Effects of empagliflozin on progression of chronic kidney disease: a prespecified secondary analysis from the empa-kidney trial

BACKGROUND

Sodium-glucose co-transporter-2 (SGLT2) inhibitors reduce progression of chronic kidney disease and the risk of cardiovascular morbidity and mortality in a wide range of patients. However, their effects on kidney disease progression in some patients with chronic kidney disease are unclear because few clinical kidney outcomes occurred among such patients in the completed trials. In particular, some guidelines stratify their level of recommendation about who should be treated with SGLT2 inhibitors based on diabetes status and albuminuria. We aimed to assess the effects of empagliflozin on progression of chronic kidney disease both overall and among specific types of participants in the EMPA-KIDNEY trial.

METHODS

EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA), and included individuals aged 18 years or older with an estimated glomerular filtration rate (eGFR) of 20 to less than 45 mL/min per 1·73 m2, or with an eGFR of 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher. We explored the effects of 10 mg oral empagliflozin once daily versus placebo on the annualised rate of change in estimated glomerular filtration rate (eGFR slope), a tertiary outcome. We studied the acute slope (from randomisation to 2 months) and chronic slope (from 2 months onwards) separately, using shared parameter models to estimate the latter. Analyses were done in all randomly assigned participants by intention to treat. EMPA-KIDNEY is registered at ClinicalTrials.gov, NCT03594110.

FINDINGS

Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and then followed up for a median of 2·0 years (IQR 1·5-2·4). Prespecified subgroups of eGFR included 2282 (34·5%) participants with an eGFR of less than 30 mL/min per 1·73 m2, 2928 (44·3%) with an eGFR of 30 to less than 45 mL/min per 1·73 m2, and 1399 (21·2%) with an eGFR 45 mL/min per 1·73 m2 or higher. Prespecified subgroups of uACR included 1328 (20·1%) with a uACR of less than 30 mg/g, 1864 (28·2%) with a uACR of 30 to 300 mg/g, and 3417 (51·7%) with a uACR of more than 300 mg/g. Overall, allocation to empagliflozin caused an acute 2·12 mL/min per 1·73 m2 (95% CI 1·83-2·41) reduction in eGFR, equivalent to a 6% (5-6) dip in the first 2 months. After this, it halved the chronic slope from -2·75 to -1·37 mL/min per 1·73 m2 per year (relative difference 50%, 95% CI 42-58). The absolute and relative benefits of empagliflozin on the magnitude of the chronic slope varied significantly depending on diabetes status and baseline levels of eGFR and uACR. In particular, the absolute difference in chronic slopes was lower in patients with lower baseline uACR, but because this group progressed more slowly than those with higher uACR, this translated to a larger relative difference in chronic slopes in this group (86% [36-136] reduction in the chronic slope among those with baseline uACR <30 mg/g compared with a 29% [19-38] reduction for those with baseline uACR ≥2000 mg/g; ptrend<0·0001).

INTERPRETATION

Empagliflozin slowed the rate of progression of chronic kidney disease among all types of participant in the EMPA-KIDNEY trial, including those with little albuminuria. Albuminuria alone should not be used to determine whether to treat with an SGLT2 inhibitor.

FUNDING

Boehringer Ingelheim and Eli Lilly.

Impact of primary kidney disease on the effects of empagliflozin in patients with chronic kidney disease: secondary analyses of the EMPA-KIDNEY trial

BACKGROUND

The EMPA-KIDNEY trial showed that empagliflozin reduced the risk of the primary composite outcome of kidney disease progression or cardiovascular death in patients with chronic kidney disease mainly through slowing progression. We aimed to assess how effects of empagliflozin might differ by primary kidney disease across its broad population.

METHODS

EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA). Patients were eligible if their estimated glomerular filtration rate (eGFR) was 20 to less than 45 mL/min per 1·73 m2, or 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher at screening. They were randomly assigned (1:1) to 10 mg oral empagliflozin once daily or matching placebo. Effects on kidney disease progression (defined as a sustained ≥40% eGFR decline from randomisation, end-stage kidney disease, a sustained eGFR below 10 mL/min per 1·73 m2, or death from kidney failure) were assessed using prespecified Cox models, and eGFR slope analyses used shared parameter models. Subgroup comparisons were performed by including relevant interaction terms in models. EMPA-KIDNEY is registered with ClinicalTrials.gov, NCT03594110.

FINDINGS

Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and followed up for a median of 2·0 years (IQR 1·5-2·4). Prespecified subgroupings by primary kidney disease included 2057 (31·1%) participants with diabetic kidney disease, 1669 (25·3%) with glomerular disease, 1445 (21·9%) with hypertensive or renovascular disease, and 1438 (21·8%) with other or unknown causes. Kidney disease progression occurred in 384 (11·6%) of 3304 patients in the empagliflozin group and 504 (15·2%) of 3305 patients in the placebo group (hazard ratio 0·71 [95% CI 0·62-0·81]), with no evidence that the relative effect size varied significantly by primary kidney disease (pheterogeneity=0·62). The between-group difference in chronic eGFR slopes (ie, from 2 months to final follow-up) was 1·37 mL/min per 1·73 m2 per year (95% CI 1·16-1·59), representing a 50% (42-58) reduction in the rate of chronic eGFR decline. This relative effect of empagliflozin on chronic eGFR slope was similar in analyses by different primary kidney diseases, including in explorations by type of glomerular disease and diabetes (p values for heterogeneity all >0·1).

INTERPRETATION

In a broad range of patients with chronic kidney disease at risk of progression, including a wide range of non-diabetic causes of chronic kidney disease, empagliflozin reduced risk of kidney disease progression. Relative effect sizes were broadly similar irrespective of the cause of primary kidney disease, suggesting that SGLT2 inhibitors should be part of a standard of care to minimise risk of kidney failure in chronic kidney disease.

FUNDING

Boehringer Ingelheim, Eli Lilly, and UK Medical Research Council.

Effects of acetate, propionate, and pH on volatile fatty acid thermodynamics in continuous cultures of ruminal contents

To investigate the effects of acetate, propionate, and pH on thermodynamics of volatile fatty acids (VFA) in the rumen, a dual-flow continuous culture study was conducted to quantify production of major VFA, interconversions among the VFA, and H₂ and CH₄ emissions in a 4 × 4 Latin square design. The 4 treatments were (1) control: pH buffered to an average of 6.75; (2) control plus 20 mmol/d of infused acetate (InfAc); (3) control plus 7 mmol/d of infused propionate (InfPr); and (4) a 0.5-unit decline in pH elicited by adjustment of the buffer (LowpH). All fermentors were fed 40 g of a pelleted diet containing whole alfalfa pellets and concentrate mix pellets (50:50) once daily. After 7 d of treatment, sequential, continuous infusions of [2-¹³C] sodium acetate (3.5 mmol/d), [U-¹³C] sodium propionate (2.9 mmol/d), and [1-¹³C] sodium butyrate (0.22 mmol/d) were carried out from 12 h before feeding for 36 h. Filtered liquid effluent (4 mL) was sampled at 0, 2, 4, 6, 8, 12, 16, and 22 h after feeding, and assessed for VFA concentrations, with another filtered sample (20 mL) used to quantify aqueous concentrations of CH₄ and H₂. Headspace CH₄ and H₂ gases were monitored continuously. Ruminal microbes were isolated from the mixed effluent samples, and the microbial community structure was analyzed using the 16S rRNA amplicon sequencing technique. The digestibility of neutral detergent fiber, acid detergent fiber, and starch and microbial C sequestrated from VFA were not affected by treatments. The LowpH treatment increased net propionate production and decreased H₂ and CH₄ headspace emissions, primarily due to shifts in metabolic pathways of VFA formation, likely due to the observed changes in bacterial community structure. Significant interconversions occurred between acetate and butyrate, whereas interconversions of other VFA with propionate were relatively small. The InfAc and InfPr treatments increased net acetate and propionate production, respectively; however, interconversions among VFA were not affected by pH, acetate, or propionate treatments, suggesting that thermodynamics might not be a primary influencer of metabolic pathways used for VFA formation.

Subdural extravasation of crystalloids and blood products through a scalp peripheral intravenous catheter into the subdural space of a neonate on veno-arterial extracorporeal membrane oxygenation

We describe a rare and devastating complication of a malpositioned scalp peripheral intravenous catheter (PIV) that resulted in subdural extravasation of infused fluids and midline shift in a critically ill neonate who required extracorporeal membrane oxygenation (ECMO). Recognition of increased intracranial pressure was hindered by the hemodynamic changes of being on ECMO and only identified by routine surveillance ultrasonography. Awareness of this complication may lead providers to seek alternate sites for vascular access in such patients, and encourage closer monitoring for this complication when an alternate site is unavailable.

Validation of the continuous glucose monitoring sensor in preterm infants

OBJECTIVE

Recent studies have highlighted the need for improved methods of monitoring glucose control in intensive care to reduce hyperglycaemia, without increasing the risk of hypoglycaemia. Continuous glucose monitoring is increasingly used in children with diabetes, but there are little data regarding its use in the preterm infant, particularly at extremes of glucose levels and over prolonged periods. This study aimed to assess the accuracy of the continuous glucose monitoring sensor (CGMS) across the glucose profile, and to determine whether there was any deterioration over a 7 day period.

DESIGN

Prospectively collected CGMS data from the NIRTURE Trial was compared with the data obtained simultaneously using point of care glucose monitors.

SETTING

An international multicentre randomised controlled trial.

PATIENTS

One hundred and eighty-eight very low birth weight control infants.

OUTCOME MEASURES

Optimal accuracy, performance goals (American Diabetes Association consensus), Bland Altman, Error Grid analyses and accuracy.

RESULTS

The mean (SD) duration of CGMS recordings was 156.18 (29) h (6.5 days), with a total of 5207 paired glucose levels. CGMS data correlated well with point of care devices (r=0.94), with minimal bias. It met the Clarke Error Grid and Consensus Grid criteria for clinical significance. Accuracy of single readings to detect set thresholds of hypoglycaemia, or hyperglycaemia was poor. There was no deterioration over time from insertion.

CONCLUSIONS

CGMS can provide information on trends in glucose control, and guidance on the need for blood glucose assessment. This highlights the potential use of CGMS in optimising glucose control in preterm infants.

SU-E-T-01: Applications of 6MV FFF Photon Beams in Optimizing Radiobiological Response for Respiratory-Gated Liver SBRT

PURPOSE

To establish a radiobiological basis for gated stereotactic body radiotherapy of primary and metastatic liver cancers using volumetric arc radiotherapy in a flattening filter free (FFF) mode.

METHODS

Human cervical carcinoma, SiHa, non-small cell lung carcinoma, H460, and Chinese hamster V79 cells were irradiated in a water bath with 6MV photons from a Varian TrueBeam linear accelerator. To establish dose-response and its sensitivity to dose rate following acute irradiation, doses of 2, 4, 6, 8 and 10 Gy were delivered in FFF mode at 400 and 1200 MU/min. To investigate whether removal of the flattening filter affects cell response, doses of 5 and 10 Gy were delivered to SiHa and H460 cells in FFF and filtered modes at 400 MU/min. Finally, to assess the effect of protracting dose delivery by gating, a dose of 10 Gy was delivered to SiHa and H460 cells acutely and also over 15, 30 and 60 min.

RESULTS

Dose-response over doses examined was independent of dose rate in FFF mode. Differences in cell survival following irradiation in FFF and filtered modes were not significant. However a significant increase in survival for both H460 and SiHa cells was observed for 15 min split-dose irradiation compared to acute irradiation but further increase in irradiation time to 60 min did not affect cell survival.

CONCLUSIONS

Dose rate and presence of a flattening filter showed no effect on cell survival, however, survival was significantly affected when dose delivery time was protracted to that typical of conformal field therapy. Volumetric arc based gated SBRT may be beneficial for tumor cell kill, though the gating window and duty cycle have to be balanced against the effect of dose delivery protraction. Research Support (Varian Medical Systems).

Circumferential resection margin (CRM) in esophageal (OC) and gastroesophageal (GOJ) cancers

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Background: We hypothesized that CRM size affect survival and local recurrence for OC and GOJ cancer. We also assessed the utility of CT in predicting margin status.

Methods: A retrospective analysis of a prospective database was carried out on all patients who had esophagectomy between January 2000 and July 2008. Patients diagnosed with OC and GOJ tumors on final pathologic examination were included. Distance from the CRM was assessed by a specialist upper GI pathologist. Two radiologists, blinded to postoperative margin status, reviewed preoperative CT scans using 16 separate parameters, comparing them to measured CRM status.

Results: 419 patients were assessed. 223 pts had OC or GOJ type 1 tumors, average age 62 years (range 36–80), mean follow-up 5.8 years (2-9.5). There were 125 deaths and median overall survival (OS) 3.33 years (95% CI 2.76-6.24). 76 patients had recurrence at a median of 1.3 years (0.1-4.7). For 144 patients had OC or GOJ type 1 T3 tumors. Selected results are presented in the Table. There was no CRM size above which there was no further reduction in recurrence. Postoperative chemoradiation did not improve OS (p=0.79) or recurrence (p=0.96) in patients with CRM of 0-1 mm. In 50 patients the CT parameters significantly correlated with margin status were largest axial diameter (p=0.003) and contact with adjacent structures (p=0.005). A complete statistical review with multivariate and subgroup analyses will be presented.

Conclusions: CRM size is strongly correlated with survival and recurrence in OC and type 1 GOJ tumors. Prediction of a close CRM could be used to select for more intensive therapy prior to undergoing radical surgery, such as chemoradiation. Preoperative CT can help in this prediction.

[Table: see text]

No significant financial relationships to disclose.

Complexity and accuracy of image registration methods in SPECT-guided radiation therapy

The use of functional imaging in radiotherapy treatment (RT) planning requires accurate co-registration of functional imaging scans to CT scans. We evaluated six methods of image registration for use in SPECT-guided radiotherapy treatment planning. Methods varied in complexity from 3D affine transform based on control points to diffeomorphic demons and level set non-rigid registration. Ten lung cancer patients underwent perfusion SPECT-scans prior to their radiotherapy. CT images from a hybrid SPECT/CT scanner were registered to a planning CT, and then the same transformation was applied to the SPECT images. According to registration evaluation measures computed based on the intensity difference between the registered CT images or based on target registration error, non-rigid registrations provided a higher degree of accuracy than rigid methods. However, due to the irregularities in some of the obtained deformation fields, warping the SPECT using these fields may result in unacceptable changes to the SPECT intensity distribution that would preclude use in RT planning. Moreover, the differences between intensity histograms in the original and registered SPECT image sets were the largest for diffeomorphic demons and level set methods. In conclusion, the use of intensity-based validation measures alone is not sufficient for SPECT/CT registration for RTTP. It was also found that the proper evaluation of image registration requires the use of several accuracy metrics.

Monte Carlo calculation of dose distribution in early stage NSCLC patients planned for accelerated hypofractionated radiation therapy in the NCIC-BR25 protocol

The dosimetric consequences of plans optimized using a commercial treatment planning system (TPS) for hypofractionated radiation therapy are evaluated by re-calculating with Monte Carlo (MC). Planning guidelines were in strict accordance with the Canadian BR25 protocol which is similar to the RTOG 0236 and 0618 protocols in patient eligibility and total dose, but has a different hypofractionation schedule (60 Gy in 15 fractions versus 60 Gy in 3 fractions). A common requirement of the BR25 and RTOG protocols is that the dose must be calculated by the TPS without tissue heterogeneity (TH) corrections. Our results show that optimizing plans using the pencil beam algorithm with no TH corrections does not ensure that the BR25 planning constraint of 99% of the PTV receiving at least 95% of the prescription dose would be achieved as revealed by MC simulations. This is due to poor modelling of backscatter and lateral electronic equilibrium by the TPS. MC simulations showed that as little as 75% of the PTV was actually covered by the 95% isodose line. The under-dosage of the PTV was even more pronounced if plans were optimized with the TH correction applied. In the most extreme case, only 23% of the PTV was covered by the 95% isodose.

The National Psychiatric Morbidity Surveys of Great Britain--initial findings from the household survey

This paper describes the Household Survey from the National Survey of Psychiatric Morbidity. This covered a sample drawn at random from the population of Britain, with the exception of the Highlands and Islands of Scotland. The Postcode Address File was used as the sampling frame. Nearly 13,000 adults aged 16-65 were selected for interview, of which 10,108 (79.4%) were successfully interviewed. Eight percent could not be contacted and 13% refused interview. Psychiatric assessment was carried out by lay interviewers using the CIS-R. Subjects were also screened for psychosis, and screen-positive individuals were examined by psychiatrists using SCAN. Sixteen per cent of subjects scored above the standard cut-off of 12 on the CIS-R. The overall one-week prevalence of neurotic disorder was 12.3% in males and 19.5% in females. Unmarried and post-marital groups had high rates of disorder, as did single parents and people living on their own. Respondents in Social Class I had notably lower rates of neurotic disorder than the remainder of the sample. Unemployment was strongly associated with disorder. Subjects living in urban areas had a higher overall prevalence, but there was no significant variation by region. Black respondents had higher rates of disorders that were entirely explained by their age, family type, and social class. Individual neurotic disorders were all significantly commoner in women, with the exception of panic disorder. The one-year prevalence of functional psychoses was four per 1000, with no sex difference. Alcohol and drug dependence was considerably more prevalent in men. For the first time, the survey provides data on the prevalence and correlates of psychiatric disorder on a nationwide sample that can be used to inform equitable and effective national psychiatric services.

Socio-economic status, standard of living, and neurotic disorder

Evidence on the association between socio-economic status and the prevalence of neurotic disorder is contradictory. We studied the association between three elements of socio-economic status and the prevalence of neurotic psychiatric disorder in a representative sample of adults aged 16-64 living in private households in the UK. A cross-sectional survey of 10,108 adults aged 16-65 resident in private households in the UK was selected by a multi-stage, clustered, random-sampling design. Neurotic disorders were defined using a standardised interview, the revised clinical interview schedule (CIS-R). Data for 9570 people were available for this study. We used housing tenure and access to cars as measures of standard of living; both were associated with the prevalence of neurotic disorder even after adjustment for other socio-economic and demographic variables, including the Registrar General's Social Class and educational attainment. Those people with no access to a car had an odds ratio for neurotic disorder of 1.4 (95% CI 1.1-1.7), compared with those who had access to two or more cars. People who rented their homes were also at increased risk (1.3 [1.1-1.5]). We estimated that about 10% of the neurotic disorder in the UK could be attributed to the increased prevalence of those without cars who rented their homes. There was a complex interaction between the Registrar General's Social Class and sex, and there was no independent association with educational attainment. There is an independent association between low standard of living and the prevalence of neurotic psychiatric disorder. The UK has experienced one of the largest increases in income inequality within western market economies over the past 20 years, and this inequality may have had adverse consequences for the mental health of the population.

The prevalence of psychiatric morbidity among adults living in institutions

This paper presents prevalence data from the 1994 OPCS survey of psychiatric morbidity among adults permanently resident in institutions catering for people with mental health problems in Great Britain. It describes briefly the survey methods used, and how diagnoses of psychiatric morbidity were derived. Its main aim is to show the prevalence of psychiatric morbidity in different types of institutional settings. Residents were eligible for the survey if they were aged 16 to 64 at the date of sampling and were permanently resident at the establishment. Residents were defined as permanently resident if they had been living in the sampled establishment for six months or more, or had no other permanent address, or were likely to stay in the establishment for the foreseeable future. In 1994, about 33,200 adults aged 16 to 64 were permanently resident in accommodation for people with mental health problems. About a third of residents were in NHS hospitals, while about two-thirds were in residential care facilities. About two-thirds of adults interviewed suffered from schizophrenia, delusional and schizoaffective disorders. About 8% suffered from neurotic disorders and 8% suffered from affective psychoses (mainly bipolar affective disorder). The prevalence of schizophrenia, delusional, and schizoaffective disorders was higher in hospitals than in residential care, while the prevalence of neurotic and related disorders was higher in residential accommodation. The prevalence of schizophrenia, delusional, and schizoaffective disorders was higher in NHS psychiatric hospitals and general hospital units than in private hospitals, clinics or nursing homes.

The circumstances of adults with a psychotic disorder

This article presents some findings about adults with a psychotic disorder who were identified in the OPCS surveys of psychiatric morbidity. The main aim of the analysis was to identify characteristics associated with differences in the circumstances and health-related behaviour of adults aged 16-64 with psychosis. The analysis covers people who were identified by the various criteria used on the surveys as having a psychotic illness and who were considered to be living in private households. First we describe briefly the survey methods used and how diagnoses of psychosis were derived. We then present results from four topic areas covered in the analysis. These are: use of medication, use of health services, difficulties with activities of daily living, and social support.

The National Psychiatric Morbidity Surveys of Great Britain--strategy and methods

This paper describes the rationale and methodology of the first National Psychiatric Morbidity Surveys to be carried out in Great Britain. The objectives of the surveys were to estimate the prevalence of psychiatric morbidity among adults aged 16-64 living in Great Britain; to identify the nature and extent of social disabilities associated with psychiatric morbidity; to describe the use of health and social services by people with psychiatric morbidity and to investigate the association between mental illness and potential environmental risk factors in a household sample. Four separate surveys were carried out in order to meet the objectives; a private household sample (n = 10,108), a sample of institutions caring for the mentally ill (n = 1191), a sample of homeless people (n = 1166), and a supplementary sample of patients with psychosis living in private households (n = 350). A two-stage assessment procedure was used, in which all subjects were given the Revised Clinical Interview Schedule (CIS-R) administered by lay interviewers to assess neurotic symptoms and disorders and a psychosis screen, including the Psychosis Screening Questionnaire. Those who were positive on the psychosis screen were then interviewed by psychiatrists using the SCAN (incorporating the tenth edition of the Present State Examination). Large scale national surveys such as this augment the inadequate data on psychiatric morbidity that are routinely available and are, therefore, an important source of information upon which to base policy and generate aetiological hypotheses. These surveys provide a possible model for similar surveys in other countries.

Substance misuse and psychiatric comorbidity: an overview of the OPCS National Psychiatric Morbidity Survey

There have been a number of national surveys of psychiatric morbidity, which have included questions on drugs, alcohol, and tobacco. These surveys have helped delineate the overlap between substance use and dependence and other psychological morbidity. There is a strong association reported between high substance consumption and other measures of psychological problems. This article provides an overview of a national household survey, a survey of institutional residents with psychiatric disorders, and a national survey of a homeless population. All three surveys used comprehensive and complex sampling strategies and lay interviewers to conduct structured diagnostic interviews. The household survey included over 10,000 households, the institutional survey interviewed 755 individuals, and the homeless survey of hostels, night shelters, day centres, and private sector leased accommodation interviewed 1,061 individuals. This overview looks at patterns of nicotine, alcohol, and other drug use in the different samples and examines interactions with other psychiatric morbidity. The survey reports that substance-related disorders are some of the commonest disorders in the community, with 5% of the household sample alcohol dependent, 7% alcohol dependent in the institutional sample and over 21% in the homeless sample recorded as alcohol dependent. Tobacco, alcohol and other drug use and dependence were dramatically higher in the homeless sample than in either of the other two samples. Substance use was significantly associated with higher rates of psychological morbidity as measured by the Clinical Interview Schedule Revised. Future service planning needs to take account of the striking disparity of prevalence of psychiatric disorders in different subsections of the population.

Chromosome mapping and phylogenetic analysis of the cytosolic acetyl-CoA carboxylase loci in wheat

The cytosolic isoform of plant acetyl-CoA carboxylase is a multidomain enzyme involved in the synthesis of very-long-chain fatty acids and in secondary metabolism. Chromosome mapping of wheat identified one locus containing cytosolic acetyl-CoA carboxylase genes (Acc-2) and a related partially processed pseudogene (Psi-Acc-2) in the distal region of the long arm of wheat homoeologous group 3 chromosomes. Multiple copies of the Acc-2 genes, whose presence was suggested by sequence analysis, are likely to be arranged in tandem repeats. At least three out of five genes cloned from hexaploid wheat map to this locus. Another locus containing Acc-2--related sequences is present in the distal region of the long arm of chromosome 5D. The identity of the hybridizing DNA present at this locus remains unknown. A system based on PCR-cloning and DNA sequence analysis of acetyl-CoA carboxylase genes was developed to address various phylogenetic and systematics questions in grasses. It was applied to reconstruct the phylogeny of the Acc-2 genes from D- and S-genome Aegilops and A-genome Triticum diploid species, AABB- and AAGG-genome tetraploid wheat, and AABBDD-genome hexaploid wheat, as well as from rye and barley. The combined cytogenetic and molecular evolution approach allowed assignment of gene sequences included in phylogenetic analysis to specific loci on homoeologous chromosomes. Recurring gene duplication followed by chromosome translocation and/or possible loss of some gene copies, as well as loss of introns, occurred in the gene family in different plant lineages. Two major Acc-2 clades appeared before the divergence of barley and rye. Nucleotide substitution rates in different parts of the Acc-2 gene were assessed. This analysis of the Acc-2 loci provides detailed information regarding evolutionary events at a low--copy-number locus containing important functional genes. These events are likely to be common and to play a significant role in shaping grass genomes.

Categories of resistance to greenbug (Homoptera: Aphididae) biotype I in Aegilops tauschii germplasm

Categories of resistance to greenbug, Schizaphisgraminum (Rondani), biotype I, were determined in goatgrass, Aegilops tauschii (Coss.) Schmal., accession 1675 (resistant donor parent), 'Wichita' wheat, Triticum aestivum L., (susceptible parent), and an Ae. tauschii-derived resistant line, '97-85-3'. Antibiosis was assessed using the intrinsic rate of increase (rm) of greenbugs confined to each of the three genotypes. Neither parent nor the resistant progeny expressed antibiosis. Mean rm values for greenbug I on Wichita (0.0956), and Ae. tauschii (0.10543) were not significantly different. Mean rm values for Wichita and 97-85-3 were also not significantly different. Antixenosis was determined by allowing aphids a choice to feed on plants of each of the three genotypes. Ae. tauschii 1675 exhibited antixenosis, but this resistance was not inherited and expressed in '97-85-3'. In experiments comparing Wichita and Ae. tauschii 1675, greenbug I population distributions were not significantly different on Wichita at 24 h, but were shifted toward Wichita at 48 h. In the second antixenosis experiment, there were no significant differences in greenbug I population distributions on 97-85-3 or Wichita at 24 or 48 h. When all three lines were compared, there were no significant differences in greenbug biotype I populations at 24 or 48 h after infestation. Comparisons of proportional dry plant weight loss (DWT) and SPAD meter readings were used to determine tolerance to greenbug I feeding. Ae. tauschii 1675 and 97-85-3 were highly tolerant compared with Wichita. Infested and uninfested Ae. tauschii 1675 DWT was nonsignificant, and infested Wichita plants weighed significantly less than uninfested plants. When Wichita and 97-85-3 were contrasted, DWT of infested and uninfested Wichita plants were significantly different, but those of 97-85-3 were not. Mean percent leaf chlorophyll losses for the three genotypes, as measured by the SPAD chlorophyll meter, were as follows: Wichita = 65%; Ae. tauschii 1675 = 25%; and 97-85-3 = 39%. Percent leaf chlorophyll losses caused by greenbug feeding was significantly different in comparisons between Wichita and Ae. tauschii 1675, and comparisons between Wichita and 97-85-3, although feeding damage was not significantly different in comparisons between Ae. tauschii 1675 and 97-85-3. These data provided further evidence of the expression of tolerance to greenbug feeding in Ae. tauschii 1675 and 97-85-3.

Investigation of BOLD signal dependence on cerebral blood flow and oxygen consumption: the deoxyhemoglobin dilution model

The relationship between blood oxygenation level-dependent (BOLD) MRI signals, cerebral blood flow (CBF), and oxygen consumption (CMR(O2)) in the physiological steady state was investigated. A quantitative model, based on flow-dependent dilution of metabolically generated deoxyhemoglobin, was validated by measuring BOLD signals and relative CBF simultaneously in the primary visual cortex (V1) of human subjects (N = 12) during graded hypercapnia at different levels of visual stimulation. BOLD and CBF responses to specific conditions were averaged across subjects and plotted as points in the BOLD-CBF plane, tracing out lines of constant CMR(O2). The quantitative deoxyhemoglobin dilution model could be fit to these measured iso-CMR(O2) contours without significant (P </= 0.05) residual error and yielded MRI-based CMR(O2) measurements that were in agreement with PET results for equivalent stimuli. BOLD and CBF data acquired during graded visual stimulation were then substituted into the model with constant parameters varied over plausible ranges. Relative changes in CBF and CMR(O2) appeared to be coupled in an approximate ratio of approximately 2:1 for all realistic parameter settings. Magn Reson Med 42:849-863, 1999.

Linear coupling between cerebral blood flow and oxygen consumption in activated human cortex

The aim of this study was to test the hypothesis that, within a specific cortical unit, fractional changes in cerebral blood flow (CBF) and cerebral metabolic rate of oxygen consumption (CMR(O(2))) are coupled through an invariant relationship during physiological stimulation. This aim was achieved by simultaneously measuring relative changes in these quantities in human primary visual cortex (V1) during graded stimulation with patterns designed to selectively activate different populations of V1 neurons. Primary visual cortex was delineated individually in each subject by using phase-encoded retinotopic mapping. Flow-sensitive alternating inversion recovery MRI, in conjunction with blood oxygenation-sensitive MRI and hypercapnic calibration, was used to monitor CBF and CMR(O(2)). The stimuli used included (i) diffuse isoluminant chromatic displays; (ii) high spatial-frequency achromatic luminance gratings; and (iii) radial checkerboard patterns containing both color and luminance contrast modulated at different temporal rates. Perfusion responses to each pattern were graded by varying luminance and/or color modulation amplitudes. For all stimulus types, fractional changes in blood flow and oxygen uptake were found to be linearly coupled in a consistent ratio of approximately 2:1. The most potent stimulus produced CBF and CMR(O(2)) increases of 48 +/- 5% and 25 +/- 4%, respectively, with no evidence of a plateau for oxygen consumption. Estimation of aerobic ATP yields from the observed CMR(O(2)) increases and comparison with the maximum possible anaerobic ATP contribution indicate that elevated energy demands during brain activation are met largely through oxidative metabolism.

Stimulus-dependent BOLD and perfusion dynamics in human V1

Blood oxygenation level-dependent (BOLD) fMRI signals often exhibit pronounced over- or undershoot upon changes in stimulation state. Current models postulate that this is due to the delayed onset or decay of perfusion-dependent attenuating responses such as increased cerebral blood volume or oxygen consumption, which are presumed to lag behind the rapid adjustment of blood flow rate to a new steady-state level. If this view is correct, then BOLD overshoot amplitudes in a specific tissue volume should be correlated with steady-state increases in perfusion, independent of stimulus type. To test this prediction, we simultaneously recorded BOLD and relative perfusion signals in primary visual cortex while inducing graded perfusion increases with three types of visual stimulus. Two of these, a diffuse chromatic stimulus with no luminance variation and a very high spatial frequency luminance grating, did not produce detectable BOLD overshoot (or undershoot) when an equal mean luminance baseline was used. Radial checkerboard stimuli, however, caused pronounced over/undershoot of both BOLD and perfusion signals even when temporal mean luminance was held constant and stimulus contrast was adjusted to produce the same steady-state blood flow increases evoked by the other stimuli. Transient amplitudes were relatively invariant in spite of large changes in steady-state response, demonstrating nonlinear BOLD and perfusion step responses in human V1. These findings suggest that, rather than a purely tissue-specific biomechanical or metabolic phenomenon, BOLD overshoot and undershoot represent transient features in the perfusion signal whose effects may be amplified by slowly evolving blood volume changes.

Substance misuse and psychiatric comorbidity: an overview of the OPCS National Psychiatric Morbidity Survey

There have been a number of national surveys of psychiatric morbidity which have included questions on drugs, alcohol and tobacco. These surveys have helped delineate the overlap between substance use and dependence and other psychological morbidity. There is a strong association reported between high substance consumption and other measures of psychological problems. This article provides an overview of a national household survey, a survey of institutional residents with psychiatric disorders and a national survey of a homeless population. All three surveys used comprehensive and complex sampling strategies and lay interviewers to conduct structured diagnostic interviews. The household survey included over 10,000 households, the institutional survey interviewed 755 individuals and the homeless survey of hostels, night-shelters, day centres and private-sector leased accommodation interviewed 1,061 individuals. This overview looks at patterns of nicotine, alcohol and other drug use in the different samples and examines interactions with other psychiatric morbidity. The survey reports that substance-related disorders are some of the commonest disorders in the community, with 5% of the household sample alcohol dependent, 7% alcohol dependent in the institutional sample and over 21% in the homeless sample recorded as alcohol dependent. Tobacco, alcohol and other drug use and dependence were dramatically higher in the homeless sample than in either of the other two samples. Substance use was significantly associated with higher rates of psychological morbidity as measured by the Clinical Interview Schedule Revised. Future service planning needs to take account of the striking disparity of prevalence of psychiatric disorders in different subsections of the population.