Clinical Impact of Routine Assessment of Patient-Reported Health Status in Heart Failure Clinic

BACKGROUND

The impact of routine clinic use of patient-reported outcome (PRO) measures on clinical outcomes in patients with heart failure (HF) has not been well-characterized. We tested if clinic-based use of a disease-specific PRO improves patient-reported quality of life at 1 year.

METHODS

PRO-HF was an open-label, parallel, patient-level randomized clinical trial of routine PRO assessment or usual care at an academic HF clinic between August 30, 2021, and June 30, 2022, with 1 year of follow-up. In the PRO assessment arm, participants completed the Kansas City Cardiomyopathy Questionnaire-12 (KCCQ-12) at each HF clinic visit and results were shared with their treating clinician. The usual care arm completed the KCCQ-12 at randomization and 1 year later, which was not shared with the treating clinician. The primary outcome was the KCCQ-12 Overall Summary Score (OSS) between 12-15 months post-randomization. Secondary outcomes included domains of the KCCQ-12, hospitalization and emergency department visit rates, HF medication therapy, clinic visit frequency, and testing rates.

RESULTS

Across 17 clinicians, 1,248 participants were enrolled and randomized to PRO assessment (n=624) or usual care (n=624). The median age was 63.9 (interquartile range [IQR] 51.8-72.8), 38.9% were women, and the median baseline KCCQ-12 OSS was 82.3 (IQR 58.3-94.8). Final KCCQ-12 (available in 87.9% of the PRO arm and 85.1% in usual care [p=0.16]) median OSS scores were 87.5 (IQR 68.8-96.9) in the PRO arm and 87.6 (IQR 69.7-96.9) in the usual care arm with a baseline-adjusted mean difference of 0.2 (95% CI: -1.7 to 2.0; p=0.85). The results were consistent across pre-specified subgroups. A post hoc analysis demonstrated a significant interaction with greater benefit among participants with baseline KCCQ-12 OSS scores of 60-80 but not in less or more symptomatic participants. No significant differences were found in 1-year mortality, hospitalizations, ED visits, medication therapy, clinic follow-up, or testing rates between arms.

CONCLUSIONS

Routine PRO assessment in HF clinic visits did not impact patient-reported quality of life or other clinical outcomes. Alternate strategies and settings for embedding PROs into routine clinical care should be tested.

Scalable Approach to Consumer Wearable Postmarket Surveillance: Development and Validation Study

Background

With the capability to render prediagnoses, consumer wearables have the potential to affect subsequent diagnoses and the level of care in the health care delivery setting. Despite this, postmarket surveillance of consumer wearables has been hindered by the lack of codified terms in electronic health records (EHRs) to capture wearable use.

Objective

We sought to develop a weak supervision-based approach to demonstrate the feasibility and efficacy of EHR-based postmarket surveillance on consumer wearables that render atrial fibrillation (AF) prediagnoses.

Methods

We applied data programming, where labeling heuristics are expressed as code-based labeling functions, to detect incidents of AF prediagnoses. A labeler model was then derived from the predictions of the labeling functions using the Snorkel framework. The labeler model was applied to clinical notes to probabilistically label them, and the labeled notes were then used as a training set to fine-tune a classifier called Clinical-Longformer. The resulting classifier identified patients with an AF prediagnosis. A retrospective cohort study was conducted, where the baseline characteristics and subsequent care patterns of patients identified by the classifier were compared against those who did not receive a prediagnosis.

Results

The labeler model derived from the labeling functions showed high accuracy (0.92; F1-score=0.77) on the training set. The classifier trained on the probabilistically labeled notes accurately identified patients with an AF prediagnosis (0.95; F1-score=0.83). The cohort study conducted using the constructed system carried enough statistical power to verify the key findings of the Apple Heart Study, which enrolled a much larger number of participants, where patients who received a prediagnosis tended to be older, male, and White with higher CHA2DS2-VASc (congestive heart failure, hypertension, age ≥75 years, diabetes, stroke, vascular disease, age 65-74 years, sex category) scores (P<.001). We also made a novel discovery that patients with a prediagnosis were more likely to use anticoagulants (525/1037, 50.63% vs 5936/16,560, 35.85%) and have an eventual AF diagnosis (305/1037, 29.41% vs 262/16,560, 1.58%). At the index diagnosis, the existence of a prediagnosis did not distinguish patients based on clinical characteristics, but did correlate with anticoagulant prescription (P=.004 for apixaban and P=.01 for rivaroxaban).

Conclusions

Our work establishes the feasibility and efficacy of an EHR-based surveillance system for consumer wearables that render AF prediagnoses. Further work is necessary to generalize these findings for patient populations at other sites.

Uptake of Sodium-Glucose Cotransporter-2 Inhibitors in Hospitalized Patients With Heart Failure: Insights From the Veterans Affairs Healthcare System

BACKGROUND

The use of sodium-glucose cotransporter-2 inhibitors (SGLT2is) in Veterans Affairs (VA) patients hospitalized with heart failure (HF) has not been reported previously.

METHODS

VA electronic health record data were used to identify patients hospitalized for HF (primary or secondary diagnosis) from 01/2019-11/2022. Patients with SGLT2i allergy, advanced/end-stage chronic kidney disease (CKD) or advanced HF therapies were excluded. We identified factors associated with discharge SGLT2i prescriptions for patients hospitalized due to HF in 2022. We also compared SGLT2i and angiotensin receptor-neprilysin inhibitor (ARNI) prescription rates. Hospital-level variations in SGLT2i prescriptions were assessed via the median odds ratio.

RESULTS

A total of 69,680 patients were hospitalized due to HF; 10.3% were prescribed SGLT2i at discharge (4.4% newly prescribed, 5.9% continued preadmission therapy). SGLT2i prescription increased over time and was higher in patients with HFrEF and primary HF. Among 15,762 patients hospitalized in 2022, SGLT2i prescription was more likely in patients with diabetes (adjusted odds ratio [aOR] 2.27; 95% confidence interval [CI]: 2.09-2.47) and ischemic heart disease (aOR 1.14; 95% CI: 1.03-1.26). Patients with increased age (aOR 0.77 per 10 years; 95% CI: 0.73-0.80) and lower systolic blood pressure (aOR 0.94 per 10 mmHg; 95% CI: 0.92-0.96) were less likely to be prescribed SGLT2i, and SGLT2i prescription was not more likely in patients with CKD (aOR 1.07; 95% CI 0.98-1.16). The adjusted median odds ratio suggested a 1.8-fold variation in the likelihood that similar patients at 2 random VA sites were prescribed SGLT2i (range 0-21.0%). In patients with EF ≤ 40%, 30.9% were prescribed SGLT2i while 26.9% were prescribed ARNI (P < 0.01).

CONCLUSION

One-tenth of VA patients hospitalized for HF were prescribed SGLT2i at discharge. Opportunities exist to reduce variation in SGLT2i prescription rates across hospitals and to promote its use in patients with CKD and older age.

Digital Health Interventions for Heart Failure Management in Underserved Rural Areas of the United States: A Systematic Review of Randomized Trials

BACKGROUND

Heart failure disproportionately affects individuals residing in rural areas, leading to worse health outcomes. Digital health interventions have been proposed as a promising approach for improving heart failure management. This systematic review aims to identify randomized trials of digital health interventions for individuals living in underserved rural areas with heart failure.

METHODS AND RESULTS

We conducted a systematic review by searching 6 databases (CINAHL, EMBASE, MEDLINE, Web of Science, Scopus, and PubMed; 2000-2023). A total of 30 426 articles were identified and screened. Inclusion criteria consisted of digital health randomized trials that were conducted in underserved rural areas of the United States based on the US Census Bureau's classification. Two independent reviewers screened the studies using the National Heart, Lung, and Blood Institute tool to evaluate the risk of bias. The review included 5 trials from 6 US states, involving 870 participants (42.9% female). Each of the 5 studies employed telemedicine, 2 studies used remote monitoring, and 1 study used mobile health technology. The studies reported improvement in self-care behaviors in 4 trials, increased knowledge in 2, and decreased cardiovascular mortality in 1 study. However, 3 trials revealed no change or an increase in health care resource use, 2 showed no change in cardiac biomarkers, and 2 demonstrated an increase in anxiety.

CONCLUSIONS

The results suggest that digital health interventions have the potential to enhance self-care and knowledge of patients with heart failure living in underserved rural areas. However, further research is necessary to evaluate their impact on clinical outcomes, biomarkers, and health care resource use.

REGISTRATION

URL: https://www.crd.york.ac.uk/prospero/; Unique identifier: CRD42022366923.

Dronedarone Versus Sotalol in Antiarrhythmic Drug-Naive Veterans With Atrial Fibrillation

BACKGROUND

Sotalol and dronedarone are both used for maintenance of sinus rhythm for patients with atrial fibrillation. However, while sotalol requires initial monitoring for QT prolongation and proarrhythmia, dronedarone does not. These treatments can be used in comparable patients, but their safety and effectiveness have not been compared head to head. Therefore, we retrospectively evaluated the effectiveness and safety using data from a large health care system.

METHODS

Using Veterans Health Administration data, we identified 11 296 antiarrhythmic drug-naive patients with atrial fibrillation prescribed dronedarone or sotalol in 2012 or later. We excluded patients with prior conduction disease, pacemakers or implantable cardioverter-defibrillators, ventricular arrhythmia, cancer, renal failure, liver disease, or heart failure. We used natural language processing to identify and compare baseline left ventricular ejection fraction between treatment arms. We used 1:1 propensity score matching, based on patient demographics, comorbidities, and medications, and Cox regression to compare strategies. To evaluate residual confounding, we performed falsification analysis with nonplausible outcomes.

RESULTS

The matched cohort comprised 6212 patients (3106 dronedarone and 3106 sotalol; mean [±SD] age, 71±10 years; 2.5% female; mean [±SD] CHA2DS2-VASC, 2±1.3). The mean (±SD) left ventricular ejection fraction was 55±11 and 58±10 for dronedarone and sotalol users, correspondingly. Dronedarone, compared with sotalol, did not demonstrate a significant association with risk of cardiovascular hospitalization (hazard ratio, 1.03 [95% CI, 0.88-1.21]) or all-cause mortality (hazard ratio, 0.89 [95% CI, 0.68-1.16]). However, dronedarone was associated with significantly lower risk of ventricular proarrhythmic events (hazard ratio, 0.53 [95% CI, 0.38-0.74]) and symptomatic bradycardia (hazard ratio, 0.56 [95% CI, 0.37-0.87]). The primary findings were stable across sensitivity analyses. Falsification analyses were not significant.

CONCLUSIONS

Dronedarone, compared with sotalol, was associated with a lower risk of ventricular proarrhythmic events and conduction disorders while having no difference in risk of incident cardiovascular hospitalization and mortality. These observational data provide the basis for prospective efficacy and safety trials.

Association of CHA2DS2-VASc and HAS-BLED to frailty and frail outcomes: From the TREAT-AF study

BACKGROUND

Morbidity and mortality associated with high CHA₂DS₂-VASc and HAS-BLED scores is not specific to atrial fibrillation (AF). Frailty could be an important contributor to this morbidity and mortality while being mechanistically independent from AF. We sought to evaluate the association of stroke and bleeding risk to noncardiovascular frail events and the association of stroke prevention therapy to outcomes in frail patients with AF.

METHODS

Using the TREAT-AF (The Retrospective Evaluation and Assessment of Therapies in AF) study from the Veterans Health Administration, we identified patients with newly diagnosed AF from 2004 to 2014. Baseline frailty was identified using a previously validated claims-based index requiring ≥2 of 12 ICD-9 diagnoses. Logistic regressions modeled the association between CHA₂DS₂-VASc and modified HAS-BLED and frailty. Cox proportional hazard regressions were used to evaluate the association between CHA₂DS₂-VASc and modified HAS-BLED and a composite of noncardiovascular frail events (fractures, urinary tract infections, bacterial pneumonia, or dehydration). We also evaluated the association of oral anticoagulant (OAC) use with stroke, bleeding, and 1-year mortality in frail patients and non-frail patients.

RESULTS

In 213,435 patients (age 70 ± 11; 98% male; CHA₂DS₂-VASc 2.4 ± 1.7) with AF, 8,498 (4%) were frail. CHA₂DS₂-VASc > 0 and HAS-BLED > 0 were strongly associated with frailty (odds ratio [OR] 13.3 (95% CI: 11.6-15.2) for CHA₂DS₂-VASc 4+ and OR 13.4 (10.2-17.5) for HAS-BLED 3+). After adjusting for covariates, CHA₂DS₂-VASc, and HAS-BLED > 0 were associated with higher risk of non-cardiovascular frail events (hazard ratio [HR] 2.1 (95% CI: 2.0-2.2) for CHA₂DS₂-VASc 4+ and HR 1.4 (95% CI: 1.3-1.5) for HAS-BLED 3+). In frail patients, OAC use was associated with significantly lower risk of 1-year mortality (HR 0.82; 95% CI 0.72-0.94, P = .0031) but did not reach significance for risk of stroke (HR 0.80; 95% CI 0.55-1.18, P = .26) or major bleeding (HR 1.08; 95% CI 0.93-1.25, P = .34).

CONCLUSIONS

High CHA₂DS₂-VASc and HAS-BLED scores are strongly associated with frailty. However, in frail patients, OAC use was associated with reduction in 1-year mortality. For this challenging clinical population with competing risks of frailty and frail events, focused prospective studies are needed to support clinical decision-making. Until then, careful evaluation of frailty should inform shared decision-making.

Warfarin Time in Therapeutic INR Range and Direct Oral Anticoagulant Adherence for Venous Thromboembolism Across the Spectrum of Weight and Body Mass Index: Findings from Veterans Health Administration

The evidence of direct oral anticoagulants (DOACs) usage for venous thromboembolism (VTE) in patients at extremes of body weight or mass index is limited. In such situations, warfarin may be more frequently used. We investigated warfarin time in the therapeutic international normalized ratio range (TTR) and DOAC adherence based on the calculated proportion of days covered (PDC) by pill coverage from a DOAC prescription in patients with VTE across all body sizes. Using data from the Veterans Health Administration (VA), we identified first-time patients with VTE between 2013 and 2018 treated with warfarin or DOACs. We analyzed 28,245 patients with warfarin TTR (N  =  10,167) or DOAC PDC(N  =  18,078). For warfarin-treated patients after index VTE, mean TTR was lower over shorter treatment durations (TTR 30 vs TTR 180 [mean  ±  SD]: 43.8% ± 33.5% vs 58.8% ± 23.5%). Mean TTR over 180 days after VTE was lowest for patients <60 kg (TTR 180 [mean  ±  SD]: <60kg: 49.3% ± 24.2% vs ≥60 to <100 kg: 57.8% ± 23.4%; P < .0001). For DOAC-treated patients over 180 days after index VTE, mean PDC was lowest for patients <60 kg (PDC 180 [mean  ±  SD]: < 60kg: 76.9% ± 33.2% vs ≥ 60 to <100 kg: 83.6% ± 27.7%; P < .0001).Most DOAC-treated patients attained sufficient adherence across the body size spectrum while warfarin-treated patients <60kg were at risk for low TTR.

Atrial fibrillation bleeding risk and prediction while treated with direct oral anticoagulants in warfarin-naïve or warfarin-experienced patients

Background

In patients with atrial fibrillation (AF) treated with direct oral anticoagulants (DOAC), bleeding risk scores provide only modest discrimination for major or intracranial bleeding. However, warfarin experience may impact HAS‐BLED  (Hypertension, Abnormal renal/liver function, Stroke, Bleeding history or predisposition, Labile international normalized ratio, Elderly (>65 years), Drugs/alcohol concomitantly) score performance in patients evaluated for DOACs, as HAS‐BLED was derived and validated in warfarin cohorts.

Methods

We performed a retrospective cohort study of patients prescribed DOAC for AF in the Veterans Health Administration between 2010 and 2017. We determined modified HAS‐BLED score discrimination and calibration for bleeding, for patients treated with DOAC, stratified by prior warfarin exposure. We also determined the association between DOAC–warfarin‐naïve status to bleeding (nonintracranial and intracranial) with DOAC–warfarin‐experienced patients as reference.

Results

The DOAC analysis cohort included 100, 492 patients with AF (age [mean ± SD]: 72.9 ± 9.6 years; 1.7% female; 90.1% White), of which 26, 760 patients (26.6%) and 73, 732 patients (73.4%) were warfarin experienced or naïve, respectively. HAS‐BLED discrimination for bleeds was modest for patients treated with DOAC, regardless of prior warfarin experience (concordance statistics: 0.53–0.59). For DOAC–warfarin‐naïve patients, as compared to DOAC–warfarin‐experienced patients, adjusted risk of intracranial bleeding was lower, while risk of nonintracranial bleeding was higher (intracranial bleeding propensity adjusted with inverse probability of treatment weights [IPTWs]: hazard ratio [HR]: 0.86, 95% confidence interval [CI]: 0.78–0.95, p = .0040) (nonintracranial bleeding propensity adjusted with IPTW: HR: 1.15, 95% CI: 1.11–1.19, p < .0001).

Conclusion

Patients’ modified HAS‐BLED score at the time of DOAC initiation, regardless of prior warfarin use, provided only modest discrimination for intracranial and nonintracranial bleeds. These data argue against maintaining DOAC eligible patients on warfarin therapy regardless of modified HAS‐BLED score.

Anticoagulation Treatment and Outcomes of Venous Thromboembolism by Weight and Body Mass Index: Insights From the Veterans Health Administration

BACKGROUND

Consensus statements have recommended against the use of direct oral anticoagulants (DOACs) in venous thromboembolism (VTE) for patients ≥120 kg and ≥40 kg/m². We sought to determine use and outcomes of DOACs for VTE across weight and body mass index (BMI).

METHODS

We performed a retrospective cohort study of patients with first-time VTE 2013 to 2018 that were treated with DOAC or warfarin in the Veterans Health Administration. The Veterans Health Administration has implemented system-wide guidance for patient selection and shared decision-making for use of DOACs in VTE at extremes of weight. We stratified patients by weight and BMI and assessed (1) association of weight and BMI category to outcomes in those prescribed DOAC; and (2) association of DOAC, as compared to warfarin, to outcomes by weight and BMI categories. Outcomes of interest included major bleeding, clinically relevant nonmajor bleeding, and recurrent VTE.

RESULTS

The analysis cohort included 51 871 patients prescribed DOAC or warfarin within 30 days of index VTE diagnosis (age 64.5±13.1 years; 6.0% female; median weight 93.4 kg [25th-75th: 80.5-108.6 kg]). For patients ≥120 kg (N=6934 patients), 38.4% were treated with DOAC, as compared to 45.4% of those ≥60 to <100 kg (N=30 645; P<0.0001). DOAC prescription was not associated with major bleeds, clinically relevant nonmajor bleeds, or recurrent VTE for those in higher weight and BMI categories as compared to those in average weight and BMI categories. DOAC prescription, as compared to warfarin, was not associated with increased recurrent VTE in any weight or BMI category.

CONCLUSIONS

Patients ≥120 kg and ≥40 kg/m² with VTE are frequently prescribed DOAC by the Veterans Health Administration, without an increase in bleeding or recurrent VTE. These findings suggest DOACs can be safe and effective in this population and may argue for broader adoption of pharmacy policies that promote careful patient selection and shared decision making.

Alcohol consumption and mortality after breast cancer diagnosis: The health and functioning in women study

OBJECTIVE

To determine the association of prediagnostic alcohol consumption with long-term mortality from breast cancer and other causes in a cohort of women with breast cancer.

METHODS

We studied a Michigan-based cohort of 939 women aged 40-84 years, who provided complete information about the type, amount and intensity of prediagnostic alcohol consumption. Associations of alcohol consumption, based on weekly volume of alcohol consumption during the year prior to breast cancer diagnosis, with mortality were evaluated in Cox proportional hazards models, with adjustment for sociodemographic factors, body mass index, smoking, comorbidity, tumor characteristics, and treatment. Differences among covariates were assessed with Pearson χ2 , Student t -tests and Wilcoxon Rank Sum tests. All statistical tests were two-sided.

RESULTS

During a median follow-up of 11 years, 724 deaths occurred overall, with 303 from breast cancer. Fifty-five percent of the women were categorized as drinkers with volume of alcohol consumption ranging from 0.75 to 36.00 drinks/week. In multivariable models, a decreased risk of other-cause mortality was associated with low alcohol drinking (0.75-3.75 drinks/week; HR = 0.61, 95% CI = 0.47-0.78), moderate volume alcohol drinking (4.00-9.75 drinks/week; HR = 0.57, 95% CI = 0.39-0.85) and low frequency (0.75-3.75 drinks/week) beer and wine intake (HR = 0.69, 95% CI = 0.50-0.96 and HR = 0.68, 95% CI = 0.52-0.88 respectively). Although the risk of breast cancer-specific mortality was not statistically significantly associated with moderate (4.00-9.75 drinks/week) and high volume (10.00-36.00 drinks/week) alcohol drinking in the overall cohort (HR = 1.43, 95% CI = 95% 0.97-2.12 and HR = 1.53, 95% CI = 0.87-2.70 respectively), there was a positive association of alcohol consumption with breast cancer-specific mortality among current smokers (HR = 1.92, 95% CI = 1.03-3.57; Pinteraction = 0.04).

CONCLUSION

In this prospective cohort study, regular consumption of 0.75-36.00 alcoholic drinks per week during the year prior to breast cancer diagnosis was associated with a reduction in other-cause mortality and with an increase in breast cancer-specific mortality among current smokers, after taking into account clinical and sociodemographic factors.

Implementation of antimicrobial stewardship interventions recommended by national toolkits in primary and secondary healthcare sectors in England: TARGET and Start Smart Then Focus

OBJECTIVES

To assess and compare the implementation of antimicrobial stewardship (AMS) interventions recommended within the national AMS toolkits, TARGET and Start Smart Then Focus, in English primary and secondary healthcare settings in 2014, to determine the prevalence of cross-sector engagement to drive AMS interventions and to propose next steps to improve implementation of AMS.

METHODS

Electronic surveys were circulated to all 211 clinical commissioning groups (CCGs; primary sector) and to 146 (out of the 159) acute trusts (secondary sector) in England. Response rates were 39% and 63% for the primary and secondary sectors, respectively.

RESULTS

The majority of CCGs and acute trusts reported reviewing national AMS toolkits formally or informally (60% and 87%, respectively). However, only 13% of CCGs and 46% of acute trusts had developed an action plan for the implementation of these toolkits. Only 5% of CCGs had antimicrobial pharmacists in post; however, the role of specialist antimicrobial pharmacists continued to remain embedded within acute trusts, with 83% of responding trusts having an antimicrobial pharmacist at a senior grade.

CONCLUSIONS

The majority of healthcare organizations review national AMS toolkits; however, implementation of the toolkits, through the development of action plans to deliver AMS interventions, requires improvement. For the first time, we report the extent of cross-sector and multidisciplinary collaboration to deliver AMS interventions in both primary and secondary care sectors in England. Results highlight that further qualitative and quantitative work is required to explore mutual benefits and promote best practice. Antimicrobial pharmacists remain leaders for implementing AMS interventions across both primary and secondary healthcare sectors.

Growth hormone-mediated breakdown of body fat: effects of GH on lipases in adipose tissue and skeletal muscle of old rats fed different diets

Lipid storage and breakdown is mainly controlled by lipoprotein lipase and hormone-sensitive lipase. The aim of this work was to elucidate whether growth hormone mediated loss of adipose tissue involves a concerted action on tissue lipases, and to what degree such events are modulated by dietary regimen. Twelve-month-old rats fed first a high-fat diet or a low-fat diet for 14 weeks were injected with saline or growth hormone (4 mg/kg/d) for four days or three weeks in different combinations with either high- or low-fat diets. In adipose tissue, growth hormone generally inhibited lipoprotein lipase and also attenuated the inhibiting effect of insulin on hormone-sensitive lipase activity. Growth hormone treatment combined with restricted high-fat feeding reduced the activity of both lipases in adipose tissue and stimulated hormone-sensitive lipase in muscle. Generally, plasma levels of free fatty acids, glycerol and cholesterol were reduced by growth hormone, and in combination with restricted high-fat feeding, triglyceride levels improved too. We conclude that growth hormone inhibits lipid storage in adipose tissue by reducing both lipoprotein lipase activity and insulin's inhibitory action on hormone-sensitive lipase. We also propose that growth hormone's effects on tissue lipases and blood lipids are modulated by dietary regimen.

Cell cycle and positional constraints on FtsZ localization and the initiation of cell division in Caulobacter crescentus

Swarmer cells of Caulobacter crescentus are devoid of the cell division initiation protein FtsZ and do not replicate DNA. FtsZ is synthesized during the differentiation of swarmer cells into replicating stalked cells. We show that FtsZ first localizes at the incipient stalked pole in differentiating swarmer cells. FtsZ subsequently localizes at the mid-cell early in the cell cycle. In an effort to understand whether Z-ring formation and cell constriction are driven solely by the cell cycle-regulated increase in FtsZ concentration, FtsZ was artificially expressed in swarmer cells at a level equivalent to that found in predivisional cells. Immunofluorescence microscopy showed that, in these swarmer cells, simply increasing FtsZ concentration was not sufficient for Z-ring formation; Z-ring formation took place only in stalked cells. Expression of FtsZ in swarmer cells did not alter the timing of cell constriction initiation during the cell cycle but, instead, caused additional constrictions and a delay in cell separation. These additional constrictions were confined to sites close to the original mid-cell constriction. These results suggest that the timing and placement of Z-rings is tightly coupled to an early cell cycle event and that cell constriction is not solely dependent on a threshold level of FtsZ.

UCP2 and UCP3 rise in starved rat skeletal muscle but mitochondrial proton conductance is unchanged

The relationship between UCP2 and UCP3 expression and mitochondrial proton conductance of rat skeletal muscle was examined. Rats were starved for 24 h and the levels of UCP2 and UCP3 mRNA and UCP3 protein were determined by Northern and Western blots. Proton conductance was measured by titrating mitochondrial respiration rate and membrane potential with malonate. Starvation increased UCP2 and UCP3 mRNA levels more than 5-fold and 4-fold, respectively, and UCP3 protein levels by 2-fold. However, proton conductance remained unchanged. These results suggest either that Northern and Western blots do not reflect the levels of active protein or that these UCPs do not catalyse the basal proton conductance in skeletal muscle mitochondria.

The open reading frame YAL048c affects the secretion of proteinase A in S. cerevisiae

Over-expression of the yeast PEP4 gene encoding the vacuolar aspartic protease proteinase A (PrA) leads to saturation of the vacuolar targeting system of the cell and missorting of PrA to the growth medium. In a screen for genes affecting the secretion of over-expressed PrA we found that multiple copies of the open reading frame (ORF) YAL048c enhanced PrA secretion. Since no function has hitherto been ascribed to YAL048c, we undertook further studies of this ORF. Deletion of YAL048c resulted in slightly reduced secretion of over-produced PrA. Furthermore, strains deleted for YAL048c showed a growth inhibition phenotype resulting in wrinkled colony morphology when grown on rich medium containing high concentrations of calcium. YAL048c is predicted to encode a polypeptide of 662 amino acid residues containing two consensus ATP/GTP-binding site motifs and a putative carboxy-terminal transmembrane region. In addition, the amino acid sequence contains two putative calcium-binding domains. The YAL048c protein may be evolutionarily conserved, as homologues exist in humans and Caenorhabditis elegans. We suggest that the YAL048c protein is involved in vesicle transport in the secretory pathway.

Cell cycle-dependent transcriptional and proteolytic regulation of FtsZ in Caulobacter

In the differentiating bacterium Caulobacter crescentus, the cell division initiation protein FtsZ is present in only one of the two cell types. Stalked cells initiate a new round of DNA replication immediately after cell division and contain FtsZ, whereas the progeny swarmer cells are unable to initiate DNA replication and do not contain FtsZ. We show that FtsZ expression is controlled by cell cycle-dependent transcription and proteolysis. Transcription of ftsZ is repressed in swarmer cells and is activated concurrently with the initiation of DNA replication. At the end of the DNA replication period, transcription of ftsZ decreases substantially. We show that the global cell cycle regulator CtrA is involved in the cell cycle control of ftsZ transcription. CtrA binds to a site that overlaps the ftsZ transcription start site. Removal of the CtrA-binding site results in transcription of the ftsZ promoter in swarmer cells. Decreasing the cellular concentration of CtrA increases ftsZ transcription and conversely, increasing the concentration of CtrA decreases ftsZ transcription. Because CtrA is present in swarmer cells, is degraded at the same time as ftsZ transcription begins, and reappears when ftsZ transcription decreases at the end of the cell cycle, we propose that CtrA is a repressor of ftsZ transcription. We show that proteolysis is an important determinant of cell type-specific distribution and cell cycle variation of FtsZ. FtsZ is stable when it is synthesized and assembles into the cytokinetic ring at the beginning of the cell cycle. After the initiation of cell division, the rate of FtsZ degradation increases as both the constriction site and the FtsZ ring decrease in diameter. When ftsZ is expressed constitutively from inducible promoters, the abundance of FtsZ still varies during the cell cycle. The coupling of transcription and proteolysis to cell division ensures that FtsZ is inherited only by the progeny cell that will begin DNA replication immediately after cell division.

Dominant C-terminal deletions of FtsZ that affect its ability to localize in Caulobacter and its interaction with FtsA

The cell division protein FtsZ is composed of three regions based on sequence similarity: a highly conserved N-terminal region of approximately 320 amino acids; a variable spacer region; and a conserved C-terminal region of eight amino acids. We show that FtsZ mutants missing different C-terminal fragments have dominant lethal effects because they block cell division in Caulobacter crescentus by two different mechanisms. Removal of the C-terminal conserved region, the linker, and 40 amino acids from the end of the N-terminal conserved region (FtsZdeltaC281) prevents the localization or the polymerization of FtsZ. Because two-hybrid analysis indicates that FtsZdeltaC281 does not interact with FtsZ, we hypothesize that FtsZdeltaC281 blocks cell division by competing with a factor required for FtsZ localization or that it titrates a factor required for the stability of the FtsZ ring. The removal of 24 amino acids from the C-terminus of FtsZ (FtsZdeltaC485) causes a punctate pattern of FtsZ localization and affects its interaction with FtsA. This suggests that the conserved C-terminal region of FtsZ is required for proper polymerization of FtsZ in Caulobacter and for its interaction with FtsA.

Heterologous expression of human cholecystokinin in Saccharomyces cerevisiae. Evidence for a lysine-specific endopeptidase in the yeast secretory pathway

Precursors of the human regulatory peptide cholecystokinin (CCK) have been expressed in Saccharomyces cerevisiae, and the post-translational processing of secreted CCK-related products analyzed. Recombinant plasmids expressing native human prepro-CCK and a hybrid molecule encompassing the prepro leader of the yeast alpha-mating pheromone fused to pro-CCK were examined. The latter construct resulted in considerably higher levels of pro-CCK secretion and was therefore analyzed in more detail. Two of the protein modifications essential for CCK bioactivity, C-terminal alpha-amidation and tyrosyl sulfation, were not detected in S. cerevisiae. Proteolytic cleavage of pro-CCK occurred C-terminally of three basic sites; (i) Arg105-Arg106 which, upon exposure to carboxypeptidase activity, leads to the production of glycine-extended CCK; (ii) Arg95 to produce CCK-8 related processing intermediates; and (iii) Lys81 resulting in CCK-22 related products. To elucidate which protease(s) are involved in these endoproteolytic cleavage events, pro-CCK was expressed in yeast mutants lacking various combinations of the Mkc7, Yap3, and Kex2 proteases. Only in S. cerevisiae strains deficient in Kex2 function was any of the above mentioned pro-CCK cleavages abolished, namely processing at the Arg105-Arg106 and Arg95 sites. This suggests that mammalian Kex2-like serine proteases may process pro-CCK at single arginine residues. Our data suggests that an as yet uncharacterized endopeptidase(s) in the S. cerevisiae secretory pathway is responsible for the lysine-specific cleavage of pro-CCK.

Supercritical fluid extraction of sulphamethazine and its metabolites from meat tissues

An investigation is reported of factors affecting the supercritical fluid extraction of sulphamethazine and five of its metabolites from spiked meat (swine liver and kidney). The addition of the polar modifier methanol to the carbon dioxide extracting fluid was found to generally enhance recoveries under subcritical and supercritical conditions. Recoveries of the ionic metabolites were increased by up to 72% when employing tetramethylammonium hydroxide for ion pairing in situ with the supercritical fluid extraction. Extraction efficiency is demonstrated to be dependent on the matrix. Extractions of the less polar compounds from the kidney are more successful than from the liver, which corresponds to their partitioning into the supercritical fluid and/or the greater fraction of highly extractable fatty materials. The kidney was more retentive than liver for the relatively more polar compounds, which suggests that the liver offers a less polar environment under the same extraction conditions.

Vacuolar and extracellular maturation of Saccharomyces cerevisiae proteinase A

The vacuolar aspartyl protease proteinase A (PrA) of Saccharomyces cerevisiae is encoded as a preproenzyme by the PEP4 gene and transported to the vacuole via the secretory route. Upon arrival of the proenzyme proPrA to the vacuole, active mature 42 kDa PrA is generated by specific proteolysis involving the vacuolar endoprotease proteinase B (PrB). Vacuolar activation of proPrA can also take place in mutants lacking PrB activity (prb1). Here an active 43 kDa species termed pseudoPrA is formed, probably by an autocatalytic process. When the PEP4 gene is overexpressed in wild-type cells, mature PrA can be found in the growth medium. We have found that prb1 strains overexpressing PEP4 can form pseudoPrA extracellularly. N-terminal amino acid sequence determination of extracellular, as well as vacuolar pseudoPrA showed that it contains nine amino acids of the propeptide, indicating a cleavage between Phe67 and Ser68 of the preproenzyme. This cleavage site is in accordance with the known substrate preference for PrA, supporting the notion that pseudoPrA is formed by autoactivation. When a multicopy PEP4 transformant of a prb1 mutant was grown in the presence of the aspartyl protease inhibitor pepstatin A, a significant level of proPrA was found in the growth medium. Our analyses show that overexpression of PEP4 leads to the secretion of proPrA to the growth medium where the zymogen is converted to pseudoPrA or mature PrA in a manner similar to the vacuolar processing reactions. Amino acid sequencing of secreted proPrA confirmed the predicted cleavage by signal peptidase between Ala22 and Lys23 of the preproenzyme.

Cell cycle regulation and cell type-specific localization of the FtsZ division initiation protein in Caulobacter

Many genes involved in cell division and DNA replication and their protein products have been identified in bacteria; however, little is known about the cell cycle regulation of the intracellular concentration of these proteins. It has been shown that the level of the tubulin-like GTPase FtsZ is critical for the initiation of cell division in bacteria. We show that the concentration of FtsZ varies dramatically during the cell cycle of Caulobacter crescentus. Caulobacter produce two different cell types at each cell division: (i) a sessile stalked cell that can initiate DNA replication immediately after cell division and (ii) a motile swarmer cell in which DNA replication is blocked. After cell division, only the stalked cell contains FtsZ. FtsZ is synthesized slightly before the swarmer cells differentiate into stalked cells and the intracellular concentration of FtsZ is maximal at the beginning of cell division. Late in the cell cycle, after the completion of chromosome replication, the level of FtsZ decreases dramatically. This decrease is probably mostly due to the degradation of FtsZ in the swarmer compartment of the predivisional cell. Thus, the variation of FtsZ concentration parallels the pattern of DNA synthesis. Constitutive expression of FtsZ leads to defects in stalk biosynthesis suggesting a role for FtsZ in this developmental process in addition to its role in cell division.

Functional importance of the carboxyl tail cysteine residues in the human D1 dopamine receptor

To assess the importance of the cysteine residues Cys347 and Cys351 in the carboxylic tail in the human D1 dopamine receptor, seven mutant receptors were constructed by PCR. The pharmacological and functional properties of the wild-type and mutant receptors were assessed following transient expression in COS-7 cells. Affinities for [3H]SCH 23390 of mutant S347 (Cys347-->Gly), T348 (Tyr348-->stop), S351 (Cys351-->Gly), T351 (Cys351-->stop), T352 (Pro352-->stop), and S347/S351 (Cys347-->Gly and Cys351-->Gly) were similar to that of wild-type receptor, whereas the expression levels were reduced up to 80%. The potency of dopaminergic antagonists for these mutant receptors was very similar to that of the wild-type receptor. However, mutant T347 (Cys347-->stop) showed a 15-25-fold reduced affinity for the antagonists SCH 23390, (+)-butaclamol, and cis-flupentixol, thus not allowing radioligand analysis. Wild-type and mutant receptors responded dose-dependently with similar potency to dopamine and SKF 38393 with an increased adenylyl cyclase activity. However, mutant receptors with the Cys347 residue changed or removed displayed a diminished ability to activate adenylyl cyclase. Dopamine preexposure desensitized wild-type and mutant S351 receptors. However, mutant receptors with Cys347 replaced or the distal part of the carboxyl tail removed were unable to desensitize. Thus, Cys347 in the cytoplasmic tail of the human D1 dopamine receptor is important for the receptor in maintaining the conformation for antagonist binding, to play a crucial role in activation of adenylyl cyclase, and to be essential for agonist-induced desensitization.

C1-Cx revisited: intramolecular synergism in a cellulase

Endoglucanase A (CenA) from the bacterium Cellulomonas fimi is composed of a catalytic domain and a nonhydrolytic cellulose-binding domain that can function independently. The individual domains interact synergistically in the disruption and hydrolysis of cellulose fibers. This intramolecular synergism is distinct from the well-known intermolecular synergism between individual cellulases. The catalytic domain corresponds to the hydrolytic Cx system and the cellulose-binding domain corresponds to the nonhydrolytic C1 system postulated by Reese et al. [Reese, E. T., Sui, R. G. H. & Levinson, H. S. (1950) J. Bacteriol. 59, 485-497] to be required for the hydrolysis of cellulose.

The cellulose-binding domain of endoglucanase A (CenA) from Cellulomonas fimi: evidence for the involvement of tryptophan residues in binding

Cellulomonas fimi endo-beta-1,4-glucanase A (CenA) contains a discrete N-terminal cellulose-binding domain (CBDCenA). Related CBDs occur in at least 16 bacterial glycanases and are characterized by four highly conserved Trp residues, two of which correspond to W14 and W68 of CBDCenA. The adsorption of CBDCenA to crystalline cellulose was compared with that of two Trp mutants (W14A and W68A). The affinities of the mutant CBDs for cellulose were reduced by approximately 50- and 30-fold, respectively, relative to the wild type. Physical measurements indicated that the mutant CBDs fold normally. Fluorescence data indicated that W14 and W68 were exposed on the CBD, consistent with their participation in binding to cellobiosyl residues on the cellulose surface.

Post-translational processing of barley beta-glucan endohydrolases in the baculovirus-insect cell expression system

Two cDNAs encoding barley (1-->3,1-->4)-beta-glucanase (EC 3.2.1.73) isoenzymes EI and EII have been expressed in Spodoptera frugiperda (Sf9) cell cultures using the baculovirus AcNPV vector. Modifications to both the 5' and 3' ends of the cDNAs were required before satisfactory levels of expression were obtained. The modified cDNAs directed high levels of (1-->3,1-->4)-beta-glucanase expression in the Sf9 insect cell cultures, with yields of approximately 10 mg/liter of isoenzyme EI (expEI) and 15 mg/liter of isoenzyme EII (expEII). Amino acid sequence analyses showed that the expressed enzymes were processed correctly at their amino termini. However, affinity chromatography of the isoenzyme expEII on concanavalin-A (conA)-Sepharose indicated that, although the enzyme is glycosylated, the structures of the carbohydrate chains differ from those of the native enzyme. When a cDNA encoding the homologous barley (1-->3)-beta-glucanase (EC 3.2.1.39) isoenzyme GII was expressed in insect cells, aberrant amino-terminal processing of the nascent polypeptide was sometimes observed. The forms with incompletely removed signal peptides retained their substrate specificity, but exhibited slightly reduced catalytic efficiency, altered chromatographic behavior, and reduced stability at elevated temperatures. The results show that high levels of expression of recombinant plant proteins can be obtained in insect cells, but they emphasize the need to characterize thoroughly the products that are expressed in the heterologous insect cell system before comparisons are made with the native enzyme or with engineered enzyme mutants.

Expression of a cytomegalovirus IE-1-factor VIII cDNA hybrid gene in transgenic mice

A construct containing the 5' end of the human cytomegalovirus major immediate early gene fused to the human coagulation factor VIII cDNA was used to produce transgenic mice. Two out of five transgenic lines transcribed the construct. The expression was consistently seen in a limited number of tissues and was highest in muscle tissues. This is in contrast to the almost ubiquitous activity demonstrated in earlier studies with the IE-1 enhancer/promoter. Human factor VIII protein was detected immunochemically in muscle tissues at levels several times higher than in human plasma.

Tissue-specific expression in the salivary glands of transgenic mice

Using a DNA construct, named Lama, derived from the murine parotid secretory protein (PSP) gene, we have obtained salivary gland specific gene expression in transgenic mice. Lama is a PSP minigene and allows analysis of the PSP gene 5' regulatory region by transgenesis. We show here that the regulatory region included in Lama with 4.6 kb of 5' flanking sequence is sufficient to direct expression specifically to the salivary glands. The expression level in the parotid gland is only about one percent of the PSP mRNA level, while that of the sublingual gland is near the PSP mRNA level. This suggests significant differences in the PSP gene regulation in the two glands. In addition, Lama is a secretory expression vector in which cDNAs or genomic fragments can be inserted. We demonstrate that the Lama construct can direct the expression of a heterologous cDNA encoding the C-terminal peptide of human factor VIII to salivary glands and that the corresponding peptide is secreted into saliva.

Expression of the Cellulomonas fimi cellulase genes cex and cenA from the divergent tet promoters of transposon Tn10

A cartridge was constructed which contained the divergent tet promoters of transposon Tn10 between an exoglucanase gene (cex) and an endoglucanase gene (cenA) of Cellulomonas fimi. When carried in a broad-host-range vector, the cartridge gave expression of cex and cenA in Escherichia coli, Rhodobacter capsulatus and Klebsiella pneumoniae.

A new HindIII restriction fragment length polymorphism in the hemophilia A locus

Using a fragment of the cDNA for human coagulation factor VIII as a hybridization probe, we have detected a new polymorphic HindIII site in intron 19 of the factor VIII gene. The frequency of the minor allele is 0.30. This polymorphism shows strong linkage disequilibrium with a previously described BclI polymorphism in intron 18.

Nucleotide sequence of the 5'-terminal coding region for pre-rRNA and mature 17S rRNA in Tetrahymena thermophila rDNA

The 5'-terminus of 35S pre-rRNA and mature 17S rRNA of Tetrahymena thermophila was mapped on cloned rDNA fragments by S1 nuclease protection experiments. A single site for transcription initiation was observed when pre-rRNA prepared by three different methods was used as RNA probe. These mapping results were unambiguously confirmed by sequencing the 5'-terminal region of in vitro capped 35S pre-rRNA. DNA sequence analysis of about 520 nucleotides upstream of the transcription initiation site revealed several distinct sets of highly conserved repeat sequences. In addition, the 840 nucleotides downstream of the transcription initiation site (+ 1) was determined and shown to include the 5'-terminus of the 17S rRNA coding region at position + 647. A region surrounding the position + 195 contains an inverted repeat sequence which could be the structural basis for the recently described premature transcription termination event in this organism (Kister et al. (1983) Nucl. Acids Res. 11, 3487-3502).

The nucleotide sequence at the transcription termination site of the ribosomal RNA gene in Tetrahymena thermophila

The sequence of 415 nucleotides surrounding the transcription termination site for ribosomal RNA in Tetrahymena thermophila has been determined. The positions of the 3'-ends of mature 26S rRNA, pre-26S rRNA and 35S pre-rRNA were localized within this sequence by hybridization of the purified RNA species to be selected DNA fragments, followed by S1 nuclease treatment of the hybrid and a precise sizing of the RNA-protected DNA fragments on sequencing gels. The 35S pre-rRNA population contained molecules with two distinct 3'-ends, one of which is identical to the end of pre-26S and 26S rRNA, while the other corresponds to a position 15 nucleotides further downstream, which is assumed to be the transcription termination site. The non-coding DNA strand contains a cluster of T's at the putative termination site, and several other T clusters are found further downstream. A short inverted repeat sequence is located near the putative termination site within the transcribed region. The possible role of these structures for transcription termination is discussed.

The intervening sequence in the 26S rRNA coding region of T. thermophila is transcribed within the largest stable precursor for rRNA

We studied the transcription of the intervening sequence in the 26S rRNA coding region of the extrachromosomal rDNA molecules in the macronucleus of T. thermophila by hybridization of purified nuclear rRNA precursors or cytoplasmic 26S rRNA to purified native rDNA or specific rDNA restriction fragments. Examination of R loop hybrids in the electron microscope and analyses of S1-protected rDNA fragments in alkaline agarose gels showed that mature 26S rRNA, nuclear pre-26S rRNA and a fraction of the pre-rRNA molecules containing both the sequences for 17S and 26S rRNA all lack the region corresponding to the intervening sequence. The rest of the pre-rRNA molecules, however, hybridize in a colinear fashion to the whole coding region, and thus must contain the intervening sequence. We can conclude from these results that the intervening sequence is transcribed within the primary transcription product of the rDNA, and that the post-transcriptional removal of the intervening RNA sequence is a very early processing event in the organism.