Accessibility and Perceived Impact of a Group Psychosocial Intervention for Women in Ecuador: A Comparative Analysis by Migration Status

There is increasing guidance promoting the provision of mental health and psychosocial support programs to both migrant and host community members in humanitarian settings. However, there is a lack of information on the respective experiences and benefits for migrant and host community members who are participating in mental health and psychosocial support programming. We evaluated a community-based psychosocial program for migrant and host community women, Entre Nosotras, which was implemented with an international non-governmental organization in Ecuador in 2021. Data on participant characteristics and psychosocial wellbeing were collected via pre/post surveys with 143 participants, and qualitative interviews were conducted with a subset (n = 61) of participants. All quantitative analyses were conducted in STATA, and qualitative analysis was done in NVivo. Attendance was higher for host community members. Specifically, 71.4% of host community members attended 4-5 sessions, whereas only 37.4% of migrants attended 4-5 sessions (p = 0.004). Qualitative analysis shows that the intervention was less accessible for migrants due to a variety of structural barriers. However, this analysis also demonstrated that both groups of women felt a greater sense of social connectedness after participating in the program and expressed gratitude for the bonds they formed with other women. Some migrant women described negative experiences with the host community because they felt as though they could not confide in host community women and speak freely in front of them. These results underscore how the migratory context influences the implementation of mental health and psychosocial support (MHPSS) programs. As humanitarian guidelines continue to emphasize the integration of host community members and displaced persons, it is critical to account for how the same intervention may impact these populations differently.

Examining implementation of an intervention to reduce psychological distress and intimate partner violence in a refugee camp setting

An integrated approach to reduce intimate partner violence and improve mental health in humanitarian settings requires coordination across health and protection services. We developed and tested the Nguvu intervention, which combined evidence-based interventions for psychological distress and intimate partner violence among Congolese refugee women in Nyarugusu refugee camp (Tanzania). We conducted 29 semi-structured interviews with Nguvu participants and stakeholders to explore the relevance, acceptability, feasibility, and impact of this intervention. Participants reported that the intervention aligned with needs and filled a gap in programming, yet further adaptations may improve the fit of the intervention. The Nguvu intervention was acceptable to participants, including group discussion of sensitive topics. Confidentiality was highly regarded among staff and participants, which improved safety and acceptability. It was feasible to train non-specialist refugee workers to deliver the intervention with adequate supervision. Facilitators noted contextual challenges that made it difficult to implement the intervention: limited infrastructure, competing priorities, and population mobility. The intervention was perceived to improve awareness of the association between violence and mental health, reduce self-blame, and build skills to improve wellbeing. Recommended adaptations reveal promising, yet challenging future directions for addressing social determinants of mental health and implementing multi-sectoral programmes in complex humanitarian settings.

Evaluating the feasibility of a group psychosocial intervention for migrant and host community women in Ecuador and Panamá: protocol for a multi-site feasibility cluster trial

BACKGROUND

Community- and strengths-based psychosocial interventions are central to mental health and psychosocial support guidelines, but rigorous evidence regarding the effectiveness of these interventions is limited. The complexity and variability that is inherent to many community-based psychosocial interventions requires innovative strategies in order to facilitate the comparability and synthesis across research studies without compromising the fit and appropriateness of interventions to specific study populations and context. Entre Nosotras is a community-based psychosocial intervention developed for migrant and host community women that is designed to be flexible enough to enable integration of external intervention components and adaptable to diverse study contexts and populations. This protocol describes a study that aims to evaluate the appropriateness, acceptability, and feasibility of integrating a standardized stress management intervention into Entre Nosotras.

METHODS

This study will evaluate the appropriateness, acceptability, feasibility, and safety of intervention and research procedures for a cluster randomized comparative effectiveness trial conducted in Ecuador and Panamá with migrant and host community women. In this feasibility trial, we will allocate communities nested within the three study sites to the integrated Entre Nosotras + stress management intervention versus Entre Nosotras alone through stratified randomization. Migrant and host community women residing in these study communities who report low to moderate levels of distress will be allocated to the intervention condition that their community is assigned (n = 220 total). We will collect quantitative measures of psychosocial wellbeing, psychological distress, coping, social support, and functioning from study participants. We will collect quantitative measures of fidelity and facilitator competencies through observation and facilitator self-assessment. Data on appropriateness, acceptability, feasibility, and safety will be gathered from participants and facilitators through quantitative assessments at 0, 5, and 10 weeks post-enrollment and qualitative interviews conducted with all facilitators and a subset of 70 study participants during the post-intervention follow-up period.

DISCUSSION

Results from this feasibility trial will determine whether a multi-site cluster randomized comparative effectiveness trial of an adaptable community-based psychosocial intervention for migrant and host community women is relevant, acceptable, and feasible.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT05130944 . Registered November 23, 2021-retrospectively registered.

Multilevel Determinants of Integrated Service Delivery for Intimate Partner Violence and Mental Health in Humanitarian Settings

Inter-agency guidelines recommend that survivors of intimate partner violence in humanitarian settings receive multisectoral services consistent with a survivor-centered approach. Providing integrated services across sectors is challenging, and aspirations often fall short in practice. In this study, we explore factors that influence the implementation of a multisectoral, integrated intervention intended to reduce psychological distress and intimate partner violence in Nyarugusu Refugee Camp, Tanzania. We analyzed data from a desk review of donor, legal, and policy documents; a gender-based violence services mapping conducted through 15 interviews and 6 focus group discussions; and a qualitative process evaluation with 29 stakeholders involved in the implementation of the integrated psychosocial program. We identified the challenges of implementing a multisectoral, integrated intervention for refugee survivors of intimate partner violence at the structural, inter-institutional, intra-institutional, and in social and interpersonal levels. Key determinants of successful implementation included the legal context, financing, inter-agency coordination, engagement and ownership, and the ability to manage competing priorities. Implementing a multisectoral, integrated response for survivors of intimate partner violence is complex and influenced by interrelated factors from policy and financing to institutional and stakeholder engagement. Further investment in identifying strategies to overcome the existing challenges of implementing multisectoral approaches that align with global guidelines is needed to effectively address the burden of intimate partner violence in humanitarian settings.

Pharmacological pre- and post-conditioning with the sphingosine-1-phosphate receptor modulator FTY720 after myocardial ischaemia-reperfusion

BACKGROUND AND PURPOSE

Our recent experiments demonstrated that the Sphingosine-1-phosphate (S1P) receptor agonist FTY720 (2-amino-2-[2-(4-octylphenyl)ethyl]-1,3-propanediol hydrochloride) improves recovery of function after myocardial ischaemia-reperfusion ex vivo. Therefore, we tested the hypothesis that pharmacological post-conditioning with FTY720 reduces infarct size after myocardial ischaemia-reperfusion in vivo.

EXPERIMENTAL APPROACH

Myocardial ischaemia was induced in Wistar rats by ligation of the left coronary artery for 45 min. FTY720 (0.5 mg kg(-1)) was applied i.p. either once, before reperfusion, or twice, 24 h before myocardial ischaemia and before reperfusion. After 24 h reperfusion, we determined infarct size by triphenyltetrazolium chloride staining and granulocyte infiltration by immunohistochemistry. Tumour necrosis factor-alpha (TNF)-alpha concentration was determined by elisa. S1P receptor expression was studied by Western blot. Calcium transients were evaluated in Indo-1-loaded cardiomyocytes.

KEY RESULTS

In both groups, FTY720 significantly reduced lymphocyte count in peripheral blood. FTY720 treatment attenuated granulocyte infiltration and TNF-alpha protein expression in reperfused myocardium. However, both treatment regimens were not able to reduce infarct size. FTY720 increased mortality due to induction of fatal ventricular tachyarrhythmias when administered once before reperfusion, but protected against reperfusion arrhythmias when given 24 h prior to ischaemia. Pretreatment selectively down-regulated S1P(1) receptor expression within the myocardium. S1P receptor agonists did not induce calcium deregulation in cardiomyocytes.

CONCLUSIONS AND IMPLICATIONS

FTY720 applied during reperfusion did not reduce infarct size but increased mortality during myocardial ischaemia-reperfusion due to induction of arrhythmias. Pretreatment with FTY720 before ischaemia abrogated the deleterious pro-arrhythmic effects without reducing infarct size.

The proinflammatory cytokines TNF-alpha and IL-1 beta impair economy of contraction in human myocardium

Considerable experimental evidence has accumulated over the past years that proinflammatory cytokines, especially TNF-alpha and IL-1beta, impair myocardial function in different animal species. On the other hand, several prospective clinical trials studying TNF-alpha antagonist in patients with chronic heart failure were not able to demonstrate a benefit. As there might be a relevant species-related discrepancy, we intended to prove our previous results demonstrating impaired myocardial economy after exogenous administration of recombinant TNF-alpha in rat myocardium. In the present study, both TNF-alpha and IL-1beta not only revealed an immediate negative inotropic effect but also increased specific oxygen demand in human right-atrial myocardium. Enhanced oxygen consumption was not caused by an elevated basal metabolism but an impaired economy of contraction. Our results suggest that proinflammatory cytokines have a considerable effect on myocardial mechano-energetic parameters in human myocardium as well.

Myokardinfarkt nach Influenza-Schutzimpfung

Influenza is a common disease in the population. Influenza vaccination is performed routinely and is usually well tolerated. Minor local or systemic side effects like fever and myalgia are described. Rarely there are more severe adverse events. Systemic vasculitis has been reported in some cases. In this case we report on a female patient with secondary vasculitis and myocardial infarction after influenza vaccination. The patient received cortisol and recovered. The literature about influenza vaccination, its side effects and recommendations about vaccination in patients with coronary artery disease is reviewed.

Effects of trifluoperazine on the contraction kinetics of the isolated intact tracheal and pulmonary artery smooth muscle

BACKGROUND

We studied the effect of the calmodulin antagonist trifluoperazine (TFP) on isolated intact rat tracheal and pulmonary artery smooth muscle contractile behaviour.

METHODS

Experimental series: 1) TFP-dose-response curves for TFP's effect on force generation were constructed using rat tracheal smooth muscles and rat pulmonary artery preparations (n = 8). A concentration of 1 micromol/l TFP was chosen for the subsequent experimental series. 2) Tracheas and pulmonary arteries (n = 14) were dissected in three segments. One of them was used immediately for experiments ("native"), the other two were treated for 12 h in 4 degrees C Tyrode solution without ("12 h cold storage") or with 1 micromol/l TFP ("12 h cold storage + TFP"). These preparations contracted after supramaximal effective electrical field stimulation. The force-clamping technique was used to analyse kinetic and mechanical parameters of smooth-muscle contraction in both types of preparation (measurement conditions: resting tension 2 mN, 37 degrees C, modified Krebs-Henseleit solution).

RESULTS

1) TFP decreased developed force dose-dependently in pulmonary artery and tracheal smooth muscle. 2) During sustained tonic activation, the contraction kinetics become slower both with and without TFP treatment (p < 0.0001). 3) TFP caused a dramatic retardation of the velocity of force generation in both types of preparation for any given time interval during the course of a tonic activation (p < 0.0005). 4) The dramatic effects of TFP on the contraction kinetics were not associated with effects on the extent of force generation.

CONCLUSIONS

These results support the assumption that tracheal and pulmonary artery smooth muscle cross-bridge rates are controlled by a calcium-calmodulin-dependent myosin light chain kinase. This finding suggests the involvement of a calmodulin-independent regulator process responsible for the changes observed in the cross-bridge cycling rates during sustained tonic activation. A direct intervention on the contractile apparatus level is a measure for reduction of smooth-muscle tone without negative inotropic side effects.

Triiodothyronine reverses depressed contractile performance after excessive catecholamine stimulation

BACKGROUND

Conflicting results have been reported regarding the acute effects of triiodothyronine (T3) on myocardial contractile performance. The present study analyzes the role of T3 in reversing the depressant effect of excessive catecholamine stimulation in isolated porcine left ventricular myocardium.

METHODS

Thirty-six left ventricular trabeculae (0.4 x 6.0 mm) obtained from 6 pigs were used for measurements of isometric force development, isotonic shortening, and intracellular calcium in three experimental series (measurement conditions: 37 degrees C; optimal length; supramaximal electrical stimulation, 1 Hz; calcium measurement, fura-2 ratio method; frequency, 225 Hz). In series 1, isometric force development was measured before and after a 60-minute incubation with 10(-7) mol/L epinephrine in preparations with (n = 6) and without (n = 6) preceding fura-2 loading for calcium measurements. In series 2, the acute effects of a 30-minute administration of T3 (10(-9) mol/L) on isometric force and intracellular calcium were analyzed (n = 6). In series 3, after simultaneous fura-2 loading and a 6-hour 10(-7) mol/L epinephrine exposure the effects of T3 (10(-9) mol/L, 30 minutes) on force development, shortening, and intracellular calcium transient were analyzed.

RESULTS

Long-term and high-dose epinephrine exposure induced a severe contractile depression with a significant reduction of isometric force development (p < 0.05) and increased diastolic (p < 0.001) and systolic calcium (p < 0.001). In normal porcine myocardium T3 had no effect on the extent of isometric force generation but accelerated the time course of force development (p < 0.05) and increased the calcium transient (p < 0.001). After induction of myocardial depression by epinephrine exposure T3 accelerated the intracellular calcium transients and reduced diastolic calcium. Triiodothyronine increased the shortening amplitude and the force amplitude (p < 0.01).

CONCLUSIONS

Triiodothyronine reverses depressed contractile performance after preceding high-dose epinephrine exposure in isolated porcine myocardium. Increased force amplitudes and unaltered or even reduced intracellular calcium transients argue in favor of a resensitization of the contractile apparatus for calcium by T3. The study supports a potential role for T3 treatment in depressed myocardium after previous excessive catecholamine exposure (eg, brain death, catecholamine treatment, ischemia).

Metabolic recovery of isolated adult rat cardiomyocytes after energy depletion: existence of an ATP threshold?

The question was investigated whether cardiomyocytes can be resuscitated after extreme energy depletion, i.e. after loss of ATP >70%. Isolated ventricular cardiomyocytes of the adult rat were exposed to metabolic inhibition with dinitrophenol and cyanide (DNP 0.2 mm; KCN 2 mm). After rapid energy depletion, cells were "reoxygenated" by wash-out of DNP and KCN. Intracellular calcium, cell length, ATP and creatine phosphate (CrP) of the cardiomyocytes were monitored. Metabolic inhibition resulted in a depletion of the stores of ATP and CrP by more than 95% of the normoxic values and caused a cytosolic Ca2+ overload. Parameters of metabolic recovery were: (i) resynthesis of CrP; (ii) recovery of a normal cytosolic Ca2+ control; and (iii) the elicitation of energy-dependent hypercontracture. "Reoxygenation", i.e. wash-out of metabolic inhibitors, reactivated oxidative phosphorylation. Consecutively, CrP levels recovered to 76.0+/-7.3%, ATP levels recovered to 10. 4+/-2.3% (means+/-s.dn=10) of the initial normoxic values, a normoxic intracellular calcium level was re-established and hypercontracture was elicited. Prolongation of metabolic inhibition with KCN (2 mm) or inhibition of the Na+/K+ pump with ouabain (0.5 mm) disabled the cardiomyocytes to recover from cytosolic Ca2+ overload and prevented hypercontracture. It is concluded that even after extensive energy depletion metabolic resuscitation of the myocardial cell remains possible and a critical range of ATP for recovery, i.e. a "threshold" of a 70% loss of ATP, does not exist.

The effect of triiodothyronine on myocardial contractile performance after epinephrine exposure: implications for donor heart management

BACKGROUND

This study analyzes in the experimental model of isolated human atrial myocardium whether the myocardial contractile depression occurring after high-dose/long-term catecholamine exposure (as typically occurring in brain-dead organ donors) can be reversed by thyroid hormone administration.

METHODS

Isolated trabeculae were prepared from atrial myocardium from patients undergoing coronary artery bypass (n = 15). Initial measurements of isometric force were carried out (measurement conditions of 37 degrees C, Krebs Henseleit solution, supramaximal electrical stimulation, 1 Hz, at optimal length). Then the trabeculae were incubated for 6 hours at 26 degrees C in a Krebs Henseleit solution containing epinephrine 10(-7) mol/L and the fluorescent dye FURA-2/AM for calcium measurements. At the end of the incubation period, isometric force, isotonic shortening, and intracellular calcium transient (FURA-2 "ratio method") were measured. After 30 minutes administration of triiodothyronine (5 x 10(-9) mol/L), the measurements were repeated. Control groups included 6 hours incubation in 4 degrees C Krebs Henseleit solution (n = 5); 6 hours incubation in 26 degrees C FURA-2/AM (n = 5); and 6 hours incubation in epinephrine 10(-7) mol/L (n = 5).

RESULTS

After 6 hours catecholamine exposure isometric force declined significantly to 56.8% (p < .0001) and isotonic shortening to 54% of its initial value (p < .01). Administration of triiodothyronine was associated with a significant recovery of the isotonic shortening amplitude (p < .005), of isometric force development (p < .01), an increased velocity of force development (p < .0001), and of diastolic force decay (p < .005). At the same time the shape of the intracellular calcium transient became smaller as a result of an accelerated diastolic decay. The amplitude of the calcium transient remained unaltered, whereas the calcium time integral was reduced (p < .05).

CONCLUSION

In the model of isolated human myocardium, experimental depression of the contractile performance resulting from long-term catecholamine exposure could be reversed by a 30-minute triiodothyronine incubation. The experimental data showing increased force amplitudes at unaltered amplitudes of the intracellular calcium transient and an even-reduced calcium time integral provide strong evidence for a sensitization of the contractile apparatus for calcium by triiodothyronine. The data provide additional knowledge to explain the successful administration of triiodothyronine in donor heart management.

Length dependence of calcium- and force-transients in normal and failing human myocardium

Two questions were analysed: (1) Is the Frank-Starling mechanism operative in failing human myocardium? (2) Are length-dependent changes in force accompanied by length-dependent changes in intracellular calcium transients in human myocardium?

METHODS

(I) in electrically stimulated left-ventricular trabeculae [normal donor heart (NDH), n = 8; end stage dilated cardiomyopathy (DCM), n = 11], isometric force development was analysed as a function of muscle length (37 degrees C, oxygenated Krebs-Henseleit solution, supramaximal electrical stimulation, frequency: 1 Hz). (II) Myocardium from the same patients were loaded with the fluorescent dye FURA-2/AM for simultaneous measurements of intracellular calcium transient (ICT) and force development at different muscle lengths. Muscle length, resting force, developed force and intracellular Calcium ("ratio method") were monitored continuously.

RESULTS

(I) developed force increased up to an optimum as a function of muscle length in NDH- and DCM-myocardium. The slope of this increase was flatter in DCM-myocardium (P < 0.01). (II) In NDH- and DCM-myocardium, diastolic and systolic calcium increased significantly with muscle length. With decreasing muscle lengths the ICT became broader, the diastolic decay was retarded and the peak of the ICT was flatter. At Lmax the calcium amplitude was 23% smaller in DCM than in NDH (P < 0.04).

CONCLUSION

there is a clear length dependence of active force in DCM-myocardium. The length dependence of force development is associated with length-dependent modulations of the ICT. The flatter slope of the length-force curve in DCM may be partly explained by altered intracellular calcium handling in failing myocardium.

Contractile behaviour and intracellular calcium during afterloaded contraction in mitral valve disease

It was the aim of the present study to analyze left-ventricular contractile behaviour (force development, shortening) and intracellular calcium handling using afterloaded contractions of papillary muscle fibres from patients operated upon for mitral valve stenosis (MVS, n = 12) or mitral valve incompetence (MVI, n = 15). Isometric force development and passive resting tension at Lmax were similar in MVI and MVS (n.s.). Isotonic shortening amplitudes were reduced in MVI (p < 0.0001) compared to MVS. The peak intracellular calcium transient (ICT) preceeded the maximum force- and shortening amplitude in MVI and MVS. The amplitude of the ICT rose with decreasing afterload, became broader during shortening and presented a prolongation of the diastolic decay. Those differences were much more pronounced in MVI. The calcium-time integral (CTI) at minimal load (isotonic contraction) was 119 +/- 5% in MVS and 165 +/- 14% in MVI (p < 0.0001). The data reveal a severe diastolic calcium overload during shortening in left-ventricular MVI myocardium. An increased dissociation rate of calcium from the contractile proteins during shortening, a depressed calcium re-uptake into the sarcoplasmic reticulum during shortening, or altered mechanosensitive ion channels in MVI may be involved.

Myocardial length-force relationship in end stage dilated cardiomyopathy and normal human myocardium: analysis of intact and skinned left ventricular trabeculae obtained during 11 heart transplantations

The Frank-Starling-mechanism (FSM) was analyzed in isolated intact and skinned human left ventricular myocardium obtained from 11 heart transplantations (normal donor hearts (NDH), n = 8; dilated cardiomyopathy (DCM), n = 11). The new technique to utilize muscle strips from normal donor hearts which were actually implanted is described in detail.

METHODS

I) In electrically stimulated left ventricular trabeculae (37 degrees C, oxygenated Krebs-Henseleit solution, supramaximal electrical stimulation, frequency 1 Hz) force development was analyzed as a function of muscle length (NDH = 8; DCM = 11). II) In an additional series left ventricular myocardium was demembranized ("skinned") by Triton-X-100. At different sarcomere lengths and calcium concentrations corresponding to pCa values of 4.3, 5.5, and 8.0 force development was measured (DCM = 11; NDH = 9).

RESULTS

I) Developed force increased up to an optimum as a function of muscle length in intact NDH- and DCM-myocardium. However, the relative increment of developed force after any length step was smaller in DCM than in NDH. Near "Lmax" (muscle length associated with maximum developed force) passive resting tension was considerably elevated in DCM, indicating significantly increased diastolic stiffness. II) In skinned left ventricular DCM- and NDH-myocardium developed force depended on sarcomere length with an optimum near 2.2 microns. However, a reduction of activator calcium concentration from pCa 4.3 to pCa 5.5 produces a smaller percent decline in force at short sarcomere lengths in DCM than it does in NDH.

CONCLUSION

The present study shows that except for diastolic stiffness and a smaller relative force increment after any length step in DCM the Frank Starling mechanism is still present in isolated human left ventricular DCM- as in NDH-myocardium. The current study does not allow to decide whether in skinned myocardium the smaller percent decline in force after reduction of activator calcium concentrations in DCM is caused by an increased calcium sensitivity at short sarcomere lengths or decreased sensitivity at long sarcomere lengths.

"Cardioplegia on the contractile apparatus level": evaluation of a new concept for myocardial preservation in perfused pig hearts

The concept of a reversible desensitization of the myocardial contractile apparatus for calcium by 2,3 Butanedione Monoxime (BDM) as a method to improve the myocardium's tolerance to cold ischemia was evaluated in normal pig hearts (n = 14). The results were compared to those obtained after application of Bretschneider's HTK cardioplegic solution.

METHODS

Series I) After BDM treatment (concentrations: 0-30 mmol/L) the isometric force output and the intracellular calcium transients (measured using the FURA-2 ratio method) of electrically driven (1 Hz) isolated left-ventricular muscle strips excised from beating pig hearts (n = 14) were recorded simultaneously in order to analyse the mode of action of BDM; Series II) The cardioprotective effects of BDM (30 mmol/L) and Bretschneider's cardioplegic solution (HTK) were compared in a large-animal model: after "in situ perfusion" of pig hearts with either 2000 ml ice-cold BDM solution (30 mmol/L) (n = 7) or 2000 ml HTK (n = 7) the hearts were explanted and stored at 4 degrees C in the same solutions for up to 42 h. The contractile properties of muscle fibres, excised after storage periods of 8, 24, and 42 h from these hearts were analyzed in terms of isometric force development and isotonic shortening. 280 muscle fibres from 14 pigs were used for measurements.

RESULTS

Series I) In pig myocardium a dose-dependent reduction of isometric force development was found after BDM application. The shape and the amplitude of the intracellular calcium transient were also affected by BDM. At 30 mmol/L BDM no force development could be elicited despite the presence of an intracellular calcium transient (amplitude < 70% of the control). Series II) Shortening, calcium transient, and force of left-ventricular muscle strips of pig myocardium excised after storage periods for up to 42 h showed complete recovery when BDM was applied. In contrast HTK perfusion allowed complete recovery of these parameters when the storage period did not exceed 6 hours.

CONCLUSION

Under the given experimental conditions reversible desensitization of the contractile apparatus for calcium results in a considerable prolongation of the tolerance to cold ischemia in explanted pig hearts. The present study shows that the protective effects of BDM are not only present when isolate muscle fibres were stored (and the extracellular space is large) but also after storage of complete hearts in a solution in a solution containing BDM. Thus BDM may become a useful agent to enlarge the storage period of donor hearts in heart transplatation considerably.

Myosin light chain-actin interaction regulates cardiac contractility

The amino-terminal domain of the essential myosin light chain (MLC-1) binds to the carboxy terminus of the actin molecule. We studied the functional role of this interaction by two approaches: first, incubation of intact and chemically skinned human heart fibers with synthetic peptide corresponding to the sequences 5 through 14 (P5-14), 5 through 8 (P5-8), and 5 through 10 (P5-10) of the human ventricular MLC-1 (VLC-1) to saturate actin-binding sites, and second, incubation of skinned human heart fibers with a monoclonal antibody (MabVLC-1) raised against the actin-interacting N-terminal domain of human VLC-1 using P5-14 as antigen to deteriorate VLC-1 binding to actin. P5-14 increased isometric tension generation of skinned human heart fibers at both submaximal and maximal Ca2+ activation, the maximal effective peptide dosage being in the nanomolar range. A scrambled peptide of P5-14 with random sequence had no effects up to 10(-8) mol/L, ie, where P5-14 was maximally effective. P5-8 and P5-10 increased isometric force to the same extent as P5-14, but micromolar concentrations were required. Amplitude of isometric twitch contraction, rate of tension development, rate of relaxation, and shortening velocity at near-zero load of electrically driven intact human atrial fibers increased significantly on incubation with P5-14. These alterations were not associated with modulation of intracellular Ca2+ transients as monitored by fura 2 fluorescence measurements. Incubation of skinned human heart fibers with MabVLC-1 increased isometric tension at both submaximal and maximal Ca2+ activation levels, having a maximal effective concentration in the femtomolar range.

Intracellular calcium transient of working human myocardium of seven patients transplanted for congestive heart failure

The afterload dependence of the intracellular calcium transient in isolated working human myocardium was analyzed in both donor and recipient hearts of seven patients undergoing transplantation because of dilated cardiomyopathy. The intracellular calcium transient (recorded by the fura 2 ratio method), force development, and muscle shortening were simultaneously recorded in small (0.6 x 4.0-mm) electrically driven (60 beats per minute) trabeculas contracting at constant preload against varying afterloads. When the fibers contracted under isometric conditions, the intracellular calcium transients of normal and failing myocardium were similar. However, in dilated cardiomyopathy, stepwise afterload reduction and the concomitant increase in shortening amplitudes were associated with extraordinary alterations in the shape of the calcium transients; the amplitude rose, the time to peak was delayed, and at minimal afterloads, a long-lasting plateau was observed, and the diastolic decay was retarded. The calcium-time integral during shortening against passive resting force was 124 +/- 5% of the isometric control in normal myocardium and 172 +/- 12% in end-stage heart failure (P < .0001). We conclude that adequate interpretation of intracellular calcium transients requires simultaneous recordings of force and shortening. The extraordinary afterload dependence of the calcium transient in end-stage heart failure may be attributed to increased dissociation of calcium from the contractile proteins, a reduced calcium reuptake rate of the sarcoplasmic reticulum, or an increased calcium inflow due to altered permeabilities of the calcium channels during shortening. A potential role of mechanosensitive calcium channels has to be considered.

Reversible desensitization of the myocardial contractile apparatus for calcium. A new concept for improving tolerance to cold ischemia in human myocardium?

The influence of 2,3-Butanedione monoxime (BDM) on the human myocardium's tolerance to cold ischemia was analyzed in two experimental series.

METHODS

I) Left ventricular human muscle fibers (0.6 x 4.0 mm) were obtained from recipient hearts (n = 10) and loaded with the fluorescent dye Fura-2. Simultaneous measurements of intracellular calcium transients ("ratio-method"; excitation wave lengths: 340 nm and 380 nm) and isometric force development of electrically driven (1 Hz) muscle fibers were carried out at BDM concentrations ranging from 0 to 30 mM at a bath temperature of 37 degrees C; II) Left ventricular human muscle strips were obtained from beating recipient hearts (n = 10), and right atrial fibers from patients operated upon for aortic valve stenosis or combined mitral valve disease (n = 14). Muscle strips of these hearts were incubated for parallel measurements in the following solutions: a) a 37 degrees C oxygenated Krebs-Henseleit solution (KHS), b) a 4 degrees C Bretschneider's cardioplegic solution (HTK) without oxygenation and c) a 4 degrees C KHS containing 30 mM BDM without oxygenation (BDM solution). After standardized time intervals the muscle fibers were removed from the storage solutions, reperfused in KHS solution at 37 degrees C and stretched to optimal length (supramaximal electrical stimulation). After obtaining a steady state of force development, the contractile behavior under isometric and isotonic measurement conditions was measured. The influence of the incubation periods and the incubation solution was analyzed.

RESULTS

I) BDM reduced the isometric force development of the electrically driven isolated human myocardial muscle strip in a dose-dependent way.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased resistance against shortening in myocardium from recipient hearts of 7 patients transplanted for dilated cardiomyopathy

The contractile behaviour of demembranized atrial and ventricular myocardium of 7 patients transplanted for end-stage heart failure (ESHF) was analyzed. Atrial muscle specimens of patients undergoing coronary artery bypass surgery (n = 9) and pig papillary muscle were used as reference preparations (n = 9). Extreme care was taken for dissection and mounting the muscle fibres (0.3 x 6 mm) in order to keep the passive series compliance small. Calcium sensitivity, cross-bridge cycling rate (estimated by the force-clamping technique and calculation of the shortening velocity at zero load [Vmax]) and isometric force development were measured. Analysis on light- and electronmicroscopic level was carried out.

RESULTS

1) Calcium sensitivity was not altered in ESHF patients; 2) the velocity of the force generating process (cross-bridge cycling rate) was normal in ventricular and reduced in atrial ESHF myocardium, 3) maximum isometric force development was reduced in ventricular, but not in atrial myocardium of ESHF patients, and 4) Vmax was significantly reduced in ventricular and atrial ESHF myocardium (p < 0.0001). Perimysial and endomysial fibrosis was present in ventricular, not in atrial myocardium of ESHF patients.

CONCLUSION

A normal cross-bridge cycling rate in left-ventricular ESHF myocardium combined with a decreased capability of muscle shortening indicates the presence of a resistance against shortening localized either on the cross-bridge level or/and due to intra- and pericellular fibrosis. Left-ventricular contractile dysfunction in patients with end-stage heart failure may be related to a normal contractile apparatus contracting within an abnormal intracellular or interstitial environment.

Contractile behaviour of skinned papillary muscle in mitral valve disease

The contractile behaviour of Triton-X 100 skinned left ventricular papillary muscle from 19 patients undergoing cardiac surgery for mitral valve stenosis: n = 6, mitral valve incompetence: n = 7, or combined mitral valve disease: n = 6 was analyzed. At supramaximal activation the "vibration induced force clamping technique" was used for isometric analysis of time course and extent of isometric postvibration force recovery. Afterloaded contractions were applied for extrapolation of the maximum shortening velocity at zero load (Vmax). The Calcium sensitivity was analysed by variation of the free EGTA-buffered Calcium concentration at a passive resting force of 2 mN at 26 degrees C. In different types of mitral valve disease the characteristics of isometric force development were unaltered in terms of maximum force development, force per square mm, Calcium sensitivity and the time course of isometric contraction after force clamping. However the capability to shorten as expressed by Vmax was reduced in mitral valve incompetence (3.87 +/- 0.37 ML/s) as compared with mitral valve stenosis (5.29 +/- 0.35 ML/s) or combined mitral valve disease (4.83 +/- 0.51 ML/s). The ratio between the inverse value of Vmax and the time constant of isometric force development after force clamping was significantly different in mitral valve incompetence as compared with other types of mitral valve disease (p < 0.0001). These data argue for the presence of different resistances against shortening in various types of mitral valve disease, due to altered cross-bridge cycling characteristics or to morphological factors.