Oxygen Uptake-Work Rate Relationship During Two Consecutive Ramp Exercise Tests

The performance of prior high intensity constant work rate (CWR) exercise significantly influences the gain of the fundamental oxygen uptake (VO2) response during subsequent high intensity CWR exercise. The purpose of the present study was to investigate whether equivalent effects could be elicited in the second of two bouts of exhaustive ramp exercise. We therefore hypothesised that a prior bout of exhaustive ramp exercise would increase the VO2-work rate (DeltaVO2/DeltaWR) slope during subsequent ramp exercise. Nine healthy males performed two ramp exercise tests to exhaustion on an electrically braked cycle ergometer separated by a 10-min period of cycling at 20 W. Pulmonary VO2 was measured breath-by-breath throughout both tests, and the mean response time (MRT) and the DeltaVO2/DeltaWR slope for exercise below the gas exchange threshold (GET) (S1), above the GET (S2), and over the S1 + S2 region (ST) were determined. Paired t-tests were used to analyse the data with significance accepted at p < 0.05. Blood [lactate] was higher at the onset of the second ramp test compared to the first (mean +/- SEM 1.2 +/- 0.1 vs. 6.2 +/- 0.7 mM; p < 0.01), but baseline VO2 was not significantly different between tests (0.93 +/- 0.05 vs. 0.99 +/- 0.06 L. min (-1)). The MRT (42 +/- 4 vs. 40 +/- 5 s) did not differ between tests, but the DeltaVO2/DeltaWR slope was steeper in the second ramp test for S2 (9.1 +/- 0.4 vs. 9.8 +/- 0.5 ml. min (-1). W (-1); p < 0.01) and ST (9.0 +/- 0.4 vs. 9.6 +/- 0.5 ml. min (-1). W (-1); p < 0.05). The demonstration that prior ramp exercise increases the DeltaVO2/DeltaWR slope during subsequent ramp exercise is consistent with the results of previous CWR studies and indicates that exercise economy is sensitive to the prior activity of the engaged muscles.

Treatment of venous leg ulcers with Dermagraft

BACKGROUND

A number of different treatment approaches have been recommended for the treatment of venous ulceration, including local ulcer treatment, compression and drug therapy. Recent advances in tissue engineering have resulted in living tissues being developed for cutaneous wound repair and skin replacement. The aim of this pilot study was to compare the rate of healing of venous ulcers in patients treated with Dermagraft (a human fibroblast-derived dermal replacement) and compression therapy or compression therapy alone.

METHODS

A total of 18 patients with venous ulceration of the leg were recruited into the pilot study. Ten patients were treated with Dermagraft and compression therapy, and eight patients were treated with compression therapy alone. Healing was assessed by ulcer tracing and computerised planimetry. Skin perfusion was measured by laser Doppler.

RESULTS

Five (50%) of the patients treated with Dermagraft and one (12.5%) control patient had healed by the end of the 12-week study period (NS). The total ulcer area rate of healing and linear rate of healing was significantly improved in patients treated with Dermagraft (P=0.001 and P=0.006, respectively, Mann-Whitney U-test). The number of capillaries increased in both the treatment and control group. Peri-ulcer skin perfusion increased by 20% in patients treated with Dermagraft, compared with 4.9% in the control group.

CONCLUSION

The data from this small pilot study suggests that Dermagraft is associated with improved healing of venous ulceration. Following this pilot study, further clinical studies are needed to confirm the validity of these results in 'hard to heal' venous leg ulcers.

Effect of Glycogen Depletion on the Oxygen Uptake Slow Component in Humans

Previous studies have indicated that the (.-)VO(2) slow component is related to the recruitment of type II muscle fibres. We therefore hypothesised that an exercise and dietary regimen designed to deplete type I muscle fibres of glycogen would result in a greater contribution of type II muscle fibres to the exercise power output and therefore a larger amplitude of the (.-)VO(2) slow component. Eight male subjects took part in this study. On day 1, the subjects reported to the laboratory at 8 a.m., and completed a 9 min constant-load cycling test at a work rate equivalent to 85 % (.-)VO(2) peak. On day 2 at 12 p.m., the subjects were fed a 4200 kJ meal (60 % protein, 40 % fat); at 6 p.m. they completed a 2 h cycling test at 60 % (.-)VO(2) peak. On day 3 at 8 a.m., the subjects performed an exercise test identical to that of day 1. Metabolic and respiratory measurements indicated that our experimental design was effective in reducing the muscle glycogen content. (.-)VO(2) was significantly higher (by approximately 140 ml x min (-1)) throughout exercise following glycogen depletion but no appreciable changes in (.-)VO(2) kinetics were found: neither the time constant of the primary response (from 35.4 +/- 2.5 to 33.2 +/- 4.4 s) nor the amplitude of the slow component (from 404 +/- 95 to 376 +/- 81 ml x min (-1)) was significantly altered. Therefore, we suggest that the increased (.-)VO(2) throughout exercise and the unaltered (.-)VO(2) slow component following glycogen depletion might be explained by a shift towards a greater reliance on fat metabolism in type I muscle fibres with no appreciable change in fibre type recruitment patterns.

Histological categorisation of fibrotic cancer stroma in advanced rectal cancer

BACKGROUND AND AIMS

Based on conflicting reports regarding the role of the fibrotic stromal response in cancer development--namely, that a desmoplastic reaction can favour either the host or the tumour--it is clear that the role of the stromal response is varied. We have classified the fibrotic stroma of rectal adenocarcinoma penetrating the muscularis propria, based on histologically identified stromal components.

METHODS

Three categories of stroma were used: mature-when the stroma was composed of mature collagen fibres (fine and elongated fibres into multiple layers); intermediate-when keloid-like collagen was intermingled with mature fibres; and immature-consisting of a myxoid stroma in which no mature fibres were included.

RESULTS

In a data set of 862 patients, 53% of patients had mature fibrotic cancer stroma, 33% had intermediate stroma, and 15% had immature stroma. Five year survival rates decreased as follows: mature stroma (80%), intermediate stroma (55%), and immature stroma (27%). The adverse tumour phenotype, tumour cell budding (conspicuous isolated cells or small clusters of cancer cells), was observed in the cancer fronts in tumours with unfavourable fibrotic stroma (p<0.0001). Based on multivariate analysis, categorised fibrotic stroma was selected as an independent prognostic parameter (hazard ratio 1.39; 95% confidence interval 1.17-1.64) together with tumour differentiation. By immunohistochemical examination, as maturation of the fibrotic stroma decreased, stromal T cells became significantly sparser. Furthermore, myofibroblasts were distributed extensively in immature fibrotic stroma compared with mature and intermediate fibrotic stroma.

CONCLUSION

The morphological categorisation of fibrotic cancer stroma highlights the role of the stromal response in relation to the behaviour and host immune reactions of rectal adenocarcinoma and would be a useful tool for predicting patient prognostic outcome.

Inflammatory markers in cystic fibrosis patients with transmissiblePseudomonas aeruginosa

Chronic Pseudomonas aeruginosa infection in cystic fibrosis (CF) leads to a damaging host inflammatory response. There are an increasing number of reports of P. aeruginosa cross-infection at CF centres. The clinical significance of acquisition of a transmissible strain for patients who already harbour P. aeruginosa is unclear. In this study, levels of inflammatory markers in clinically stable adult CF patients who harbour transmissible and sporadic strains of P. aeruginosa have been compared. Patients with CF and chronic P. aeruginosa infection were grouped into those who harbour a transmissible P. aeruginosa and those who harbour their own sporadic strains. Total white cell and differential counts, sputum neutrophil elastase (NE), interleukin (IL)-8, tumour necrosis factor (TNF)-alpha, plasma IL-6 and NE/alpha1-antitrypsin complexes, serum C-reactive protein, and urine TNF receptor 1 were all measured in clinically stable patients 4-6 weeks following completion of intravenous antibiotic therapy. The two groups (both n=20) were well matched for per cent predicted forced expiratory volume in one second, per cent predicted forced vital capacity and body mass index. There were no significant differences in levels of white cell counts or inflammatory markers between the two groups. At times of clinical stability, cystic fibrosis patients infected with transmissible Pseudomonas aeruginosa do not have a heightened inflammatory response above that of those harbouring sporadic strains.

Identification of airborne dissemination of epidemic multiresistant strains of Pseudomonas aeruginosa at a CF centre during a cross infection outbreak

BACKGROUND

Chronic Pseudomonas aeruginosa infection is a major cause of morbidity and mortality for individuals with cystic fibrosis (CF). P aeruginosa cross infection outbreaks have recently been reported at CF holiday camps and specialist centres. The mechanism of cross infection is unknown. A study was performed to look for the presence of epidemic strains of P aeruginosa in the environment of a CF centre during a cross infection outbreak and to examine their potential modes of spread between patients.

METHODS

Microbiological sampling of the environment of the CF facility was performed, including room air sampling. Individual P aeruginosa strains were identified by bacterial fingerprinting. The typing patterns were compared with those of epidemic strains responsible for cross infection among the patients.

RESULTS

Epidemic P aeruginosa strains were isolated from room air when patients performed spirometric tests, nebulisation, and airway clearance, but were not present in other areas of the inanimate environment of the CF centre.

CONCLUSIONS

Aerosol dissemination may be the most important factor in patient-to-patient spread of epidemic strains of P aeruginosa during recent cross infection outbreaks at adult CF centres.

The quinolones: decades of development and use

The discovery of nalidixic acid in 1962, and its introduction for clinical use in 1967, marks the beginning of five decades of quinolone development and use. It was not until the discovery and licensing of the fluoroquinolones in the 1970s and 1980s that these drugs began to establish their place in the armamentarium of clinically useful antimicrobials. At the beginning of the 21st century, in their fifth decade of discovery and use, our understanding of structure-function relationships has improved, and better compounds, in terms of both spectrum of antimicrobial cover and pharmacokinetics, have been developed. The clinical utility of this expanding class of antimicrobial agents, and the lower propensity for the development of resistance with the "newer" fluoroquinolones will need to be continually monitored in the changing therapeutic environment. Antibiotic drug choice will remain difficult in the presence of increasing resistance, but the introduction of the new fluoroquinolones has created a new and exciting era in antimicrobial treatment. The role of these agents has already been acknowledged in a number of clinical guidelines, and appropriate use of these agents may help to preserve their clinical utility, enabling them to realize their full therapeutic potential.

A novel technique for the examination of skin biopsies by laser capture microdissection

BACKGROUND

Skin is an inherently heterogeneous tissue, thus the procurement of pure cell populations is critical for the accurate correlation of a molecular profile to a particular cell type or histological location. Laser Capture Microdissection (LCM) permits the efficient procurement of cells and mapping of genetic changes from histologically prepared samples.

METHODS

This paper describes a robust LCM protocol established in our laboratory for the extraction of high quality DNA which sequenced from 100% of microdissected samples without the need for cloning. The unique properties of skin, in particular its strong intercellular adhesive forces, have dictated a significant modification to the normal procedure of tissue preparation to ensure reliable cell procurement.

RESULTS

Using the methods outlined below we were able to precisely map the pattern of genomic mutations in our target gene of interest in normal skin, actinic keratosis and squamous cell carcinoma.

CONCLUSIONS

The capability to select pure cell populations from the skin will revolutionise our ability to understand the processes involved in cutaneous tumourigenesis.

Prospective, placebo-controlled trial of 5 vs 10 days of oral prednisolone in acute adult asthma

BACKGROUND

The optimal duration of oral steroid treatment in the management of acute adult asthma is unclear. We prospectively studied the effect of 5 vs. 10 days of oral prednisolone in patients with acute asthma requiring hospital admission.

METHODS

Each patient received 40 mg of enteric-coated prednisolone daily for 5 days, followed by 5 days of 40 mg prednisolone daily (n=24) or placebo (n=20). All were given their usual inhaled asthma therapy including inhaled corticosteroids. Patients kept PEF and symptom diaries for 21 days.

RESULTS

For the 5-day treatment group mean (95% CI) early morning PEF was 6 (-47,+36) l/min lower to day 21 (P=0.78). There was no evidence of differences in other PEF measures (morning post-bronchodilator, evening or worst of day). One patient in each group had an exacerbation requiring further oral steroids during the 21-day observation period. Asthma symptom scores were worse in the 5-day group on days 6-21 but the significance of this finding was uncertain, as a difference had emerged by day 5 (prior to trial entry).

CONCLUSIONS

It may be possible to reduce the standard steroid course to 5 days in acute adult asthma, provided all patients receive inhaled steroids and a personal asthma management plan.

Increased treatment requirements of patients with cystic fibrosis who harbour a highly transmissible strain of Pseudomonas aeruginosa

BACKGROUND

A group of patients who harbour the same highly transmissible strain of Pseudomonas aeruginosa were identified at a cystic fibrosis (CF) centre. Isolates of this strain display a number of unusual phenotypic features including resistance to most typical antipseudomonal antibiotics. A study was undertaken to see if there was a difference in treatment requirements between CF patients with chronic infection with their own unique P aeruginosa strains (group 1) and those who harbour a highly transmissible strain (group 2).

METHODS

Data on treatment requirements for the year 2000 were collected from the case records of CF patients with chronic P aeruginosa infection who had received inpatient treatment. Patients co-infected with Burkholderia cepacia or other highly transmissible strains of P aeruginosa were excluded.

RESULTS

There were 2/56 and 3/22 deaths in groups 1 and 2, respectively; these patients were excluded from the analysis. No difference was found between the two groups for mean age, % predicted forced expiratory volume in 1 second (FEV(1)), % predicted forced vital capacity (FVC), and body mass index. Patients in group 2 had a greater median (range) number of intravenous antibiotic days (60 (17-216) v 33 (4-237) days; p=0.01), inpatient days (39 (7-183) v 16 (1-172) days; p<0.01), and inpatient episodes (3 (1-9) v 2 (1-6); p<0.01), and more respiratory exacerbations (mean (SD) 8.2 (3.4) v 6.1 (3.2); p=0.01).

CONCLUSIONS

Patients who harbour the highly transmissible P aeruginosa strain have a greater treatment burden than patients with CF who harbour their own unique strains. These findings support the need for microbiological surveillance for highly transmissible P aeruginosa and the implementation of infection control measures to prevent cross infection.

Bioenergetic constraints on tactical decision making in middle distance running

BACKGROUND

The highest velocity that a runner can sustain during middle distance races is defined by the intersection of the runner's individual velocity-time curve and the distance-time curve. The velocity-time curve is presumably fixed at the onset of a race; however, whereas the race distance is ostensibly fixed, the actual distance-time curve is not. That is, it is possible for a runner to run further than the race distance if he or she runs wide on bends in track races. In this instance, the point of intersection of the individual velocity-time curve and the distance-time curve will move downwards and to the right, reducing the best average velocity that can be sustained for the distance.

METHODS

To illustrate this point, the race tactics used by the gold and silver medallists at 800 m and 5000 m in the Sydney Olympics were analysed. The paths taken by the runners were carefully tracked and the total distance they covered during the races and the average velocity they sustained over the distances they actually covered were calculated.

RESULTS

In both the Olympic 800 m and 5000 m finals, for example, the winner was not the runner who ran at the highest average velocity in the race. Rather, the winners of these races were able to husband their metabolic resources to better effect by running closer to the actual race distance.

CONCLUSIONS

Race results in middle distance running events are dependent not just on the energetic potential of the runners at the start of the race and their strategy for pace allocation, but also on the effect of their tactical approach to positioning on the total distance covered in the race. Middle distance runners should be conscious of minimising the distance covered in races if they wish to optimise their performance.

Mitochondrial involvement in tracheary element programmed cell death

The mitochondria pathway is regarded as a central component of some types of programmed cell death (PCD) in animal cells where specific signals cause the release of cytochrome c from mitochondria to trigger a proteolytic cascade involving caspases. However, plant cells lack canonical caspases, therefore a role for the mitochondria in programmed cell death in plant cells is not obvious. Using plant cells which terminally differentiate, we provide evidence supporting the involvement of mitochondria in PCD, however the release of cytochrome c is insufficient to trigger the PCD. Prior to execution of cellular autolysis initiated by the rupture of the large central vacuole to release sequestered hydrolases, mitochondria adopt a definable morphology, the inner membrane depolarizes prior to death, and cytochrome c is released from mitochondria. However, PCD can be blocked despite translocation of cytochrome c. These results suggest a role for the mitochondria in this PCD but do not support the current animal model for a causative role of cytochrome c in triggering PCD.

Running economy is negatively related to sit-and-reach test performance in international-standard distance runners

The purpose of this study was to investigate the relationship between running economy (RE) and lower body flexibility. Thirty-four international-standard male distance runners (mean +/- s, age 27 +/- 5 years; body mass 64.9 +/- 4.2 kg; VO(2)max 72.8 +/- 3.7 ml x kg(-1) x min(-1)) gave written consent to participate in this study. The subjects performed an incremental treadmill test for the assessment of RE, lactate threshold and VO(2)max, and the sit-and-reach test was used to assess their general lower body and trunk flexibility. Running speeds below the lactate threshold were used to explore the relationship between running economy and sit-and-reach test performance. At 16.0 km x h(-1), the VO(2) was 50.6 +/- 3.7 ml x kg(-1) x min(-1) (range: 44.2 to 57.1 ml x kg(-1) x min(-1)). Pearson product moment correlation coefficients revealed no significant relationships between aerobic demand at 16.0 km x h(-1) and age (r = - 0.19), height (r = 0.15), body mass (r = - 0.18), or VO(2)max (r = - 0.004). However, there was a highly significant relationship between aerobic demand at 16.0 km x h(-1) and the sit-and-reach test score (r = 0.68; p < 0.0001). These results suggest that the least flexible runners are also the most economical. It is possible that stiffer musculotendinous structures reduce the aerobic demand of submaximal running by facilitating a greater elastic energy return during the shortening phase of the stretch-shortening cycle.

Echocardiographic features and outcome of truncus arteriosus diagnosed during fetal life

There are few data on the outcome of truncus arteriosus when this diagnosis is made during fetal life. Such prognostic information is important to assist parental counseling during pregnancy. This study aimed to analyze, retrospectively, the echocardiographic features and outcome of fetuses with truncus arteriosus. A database of those presenting to a tertiary center for fetal cardiology between 1990 and 1999 was reviewed. Cases in which truncus arteriosus was identified as a firm or differential diagnosis were selected. Outcome data were derived from clinical records, and fetal echocardiograms were reviewed retrospectively. At presentation, truncus arteriosus was firmly diagnosed in 16 patients and was a differential diagnosis in 12. Fourteen of 16 (87%) of the firm diagnoses were correct. There were 17 confirmed cases of truncus arteriosus. Pregnancy was terminated in 4 patients (24%) and there were 13 live births. One child was not actively treated, 4 (31%) died preoperatively, and 8 (61%) underwent surgery. Thirty-day surgical mortality was 2 of 8 (25%). There was 1 late death after cardiac catheterization, and overall survival on an intention-to-treat basis was 5 of 12 (42%). Five of 6 patients with a prenatal truncal valve Doppler velocity above the normal aortic range were found to have postnatal truncal valve stenosis. Two fetuses with stenotic valves died preoperatively with sudden cardiovascular collapse. Counseling of parents for fetuses with truncus arteriosus should include the relatively high nonsurgical mortality as well as surgical results. Elevated prenatal truncal valve Doppler velocity predicts postnatal truncal valve stenosis. Fetuses with truncal valve stenosis may be at risk of early sudden death.

Switch junction sequences in PMS2-deficient mice reveal a microhomology-mediated mechanism of Ig class switch recombination

Isotype switching involves a region-specific, nonhomologous recombinational deletion that has been suggested to occur by nonhomologous joining of broken DNA ends. Here, we find increased donor/acceptor homology at switch junctions from PMS2-deficient mice and propose that class switching can occur by microhomology-mediated end-joining. Interestingly, although isotype switching and somatic hypermutation show many parallels, we confirm that PMS2 deficiency has no major effect on the pattern of nucleotide substitutions generated during somatic hypermutation. This finding is in contrast to MSH2 deficiency. With MSH2, the altered pattern of switch recombination and hypermutation suggests parallels in the mechanics of the two processes, whereas the fact that PMS2 deficiency affects only switch recombination may reflect differences in the pathways of break resolution.

The role of auxin-binding protein 1 in the expansion of tobacco leaf cells

Tobacco leaf was used to investigate the mechanism of action of auxin-binding protein 1 (ABP1). The distributions of free auxin, ABP1, percentage of leaf nuclei in G2 and the amount of auxin-inducible growth were each determined in control tobacco leaves and leaves over-expressing Arabidopsis ABP1. These parameters were compared with growth of tobacco leaves, measured both spatially and temporally throughout the entire expansion phase. Within a defined window of leaf development, juvenile leaf cells that inducibly expressed Arabidopsis ABP1 prematurely advanced nuclei to the G2 phase. The ABP1-induced increase in cell expansion occured before the advance to the G2 phase, indicating that the ABP1-induced G2 phase advance is an indirect effect of cell expansion. The level of ABP1 was highest at the position of maximum cell expansion, maximum auxin-inducible growth and where the free auxin level was the lowest. In contrast, the position of maximum cell division correlated with higher auxin levels and lower ABP1 levels. Consistent with the correlations observed in leaves, tobacco cells (BY-2) in culture displayed two dose-dependent responses to auxin. At a low auxin concentration, cells expanded, while at a relatively higher concentration, cells divided and incorporated [3H]-thymidine. Antisense suppression of ABP1 in these cells dramatically reduced cell expansion with negligible effect on cell division. Taken together, the data suggest that ABP1 acts at a relatively low level of auxin to mediate cell expansion, whereas high auxin levels stimulate cell division via an unidentified receptor.

Activity analysis of English Premiership rugby football union refereeing

Little is known about the physiological demands placed on officials during sporting activities. The purpose of this study was to ascertain the movement activities of referees during English Premiership rugby football union matches, and to determine the frequency and duration of these activities. Nine referees who were ranked in the top 20 referees in England were videotaped during a total of 19 matches. During playback of the videotapes, a single observer coded the referees' activities into one of six distinct categories (standing, walking forwards, walking backwards, jogging, running and sprinting) using a computerized video editing system (Observer Video-Pro). The referees were timed over a 20 m distance for the modes of locomotory activity, and the average velocity of the referee for each activity was used to calculate the total distance covered in each mode of activity during matches. The total distance covered during a match was (chi +/- SD) 8581 +/- 668 m. The mean percentage of total playing time spent in each activity was: standing still, 37.0 +/- 11.0%; walking forward, 29.5 +/- 7.2%; walking backward, 9.9 +/- 3.2%; jogging, 12.8 +/- 3.2%; running, 9.8 +/- 2.3%; and sprinting, 1.0 +/- 0.4%. There were a total of 672 transitions between modes of activity during a match. The results of this study suggest that refereeing top English rugby football union matches is physically demanding. Although the major physiological load is placed on the oxygen transport system, frequent sprint bouts and the associated requirements for acceleration and deceleration impose additional metabolic demands on referees. This information may be used in the design of physical training programmes to optimize performance in referees.

Stroke prevention in sickle cell disease (STOP) study guidelines for transcranial Doppler testing

The Stroke Prevention in Sickle Cell Disease (STOP) trial used transcranial Doppler (TCD) to screen children with sickle cell disease with no history of stroke. Children (who consented) who had time-averaged mean of the maximum (TAMM) velocities in the middle cerebral artery and/or distal internal carotid artery were randomized to transfusion or standard. Over a slightly more than 20-month average follow-up, there were 11 strokes in the standard care arm and 1 stroke in the transfusion arm. This study has caused a great deal of interest in using TCD to screen children with sickle cell disease. For the STOP TCD data to be applied appropriately, it is necessary for users of TCD to understand how the STOP TCD examinations were performed, how the TCD velocities were measured, and which velocities were used. This article will review the STOP TCD scanning protocol and the reading protocol and review the TAMM velocity and how it differs from other velocity measurements.

X-linked lymphoproliferative disease: three atypical cases

Common variable immunodeficiency (CVID) is the most frequently occurring primary immunodeficiency in both children and adults. The molecular basis of CVID has not been defined, and diagnosis involves exclusion of other molecularly defined disorders. X-linked lymphoproliferative disease (XLP) is a rare disorder in which severe immunodysregulatory phenomena typically follow Epstein-Barr virus (EBV) infection. Boys who survive initial EBV infection have a high incidence of severe complications, including progressive immunodeficiency, aplastic anaemia, lymphoproliferative disease and lymphoma. Survival beyond the second decade is unusual, although bone marrow transplantation can be curative. Until recently reliable diagnostic testing for XLP has not been available, but the identification of the XLP gene, known as SH2D1A, and coding for a protein known as SAP, means that molecular diagnosis is now possible, both by protein expression assays, and mutation detection, although the mutation detection rate in several series is only 55-60%. We describe three male patients initially diagnosed as affected by CVID, one of whom developed fatal complications suggestive of XLP, and all of whom lack expression of SAP. Two out of three have disease-causing mutations in the SAP gene, consistent with published data for XLP. These findings raise the possibility that a subgroup of patients with CVID may be phenotypic variants of XLP. Further studies are necessary to investigate this possibility, and also to clarify the prognostic significance of SAP abnormalities in such patients in the absence of typical features of XLP.

Spread of a multiresistant strain of Pseudomonas aeruginosa in an adult cystic fibrosis clinic

We initiated a prospective surveillance study to investigate possible Pseudomonas aeruginosa cross-infection in our cystic fibrosis centre. We characterised isolates by pyocin typing and pulsed-field gel electrophoresis. 22 (14%) of 154 patients with chronic P aeruginosa had isolates with similar and new pyocin and pulsed-field gel electrophoresis types. The shared isolates showed unusual phenotypic features: they were non-pigmented, non-motile, and resistant to a number of antipseudomonal antibiotics. Cross-infection by a multiresistant P aeruginosa strain has therefore occurred in patients attending our cystic fibrosis centre. We recommend microbiological surveillance in other cystic fibrosis centres.

Outcome of varicella pneumonitis in immunocompetent adults requiring treatment in a high dependency unit

OBJECTIVES

The incidence of varicella infection is increasing in adults, where primary pneumonitis is the main complication. Little information exists concerning treatment of those patients who require admission to a high dependency unit (HDU) facility. A study was performed to examine the risk factors for developing varicella pneumonitis (VP), to document disease progression and assess prognosis for patients with VP requiring HDU admission.

METHODS

A 10-year retrospective casenote review of patients admitted to the Regional Infectious Diseases Unit HDU. Varicella pneumonitis (VP) was defined as diffuse nodular shadowing on a chest X-ray (CXR) of a patient with a classical chickenpox rash. Severe pneumonitis was defined as an hypoxaemia index (pO2 in mmHG/FiO2) of less than 150 at any time during hospital stay. All patients were treated with intravenous acyclovir at a dose of 10 mg/kg.

RESULTS

A total of 33 patients were admitted to the HDU with VP over the study period, 30 were included in the study. Annual admission rates remained constant. Most patients (76.7%) had at least one recognised risk factor for severe VP: smoking 18/30, pregnancy 9/30, chronic lung disease 7/30. Twelve (40%) patients had severe VP, eight (26.7%) required assisted ventilation. The presence of greater than one risk factor (p < 0.02) was associated with progression to severe VP. There was one death: a 63-year-old man with a long history of chronic airflow limitation whose treatment had included domicillary long-term oxygen therapy. Nine (30%) patients developed secondary bacterial pneumonia; all recovered with appropriate antibiotic treatment. The period of stay in HDU for the majority of patients was short (mean 4.5 days).

CONCLUSIONS

The prognosis for severe adult VP with current available treatment is good. The only predictor on admission for severe VP is the presence of more than one recognised risk factor for developing VP.

The relationship between critical velocity, maximal lactate steady-state velocity and lactate turnpoint velocity in runners

In cycle exercise, it has been suggested that critical power, maximal lactate steady state, and lactate turnpoint all demarcate the transition between the heavy exercise domain (in which blood lactate is elevated above resting values but remains stable over time) and the very heavy exercise domain (in which blood lactate increases continuously throughout constant-intensity exercise). The purpose of the present study was to assess the level of agreement between critical velocity (CV), maximal lactate steady-state velocity (MLSSV), and lactate turnpoint velocity (LTPV) during treadmill running. Eight male subjects [mean (SD) age 28 (5) years, body mass 71.2 (8.0) kg, maximum oxygen uptake 54.9 (3.2) ml.kg(-1).min(-1)) performed an incremental treadmill test for the determination of LTPV (defined as a sudden and sustained increase in blood lactate concentration ([La]) at approximately equals 2.0-5.0 mM). The subjects returned to the laboratory on eight or nine occasions for the determination of CV and MLSSV. The CV was determined from four treadmill runs at velocities that were chosen to result in exhaustion within 2-12 min. The MLSSV was determined from four or five treadmill runs of up to 30 min duration and defined as the highest velocity at which blood [La] increased by no more than 1.0 mM after between 10 and 30 min of exercise. Analysis of variance revealed no significant differences between [mean (SD)] CV [14.4 (1.1) km.h(-1)], MLSSV [13.8 (1.1) km.h(-1)] and LTPV [13.7 (0.6) km.h(-1)]. However, the bias +/-95% limits of agreement for comparisons between CV and MLSSV [0.6 (2.2) km.h(-1)], CV and LTPV [0.7 (2.7) km.h(-1)], and MLSSV and LTPV [0.1 (1.8) km.h(-1)] suggest that the extent of disagreement is too great to allow one variable to be estimated accurately from another in individual subjects. Direct determination of MLSSV is necessary if precision is required in experimental studies.

Comparison of transcranial color Doppler imaging (TCDI) and transcranial Doppler (TCD) in children with sickle-cell anemia

BACKGROUND

Transcranial Doppler (TCD) has been demonstrated to identify those at highest risk of stroke among children with sickle-cell disease. Based on a randomized clinical trial [Stroke Prevention in Sickle-Cell Anemia Trial (STOP)], which ended in 1997, the National Heart Lung and Blood Division of NIH has recommended TCD screening and chronic blood transfusion based on Nicolet TC 2000 dedicated Doppler (TCD). Studies performed using TCD imaging modalities need to be correlated to that used in the clinical trial to provide information for treatment decisions when screening with TCDI.

OBJECTIVE

To correlate transcranial arterial time-averaged mean velocities obtained from an Acuson Transcranial Doppler Imaging to those obtained using the TCD as the gold standard for treatment decisions based on STOP.

MATERIALS AND METHODS

A total of 29 children with sickle-cell disease, age 3-16 years, were studied at one of two scanning sessions using both techniques and a scanning protocol based on that used in STOP performed and read independently. The average difference in the measured velocities for each arterial segment was tested to determine difference from zero. Differences were compared before and after modifications to the TCDI technique were made to mimic the STOP protocol more closely.

RESULTS

TCDI velocities were generally lower than TCD velocities for the same segment, but the difference was reduced (from 15 % to 10% for the middle cerebral artery) by modifications to the TCDI protocol.

CONCLUSIONS

Measurements using the Acuson system are modestly lower than those obtained with dedicated Doppler using the Nicolet TCD.