A Sequential Adaptive Intervention Strategy Targeting Remission and Functional Recovery in Young People at Ultrahigh Risk of Psychosis: The Staged Treatment in Early Psychosis (STEP) Sequential Multiple Assignment Randomized Trial

Importance

Clinical trials have not established the optimal type, sequence, and duration of interventions for people at ultrahigh risk of psychosis.

Objective

To determine the effectiveness of a sequential and adaptive intervention strategy for individuals at ultrahigh risk of psychosis.

Design, Setting, and Participants

The Staged Treatment in Early Psychosis (STEP) sequential multiple assignment randomized trial took place within the clinical program at Orygen, Melbourne, Australia. Individuals aged 12 to 25 years who were seeking treatment and met criteria for ultrahigh risk of psychosis according to the Comprehensive Assessment of At-Risk Mental States were recruited between April 2016 and January 2019. Of 1343 individuals considered, 342 were recruited.

Interventions

Step 1: 6 weeks of support and problem solving (SPS); step 2: 20 weeks of cognitive-behavioral case management (CBCM) vs SPS; and step 3: 26 weeks of CBCM with fluoxetine vs CBCM with placebo with an embedded fast-fail option of ω-3 fatty acids or low-dose antipsychotic medication. Individuals who did not remit progressed through these steps; those who remitted received SPS or monitoring for up to 12 months.

Main Outcomes and Measures

Global Functioning: Social and Role scales (primary outcome), Brief Psychiatric Rating Scale, Scale for the Assessment of Negative Symptoms, Montgomery-Åsberg Depression Rating Scale, quality of life, transition to psychosis, and remission and relapse rates.

Results

The sample comprised 342 participants (198 female; mean [SD] age, 17.7 [3.1] years). Remission rates, reflecting sustained symptomatic and functional improvement, were 8.5%, 10.3%, and 11.4% at steps 1, 2, and 3, respectively. A total of 27.2% met remission criteria at any step. Relapse rates among those who remitted did not significantly differ between SPS and monitoring (step 1: 65.1% vs 58.3%; step 2: 37.7% vs 47.5%). There was no significant difference in functioning, symptoms, and transition rates between SPS and CBCM and between CBCM with fluoxetine and CBCM with placebo. Twelve-month transition rates to psychosis were 13.5% (entire sample), 3.3% (those who ever remitted), and 17.4% (those with no remission).

Conclusions and Relevance

In this sequential multiple assignment randomized trial, transition rates to psychosis were moderate, and remission rates were lower than expected, partly reflecting the ambitious criteria set and challenges with real-world treatment fidelity and adherence. While all groups showed mild to moderate functional and symptomatic improvement, this was typically short of remission. While further adaptive trials that address these challenges are needed, findings confirm substantial and sustained morbidity and reveal relatively poor responsiveness to existing treatments.

Trial Registration

ClinicalTrials.gov Identifier: NCT02751632.

The experience of young people receiving cognitive behavioural therapy for major depression: A qualitative study

AIM

Major depressive disorder (MDD) has far reaching impacts for young people, their families and society. Cognitive behavioural therapy (CBT) is one of the first-line treatments for young people experiencing MDD; however, there is limited research examining how young people with MDD experience CBT. The aim of this study was to explore their experience and their views of this intervention.

METHODS

We employed a qualitative research design, with semi-structured interviews and thematic analysis. Eight participants aged between 17 and 24 years who received CBT for MDD in a randomized controlled trial were recruited.

RESULTS

Five themes were identified: the importance of relationship with clinician; the range of useful components within CBT; the ability for CBT to accommodate different techniques and presenting issues; the importance of checking in with clients during the process of therapy; and the impacts of MDD on therapy.

CONCLUSIONS

The findings highlight the importance of clinicians having a youth friendly and collaborative approach that allows a modular delivery of a range of CBT techniques to suit the client's presenting issue and formulation. There is a need to continually check how young people are responding to interventions, and to be aware of potential cognitive deficits and adjust therapy accordingly. This is a small study that provides insight into how young people with MDD experience CBT and avenues to explore for tailoring provision of CBT to enhance the therapeutic experience for this population.

Hospitalisation and mortality risk of SARS-COV-2 variant omicron sub-lineage BA.2 compared to BA.1 in England

The Omicron variant of SARS-CoV-2 became the globally dominant variant in early 2022. A sub-lineage of the Omicron variant (BA.2) was identified in England in January 2022. Here, we investigated hospitalisation and mortality risks of COVID-19 cases with the Omicron sub-lineage BA.2 (n = 258,875) compared to BA.1 (n = 984,337) in a large cohort study in England. We estimated the risk of hospital attendance, hospital admission or death using multivariable stratified proportional hazards regression models. After adjustment for confounders, BA.2 cases had lower or similar risks of death (HR = 0.80, 95% CI 0.71-0.90), hospital admission (HR = 0.88, 95% CI 0.83-0.94) and any hospital attendance (HR = 0.98, 95% CI 0.95-1.01). These findings that the risk of severe outcomes following infection with BA.2 SARS-CoV-2 was slightly lower or equivalent to the BA.1 sub-lineage can inform public health strategies in countries where BA.2 is spreading.

Hematopoietic Stem Cell Transplant for Sickle Cell Disease: PATIENT SELEction and Timing Based on Sickle Cell-Related Multiple Chronic Conditions

Hematopoietic stem cell transplant (HSCT) is the only cure for patients with sickle cell disease (SCD). Although most SCD patients experience progressive end-organ damage and shortened lifespans, not all patients follow the same disease course, tempo, or outcome. Therefore, the dilemma facing physicians is weighing the selection of patients and timing for the procedure against donor type and transplant-related mortality and morbidity that go up with increasing age. On the other hand, the dilemma facing the patients and families is how acceptable HSCT that carries some mortality risks to them. We have analyzed the chronic conditions due to SCD in 449 patients to determine whether SCD-related multiple chronic conditions (MCC) can be risk-stratified to identify the group of patients predicted to not only have shortened lifespans but also functional limitation and poor quality of life so that these at-risk patients can be offered HSCT early and before MCC develops. We identified that the age of onset of the first SCD-related chronic conditions strongly predicted for the risks for disease-related MCC. SCD patients who suffered their first disease-related chronic condition before age 30 years developed MCC at a rate of 19.1 times faster than those at a later age. These patients are therefore high-risk patients and should be offered HSCT early in the course of their disease before multiple organ damage intervenes, even if matched-related donors are not available. This patient selection and timing approach provides a forum for an easy-to-understand and real-time discussion, including the choice of donor type, with SCD patients and families when considering HSCT.

Obesity and diabetes mellitus in patients with sickle cell disease

Obesity and diabetes mellitus are prevalent among the African-American/Black population. They result in multiple chronic conditions that impact the quality and lifespan of the patients. Their occurrence in patients with sickle cell disease (SCD) will increase the risks for multimorbidity in these patients. We have carried out a chart survey of a cohort of 449 patients with SCD to determine the prevalence rates of obesity and diabetes mellitus in these patients. SCD patients were less likely to develop obesity and diabetes mellitus, compared to their peers of the same race/ethnicity. The lower prevalence rates were observed in those over the age of 6 years, irrespective of the gender of the patients. Their life-time probabilities for obesity and diabetes mellitus were also low. Within this group of SCD patients, obesity was associated with significantly higher prevalence of diabetes mellitus. The underlying reasons for our observed results of low prevalence rate of obesity in SCD remain speculative but may be related to reduced calorie intake, increased calorie use due to hypermetabolism, reduced intestinal absorption, or intestinal dysbiosis.

28 Can Comprehensive Geriatric Assessment be Achieved in the Emergency Department?

Background

Our National Health Service is facing unprecedented challenges to accommodate our frailer healthcare users. The gold standard tool for the identification and management of frailty is the Comprehensive Geriatric Assessment (CGA) and has been shown to lead to better outcomes in terms of morbidity and mortality.

Introduction

With a largely elderly demographic profile in the East of England, the Norfolk and Norwich University Hospital opened the first Older People’s Emergency Department (OPED) in the UK in 2017. This work reviews the effectiveness of a geriatrician-led CGA in a dedicated OPED, which operates during daylight hours, compared to usual care in Accident & Emergency (A&E).

Methods

99 patients assessed in OPED and 99 patients assessed overnight in A&E during February 2019 were included in this retrospective study. Electronic case notes for each patient were reviewed by the authors and results were expressed as percentages.

Results

OPED outperformed A&E in all components of the CGA; strongest areas included assessing for pain, falls risk and activities of daily living. Both departments performed well in reviewing medications and assessing for safeguarding concerns. Areas for improvement include assessing for mood disorders, sensory impairment, discussing Do Not Attempt Cardiopulmonary Resuscitation status, and end of life care plans. The average length of stay of OPED patients was only 7.3 days compared to 8.7 days in A&E, and 89% of OPED patients were discharged back to their usual residences compared to 87% in A&E.

Conclusions

The improved CGA process in OPED has led to better outcomes, notably through a reduction in the average length of inpatient stay. Nevertheless, certain components of the CGA still require improvement. Further examination is needed to assess long-term mortality to support the use of CGA in the emergency setting.

Diabetes insipidus after discontinuation of vasopressin infusion for septic shock

WHAT IS KNOWN AND OBJECTIVE

Despite widespread use of vasopressin for the treatment of septic shock, few cases of diabetes insipidus (DI) following its discontinuation have been reported.

CASE SUMMARY

A 54-year-old man presented with pneumonia progressing to septic shock, requiring norepinephrine and vasopressin for refractory hypotension. After clinical improvement, the patient on 3 separate occasions developed polyuria and severe hypernatremia upon discontinuation of vasopressin, with prompt recovery upon its resumption.

WHAT IS NEW AND CONCLUSION

Occurrence of DI upon discontinuation of vasopressin infusion appears to be rare, but incidence may be underestimated due to a paucity of published reports. Actual incidence and underlying mechanism of this phenomenon remain to be elucidated.

Increasing patient engagement in rehabilitation activities

Despite evidence that intensive rehabilitation speeds recovery from acute illness, several studies on British rehabilitation units have shown that the time spent by patients in therapeutic activities is low and that levels of 'engagement' are poor. We carried out an observational study of patient activity on four rehabilitation wards for the elderly (51 patients observed at half-hourly intervals between 8 a.m. and 5 p.m. on five successive days).

Patients were found to be engaged in therapeutically useful activities at only 17% of the observation points. When time spent in the therapy departments (where activities were not monitored) was excluded the proportion of useful activities fell to 11%. Similar patterns of activity were seen in all patient subgroups.

An intervention scheme was therefore devised, whereby an hourly activities programme tailored to the needs of each patient was worked out by therapists and ward staff, to be supervised by nurses. One nurse also organized regular group activities. The intervention programme, which required no extra resources, was instituted on two of the four wards.

A repeat survey conducted two months later showed a 55% increase in the proportion of time spent in useful activities on the two intervention wards but no change on the other two wards.

Accounting for uncertainty in the quantification of the environmental impacts of Canadian pig farming systems

The objective of the study was to develop a life cycle assessment (LCA) for pig farming systems that would account for uncertainty and variability in input data and allow systematic environmental impact comparisons between production systems. The environmental impacts of commercial pig production for 2 regions in Canada (Eastern and Western) were compared using a cradle-to-farm gate LCA. These systems had important contrasting characteristics such as typical feed ingredients used, herd performance, and expected emission factors from manure management. The study used detailed production data supplied by the industry and incorporated uncertainty/variation in all major aspects of the system including life cycle inventory data for feed ingredients, animal performance, energy inputs, and emission factors. The impacts were defined using 5 metrics-global warming potential, acidification potential, eutrophication potential (EP), abiotic resource use, and nonrenewable energy use-and were expressed per kilogram carcass weight at farm gate. Eutrophication potential was further separated into marine EP (MEP) and freshwater EP (FEP). Uncertainties in the model inputs were separated into 2 types: uncertainty in the data used to describe the system (α uncertainties) and uncertainty in impact calculations or background data that affects all systems equally (β uncertainties). The impacts of pig production in the 2 regions were systematically compared based on the differences in the systems (α uncertainties). The method of ascribing uncertainty influenced the outcomes. In eastern systems, EP, MEP, and FEP were lower (P < 0.05) when assuming that all uncertainty in the emission factors for leaching from manure application was β. This was mainly due to increased EP resulting from field emissions for typical ingredients in western diets. When uncertainty in these emission factors was assumed to be α, only FEP was lower in eastern systems (P < 0.05). The environmental impacts for the other impact categories were not significantly different between the 2 systems, despite their aforementioned differences. In conclusion, a probabilistic approach was used to develop an LCA that systematically dealt with uncertainty in the data when comparing multiple environmental impacts measures in pig farming systems for the first time. The method was used to identify differences between Canadian pig production systems but can also be applied for comparisons between other agricultural systems that include inherent variation.

An evolutionary approach to financial history

Financial history is not conventionally thought of in evolutionary terms, but it should be. Traditional ways of thinking about finance, dating back to Hilferding, emphasize the importance of concentration and economies of scale. But these approaches overlook the rich "biodiversity" that characterizes the financial world. They also overlook the role of natural selection. To be sure, natural selection in the financial world is not exactly analogous to the processes first described by Darwin and elaborated on by modern biologists. There is conscious adaptation as well as random mutation. Moreover, there is something resembling "intelligent design" in finance, whereby regulators and legislators act in a quasidivine capacity, putting dinosaurs on life support. The danger is that such interventions in the natural processes of the market may ultimately distort the evolutionary process, by getting in the way of Schumpeter's "creative destruction."

The misuse of 'no significant difference' in British orthopaedic literature

INTRODUCTION

Many studies published in medical journals do not consider the statistical power required to detect a meaningful difference between study groups. As a result, these studies are often underpowered: the sample size may not be large enough to pick up a statistically significant difference (or other effect of interest) of a given size between the study groups. Therefore, the conclusion that there is no statistically significant difference between groups cannot be made unless a study has been shown to have sufficient power. The aim of this study was to establish the prevalence of negative studies with inadequate statistical power in British journals to which orthopaedic surgeons regularly submit.

MATERIALS AND METHODS

We assessed all papers in the last consecutive six issues prior to the start of the study (April 2005) in The Journal of Bone and Joint Surgery (British), Injury, and Annals of the Royal College of Surgeons of England. We sought published evidence that a power analysis had been performed in association with the main hypothesis of the paper.

RESULTS

There were a total of 170 papers in which a statistical comparison of two or more groups was undertaken. Of these 170 papers, 49 (28.8%) stated as their primary conclusion that there was no statistically significant difference between the groups studied. Of these 49 papers, only 3 (6.1%) had performed a power analysis demonstrating adequate sample size.

CONCLUSIONS

These results demonstrate that the majority of negative studies in the British orthopaedic literature that we have looked at have not performed the statistical analysis necessary to reach their stated conclusions. In order to remedy this, we recommend that the journals sampled include the following guidance in their instructions to authors: the statement 'no statistically significant difference was found between study groups' should be accompanied by the results of a power analysis.

High subsoil chloride concentrations reduce soil water extraction and crop yield on Vertosols in north-eastern Australia

Salinity, sodicity, acidity, and phytotoxic levels of chloride (Cl) in subsoils are major constraints to crop production in many soils of north-eastern Australia because they reduce the ability of crop roots to extract water and nutrients from the soil. The complex interactions and correlations among soil properties result in multi-colinearity between soil properties and crop yield that makes it difficult to determine which constraint is the major limitation. We used ridge-regression analysis to overcome colinearity to evaluate the contribution of soil factors and water supply to the variation in the yields of 5 winter crops on soils with various levels and combinations of subsoil constraints in the region. Subsoil constraints measured were soil Cl, electrical conductivity of the saturation extract (ECse), and exchangeable sodium percentage (ESP). The ridge regression procedure selected several of the variables used in a descriptive model, which included in-crop rainfall, plant-available soil water at sowing in the 0.90–1.10 m soil layer, and soil Cl in the 0.90–1.10 m soil layer, and accounted for 77–85% of the variation in the grain yields of the 5 winter crops. Inclusion of ESP of the top soil (0.0–0.10 m soil layer) marginally increased the descriptive capability of the models for bread wheat, barley and durum wheat. Subsoil Cl concentration was found to be an effective substitute for subsoil water extraction. The estimates of the critical levels of subsoil Cl for a 10% reduction in the grain yield were 492 mg cl/kg for chickpea, 662 mg Cl/kg for durum wheat, 854 mg Cl/kg for bread wheat, 980 mg Cl/kg for canola, and 1012 mg Cl/kg for barley, thus suggesting that chickpea and durum wheat were more sensitive to subsoil Cl than bread wheat, barley, and canola.

Safety of Mycoplasma gallisepticum Vaccine Strain 6/85 After Backpassage in Turkeys

The objective of this research was to evaluate the safety of the 6/85 strain vaccine strain of Mycoplasma gallisepticum in turkeys by backpassing the vaccine strain up to 10 times by contact infection in turkeys and challenging turkeys with the resulting backpassaged strain. The vaccine strain, however, did not spread to in-contact turkeys, and it was necessary to reisolate the organism before challenging turkeys for the next passage. The challenge strain, therefore, was one that had been backpassaged four times in turkeys, with a total in vivo time in turkeys of 66 days. The backpassaged 6/85 vaccine strain was no different in pathogenicity than the original vaccine strain, except that at 10 days postchallenge, it was isolated in higher numbers from air sacs. Both the original 6/85 vaccine strain and the backpassaged strain were apathogenic in turkeys, except for a slightly increased diameter of the tracheal mucosa at 10 days postchallenge; at 20 days postchallenge the tracheal mucosal thickness was no different from that of controls.

Intellectual prognosis of the Dandy-Walker malformation in children: the importance of vermian lobulation

Half of patients with the Dandy-Walker malformation (DWM) have normal intellectual development. We aimed to identify feature on MRI associated with good intellectual prognosis. We reviewed 20 patients with DWM diagnosed on MRI, mean age 14.6+/-9.9 years. We assessed their intellectual development and related it to the MRI features. We found two groups with a statistically different intellectual outcome. All 14 patients with normal intellectual development had a normal lobulation of the vermis, without supratentorial anomalies. Of the six patients with mental retardation, three had an abnormal vermis, together with dysgenesis of the corpus callosum. In the other three, there were normal vermian anatomy with associated anomalies. Normal lobulation of the vermis, in the absence of any supratentorial anomaly, appears to be a good prognostic factor in DWM. Preservation of cerebrocerebellar pathways and neonatal plasticity could explain the normal intellectual development. These findings might be useful in prenatal diagnosis.

Isolation and characterization of a 6/85-like Mycoplasma gallisepticum from commercial laying hens

Eighty-three-week-old table egg layers with swollen sinuses were presented with a history of increased mortality. Serology revealed positive titers to Mycoplasma gallisepticum (MG). The birds were part of a flock in which some birds had been vaccinated with 6/85 live MG vaccine at 18 wk of age. Tracheal cultures were obtained from both vaccinated and unvaccinated birds within the flock. The cultures were indistinguishable from 6/85 vaccine by both random amplified polymorphic DNA analysis and DNA sequence analysis. Challenge studies were performed to compare the field isolates with 6/85 vaccine and the R strain of MG. The field isolates produced a greater antibody response by serum plate agglutination than did the 6/85 vaccine. The isolates effectively colonized the trachea without increasing the tracheal mucosal thickness; however, they did not extensively colonize the air sacs or cause airsacculitis in the experimental birds.

Using flexible loop mimetics to extend phi-value analysis to secondary structure interactions

Chemical synthesis allows the incorporation of nonnatural amino acids into proteins that may provide previously untried probes of their folding pathway and thermodynamic stability. We have used a flexible thioether linker as a loop mimetic in the human yes kinase-associated protein (YAP 65) WW domain, a three-stranded, 44-residue, beta-sheet protein. This linkage avoids problems of incorporating sequences that constrain loops to the extent that they significantly change the nature of the denatured state with concomitant effects on the folding kinetics. An NMR solution structure shows that the thioether linker had little effect on the global fold of the domain, although the loop is apparently more dynamic. The thioether variants are destabilized by up to 1.4 kcal/mol (1 cal = 4.18 J). Preliminary Phi-value analysis showed that the first loop is highly structured in the folding transition state, and the second loop is essentially unstructured. These data are consistent with results from simulated unfolding and detailed protein-engineering studies of structurally homologous WW domains. Previously, Phi-value analysis was limited to studying side-chain interactions. The linkers used here extend the protein engineering method directly to secondary-structure interactions.

Ultrafast folding of WW domains without structured aromatic clusters in the denatured state

Ultrafast-folding proteins are important for combining experiment and simulation to give complete descriptions of folding pathways. The WW domain family comprises small proteins with a three-stranded antiparallel beta-sheet topology. Previous studies on the 57-residue YAP 65 WW domain indicate the presence of residual structure in the chemically denatured state. Here we analyze three minimal core WW domains of 38-44 residues. There was little spectroscopic or thermodynamic evidence for residual structure in either their chemically or thermally denatured states. Folding and unfolding kinetics, studied by using rapid temperature-jump and continuous-flow techniques, show that each domain folds and unfolds very rapidly in a two-state transition through a highly compact transition state. Folding half-times were as short as 17 micros at 25 degrees C, within an order of magnitude of the predicted maximal rate of loop formation. The small size and topological simplicity of these domains, in conjunction with their very rapid two-state folding, may allow us to reduce the difference in time scale between experiment and theoretical simulation.

Anaerobic co-digestion of aircraft deicing fluid and municipal wastewater sludge

At many airports, aircraft deicing fluid and precipitation mix, becoming aircraft deicing runoff having a 5-day biochemical oxygen demand (BOD5) of 10(2) to 10(6) mg/L. Publicly owned treatment works can be used for aerobic biological treatment; however, it may be more economical to use anaerobic digesters to codigest a mixture of aircraft deicing fluid and sludge. The objectives of this investigation were to determine benefits and appropriate propylene glycol aircraft deicing fluid loadings to anaerobic codigesters. Results demonstrate aircraft deicing fluid can be successfully codigested to produce methane; supernatant BOD5 and Kjeldahl nitrogen concentration were not higher in codigesters compared to a conventional digester. Aircraft deicing fluid loadings as high as 1.6 g chemical oxygen demand (COD)/L x d were sustainable in codigesters, whereas system fed only aircraft deicing fluid with nutrients and alkalinity achieved a loading of 0.65 g COD/L x d. The sludge used increased digester alkalinity and provided nitrogen, iron, nickel, cobalt, and biomass required for methanogenesis. The deicer provides organics for increased methane production.

Using chimeric immunity proteins to explore the energy landscape for alpha-helical protein folding

To address the role of sequence in the folding of homologous proteins, the folding and unfolding kinetics of the all-helical bacterial immunity proteins Im2 and Im9 were characterised, together with six chimeric derivatives of these proteins. We show that both Im2 and Im9 fold rapidly (k(UN)(H(2)O)) approximately 2000 s(-1) at pH 7.0, 25 degrees C) in apparent two-state transitions, through rate-limiting transition states that are highly compact (beta(TS)0.93 and 0.96, respectively). Whilst the folding and unfolding properties of three of the chimeras (Im2 (1-44)(Im9), Im2 (1-64)(Im9 )and Im2 (25-44)(Im9)) are similar to their parental counterparts, in other chimeric proteins the introduced sequence variation results in altered kinetic behaviour. At low urea concentrations, Im2 (1-29)(Im9) and Im2 (56-64)(Im9) fold in two-state transitions via transition states that are significantly less compact (beta(TS) approximately 0.7) than those characterised for the other immunity proteins presented here. At higher urea concentrations, however, the rate-limiting transition state for these two chimeras switches or moves to a more compact species (beta(TS) approximately 0.9). Surprisingly, Im2 (30-64)(Im9) populates a highly collapsed species (beta(I)=0.87) in the dead-time (2.5 ms) of stopped flow measurements. These data indicate that whilst topology may place significant constraints on the folding process, specific inter-residue interactions, revealed here through multiple sequence changes, can modulate the ruggedness of the folding energy landscape.

Children's conceptions of characteristic features of category members

The authors investigated children's conceptions of the characteristic features of category members and found that their conceptions underwent qualitative developmental changes. They hypothesized that (a) children initially tend to perceive category members in terms of individual characteristics (i.e., internal dispositions and behavioral patterns) and (b) only later do they conceive of category members in terms of their shared beliefs and values. They explored these hypotheses in 2 studies: In Study 1, they investigated how Protestant and Catholic children in Northern Ireland understood the religious intergroup context in their own country; in Study 2, children in Italy were presented with a fictional scenario of intergroup conflict and asked to explain the causes of the conflict. The results of both studies confirmed the 2 hypotheses.

Rapid folding with and without populated intermediates in the homologous four-helix proteins Im7 and Im9

The kinetics and thermodynamics of the folding of the homologous four-helix proteins Im7 and Im9 have been characterised at pH 7.0 and 10 degrees C. These proteins are 60 % identical in sequence and have the same three-dimensional structure, yet appear to fold by different kinetic mechanisms. The logarithm of the folding and unfolding rates of Im9 change linearly as a function of urea concentration and fit well to an equation describing a two-state mechanism (with a folding rate of 1500 s-1, an unfolding rate of 0. 01 s-1, and a highly compact transition state that has approximately 95 % of the native surface area buried). By contrast, there is clear evidence for the population of an intermediate during the refolding of Im7, as indicated by a change in the urea dependence of the folding rate and the presence of a significant burst phase amplitude in the refolding kinetics. Under stabilising conditions (0.25 M Na2SO4, pH 7.0 and 10 degrees C) the folding of Im9 remains two-state, whilst under similar conditions (0.4 M Na2SO4, pH 7.0 and 10 degrees C) the intermediate populated during Im7 refolding is significantly stabilised (KUI=125). Equilibrium denaturation experiments, under the conditions used in the kinetic measurements, show that Im7 is significantly less stable than Im9 (DeltaDeltaG 9.3 kJ/mol) and the DeltaG and m values determined accord with those obtained from the fit to the kinetic data. The results show, therefore, that the population of an intermediate in the refolding of the immunity protein structure is defined by the precise amino acid sequence rather than the global stability of the protein. We discuss the possibility that the intermediate of Im7 is populated due to differences in helix propensity in Im7 and Im9 and the relevance of these data to the folding of helical proteins in general.

Structural and mechanistic basis of immunity toward endonuclease colicins

The crystal structure of the cytotoxic endonuclease domain from the bacterial toxin colicin E9 in complex with its cognate immunity protein Im9 reveals that the inhibitor does not bind at the active site, the core of which comprises the HNH motif found in intron-encoded homing endonucleases, but rather at an adjacent position leaving the active site exposed yet unable to bind DNA because of steric and electrostatic clashes with incoming substrate. Although its mode of action is unorthodox, Im9 is a remarkably effective inhibitor since it folds within milliseconds and then associates with its target endonuclease at the rate of diffusion to form an inactive complex with sub-femtomolar binding affinity. This hyperefficient mechanism of inhibition could be well suited to other toxic enzyme systems, particularly where the substrate is a polymer extending beyond the boundaries of the active site.

The effect of antibody-dependent enhancement on the transmission dynamics and persistence of multiple-strain pathogens

Cross-reactive antibodies produced by a mammalian host during infection by a particular microparasitic strain usually have the effect of reducing the probability of the host being infected by a different, but closely related, pathogen strain. Such cross-reactive immunological responses thereby induce between-strain competition within the pathogen population. However, in some cases such as dengue virus, evidence suggests that cross-reactive antibodies act to enhance rather than restrict the severity of a subsequent infection by another strain. This cooperative mechanism is thought to explain why pre-existing immunity to dengue virus is an important risk factor for the development of severe disease (i.e., dengue shock syndrome and dengue hemorrhagic fever). In this paper, we explore the effect of antibody-dependent enhancement on the transmission dynamics of multistrain pathogen populations. We show that enhancement frequently may generate complex and persistent cyclical or chaotic epidemic behavior. Furthermore, enhancement acts to permit the coexistence of all strains where in its absence only one or a subset would persist.

Chaos, persistence, and evolution of strain structure in antigenically diverse infectious agents

The effects of selection by host immune responses on transmission dynamics was analyzed in a broad class of antigenically diverse pathogens. Strong selection can cause pathogen populations to stably segregate into discrete strains with nonoverlapping antigenic repertoires. However, over a wide range of intermediate levels of selection, strain structure is unstable, varying in a manner that is either cyclical or chaotic. These results have implications for the interpretation of longitudinal epidemiological data on strain or serotype abundance, design of surveillance strategies, and the assessment of multivalent vaccine trials.

Multiplicity of fibronectin-binding alpha V integrin receptors in colorectal cancer

Current data from in vitro and in vivo animal models indicate that fibronectin-binding integrin receptors expressed by colon cancer cells may regulate tumour growth. While individual members of the beta 1 subfamily of integrins have now been clearly identified in colorectal cancer, little information exists with respect to the alpha V subfamily. In the present study we show that alpha V can associate with multiple and different beta subunits capable of binding fibronectin in this tumour type. This is likely to have functional implications for growth and spread of colorectal cancer.

Sexuality in a natural population of bacteria– Bacillus subtilis challenges the clonal paradigm

Reproduction by binary fission necessarily establishes a clonal genotypic structure in bacterial populations unless a high rate of genetic recombination opposes it. Several genetic properties were examined for a wild population of Bacillus subtilis in the Sonoran Desert of Arizona to assess the extent of recombination in a natural population. These properties included allozyme variation revealed by multilocus enzyme electrophoresis, phage and antibiotic resistance, and restriction fragment length polymorphism with Southern hybridization. Evidence of extensive genetic recombination was found along with evidence of modest clonal structure. Recombination must be frequent relative to binary fission in this population. This mixed population structure provides broader options for bacterial evolution than would a purely clonal structure.

Autopsies in an area health service: a quality assurance review

The Hunter Area Health Service Quality Liaison Group reviewed autopsy practice in the Hunter Area, focussing upon clinical and resource utilisation effectiveness. Findings are discussed. Conclusions support views expressed in recent literature on the subject. The conclusion is reached that despite increase in consumption of limited resources, autopsies remain an integral component of quality care and should increase in number. Some recommendations are proffered to maximise utility and cost effectiveness in the future.

Pictographs and prereading skills

This paper draws upon data collected in conjunction with the Schools Council (Great Britain) Research and Development Project in Compensatory Education to demonstrate that a picture reading task can provide a fairly good prediction of the later reading performance of 100 5-year-olds and that it is a sufficiently interesting clinical tool to merit further consideration from nursery and infant school teachers. The test's success seems to relate to its ability to measure differences in children's understanding of the nature and purpose of reading.

Autoantibody to microtubules in infectious mononucleosis

An autoantibody, reacting with a cytoplasmic component of many types of glass-adherent cells in tissue culture has been detected in the serum of patients with infectious mononucleosis.

Evidence is presented that the structures with which this antibody reacts are closely related to cytoplasmic microtubules.

Surface and Wake Flow Phenomena of the Vortex-Excited Oscillation of a Circular Cylinder

Using an original design of acoustic-level pressure transducer, measurements were made of fluctuating pressures on the surface and in the wake of a circular cylinder at rest and in vortex-excited oscillation at subcritical Reynolds numbers. Frequency, amplitude, and phase, where relevant, of the cylinder oscillation were also measured, and some effects of cylinder oscillation on the organized wake geometry were observed. The new results are compared with relevant existing information for the stationary cylinder, and with the few measurements previously available for the oscillating cylinder, and some analysis is made.