In vivo emergence of HIV-1 variants resistant to multiple protease inhibitors

Inhibitors of the human immunodeficiency virus type 1 (HIV-1) protease have entered clinical study as potential therapeutic agents for HIV-1 infection. The clinical efficacy of HIV-1 reverse transcriptase inhibitors has been limited by the emergence of resistant viral variants. Similarly, variants expressing resistance to protease inhibitors have been derived in cell culture. We now report the characterization of resistant variants isolated from patients undergoing therapy with the protease inhibitor MK-639 (formerly designated L-735,524). Five of these variants, isolated from four patients, exhibited cross-resistance to all members of a panel of six structurally diverse protease inhibitors. This suggests that combination therapy with multiple protease inhibitors may not prevent loss of antiviral activity resulting from resistance selection. In addition, previous therapy with one compound may abrogate the benefit of subsequent treatment with a second inhibitor.

Genetic correlates of in vivo viral resistance to indinavir, a human immunodeficiency virus type 1 protease inhibitor

Indinavir (IDV) (also called CRIXIVAN, MK-639, or L-735,524) is a potent and selective inhibitor of the human immunodeficiency virus type 1 (HIV-1) protease. During early clinical trials, in which patients initiated therapy with suboptimal dosages of IDV, we monitored the emergence of viral resistance to the inhibitor by genotypic and phenotypic characterization of primary HIV-1 isolates. Development of resistance coincided with variable patterns of multiple substitutions among at least 11 protease amino acid residues. No single substitution was present in all resistant isolates, indicating that resistance evolves through multiple genetic pathways. Despite this complexity, all of 29 resistant isolates tested exhibited alteration of residues M-46 (to I or L) and/or V-82 (to A, F, or T), suggesting that screening of these residues may be useful in predicting the emergence of resistance. We also extended our previous finding that IDV-resistant viral variants exhibit various patterns of cross-resistance to a diverse panel of HIV-1 protease inhibitors. Finally, we noted an association between the number of protease amino acid substitutions and the observed level of IDV resistance. No single substitution or pair of substitutions tested gave rise to measurable viral resistance to IDV. The evolution of this resistance was found to be cumulative, indicating the need for ongoing viral replication in this process. These observations strongly suggest that therapy should be initiated with the most efficacious regimen available, both to suppress viral spread and to inhibit the replication that is required for the evolution of resistance.

Reliability of immunohistochemical demonstration of oestrogen receptors in routine practice: interlaboratory variance in the sensitivity of detection and evaluation of scoring systems

AIMS

To investigate interlaboratory variance in the immunohistochemical (IHC) detection of oestrogen receptors so as to determine the rate of false negatives, which could adversely influence the decision to give adjuvant tamoxifen treatment.

METHODS

To ensure that similar results are obtained by different institutions, 200 laboratories from 26 countries have joined the UK national external quality assessment scheme for immunocytochemistry (NEQAS-ICC). Histological sections from breast cancers having low, medium, and high levels of oestrogen receptor expression were sent to each of the laboratories for immunohistochemical staining. The results obtained were evaluated for the sensitivity of detection, first by estimating threshold values of 1% and 10% of stained tumour cells, and second by the Quick score method, by a panel of four assessors judging individual sections independently on a single blind basis. The results were also evaluated using participants' own threshold values.

RESULTS

Over 80% of laboratories were able to demonstrate oestrogen receptor positivity on the medium and high expressing tumours, but only 37% of laboratories scored adequately on the low expressing tumour. Approximately one third of laboratories failed to register any positive staining in this tumour, while one third showed only minimal positivity.

CONCLUSIONS

There is considerable interlaboratory variability, especially in relation to the detection of breast cancers with low oestrogen receptor positivity, with a false negative rate of between 30% and 60%. This variability appears to be caused by minor differences in methodology that may be rectified by fine adjustment of overall technique.

Base excess and lactate as prognostic indicators for patients admitted to intensive care

OBJECTIVE

To examine whether values of arterial base excess or lactate taken on admission to a general intensive care unit indicate prognosis, and whether this can be used as a screening tool for future intensive care admissions.

DESIGN

Observational study.

SETTING

University teaching hospital general adult intensive care unit.

PATIENTS

148 consecutive patients admitted to the intensive care unit.

INTERVENTIONS

Arterial blood samples were obtained on admission to the intensive care unit and 24 h following admission.

MEASUREMENTS AND RESULTS

Arterial base excess and lactate concentrations were measured from the blood samples. Both base excess and arterial lactate samples on admission have good prognostic abilities (area under the curve on receiver operator characteristic analysis of 0.73, 0.78, respectively). The value of base excess on admission with the best predictive ability was a base excess more negative than -4 mmol/l, and the corresponding value for lactate was greater than 1.5 mmol/l. The combination of these two markers on admission to the intensive care unit led to a sensitivity of 80.3 % and a specificity of 58.7 % for mortality. The achievement of this combination was associated with an increased mortality (50.6 % vs. 15 %, p < 0.0001), older age (70 vs. 61.5 years, p < 0.05), a greater requirement for inotropic support (30.9 % vs. 4.5%, p < 0.0001) and higher organ failure scores both on admission and for the subsequent 24 h.

CONCLUSIONS

Both base excess and lactate, or the combination of the two, can be used to predict outcome in patients admitted to the intensive care unit. These variables could be utilized to identify patients who have a high risk for mortality and thus who should be admitted to the intensive care unit.

Goal-directed therapy in cardiac surgery: a systematic review and meta-analysis

BACKGROUND

Perioperative mortality after cardiac surgery has decreased in recent years although postoperative morbidity is still significant. Although there is evidence that perioperative goal-directed haemodynamic therapy (GDT) may reduce surgical mortality and morbidity in non-cardiac surgical patients, the data are less clear after cardiac surgery. The objective of this review is to perform a meta-analysis on the effects of perioperative GDT on mortality, morbidity, and length of hospital stay in cardiac surgical patients.

METHODS

We conducted a systematic review using Medline, EMBASE, and the Cochrane Controlled Clinical Trials Register. Additional sources were sought from experts. The inclusion criteria were randomized controlled trials, mortality reported as an outcome, pre-emptive haemodynamic intervention, and cardiac surgical population. Included studies were examined in full and subjected to quantifiable analysis, subgroup analysis, and sensitivity analysis where possible. Data synthesis was obtained by using odds ratio (OR) and mean difference (MD) for continuous data with 95% confidence interval (CI) utilizing a random-effects model.

RESULTS

From 4986 potential studies, 5 met all the inclusion criteria (699 patients). The quantitative analysis showed that the use of GDT reduced the postoperative complication rate (OR 0.33, 95% CI 0.15-0.73; P=0,006) and hospital length of stay (MD -2.44, 95% CI -4.03 to -0.84; P=0,003). There was no significant reduction in mortality.

CONCLUSION

The use of pre-emptive GDT in cardiac surgery reduces morbidity and hospital length of stay.

Use of early corticosteroid therapy on ICU admission in patients affected by severe pandemic (H1N1)v influenza A infection

INTRODUCTION

Early use of corticosteroids in patients affected by pandemic (H1N1)v influenza A infection, although relatively common, remains controversial.

METHODS

Prospective, observational, multicenter study from 23 June 2009 through 11 February 2010, reported in the European Society of Intensive Care Medicine (ESICM) H1N1 registry.

RESULTS

Two hundred twenty patients admitted to an intensive care unit (ICU) with completed outcome data were analyzed. Invasive mechanical ventilation was used in 155 (70.5%). Sixty-seven (30.5%) of the patients died in ICU and 75 (34.1%) whilst in hospital. One hundred twenty-six (57.3%) patients received corticosteroid therapy on admission to ICU. Patients who received corticosteroids were significantly older and were more likely to have coexisting asthma, chronic obstructive pulmonary disease (COPD), and chronic steroid use. These patients receiving corticosteroids had increased likelihood of developing hospital-acquired pneumonia (HAP) [26.2% versus 13.8%, p < 0.05; odds ratio (OR) 2.2, confidence interval (CI) 1.1-4.5]. Patients who received corticosteroids had significantly higher ICU mortality than patients who did not (46.0% versus 18.1%, p < 0.01; OR 3.8, CI 2.1-7.2). Cox regression analysis adjusted for severity and potential confounding factors identified that early use of corticosteroids was not significantly associated with mortality [hazard ratio (HR) 1.3, 95% CI 0.7-2.4, p = 0.4] but was still associated with an increased rate of HAP (OR 2.2, 95% CI 1.0-4.8, p < 0.05). When only patients developing acute respiratory distress syndrome (ARDS) were analyzed, similar results were observed.

CONCLUSIONS

Early use of corticosteroids in patients affected by pandemic (H1N1)v influenza A infection did not result in better outcomes and was associated with increased risk of superinfections.

Best Practice No 176: Updated recommendations for HER2 testing in the UK

This paper serves to update previously published guidance on rationale and methodology for HER2 laboratory testing following the recommendation for the use of HER2 targeted treatment in the management of advanced breast cancer in the UK. Emphasis is placed on the standardisation of methodology and assessment and strategies to achieve high quality performance. A two phase testing algorithm based on first line immunocytochemistry evaluation and second line fluorescence in situ hybridisation assessment of borderline cases is recommended. To ensure maintenance of expertise, an annual caseload volume of at least 250 cases is recommended for laboratories providing a testing service.

Risk factors for target non-attainment during empirical treatment with β-lactam antibiotics in critically ill patients

PURPOSE

Risk factors for β-lactam antibiotic underdosing in critically ill patients have not been described in large-scale studies. The objective of this study was to describe pharmacokinetic/pharmacodynamic (PK/PD) target non-attainment envisioning empirical dosing in critically ill patients and considering a worst-case scenario as well as to identify patient characteristics that are associated with target non-attainment.

METHODS

This analysis uses data from the DALI study, a prospective, multi-centre pharmacokinetic point-prevalence study. For this analysis, we assumed that these were the concentrations that would be reached during empirical dosing, and calculated target attainment using a hypothetical target minimum inhibitory concentration (MIC), namely the susceptibility breakpoint of the least susceptible organism for which that antibiotic is commonly used. PK/PD targets were free drug concentration maintained above the MIC of the suspected pathogen for at least 50 % and 100 % of the dosing interval respectively (50 % and 100 % f T (>MIC)). Multivariable analysis was performed to identify factors associated with inadequate antibiotic exposure.

RESULTS

A total of 343 critically ill patients receiving eight different β-lactam antibiotics were included. The median (interquartile range) age was 60 (47-73) years, APACHE II score was 18 (13-24). In the hypothetical situation of empirical dosing, antibiotic concentrations remained below the MIC during 50 % and 100 % of the dosing interval in 66 (19.2 %) and 142 (41.4 %) patients respectively. The use of intermittent infusion was significantly associated with increased risk of non-attainment for both targets; creatinine clearance was independently associated with not reaching the 100 % f T( >MIC) target.

CONCLUSIONS

This study found that-in empirical dosing and considering a worst--case scenario--19 % and 41 % of the patients would not achieve antibiotic concentrations above the MIC during 50 % and 100 % of the dosing interval. The use of intermittent infusion (compared to extended and continuous infusion) was the main determinant of non-attainment for both targets; increasing creatinine clearance was also associated with not attaining concentrations above the MIC for the whole dosing interval. In the light of this study from 68 ICUs across ten countries, we believe current empiric dosing recommendations for ICU patients are inadequate to effectively cover a broad range of susceptible organisms and need to be reconsidered.

Frequency of oestrogen and progesterone receptor positivity by immunohistochemical analysis in 7016 breast carcinomas: correlation with patient age, assay sensitivity, threshold value, and mammographic screening

AIMS

A routine immunohistochemical (IHC) assay is now commonly used for determining the oestrogen receptor (ER) and progesterone receptor (PR) status of women with breast cancer. To date, no large studies have been conducted that report the expected frequency of receptor positivity in relation to patient age and sensitivity of the IHC assay. Data on 7016 breast carcinomas from 71 laboratories were analysed to determine the frequency of receptor positivity and investigate possible causes of the observed variation in detection rates.

METHODS

Members of UK NEQAS-ICC (UK National External Quality Assessment Scheme for Immunocytochemistry) provided data on the receptor status of cases routinely assayed in their departments over a period of two to 26 months between June 1996 and September 1998. Data on 7016 breast carcinomas were stratified according to patient age and receptor status. Frequency of receptor positivity was correlated with IHC assay sensitivity, the threshold value used to determine receptor positivity, and the presence or absence of mammographic screening in the hospitals or clinics served by the laboratories.

RESULTS

The highest proportion of receptor positive cases occurred in patients in the age ranges > 65 years for ER and 41-50 years for PR. There was a significant positive correlation between frequency of receptor positivity and the sensitivity of the IHC assay, for both ER (rs = 0.346; p = 0.019; two tailed) and PR (rs = 0.561; p = 0.003; two tailed). The mean frequency of receptor positivity for laboratories using the same 10% threshold value was 77% for ER (95% confidence interval (CI), 74% to 80%) in laboratories with high sensitivity and 72% (95% CI, 68% to 76%) for those with low assay sensitivity (p = 0.025). For PR, the mean frequency of receptor positivity for laboratories using the same 10% threshold value and having high assay sensitivity was 63% (95% CI, 57% to 69%), and 51% (95% CI, 38% to 65%) for laboratories with assays of low sensitivity (p = 0.022). The mean frequency of ER positivity for laboratories serving hospitals and clinics where mammographic screening does and does not take place was 73.4% and 75.7%, respectively (p = 0.302; two tailed).

CONCLUSIONS

Of the parameters investigated, patient age and IHC assay sensitivity were found to be the main variables influencing the frequency of receptor positivity. We recommend the range of receptor values obtained by laboratories achieving high assay sensitivity as a useful guide against which all laboratories can gauge their own results.

Immunohistochemical demonstration of oestrogen and progesterone receptors: correlation of standards achieved on in house tumours with that achieved on external quality assessment material in over 150 laboratories from 26 countries

AIMS

To investigate the sensitivity of immunohistochemical (IHC) assays for oestrogen receptors (ER) and progesterone receptors (PR) achieved by laboratories on breast tumours fixed and processed in their own department, and to compare this with the degree of sensitivity they achieve on tumours circulated as part of an external quality assessment (EQA) programme.

METHODS

On 10 occasions between April 1994 and June 1998, histological sections from breast cancers showing various degrees of expression of ER and PR were circulated for IHC staining to laboratories participating in the UK national external quality assessment scheme for immunocytochemistry (UK NEQAS-ICC). The staining of these tumours, in addition to that of tumours fixed and processed in the participants own laboratories (in house tumours), was assessed by a panel of four assessors, using the established UK NEQAS-ICC scoring system. For a selected assessment run, the degree of expression of participants in house tumours was evaluated by means of the semiquantitative quick score method.

RESULTS

Although the scores awarded for the staining of in house tumours were generally higher than those awarded for the staining of UK NEQAS tumours, there was also a significant positive correlation between the two sets of scores. Using the quick score method of evaluation for one of the assessment runs, 47% of in house tumours were classified as having a high degree of ER expression. Of the remaining cases, a significant proportion initially classified as having only low or medium expression of ER were found to have higher expression when stained by the organising laboratory. The UK NEQAS-ICC centre's routine assay for hormonal receptors was found to be 90-100% efficient in achieving optimal demonstration of breast tumours from over 150 different laboratories.

CONCLUSIONS

The significant positive correlation between the results obtained on the UK NEQAS tumours and the in house tumours provides evidence for the view that results achieved on EQA material are accurate indicators of in house laboratory performance. Although most laboratories adequately detected tumours with high receptor expression, a large proportion of in house tumours classified initially by participants' staining as being of low or medium ER expression had a higher degree of expression when stained by the UK NEQAS-ICC centre. The efficiency of the organising centre's routine IHC method for ER and PR in optimally demonstrating participants in house breast tumours shows that variations in fixation and tissue preparation are not limiting factors preventing a different laboratory achieving optimal demonstration.

Study of interlaboratory reliability and reproducibility of estrogen and progesterone receptor assays in Europe. Documentation of poor reliability and identification of insufficient microwave antigen retrieval time as a major contributory element of unreliable assays

Immunohistochemical assays for estrogen receptors (ERs) and progesterone receptors (PRs) have not been surveyed for technical validity. In the present study, the reliability of the immunohistochemical assay for ER and PR was evaluated using data from 105 laboratories participating in external quality assessment (EQA) during a 2-year period. Technical variables associated with reliable immunostaining were analyzed. The efficiency of the antigen retrieval step was identified as the single most important contributory factor influencing the overall reproducibility of the assays. Reliable assays were found in 24 (36%) of 66 laboratories participating in continual EQA, including the majority of centers known to have clinically validated results. Inadequate assay sensitivity, with subsequent weak staining, was the main cause of poor and variable results by laboratories using microwave antigen retrieval; too short a heating time was identified as the principal contributory factor. Extension of the heating time resulted in significant improvement regardless of all other variables in the immunohistochemical protocol. Continual participation in EQA is an effective means for identifying and ameliorating variables that influence the reliability of immunohistochemical assays for predictive markers, thereby assisting in technical validation and standardization.

The strong ion gap does not have prognostic value in critically ill patients in a mixed medical/surgical adult ICU

OBJECTIVE

To examine whether the strong ion gap (SIG) or standard base excess corrected for abnormalities of serum chloride and albumin (BE(UA)) can predict outcome and to compare the prognostic abilities of these variables with standard base excess (SBE), anion gap (AG), pH, and lactate, the more traditional markers of acid-base disturbance.

DESIGN

Prospective, observational study.

SETTING

University teaching hospital, general adult ICU.

PATIENTS

One hundred consecutive patients on admission to the ICU.

MEASUREMENTS AND RESULTS

The anion gap (AG) was calculated and corrected for abnormal serum albumin (AG(corrected)). Serum lactate was measured and SBE, BE(UA), SIG, and APACHE II scores calculated for each patient. 28-day survival was recorded. There was a significant difference between the mean APACHE II (P < 0.001), SBE (P < 0.001), lactate (P = 0.008), AG (P = 0.007), pH (P < 0.001), and BE(UA) (P = 0.009) of survivors and non-survivors. There was no significant difference between the mean SIG (P = 0.088), SIDeff (P = 0.025), and SID app (P = 0.254) between survivors and non-survivors. The pH and SBE demonstrated the best ability of the acid-base variables to predict outcome (AUROC curves 0.72 and 0.71, respectively). Neither of these were as good as the APACHE II score (AUROC 0.76)

CONCLUSION

Traditional indices of SBE, BE(UA,) lactate, pH, AG, and APACHE II all discriminated well between survivors and non-survivors. In this group of patients the SIG, SIDeff, and SIGapp appear to offer no advantage in prediction of outcome and their use as prognostic markers can therefore not be advocated.

A prospective study of the use of a dobutamine stress test to identify outcome in patients with sepsis, severe sepsis, or septic shock

OBJECTIVE

To more clearly define the relationship between an oxygen flux test, oxygen supply dependency, and outcome in patients with sepsis, severe sepsis, or septic shock.

DESIGN

Prospective, interventional clinical trial.

SETTING

A teaching hospital general intensive care unit in London, UK.

PATIENTS

A total of 36 patients with sepsis, severe sepsis, or septic shock were studied during a 10-month period.

INTERVENTIONS

After resuscitation, patients were given an intravenous infusion of dobutamine at 10 microg/kg/min for 1 hr. Cardiac and respiratory variables were measured before the infusion and then while the infusion was in progress. Any patient who was able to increase his or her oxygen consumption by >15% was designated a responder to the test.

MEASUREMENTS AND MAIN RESULTS

Hemodynamic, oxygen transport, and lactate measurements were made at baseline and after 1 hr of the dobutamine infusion. All patients were then followed up until hospital discharge. Responders to this test had a hospital mortality of 14%, whereas nonresponders had a mortality of 91% (p<.01). The responders were characterized by being younger (p<.05), having higher Acute Physiology and Chronic Health Evaluation III scores (p<.05), and having a greater requirement for inotropic support (p<.05). After the test, the responders had significantly higher oxygen delivery (p<.01) and oxygen consumption (p<.05) than the nonresponders, as well as a significantly greater temperature increase as a result of the infusion (p<.05). The nonresponders were unable to increase either oxygen delivery or oxygen consumption to the dobutamine. This test was highly predictive of outcome (p<.0001). The identification of an increase in both oxygen delivery and oxygen consumption (oxygen supply dependency) was not associated with a poor outcome.

CONCLUSION

A dobutamine oxygen flux test provides evidence of the intrinsic function of cells. The inability of these cells to increase oxidative metabolism during sepsis, as indicated by the dobutamine test, is associated with a high mortality.

Cardiac complications associated with goal-directed therapy in high-risk surgical patients: a meta-analysis

Patients with limited cardiopulmonary reserve are at risk of mortality and morbidity after major surgery. Augmentation of oxygen delivery index (DO2I) with i.v. fluids and inotropes (goal-directed therapy, GDT) has been shown to reduce postoperative mortality and morbidity in high-risk patients. Concerns regarding cardiac complications associated with fluid challenges and inotropes may prevent clinicians from performing GDT in patients who need it most. We hypothesized that GDT is not associated with an increased risk of cardiac complications in high-risk, non-cardiac surgical patients. We performed a systematic search of Medline, Embase, and CENTRAL databases for randomized controlled trials (RCTs) of GDT in high-risk surgical patients. Studies including cardiac surgery, trauma, and paediatric surgery were excluded. We reviewed the rates of all cardiac complications, arrhythmias, myocardial ischaemia, and acute pulmonary oedema. Meta-analyses were performed using RevMan software. Data are presented as odds ratios (ORs), [95% confidence intervals (CIs)], and P-values. Twenty-two RCTs including 2129 patients reported cardiac complications. GDT was associated with a reduction in total cardiovascular (CVS) complications [OR=0.54, (0.38-0.76), P=0.0005] and arrhythmias [OR=0.54, (0.35-0.85), P=0.007]. GDT was not associated with an increase in acute pulmonary oedema [OR=0.69, (0.43-1.10), P=0.12] or myocardial ischaemia [OR=0.70, (0.38-1.28), P=0.25]. Subgroup analysis revealed the benefit is most pronounced in patients receiving fluid and inotrope therapy to achieve a supranormal DO2I, with the use of minimally invasive cardiac output monitors. Treatment of high-risk surgical patients GDT is not associated with an increased risk of cardiac complications; GDT with fluids and inotropes to optimize DO2I during early GDT reduces postoperative CVS complications.

Macrophage-tropic strains of human immunodeficiency virus type 1 utilize the CD4 receptor

To characterize the role of CD4 in human immunodeficiency virus type 1 (HIV-1) infection of macrophages, we examined the expression of CD4 by primary human monocyte-derived macrophages and studied the effect of recombinant soluble CD4 and anti-CD4 monoclonal antibodies on HIV-1 infection of these cells. Immunofluorescence and Western blot (immunoblot) studies demonstrated that both monocytes and macrophages display low levels of surface CD4, which is identical in mobility to CD4 in lymphocytes. Recombinant soluble CD4 and the anti-CD4 monoclonal antibody Leu3a blocked infection of macrophages by three different macrophage-tropic HIV isolates, and the cytopathic effects of HIV-1 infection were similarly prevented. Dose-response experiments using a prototype isolate which replicates in both macrophages and T lymphocytes showed that recombinant soluble CD4 inhibited infection of macrophages more efficiently than in lymphocytes. These results indicate that CD4 is the dominant entry pathway for HIV-1 infection of macrophages. In addition, recombinant soluble CD4 effectively blocks HIV-1 infection by a variety of macrophage-tropic strains and thus has the potential for therapeutic use in macrophage-dependent pathogenesis in HIV disease.

Unintentional weight loss in long-term care: predictor of mortality in the elderly

We retrospectively reviewed the medical records of 153 long-term care residents. Of these, 24 had lost at least 5% of their body weight during a 1-month interval. An unmatched control group of 51 patients was randomly selected from the remaining patients. Subjects who lost at least 5% body weight in 1 month were 4.6 times more likely to die within 1 year. Using multiple logistic regression, the odds ratio for weight loss and mortality was 5.1 (95% confidence interval 1.5 to 17.1) after adjustment for potential confounding by age and sex. The relatively simple anthropometric measure of body weight could be used by a multidisciplinary team in long-term care settings to identify patients at increased risk of dying. Further work is needed to clarify the role that nutrition could play in decreasing mortality in long-term care facilities.

Neoadjuvant systemic fluorouracil and mitomycin C prior to synchronous chemoradiation is an effective strategy in locally advanced rectal cancer

This study was designed to evaluate the benefits of neoadjuvant chemotherapy prior to chemoradiation and surgery in patients with locally advanced rectal cancer. Patients with previously untreated primary rectal cancer, reviewed in a multidisciplinary meeting and considered to have locally advanced disease on the basis of physical examination and imaging (MRI+CT n=30, CT alone n=6), were recruited. Patients received protracted venous infusion 5-FU (300 mg m(-2) day(-1) for 12 weeks) with mitomycin C (MMC) (7 mg m(-2) i.v. bolus every 6 weeks). Starting on week 13, 5-FU was reduced to 200 mg m(-2) day(-1) and concomitant pelvic radiotherapy 45 Gy in 25 fractions was commenced followed by 5.4-9 Gy boost to tumour bed. Surgery was planned 6 weeks after chemoradiation. Postoperatively, patients received 12 weeks of MMC and 5-FU at the same preoperative doses. Between January 99 and August 01, 36 eligible patients were recruited. Median age was 63 years (range=40-85). Following neoadjuvant chemotherapy, radiological tumour response was 27.8% (one CR and nine PRs) and no patient had progressive disease. In addition, 65% of patients had a symptomatic response including improvement in diarrhoea/constipation (59%), reduced rectal bleeding (60%) and diminished pelvic pain/tenesmus (78%). Following chemoradiation, tumour regression occurred in 80.6% (six CRs and 23 PRs; 95% CI=64-91.8%) and only one patient still had an inoperable tumour. R0 resection was achieved in 28 patients (82%). When compared with initial clinical staging, the pathological downstaging rate in T and/or N stage was 73.5% and pathological CR was found in one patient. Neoadjuvant systemic chemotherapy as a prelude to synchronous chemoradiation can be administered with negligible risk of disease progression and produces considerable symptomatic response with associated tumour regression.

Inhibition of human immunodeficiency virus replication in cell culture by endogenously synthesized antisense RNA

Antisense RNA, which has a sequence complementary to mRNA, may provide the basis for antiviral therapies of high selectivity. We have explored the inhibitory effect of six antisense RNAs upon the replication of human immunodeficiency virus (HIV) in cell culture. We chose regions of the HIV genome to test whether sequences required for splicing or for translation initiation were more susceptible to antisense RNA interference. Our results suggest that inhibitory antisense RNAs contain sequences complementary to the AUG initiation codon of the tat gene and have a comparatively low tendency to form intramolecular base pairs which would interfere with intermolecular duplex formation. Inhibition can be substantial (over 70%) but is transient. Transience does not result from mutation of the input virus. Inhibition was not a consequence of the induction of interferon by antisense RNA-mRNA duplex formation. Our results suggest that at least part of the inhibitory effect is at the posttranscriptional level.

Characterization of the dimerization of metabotropic glutamate receptors using an N-terminal truncation of mGluR1alpha

The metabotropic glutamate receptor mGluR1alpha in membranes isolated both from rat brain and from cell lines transfected with cDNA coding for the receptor migrates as a disulphide-bonded dimer on sodium dodecyl sulphate-polyacrylamide gels. Dimerization of mGluR1alpha takes place in the endoplasmic reticulum because it is not prevented by exposing transfected human embryonic kidney (HEK) 293 cells to the drug brefeldin A, a drug that prevents egress of proteins from the endoplasmic reticulum. Dimerization was also not dependent on protein glycosylation as it was not prevented by treatment of the cells with tunicamycin. Using a mammalian expression vector containing the N-terminal domain of mGluR1alpha, truncated just before the first transmembrane domain (NT-mGluR1alpha), we show that the N-terminal domain is secreted as a soluble disulphide-bonded dimeric protein. In addition, the truncated N-terminal domain can form heterodimers with mGluR1alpha when both proteins are cotransfected into HEK 293 cells. However, mGluR1alpha and its splice variant mGluR1beta did not form heterodimers in doubly transfected HEK 293 cells. These results show that although the N-terminal domain of mGluR1alpha is sufficient for dimer formation, other domains in the molecule must regulate the process.

Acid-base physiology: the 'traditional' and the 'modern' approaches

The interpretation and understanding of acid-base dysfunction has recently been revisited. The 'traditional' approach developed from the pioneering work of Henderson and Hasselbalch and is still the most widely used in clinical practice. There are a number of problems identified with this approach, however. The 'modern' approach derives from Stewart's work in physical chemistry. In this review we describe the origins of the traditional approach and discusses related concepts. We then describe Stewart's approach, including how it is derived and how it may be used to classify acid-base derangements. The applications of Stewart's approach to clinical scenarios in intensive care is then discussed briefly before we examine some published clinical studies based on his work.

The generation and characterization of antagonist RNA aptamers to human oncostatin M

Oncostatin M (OSM) is a multifunctional member of the interleukin-6 cytokine family. OSM has been implicated as a powerful proinflammatory mediator and may represent a potentially important, novel therapeutic opportunity for treatment of established rheumatoid arthritis. To further investigate the role of OSM in inflammatory disorders, we have isolated a series of RNA aptamers that bind specifically to human OSM. The highest affinity aptamer, designated ADR58, has been characterized in a series of in vitro and cell based assays. ADR58 has an affinity of 7 nm for human OSM, and it can antagonize OSM binding to the gp130 receptor and specifically antagonize OSM mediated signaling. The aptamer has been truncated in length to 33 bases, all pyrimidine positions are substituted with 2' fluorine, and 14 of 18 purine positions have been substituted with 2' O-methyl to increase stability toward nucleases. This truncated, modified form of ADR58 retains complete affinity and functional activity for OSM. This aptamer may be used as a tool to further investigate the role of OSM in inflammatory disorders and may also have role as a therapeutic agent.