Measuring and increasing rates of self-isolation in the context of COVID-19: a systematic review with narrative synthesis.

OBJECTIVES: This study aimed to investigate (1) definitions of self-isolation used during the COVID-19 pandemic; (2) measures used to quantify adherence and their reliability, validity, and acceptability; (3) rates of self-isolation adherence; and (4) factors associated with adherence. STUDY DESIGN: This was a systematic review following Preferred Reporting Items for Systematic Reviews and Meta-Analyses and Synthesis Without Meta-analysis (PRISMA) guidelines (PROSPERO record CRD42022377820). METHODS: MEDLINE, PsycINFO, Embase, Web of Science, PsyArXiv, medRxiv, and grey literature sources were searched (1 January 2020 to 13 December 2022) using terms related to COVID-19, isolation, and adherence. Studies were included if they contained original, quantitative data of self-isolation adherence during the COVID-19 pandemic. We extracted definitions of self-isolation, measures used to quantify adherence, adherence rates, and factors associated with adherence. RESULTS: We included 45 studies. Self-isolation was inconsistently defined. Four studies did not use self-report measures. Of 41 studies using self-report, one reported reliability; another gave indirect evidence for the lack of validity of the measure. Rates of adherence to self-isolation for studies with only some concerns of bias were 51%-86% for COVID-19 cases, 78%-94% for contacts, and 16% for people with COVID-19-like symptoms. There was little evidence that self-isolation adherence was associated with sociodemographic or psychological factors. CONCLUSIONS: There was no consensus in defining, operationalising, or measuring self-isolation, resulting in significant risk of bias in included studies. Future definitions of self-isolation should state behaviours to be enacted and duration. People recommended to self-isolate should be given support. Public health campaigns should aim to increase perceived effectiveness of self-isolation and promote accurate information about susceptibility to infection.

Gait analysis of the lower limb in patients with rheumatoid arthritis: a systematic review.

INTRODUCTION: In rheumatoid arthritis (RA), signs and symptoms of feet and ankle are common. To evaluate the dynamic function of feet and ankles, namely walking, a variety of gait studies have been published. In this systematic review, we provide a systematic overview of the available gait studies in RA, give a clinimetrical assignment, and review the general conclusions regarding gait in RA. METHODS: A systematic literature search within the databases PubMed, CINAHL, sportdiscus, Embase, and Scopus was described and performed and delivered 78 original gait studies that were included for further data extraction. RESULTS: The clinimetrical quality of the 78 included RA gait studies measured according a tailored QUADAS item list and proposed clinimetrical criteria by Terwee and coworkers are moderate. General conclusions regarding the walking abnormalities of RA patients point to a slower walk, longer double support time, and avoidance of extreme positions. Frequently found static features in RA are hallux valgus, pes planovalgus, and hind foot abnormalities. CONCLUSIONS: Gait studies in RA patients show moderate clinimetrical properties, but are a challenging way of expressing walking disability. Future gait research should focus on more uniformity in methodology. When this need is satisfied, more clinical applicable conclusions can be drawn.

Magnetic resonance imaging of the rheumatic foot according to the RAMRIS system is reliable.

OBJECTIVE: In rheumatology, magnetic resonance imaging (MRI) is predominantly applied in the assessment and outcome measurement of rheumatoid arthritis (RA) in hands and wrists, leading to the development of the RAMRIS (RA-MRI-Scoring) system. It was initiated by the Outcome Measures in Rheumatoid Arthritis Clinical Trials (OMERACT). The RAMRIS system has not been applied widely in the measurement of feet. We investigated the interreader and intrareader agreement of the RAMRIS scoring system in the assessment of feet in RA. METHODS: Twenty-nine patients with RA who had radiological damage and/or arthritis underwent MRI. Two experienced readers independently read both complete sets. One reader read 6 random sets after the initial session, in order to assess the intrareader agreement. For evaluation of the intrareader and interreader reliability, quadratic-weighted κ scores were calculated per joint and lesion. RESULTS: For the forefeet, interreader scores were excellent, ranging from 0.77 (bone edema) to 0.95 (bone erosion). Hindfoot interreader agreement scores were highest for erosion (0.90) and synovitis global score (0.88), but edema and synovial thickness agreement were also acceptable (0.83 and 0.86). Intrareader scores were on the whole slightly lower, but excellent. CONCLUSION: Reliability (interreader and intrareader agreement) in the assessment of the rheumatoid foot according to the RAMRIS method is excellent.

[Optimization of sentinel lymph node biopsy in breast cancer by intraoperative axillary palpation]. / Optimización de la biopsia selectiva de ganglio centinela en el cáncer de mama mediante palpación axilar intraoperatoria.

INTRODUCTION: Sentinel node biopsy (SNB) by radioisotopes is a widely accepted and reliable surgical method for staging breast cancer in patients with unknown positive axillary lymph nodes involvement. The main limitation of this method is due to the appearance of false negatives that may be caused by tumor lymph node blockage of the sentinel lymph node and uptake in the neighboring lymph nodes. Infiltered sentinel nodes are generally increased in size and firm. Thus, they can be detected by intraoperative palpation, even when there is no uptake by the radiotracer. AIM: To reduce the false negative rates by applying intraoperative axillary palpation after SNB. METHOD: Over a two-year period, we complemented the SNB in 168 patients with careful intraoperative axillary palpation, detecting and removing all the palpable suspicious lymph nodes (SLN) that were analyzed as sentinel nodes RESULTS: In 32 out of 168 patients, 50 palpable SLN were found. In 3 out of 32 patients, 4 infiltrated SLNs were demonstrated with negative SNB and positive axillary lymphadenectomy. Thus, intraoperative palpation avoided false negative results. In one patient, one palpable SLN with tumor involvement was observed and SNB was also positive. In the remaining 28 patients, the histological analysis of 45 SLN was negative for tumor but SNB was positive in 3 patients. CONCLUSION: Intraoperative axillary palpation, once the SNB was done, reduced the false negative rate. Thus, we consider that it should be included as one more part of this procedure.

Utilización inadecuada deun Servicio de UrgenciaHospitalario / No disponible

Objetivo: Determinar la frecuencia de utilización inadecuadade un servicio de urgencias hospitalario (SUH) y elperfil del paciente.Sujetos y métodos:—Diseño: estudio descriptivo retrospectivo.—Ámbito: hospital de tercer nivel.—Sujetos: mayores de 14 años, salvo urgencias ginecoobstétricas,que acudieron a urgencias hospitalarias deenero a marzo de 2005, no precisando ni interconsultas nipruebas complementarias (PC), salvo las accesibles enAtención Primaria como glucemia capilar, análisis con tirareactiva en orina, electrocardiograma, pulsioximetría y tinciónocular con fluoresceína.—Mediciones: se calculó el tamaño muestral para unapoblación finita de 21.560 (prevalencia: 30%, precisión: 5%,pérdidas: 20%), siendo necesarios 396 informes. Selecciónaleatoria de los informes de alta. Variables: datos demográficos,día y hora, síntomas y tiempo de evolución, diagnóstico,PC y medicación.Resultados: De los 1.742 informes de alta revisados, el24,1% (IC95%: 20,04-28,16%) de las consultas fueron inadecuadas.El 70% eran menores de 45 años y un 40% menoresde 30. El día en el que se registra mayor proporción de consultasinadecuadas fue el viernes (30,61%). Un 40,7% acudióen horario de mañana, 36,8% por la tarde y el 22,5% denoche. El 81,8% vivía a menos de 10 km. Y el 86% acudió apetición propia o de un familiar.Los motivos más frecuentes fueron: traumatológicos(15,24%), digestivos (13,33%), generales (9,76%), cardiorrespiratorios(8,33%) y musculares (7,14%). En el 49 % la evoluciónera inferior a 24 horas. El 46,6% requirió medicación (41% analgésicos-antiinflamatorios, 14% benzodiacepinas,11% procinéticos, 9% fármacos inhalados, 7% corticoidessistémicos).Conclusiones: Una de cada cuatro visitas al SUH es inadecuada.Son sujetos jóvenes, que viven cerca, mayoritariamenteacuden en horario de mañana, por decisión propia ymotivos diversos (AU)

Objective: to determine the frequency of inadequate useat a hospital emergency service (HES) and the patients’ characteristics.Subjects and Method:—Design: retrospective descriptive study.—Setting: third-level hospital.—Subjects: older tan 14 years, gyneco-obstrectic emergenciesexcluded, that visited our HES from January toMarch 2005. They didn’t need consultation to other specialistsnor complementary test (CT), except those who can beused in in primary care, such as capillary glycaemia, urinarytest, electrocardiogram, oxymetry and fluorescein staining.—Measurements: the sample size was calculated consideringa limited population of 21,560 (prevalence: 30%, precision:5%, lost: 20%), being needed 396 reports. Randomselectionof all reports. Variables: demographics, date and hour,symptoms and evolution, diagnosis, CT and medication.Results: of the 1,742 reports revised, 24.1% (CI95%:20.04-28.16%) of the visits were inadequate. 70% wereyounger than 45 years old and 40% younger than 30. Themost frequent assistance day was Friday (30.61%). 40,7%came in the morning, 36.8% in the afternoon and 22.5 atnight. 83.5% lived nearer than 10 km. 86% came by theirown decision or by a family decision.They most frequent reasons were traumatic (15.24%),digestive (13.33%), generals (9.76%), cardio-respiratory(8.33%) and muscular (7.14%). In 49% the evolution wasinferior to 24 hours. A 46.6% needed medication (41%analgesic-antiinflammatory, 14% benzodiazepines, 11%procinetics, 9% inhaled drugs, 7% systemic corticosteroids). Conclussions: One of every four visits to our HES is inadequate.The patients are young, live near, come during themorning, by themselves and for different reasons (AU)

Cost-effectiveness of intensive exercise therapy directly following hospital discharge in patients with arthritis: results of a randomized controlled clinical trial.

OBJECTIVE: To estimate the cost-utility and cost-effectiveness of a 3-week intensive exercise training (IET) program directly following hospital discharge in patients with rheumatic diseases. METHODS: Patients with arthritis who were admitted to the hospital because of a disease activity flare or for elective hip or knee arthroplasty were randomly assigned to either the IET group or usual care (UC) group. Followup lasted 1 year. Quality-adjusted life years (QALYs) were derived from Short Form 6D scores and a visual analog scale (VAS) rating personal health. Function-related outcome was measured using the Health Assessment Questionnaire, the McMaster Toronto Arthritis (MACTAR) Patient Preference Disability Questionnaire, and the Escola Paulista de Medicina Range of Motion scale (EPMROM). Costs were reported from a societal perspective. Differences in costs and incremental cost-effectiveness ratios (ICERs) were estimated. RESULTS: Data from 85 patients (50 IET and 35 UC) could be used for health-economic analysis. VAS personal health-based QALYs were in favor of IET. Function-related outcome showed statistically significant improvements in favor of IET over the first 6 months, according to the MACTAR (P < 0.05) and the EPMROM (P < 0.01). At 1-year followup, IET was euro718 less per patient. The ICER showed a reduction in mean total costs per QALY. In 70% of cases the intervention was cost-saving. CONCLUSION: IET results in better quality of life at lower costs after 1 year. Thus, IET is the dominant strategy compared with UC. This highlights the need for implementation of IET after hospital discharge in patients with arthritis.

Flexor Hallucis Longus tendon rupture in RA-patients is associated with MTP 1 damage and pes planus.

BACKGROUND: To assess the prevalence of and relation between rupture or tenosynovitis of the Flexor Hallucis Longus (FHL) tendon and range of motion, deformities and joint damage of the forefoot in RA patients with foot complaints. METHODS: Thirty RA patients with painful feet were analysed, their feet were examined clinically for the presence of pes planus and range of motion (ROM), radiographs were scored looking for the presence of forefoot damage, and ultrasound examination was performed, examining the presence of tenosyovitis or rupture of the FHL at the level of the medial malleolus. The correlation between the presence or absence of the FHL and ROM, forefoot damage and pes planus was calculated. RESULTS: In 11/60(18%) of the feet, a rupture of the FHL was found. This was associated with a limited motion of the MTP1-joint, measured on the JAM (chi2 = 10.4, p = 0.034), a higher prevalence of pes planus (chi2 = 5.77, p = 0.016) and a higher prevalence of erosions proximal at the MTP-1 joint (chi2 = 12.3, p = 0.016), and joint space narrowing of the MTP1 joint (chi2 = 12.7, p = 0.013). CONCLUSION: Rupture of the flexor hallucis longus tendon in RA-patients is associated with limited range of hallux motion, more erosions and joint space narrowing of the MTP-1-joint, as well as with pes planus.

Patient-perceived satisfactory improvement (PPSI): interpreting meaningful change in pain from the patient's perspective.

The assessment of clinically meaningful changes in patient-reported pain has become increasingly important when interpreting results of clinical studies. However, proposed response criteria, such as the minimal clinically important difference, do not correspond with the growing need for information on truly meaningful, individual improvements. The aim of the present study was to investigate satisfactory improvements in pain from the patient's perspective. Data were collected in a 2-week prospective study of 181 arthritis patients treated with a local corticosteroid injection. Baseline and follow-up pain were assessed on 100mm visual analogue scales for pain intensity (VAS-PI). At baseline, patients also marked a hypothetical level on a VAS-PI representing a satisfactory improvement in pain. Patient-perceived satisfactory improvement (PPSI) was constructed using a 5-point categorical rating of change scale at follow-up as the anchor. PPSI was associated with a minimal reduction of 30mm or 55% on the VAS-PI. Since absolute change in pain associated with satisfactory improvement proved highly dependent on baseline pain, percent change scores performed better in classifying improved patients. The 55% threshold for satisfactory improvement was consistent over the course of treatment and reasonably consistent across groups of patients. Our data suggest that PPSI is a clinically relevant and stable concept for interpreting truly meaningful improvements in pain from the individual perspective.

Incremental cost-effectiveness of cyclooxygenase 2-selective versus nonselective nonsteroidal anti-inflammatory drugs in a cohort of coumarin users: a pharmacoeconomic analysis linked to a case-control study.

BACKGROUND: A previous case-control study involving concomitant users of coumarin and nonsteroidal anti-inflammatory drugs (NSAIDs) found that cyclooxygenase 2 (COX-2)-selective NSAIDs were associated with fewer bleeding complications than nonselective NSAIDs. OBJECTIVE: The goal of this study was to determine the incremental cost-effectiveness of COX-2-selective versus nonselective NSAIDs in relation to the occurrence of bleeding complications in a cohort of concomitant coumarin users. METHODS: The pharmacoeconomic evaluation was linked to a case-control analysis (patients with and without bleeding complications) based on data from the earlier study in users of concomitant coumarin and NSAIDs. Medical costs associated with NSAID use and bleeding complications were estimated according to Dutch guidelines for pharmacoeconomic analyses, based on Dutch drug prices and national averages for health care costs. Rofecoxib, meloxicam, and nabumetone were considered COX-2 selective. Total costs were calculated and compared for 2 hypothetical scenarios in which patients used either COX-2-selective or nonselective NSAIDs. Sensitivity analyses were performed in which both the odds ratios (ORs) and the costs of NSAIDs and bleeding episodes were varied. RESULTS: A total of 1,491 bleeding complications occurred in 4400 coumarin users: among the 221 (15%) NSAID users with a bleeding episode, 96% used a nonselective NSAID and 4% used a COX-2-selective NSAID. The adjusted OR of a bleeding episode for nonselective compared with COX-2-selective NSAIDs was 3.07 (95% CI, 1.18-8.03). The estimated mean cost of a bleeding episode was 478 per patient. Factoring in the excess cost of a COX-2-selective NSAID compared with a nonselective NSAID, as well as the cost savings in averted bleeding episodes, it was determined that there would be net medical cost savings of 53,800 and 162 averted bleeding episodes if the entire patient group received COX-2-selective NSAIDs rather than nonselective NSAIDs. The sensitivity analysis showed these results to be robust. CONCLUSION: In this study population of concomitant coumarin and NSAID users, the reduction in bleeding complications with the use of more expensive COX-2-selective inhibitors was associated with net medical cost savings compared with nonselective NSAIDs.

Concomitant coumarin-NSAID therapy and risk for bleeding.

OBJECTIVE: To investigate the risk of bleeding complications during the combined use of coumarin derivatives and nonsteroidal antiinflammatory drugs (NSAIDs) compared with the use of coumarin derivatives alone. SUBJECTS AND METHODS: In this 1-year observational study, the local outpatient anticoagulation office detected all coumarin users with bleeding complications. These patients were sent questionnaires regarding the type and consequences of the bleeding as well as previous NSAID use. The local pharmacists detected patients with concomitant coumarin and NSAID prescriptions (but no bleeding). The relative risk for bleeding due to concomitant coumarin and NSAID use was estimated. RESULTS: During 1 year, 738 hemorrhages were identified in 681 coumarin users. In 12.2% of these cases, an NSAID was involved. In contrast, in the whole population of coumarin users, 2.5% were prescribed an NSAID. Therefore, the relative risk of NSAID use with regard to bleeding complications was 5.8 (95% CI 2.3 to 13.6). CONCLUSIONS: NSAID use during coumarin therapy considerably increases the bleeding risk compared with coumarin therapy alone. Although in daily practice these medications are frequently prescribed concomitantly, our results underscore the contraindication of concomitant use of NSAIDs and coumarin derivatives.

[Identification of quality problems in the clinical information to hospital emergency department patients]. / Identificación de problemas de calidad en la información clínica a usuarios de un servicio de Urgencias hospitalario.

OBJECTIVES: To evaluate the comprehension level of the information provided to patients and relatives attending an emergency department and to know their satisfaction degree. METHODS: A cross-sectional descriptive study was designed. The selection of study patients was made by means of a simple randomized sampling and the total of patients was 213. At discharge, these patients and their relatives answered a written, anonymous questionnaire. To evaluate the comprehension of the information provided, the questionnaire responses were checked against the clinical records. RESULTS: The self-identification of the health care providers, information on the estimated length of stay at the ED, the explanation of complementary tests and their results significantly determined the satisfaction score on the provided information, which for the patients was 6.3 on a 10-point scale. The percentages of patients who were knowledgeable of the performed tests, diagnosis, and administered treatment were 61.5%, 50.7%, and 35.2%, respectively. Understanding the diagnosis and the administered treatment differed according to age (p < 0.001) and the assimilation of the information on recommendations at patients's discharge differed according to the education level (p < 0.05). CONCLUSIONS: The self-identification of health care personnel would allow for a better bi-directional information flow. Given the socio-cultural characteristics of our population, the information provided should be clear and concise. The transmission of information to most emergency department users would be best achieved with previous information of the workflow at the emergency department in the form of booklets at the entrance, and also establishing protocols for the informed consent on different diagnostic and treatment techniques inherent to emergency care.

Identificación de problemas de calidad en la información clínica a usuarios de un servicio de Urgencias hospitalario / Identification of quality problems in the clinical information to hospital emergency department patients

Objetivos. Valorar el nivel de asimilación de la información facilitada a los pacientes y familiares en el servicio de Urgencias y conocer el grado de satisfacción. Métodos. Se diseñó un estudio descriptivo transversal. La selección de los sujetos a estudio se realizó mediante un muestreo aleatorio simple, obteniéndose una muestra de 213 pacientes. En el momento del alta estos pacientes con sus acompañantes contestaron una encuesta escrita y anónima. Para valorar la comprensión de la información se contrastaron las respuestas del cuestionario con la historia clínica. Resultados. La presentación del médico, la información sobre el tiempo de estancia aproximado en Urgencias, la explicación de las pruebas complementarias a realizar y de los resultados de las mismas determinó significativamente la puntuación de satisfacción sobre la información ofrecida, que para los pacientes fue de 6,3 puntos sobre 10. El porcentaje de pacientes que tenía conocimiento puntual de las pruebas realizadas fue del 61,5 por ciento, del diagnóstico el 50,7 por ciento y del tratamiento administrado el 35,2 por ciento. La comprensión del diagnóstico y del tratamiento administrado fue diferente según la edad (p < 0,001), y la asimilación de la información sobre las recomendaciones al alta fue diferente según el nivel de estudios (p < 0,05).Conclusiones. La identificación del personal sanitario permitiría un mejor flujo bidireccional de la información. Dadas las características socioculturales de nuestro medio, la información debe ser clara y concisa. Para que la información se transmitiera a la mayoría de los usuarios del servicio de Urgencias sería útil la información previa sobre el funcionamiento del servicio en forma de folletos en la entrada y establecer protocolos para el consentimiento informado sobre diversas técnicas diagnósticas y de tratamiento propias de la Medicina de urgencias (AU)

Expression of slow skeletal troponin I in adult transgenic mouse heart muscle reduces the force decline observed during acidic conditions.

1. Acidosis in cardiac muscle is associated with a decrease in developed force. We hypothesized that slow skeletal troponin I (ssTnI), which is expressed in neonatal hearts, is responsible for the observed decreased response to acidic conditions. To test this hypothesis directly, we used adult transgenic (TG) mice that express ssTnI in the heart. Cardiac TnI (cTnI) was completely replaced by ssTnI either with a FLAG epitope introduced into the N-terminus (TG-ssTnI) or without the epitope (TG-ssTnI) in these mice. TG mice that express cTnI were also generated as a control TG line (TG-cTnI). Non-transgenic (NTG) littermates were used as controls. 2. We measured the force-calcium relationship in all four groups at pH 7.0 and pH 6.5 in detergent-extracted fibre bundles prepared from left ventricular papillary muscles. The force-calcium relationship was identical in fibre bundles from NTG and TG-cTnI mouse hearts, therefore NTG mice served as controls for TG-ssTnIand TG-ssTnI mice. Compared to NTG controls, the force generated by fibre bundles from TG mice expressing ssTnI was more sensitive to Ca(2+). The shift in EC(50) (the concentration of Ca(2+) at which half-maximal force is generated) caused by acidic pH was significantly smaller in fibre bundles isolated from TG hearts compared to those from NTG hearts. However, there was no difference in the force-calcium relationship between hearts from the TG-ssTnIand TG-ssTnI groups. 3. We also isolated papillary muscles from the right ventricle of NTG and TG mouse hearts expressing ssTnI and measured isometric force at extracellular pH 7.33 and pH 6.75. At acidic pH, after an initial decline, twitch force recovered to 60 +/- 3 % (n = 7) in NTG papillary muscles, 98 +/- 2 % (n = 5) in muscles from TG-ssTnIand 96 +/- 3 % (n = 7) in muscles from TG-ssTnI hearts. Our results indicate that TnI isoform composition plays a crucial role in the determination of myocardial force sensitivity to acidosis.

Localization of regions of troponin I important in deactivation of cardiac myofilaments by acidic pH.

Ca2+-activation of cardiac muscle myofilaments is more sensitive to depression by acidic pH than is the case with skeletal myofilaments. We tested the hypothesis that this difference is related to specific regions of the TnI (troponin I) isoforms in these muscles. We exchanged native Tn complex in detergent-extracted fiber bundles from mouse ventricles with Tn containing various combinations of fast (fsTnI) or slow skeletal (ssTnI) complexed with either cardiac TnC (cTnC) or fsTnC, and with cTnC complexed with the following chimeras: (1) fsTnI N-terminal region (fN) plus cTnI inhibitory peptide (cIp) and cTnI C-terminal region (cC); and (2) cTnI N-terminal region (cN)-cIp-fsTnI C-terminal region (fC). We determined the change in half maximal Ca2+(DeltaEC50) for tension activation at pH 7.0 and pH 6.5. Similar DeltaEC50 values were obtained for unextracted controls (5.53+/-0.30 microm), for preparations containing cTnI-cTnC (5.74+/-0.40 microm), and preparations exchanged with cTnI-fsTnC (5.63+/-0.40 microm). However, replacement of cTnI with fsTnI significantly decreased DeltaEC50 to 3.95+/-0.17 microm. Replacement of cTnI with ssTnI also significantly depressed DeltaEC50 to 2.07+/-0.15 microm. Results of studies using the chimeras demonstrated that the C-terminal domains of cTnI and fsTnI are responsible for these differences. This conclusion also fits with data from experiments in which we measured Ca2+-binding to the regulatory site of cTnC in binary complexes containing cTnC with cTnI, fsTnI, or the chimeras. Our results localize a region of TnI important in effects of acidosis on cardiac myofilaments and extend our earlier data indicating that C-terminal regions of cTnI outside the Ip are critical for activation by Ca2+.

Phosphorylation of troponin I by protein kinase A accelerates relaxation and crossbridge cycle kinetics in mouse ventricular muscle.

Phosphorylation of cardiac myofibrils by cAMP-dependent protein kinase (PKA) can increase the intrinsic rate of myofibrillar relaxation, which may contribute to the shortening of the cardiac twitch during beta-adrenoceptor stimulation. However, it is not known whether the acceleration of myofibrillar relaxation is due to phosphorylation of troponin I (TnI) or of myosin binding protein-C (MyBP-C). To distinguish between these possibilities, we used transgenic mice that overexpress the nonphosphorylatable, slow skeletal isoform of TnI in the myocardium and do not express the normal, phosphorylatable cardiac TNI: The intrinsic rate of relaxation of myofibrils from wild-type and transgenic mice was measured using flash photolysis of diazo-2 to rapidly decrease the [Ca(2+)] within skinned muscles from the mouse ventricles. Incubation with PKA nearly doubled the intrinsic rate of myofibrillar relaxation in muscles from wild-type mice (relaxation half-time fell from approximately 150 to approximately 90 ms at 22 degrees C) but had no effect on the relaxation rate of muscles from the transgenic mice. In parallel studies with intact muscles, we assessed crossbridge kinetics indirectly by determining f(min) (the frequency for minimum dynamic stiffness) during tetanic contractions. Stimulation of beta-adrenoceptors with isoproterenol increased f(min) from 1.9 to 3.1 Hz in muscles from wild-type mice but had no effect on f(min) in muscles from transgenic mice. We conclude that the acceleration of myofibrillar relaxation rate by PKA is due to phosphorylation of TnI, rather than MyBP-C, and that this may be due, at least in part, to faster crossbridge cycle kinetics.

Myosin isoforms in female human detrusor.

The aim of this study was to document the relative proportions of two isoforms of myosin heavy chain in detrusor smooth muscle of women with detrusor overactivity and in asymptomatic controls. Women aged 35-65 with documented detrusor overactivity and without a history of neurologic disease, prior incontinence surgery, elevated post-void residual urine volume, or indwelling urinary catheter were eligible for the study. Full-thickness biopsies of extraperitoneal bladder dome were obtained at the time of laparotomy in six patients with documented detrusor overactivity and in a control group of eight continent patients. Biopsies were frozen in liquid nitrogen, crushed with a frozen mortar and pestle at -80 degrees C, and homogenized in buffer, and the extracts were electrophoresed on 6% polyacrylamide sodium dodecyl sulfate gels and stained with Coomassie blue. The gels were de-stained and then the protein bands were scanned with a densitometer. The mean patient age was 48 years (range, 36-59). Seven patients were Caucasian and seven patients were African American. Detrusor smooth muscle contains a mean of 34% (range, 27-43%) SM1 and 66% (range, 57-73%) SM2 isoforms. There was no difference in isoform composition when patients were compared according to urogynecologic diagnosis or according to race. In detrusor biopsies from women, approximately 34% of myosin is of the SM1 isoform and approximately 66% is of the SM2 isoform. This ratio is relatively constant in the two races studied and unchanged in women with detrusor overactivity. Animal models utilizing outlet obstruction of the bladder to provoke detrusor instability and detrusor hypertrophy are known to alter myosin isoform distribution and may not be appropriate models of detrusor instability in human females.

Impaired cardiomyocyte relaxation and diastolic function in transgenic mice expressing slow skeletal troponin I in the heart.

1. To assess the specific functions of the cardiac isoform of troponin I (cTnI), we produced transgenic mice that expressed slow skeletal troponin I (ssTnI) specifically in cardiomyocytes. Cardiomyocytes from these mice displayed quantitative replacement of cTnI with transgene-encoded ssTnI. 2. The ssTnI transgenic mice were viable and fertile and did not display increased mortality or detectable cardiovascular histopathology. They exhibited normal ventricular weights and heart rates. 3. Permeabilized transgenic cardiomyocytes demonstrated an increased Ca2+ sensitivity of tension and a lack of contractile responsiveness to cAMP-dependent protein kinase (PKA). Isolated cardiomyocytes from transgenic mice had normal velocities of unloaded shortening but unlike wild-type controls exhibited no enhancement of the velocity of shortening in response to treatment with isoprenaline. Transgenic cardiomyocytes exhibited greater extents of shortening than non-transgenic cardiomyocytes at baseline and after treatment with isoprenaline. 4. The rates of rise of intracellular [Ca2+] and the peak amplitudes of the intracellular [Ca2+] transients were similar in transgenic and wild-type myocytes. However, the half-time of intracellular [Ca2+] decay was significantly greater in the transgenic myocytes. This change in decay of intracellular [Ca2+] was correlated with an increase in the re-lengthening time of the transgenic cells. 5. These changes in cardiomyocyte function in vitro were manifested in vivo as impaired diastolic function both at baseline and after stimulation with isoprenaline. 6. Thus, cTnI has important roles in regulating the Ca2+ sensitivity of cardiac myofibrils and controlling cardiomyocyte relaxation and cardiac diastolic function. cTnI is also required for the normal responsiveness of cardiomyocytes to beta-adrenergic receptor stimulation.

Interactions at the NH2-terminal interface of cardiac troponin I modulate myofilament activation.

Cardiac troponin I (cTnI) is an essential element in activation of myofilaments by Ca2+ binding to cardiac troponin C (cTnC). Yet, its role in transduction of the Ca2+ binding signal to cardiac troponin T (cTnT) and tropomyosin-actin remain poorly understood. We have recently discovered that regions of cTnI C-terminal to a previously defined inhibitory peptide are essential for full inhibitory activity and Ca(2+)-sensitivity of cardiac myofilaments (Rarick et al., 1997). However, apart from its role in structural binding to cTnC, there is little knowledge concerning the role of the N-terminus of cTnI in the activation and regulation of cardiac myofilaments. To address this question, we generated wild-type mouse cardiac TnI (WT-cTnI; 211 residues) and two N-terminal deletion mutants of mouse cTnI, cTnI54-211 (missing 53 residues), and cTnI80-211 (missing 79 residues). The cTnI54-211 mutant retained the ability to bind to cTnT, but lost the ability to bind to cTnC, whereas the cTnI80-211 mutant lost the ability to bind to cTnT, but bound weakly to cTnC. Both mutants bound to F-actin. In the absence of Ca2+, cTnI54-211 was able to inhibit the unregulated MgATPase activity of myofibrils lacking endogenous cTnI-cTnC to the same extent as WT-cTnI, whereas cTnI80-211 had some impairment of its inhibitory capability. Reconstitution with cTnI54-211/cTnC complex did not restore Ca(2+)-activation of myofibrillar MgATPase activity at all, however, the cTnI80-211/cTnC complex restored Ca(2+)-activation to nearly 50% of that obtained with WT-cTnI/cTnC. These data provide the first evidence of a significant function of a cTnT-binding domain on cTnI. They also indicate that the structural cTnC binding site on cTnI is required for Ca(2+)-dependent activation of cardiac myofilaments, and that cTnT binding to the N-terminus of cTnI is a negative regulator of activation.

Cardiac myofilament protein function is altered during sepsis.

Male Sprague-Dawley rats (350-500 g) were made septic by intraperitoneal injection of 200 mg/kg cecal material in 5% dextrose in water (D5W; 5 ml/kg). Control rats (n = 11) received D5W. Preparations were studied on days 1 (n = 7), 3 (n = 7), and 7 (n = 8) of sepsis. In isolated hearts, ventricular function was depressed on days 3 and 7 of sepsis. Densitometric analysis of myofilament proteins from septic rats separated by SDS-PAGE showed no differences in relative amounts of actin, troponin, tropomyosin and myosin light chains compared to control. Myofilament function, assessed by measuring ATPase activities, was altered during sepsis. CA(2+)-independent Mg-ATPase activity was elevated on days 1 and 3 of sepsis, returning toward control by day 7. Maximal ATPase activity was unchanged on day 1, but was increased on days 3 and 7 sepsis. Myofibrillar myosin K(EDTA)-, Ca(2+)-, and Mg(2+)-ATPase activities were not altered, nor were there any apparent changes in myosin heavy chain isoform populations. Our data are the first to demonstrate alterations in minimal and maximal ATPase activities and myofilament CA(2+)-sensitivity during chronic peritoneal sepsis. These alterations may contribute to observed changes in ventricular function.