild-type enzyme. The redox potentials of hemes a and a3 in the mutant enzyme were found to be shifted by about +30 and -70 mV, respectively, as compared to the wild-type enzyme. During the reaction of the fully-reduced FQ(I-391) mutant enzyme with O2 a rapid kinetic phase with a rate constant of 1.2 x 10(5) s-1, presumably associated with O2 binding, was followed by formation of the P intermediate with electrons from heme a3 and CuB with a rate of approximately 4 x 10(3) s-1, and oxidation of the enzyme with a rate of approximately 30 s-1. The dramatically slower electron transfer between the hemes during O2 reduction in the mutant enzyme is not only due to the slower intrinsic electron transfer, but also due to the altered redox potentials. In addition, the results show that the reduced overall activity of the mutant enzyme is due to the slower electron transfer from heme a to the binuclear center during O2 reduction. The relation between the intrinsic heme a/heme a3 electron-transfer rate and equilibrium constant, and the electron-transfer rate from heme a to the binuclear center during O2 reduction is discussed.

The degradation of apolipoprotein B100 is mediated by the ubiquitin-proteasome pathway and involves heat shock protein 70

Apolipoprotein B (apoB) is the major protein component of atherogenic lipoproteins of hepatic origin. In HepG2 cells, the standard cell culture model of human hepatic lipoprotein metabolism, there is a limited availability of core lipids in the endoplasmic reticulum for association with nascent apoB. Under these conditions, apoB is partially translocated, interacts with cytosolic Hsp70, and undergoes rapid degradation. We show that increasing the expression of Hsp70 in HepG2 cells promotes apoB degradation. In addition, apoB is polyubiquitinated and its degradation both normally and after Hsp70 induction is blocked by inhibitors of the proteasome. The apoB that accumulates after proteasome inhibition is endoplasmic reticulum-associated and can be assembled into lipoproteins and secreted if new lipid synthesis is stimulated. Thus, apoB is the first example of a wild-type mammalian protein whose secretion is regulated by degradation in the cytosol via the ubiquitin-proteasome pathway. Furthermore, targeting of this secretory protein to the proteasome is regulated by the molecular chaperone Hsp70 and the availability of apoB's lipid-ligands.

Aspects of HIV infection: current infection control policies for HIV

A coherent infection control policy within healthcare facilities designed for patients with human immunodeficiency virus (HIV) infection requires the application of a risk management strategy. The central feature is the adoption of universal precautions whereby it is assumed that all patients could potentially be infected by HIV. The major tenets of this are the adoption of good clinical hygiene and the adoption of agreed infection control policies with a consistent approach throughout the institution. This involves a teaching and training programme, and clearly defined policies to protect individuals from HIV infection itself and infection with other pathogens, in particular tuberculosis. Special attention is required for bronchoscopy and lung function, as well as a coherent and proactive policy regarding chemoprophylaxis for HIV infection following accidental injury such as needlestick.

Pulmonary artery occlusion by tuberculous mediastinal lymphadenopathy

Two cases of tuberculous mediastinal lymphadenopathy are presented in which the clinical features mimicked those of pulmonary embolism, causing striking abnormalities on radionuclide scintigraphy. It is concluded that tuberculous mediastinal lymphadenopathy should be included in the differential diagnosis of reduced lung perfusion due to proximal pulmonary artery occlusion.

Induction of 8-oxo-7,8-dihydro-2'-deoxyguanosine by ultraviolet radiation in calf thymus DNA and HeLa cells

The levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) in purified calf thymus DNA and HeLa cells were measured following exposure to either UVC, UVB or UVA wavelengths. This DNA damage was quantitated using HPLC coupled with an electrochemical detector. The 8-oxodGuo was induced in purified DNA in a linear dose-dependent fashion by each portion of the UV spectrum at yields of 100, 0.46 and 0.16 8-oxodGuo per 10(5) 2'-deoxyguanosine (dGuo) per kJ/m2 for UVC, UVB and UVA, respectively. However, the amount of 8-oxodGuo in HeLa cells irradiated with these UV sources decreased to approximately 2.0, 0.013 and 0.0034 8-oxodGuo per 10(5) dGuo per kJ/m2, respectively. In contrast, the levels of cyclobutyl pyrimidine dimers were similar in both irradiated DNA and cells. Therefore, 8-oxodGuo is induced in cells exposed to wavelengths throughout the UV spectrum although it appears that protective precesses exist within cells that reduce the UV-induced formation of this oxidative DNA damage. Cell survival was also measured and the number of dimers or 8-oxodGuo per genome per lethal event determined. These calculations are consistent with the conclusion that dimers play a major role in cell lethality for UVC- or UVB-irradiated cells but only a minor role in cells exposed to UVA wavelengths. In addition, it was found that the relative yield of 8-oxodGuo to dimers increased nearly 1000-fold in both UVA-irradiated cells and DNA compared with cells subjected to either UVC or UVB. These results are supportive of the hypothesis that 8-oxodGuo, and possible other forms of oxidative damage, play an important role in the induction of biological effects caused by wavelengths in the UVA portion of the solar spectrum.

FTIR study of conformational substates in the CO adduct of cytochrome c oxidase from Rhodobacter sphaeroides

Fourier transform infrared (FTIR) spectroscopy of cytochrome c oxidase from Rhodobacter sphaeroides reveals multiple CO stretch bands that are associated with different conformational substates of the enzyme. Here we report the temperature dependence of the infrared bands for the CO bound to the Fea3 heme iron and to CuB. We have also studied the kinetics of ligand return from Fea3 to CuB using temperature derivative spectroscopy (TDS). Two classes of substates (alpha/beta) can be distinguished from their different properties with regard to the width of the IR band, the temperature dependence of the peak position, and the peak of the enthalpy distribution. The pronounced temperature dependence of the stretch frequencies in the beta conformation and the lack thereof in the alpha conformation implies very different dynamic behavior in the active site and reflects structural differences between the two conformations, most likely a shift of the position of CuB in response to a change in its stereochemical environment. Similar conformational changes will be necessary during the catalytic cycle of the enzyme when dioxygen is bound in the active site.

Site-directed mutagenesis of residues lining a putative proton transfer pathway in cytochrome c oxidase from Rhodobacter sphaeroides

Several putative proton transfer pathways have been identified in the recent crystal structures of the cytochrome oxidases from Paracoccus denitrificans [Iwata et al. (1995) Nature 376, 660-669] and bovine [Tsukihara (1996) Science 272, 1138-1144]. A series of residues along one face of the amphiphilic transmembrane helix IV lie in one of these proton transfer pathways. The possible role of these residues in proton transfer was examined by site-directed mutagenesis. The three conserved residues of helix IV that have been implicated in the putative proton transfer pathway (Ser-201, Asn-207, and Thr-211) were individually changed to alanine. The mutants were purified, analyzed for steady-state turnover rate and proton pumping efficiency, and structurally probed with resonance Raman spectroscopy and FTIR difference spectroscopy. The mutation of Ser-201 to alanine decreased the enzyme turnover rate by half, and was therefore further characterized using EPR spectroscopy and rapid kinetic methods. The results demonstrate that none of these hydrophilic residues are essential for proton pumping or oxygen reduction activities, and suggest a model of redundant or flexible proton transfer pathways. Whereas previously reported mutants at the start of this putative channel (e.g., Asp-132-Asn) dramatically influence both enzyme turnover and coupling to proton pumping, the current work shows that this is not the case for all residues observed in this channel.

Serum type III procollagen aminopeptide for assessing liver damage in methotrexate-treated psoriatic patients

This study was designed to establish whether measurement of a serological marker of fibrosis might reduce the need for liver biopsy in psoriatic patients receiving methotrexate (MTX). Levels of type III procollagen aminopeptide (PIIINP-O and PIIINP-B) and laminin P1 (LamP1-B) were measured in 147 serum samples taken at the time of liver biopsy in 87 patients receiving long-term MTX treatment for severe psoriasis. Biopsies were classified as: (1) normal, (2) steatosis, (3) inflammation, (4) fibrosis, or (5) cirrhosis. Groups 3-5 were considered to show clinically relevant abnormality. Compared with controls, PIIINP-O was significantly raised in the group of MTX-treated psoriatics (P < 0.001). Within this group, levels were significantly higher in patients with inflammation, fibrosis or cirrhosis compared with those with normal histology or steatosis alone (P < 0.0001). In contrast, PIIINP-B and LamP1-B did not distinguish between controls and MTX-treated patients or between histological groups. Forty-two patients had two or more biopsies with simultaneous PIIINP-O measurement. PIIINP-O levels at the time of the first biopsy were normal in six of the seven patients whose histology was initially normal and subsequently became abnormal. A single measurement of PIIINP-O thus did not predict which patients might develop abnormal histology following further MTX. In a group of 17 patients, PIIINP-O was measured 3-monthly for up to 6 years during MTX treatment. PIIINP-O was elevated at some time during follow-up in all three patients who developed abnormal histology but was consistently normal in eight of the 11 patients whose histology remained or became normal. Our findings indicate that PIIINP-O is of value in detecting liver damage and, particularly if measured serially, may reduce the need for liver biopsy in MTX-treated patients. Although the test does not detect all patients with fibrosis, it would appear that the risk of missing significant liver damage in patients with persistently normal PIIINP-O is low.

"Crack lung" caused by an impure preparation

Pulmonary complications of crack cocaine have been reported mainly from American centres. Crack usage is now on the increase in the UK. Three cases of "crack lung" are reported in patients who acquired the drug from the same source. The pulmonary syndrome they developed was due to an impure form of crack.

Polar residues in helix VIII of subunit I of cytochrome c oxidase influence the activity and the structure of the active site

The aa3-type cytochrome c oxidase from Rhodobacter sphaeroides is closely related to eukaryotic cytochrome c oxidases. Analysis of site-directed mutants identified the ligands of heme a, heme a3, and CuB [Hosler et al. (1993) J. Bioenerg. Biomembr. 25, 121-133], which have been confirmed by high-resolution structures of homologous oxidases [Iwata et al. (1995) Nature 376, 660; Tsukihara et al. (1995) Science 269, 1069; (1996) 272, 1136]. Since the protons used to form water originate from the inner side of the membrane, and the heme a3-CuB center is located near the outer surface, the protein must convey these substrate protons to the oxygen reduction site. Transmembrane helix VIII in subunit I is close to this site and contains several conserved polar residues that could function in a rate-determining proton relay system. To test this role, apolar residues were substituted for T352, T359, and K362 in helix VIII and the mutants were characterized in terms of activity and structure. Mutation of T352, near CuB, strongly decreases enzyme activity and disrupts the spectral properties of the heme a3-CuB center. Mutation of T359, below heme a3, substantially reduces oxidase activity with only minor effects on metal center structure. Two mutations of K362, approximately 15 A below the axial ligand of heme a3, are inactive, make heme a3 difficult to reduce, and cause changes in the resonance Raman signal specific for the iron-histidine bond to heme a3. The results are consistent with a key role for T352, T359, and K362 in oxidase activity and with the involvement of T359 and K362 in proton transfer through a relay system now plausibly identified in the crystal structure. However, the characteristics of the K362 mutants raise some questions about the assignment of this as the substrate proton channel.

A pH-dependent polarity change at the binuclear center of reduced cytochrome c oxidase detected by FTIR difference spectroscopy of the CO adduct

A pH-dependent polarity change at the heme-copper binuclear center of the aa3-type cytochrome c oxidase from Rhodobacter sphaeroides has been identified by low-temperature FTIR difference spectroscopy. "Light"-minus-"dark" FTIR difference spectra of the fully reduced CO-enzyme adduct were recorded at a range of pH, and the dominance of different populations of bound CO, alpha and beta, was found to vary with pH. An apparent pKa of about 7.3 for the transition was obtained. The alpha and beta forms are differentiated by different polarities at the heme-copper binuclear center of the enzyme, sensed by the stretching frequencies of CO bound either to the heme alpha 3 Fe or to CuB. Several site-directed mutants in the vicinity of the heme-copper center are shown to favor either the alpha or the beta forms of the enyzme, suggesting that what is being monitored is an equilibrium between two conformations of the reduced form of the oxidase. Recent resonance Raman evidence has been presented demonstrating that the alpha and beta forms of the R. sphaeroides oxidase exist at room temperature; therefore, the pH-dependent change in the polarity in the vicinity of the heme-copper center may be functionally significant.

The lung in HIV infection: can pulmonary function testing help?

Simple lung function tests have been used to evaluate respiratory symptoms in human immunodeficiency virus (HIV) infected individuals. Abnormalities of simple lung function tests, in particular decreases in the transfer factor of the lung for carbon monoxide (TL,CO) have been described in patients with acquired immune deficiency syndrome (AIDS) who have respiratory disease. Early studies showed marked reductions in TL,CO in patients with pneumocystis pneumonia but other forms of pulmonary infection or neoplasm also resulted in reductions in TL,CO values. Lung function studies in larger numbers of patients have shown reductions in all lung function measurements, particularly in TL,CO. in all categories of HIV disease. The most marked reductions in TL,CO are seen in patients with pneumocystis pneumonia but reductions also occur in pulmonary bacterial infection, tuberculosis and pulmonary Kaposi's sarcoma. TL,CO values improved following recovery from pneumocystis pneumonia but rarely returned to normal. Zidovudine therapy does not contribute to the abnormalities of lung function but smokers generally have worse lung function tests in all categories of HIV disease. The diagnostic usefulness of simple lung function tests is limited. A reduced TL,CO is a highly sensitive index for the presence of pneumonitis (pneumocystis or otherwise) in HIV-infected individuals but lacks the necessary specificity to be a satisfactory diagnostic tool. Simple lung function tests have limitations but have a value as a simple screening test to determine the presence of underlying organic disease in HIV seropositive patients with respiratory symptoms. The presence of a normal TL,CO value makes the presence of pneumonitis unlikely.

Oligoclonal V gene usage by T lymphocytes in bronchoalveolar lavage fluid from sarcoidosis patients

The T-cell antigen receptor (TCR) repertoire was examined in lymphocytes isolated from the lungs and blood of 12 sarcoidosis patients and nine control patients. This analysis, by polymerase chain reaction (PCR), examined the variable (V)-domain genes of both the alpha and beta chains of the TCR. This is the first study to examine the usage of all known V alpha gene segments in sarcoidosis. A similar degree of diversity was observed in the TCR repertoire in the lungs and blood of the sarcoidosis patients. However, 11 of the 12 sarcoidosis patients showed an increased use of particular TCR V alpha and V beta genes in lung T cells as compared with blood. The pattern of TCR V gene bias in the lung T cells was specific for each patient. The clonality of selected V genes was examined by determining the third complementarity-determining region (CDR3) length polymorphism of particular PCR products. The majority of lung T cells with biased TCR V gene segments were oligoclonal. Altogether, these results suggest oligoclonal expansion of lung T cells in response to a local antigenic stimulus, with additional nonspecific T-cell accumulation. The variability in the V gene segments used by the expanded T-cell subsets in different sarcoidosis patients may reflect different epitopes or antigens being recognized in the lung, as well as variations in major histocompatibility complex (MHC) haplotype between the patients.

A ligand-exchange mechanism of proton pumping involving tyrosine-422 of subunit I of cytochrome oxidase is ruled out

The molecular mechanism by which proton pumping is coupled to electron transfer in cytochrome c oxidase has not yet been determined. However, several models of this process have been proposed which are based on changes occurring in the vicinity of the redox centers of the enzyme. Recently, a model was described in which a well-conserved tyrosine residue in subunit I (Y422) was proposed to undergo ligand exchange with the histidine ligand (H419) of the high-spin heme a3 during the catalytic cycle, allowing both residues to serve as part of a proton transporting system. Site-directed mutants of Y422 have been constructed in the aa3-type cytochrome c oxidase of Rhodobacter sphaeroides to test this hypothesis (Y422A, Y422F). The results demonstrate that Y422 is not an essential residue in the electron transfer and proton pumping mechanisms of cytochrome c oxidase. However, the results support the predicted proximity of Y422 to heme a3, as now confirmed by crystal structure. In addition, it is shown that the pH-dependent reversed electron transfer between heme a and heme a3 is normal in the Y422F mutant. Hence, these data also demonstrate that Y422 is not the residue previously postulated to interact electrostatically with heme a3, nor is it responsible for the unique EPR characteristics of heme a in this bacterial oxidase.

Pulmonary complications of HIV disease: 10 year retrospective evaluation of yields from bronchoalveolar lavage, 1983-93

BACKGROUND

Pulmonary disease is a major contributor to morbidity and mortality in patients with HIV infection and AIDS. The aim of this study was to describe bronchoscopic findings and the spectrum of pulmonary pathogens in HIV seropositive patients undergoing investigation of respiratory disease over a 10 year period in a major UK referral centre.

METHODS

Recruitment was procedure based with data being captured when bronchoscopy was clinically indicated. Data were evaluated from 580 HIV seropositive patients (559 men, age 13-65 years) over a 10 year period from June 1983 to March 1993.

RESULTS

A total of 947 bronchoscopies was performed. The most frequent pulmonary pathogen isolated from bronchoalveolar lavage (BAL) fluid in 44% of all bronchoscopies was Pneumocystis carinii. Of all patients studied, 324 (55%) had at least one cytologically confirmed episode of P carinii pneumonia; this was AIDS defining in 219 (38%) of patients who underwent bronchoscopy. Between 1987 and 1993 the overall diagnostic yield from BAL fluid was 76%; 25% of all bronchoscopies yielded positive microbiological results, the most frequent isolates being Staphylococcus aureus, Streptococcus pneumoniae, Pseudomonas spp, and Haemophilus influenzae. Mycobacteria were identified in 8% of patients; M tuberculosis was the most common being identified in 3% of lavage samples and in 4% of patients. No drug-resistant M tuberculosis was found. Viral isolates (mainly cytomegalovirus) were identified in up to 31% of BAL fluid samples. Endobronchial Kaposi's sarcoma was seen in 15% of patients at bronchoscopy.

CONCLUSIONS

Of the 1956 newly diagnosed HIV seropositive patients receiving clinical care at St Mary's Hospital over this period, approximately 30% underwent bronchoscopy. Diagnostic rates for P carinii pneumonia, endobronchial Kaposi's sarcoma, and bacterial and mycobacterial infection have remained largely constant since 1989. Bronchoalveolar lavage produces high diagnostic yields generally, and P carinii pneumonia remains a common cause of pulmonary disease in these patients.

EPR studies of wild-type and several mutants of cytochrome c oxidase from Rhodobacter sphaeroides: Glu286 is not a bridging ligand in the cytochrome a3-CuB center

Wild-type and several mutants of cytochrome c oxidase from Rhodobacter sphaeroides were characterized by EPR spectroscopy. A pH-induced g12 signal, seen previously in mammalian cytochrome oxidase and assigned to the presence of a bridging carboxyl ligand in the bimetallic cytochrome a3-CuB site, is found also in the bacterial enzyme. Mutation of glutamate-286 to glutamine inactivates the enzyme but does not affect this signal, demonstrating that the carboxyl group of this residue is not the bridging ligand. Three mutants, M106Q, located one helix turn below a histidine ligand to cytochrome a, and T352A as well as F391Q, located close to the bimetallic center, are shown to affect dramatically the low-spin heme signal of cytochrome a. These mutants are essentially inactive, suggesting that these three mutations result in alterations to cytochrome a that render the oxidase non-functional.

Sequential liver biopsies during long-term methotrexate treatment for psoriasis: a reappraisal

One hundred and eighty-two liver biopsies were performed over a 10-year period on patients receiving long-term, low-dose, once weekly oral methotrexate (MTX) for severe psoriasis. Forty-nine patients had two or more biopsies during continued treatment and formed the study population for our analysis. The first and last biopsies were compared to determine progression of any histological abnormalities. Liver biopsies were assessed without knowledge of the MTX dose and allocated to one of five groups according to the severity of the histological abnormalities. These were defined as: (1) normal; (2) steatosis alone; (3) inflammation without fibrosis; (4) fibrosis; and (5) cirrhosis. The mean cumulative dose of MTX at the time of the first biopsy was 2743 mg (range 315-10,024), given over 275 weeks (range 26-738). In the interval between the first and last biopsies, patients received, on average, a further 2362 mg (range 390-7155) over 225 weeks (range 60-460). There was improvement in the histological assessment in 12 patients, no change in 28 patients, and deterioration in nine patients. None developed cirrhosis. Liver biopsy findings prompted discontinuation of MTX in four of the 49 patients on long-term treatment. This has to be weighed against the cost and morbidity of the 124 biopsies performed in these patients. Our results suggest that, with careful follow-up, the risk of development or progression of liver disease in patients receiving long-term, low-dose, once weekly oral MTX for psoriasis is modest, and that the requirement for performing routine liver biopsies in these patients needs to be reconsidered.

Mycobacterial infection in HIV seropositive and seronegative populations, 1987-93

BACKGROUND

Although the causes of the worldwide resurgence of tuberculosis are multifactorial, the HIV epidemic is believed to have had a central role. Control is further threatened by the emergence of multidrug-resistant tuberculosis.

METHODS

A retrospective evaluation was undertaken of trends in pulmonary and extrapulmonary culture positive mycobacterial pathology, and the prevalence of drug-resistant tuberculosis in both HIV seropositive and, presumptively, HIV seronegative patients receiving their clinical care at St Mary's Hospital, London. Five hundred and thirty eight patients (188 of whom were known to be HIV seropositive) with positive mycobacterial isolates between January 1987 and March 1993 were identified from laboratory records. These were cross referenced with drug surveillance records.

RESULTS

Overall, between 1987 and 1992 there was a progressive 3.5 fold increase in positive mycobacterial isolates and a 2.5 fold increase in patients with proven mycobacterial infection. This increase was greater within the HIV seropositive population. A total of 663 positive mycobacterial isolates was evaluated; the major pathogen identified was Mycobacterium tuberculosis (379 isolates, 57%). Three hundred and fourteen patients were diagnosed as having M tuberculosis, 49 of whom were HIV seropositive. M tuberculosis was predominantly isolated from the lung. Of 358 positive cultures for M tuberculosis (68 HIV seropositive, 290 presumptively HIV seronegative), only 27 isolates (7.6%), almost exclusively derived from presumed HIV seronegative patients, were resistant to either isoniazid, rifampicin, or both drugs together. No increases in drug-resistant isolates were observed over this period.

CONCLUSIONS

There has been a considerable increase in the incidence of tuberculosis in both HIV seronegative and seropositive populations during the study period. The emergence of drug-resistant tuberculosis was not observed.