Stakeholder-engaged process for refining the design of a clinical trial in home hospice

Background

Clinical trials in home hospice settings are important to build the evidence base for practice, but balancing the burden and benefit of clinical trial conduct for clinicians, patients, and family caregivers is challenging. A stakeholder-engaged process can help inform and refine key aspects of home hospice clinical trials. The aim of this study was to describe a stakeholder-engaged process to refine, design, and implement aspects of an educational intervention trial in home hospice, including recommendations for refining intervention content and delivery, recruitment and enrollment strategies, and content and frequency of outcome measurement.

Methods

A panel of interprofessional (1 hospice administrator, 3 nurses, 2 physicians, 2 pharmacists) and 2 former family caregiver stakeholders was systematically selected and invited to participate based on expertise, representing 2 geographically distinct hospices who were participating in the clinical trial. Teleconferences followed a predetermined procedural sequence: 1. pre-meeting materials distribution and review; 2. pre-meeting email solicitation of concerns in response to materials; 3. teleconference with structured and guided discussion; and 4. documentation and distribution of minutes for accuracy review and future meeting guidance. Discussion topics were distinct for each panel meeting. Written reflections on the stakeholder engagement process were collected from panel members to further refine our process.

Results

Five initial biweekly teleconferences resulted in recommendations for recruitment strategy, enrollment process, measurement frequency, patient inclusion, and primary care physician notification of the patient’s trial involvement. The panel continues to participate in quarterly teleconferences to review progress and unexpected questions and concerns. Panelist reflections reveal personal and professional benefit from participation.

Conclusions

An interprofessional stakeholder process is feasible and invaluable for developing home hospice intervention studies, contributing to better science, successful trial implementation, and relevant, valid outcomes.

Trial registration

Clinicaltrials.gov, NCT03972163, Registered June 3, 2019.

COmmuNity-engaged SimULation Training for Blood Pressure Control (CONSULT-BP): A study protocol

BACKGROUND

Healthcare professionals have negative implicit biases toward minority and poor patients. Few communication skills interventions target implicit bias as a factor contributing to disparities in health outcomes. We report the protocol from the COmmuNity-engaged SimULation Training for Blood Pressure Control (CONSULT-BP), a trial evaluating a novel educational and training intervention targeting graduate medical and nursing trainees that is designed to mitigate the effects of implicit bias in clinical encounters. The CONSULT-BP intervention combines knowledge acquisition, bias awareness, and practice of bias mitigating skills in simulation-based communication encounters with racially/ethnically diverse standardized patients. The trial evaluates the effect of this 3-part program on patient BP outcomes, self-reported patient medication adherence, patient-reported quality of provider communication, and trainee bias awareness.

METHODS

We are conducting a cluster randomized trial of the intervention among cohorts of internal medicine (IM), family medicine (FM), and nurse practitioner (NP) trainees at a single academic medical center. We are enrolling entire specialty cohorts of IM, FM, and NP trainees over a 3-year period, with each academic year constituting an intervention cycle. There are 3 cycles of implementation corresponding to 3 sequential academic years. Within each academic year, we randomize training times to 1 of 5 start dates using a stepped wedge design. The stepped wedge design compares outcomes within training clusters before and after the intervention, as well as across exposed and unexposed clusters. Primary outcome of blood pressure control is measured at the patient-level for patients clustered within trainees. Eligible patients for outcomes analysis are: English-speaking; non-White racial/ethnic minority; Medicaid recipient (regardless of race/ethnicity); hypertension; not have pregnancy, dementia, schizophrenia, bipolar illness, or other serious comorbidities that would interfere with hypertension self-control; not enrolled in hospice. Secondary outcomes include trainee bias awareness. A unique feature of this trial is the engagement of academic and community stakeholders to design, pilot test and implement a training program addressing healthcare.

DISCUSSION

Equipping clinicians with skills to mitigate implicit bias in clinical encounters is crucial to addressing persistent disparities in healthcare outcomes. Our novel, integrated approach may improve patient outcomes.

TRIAL REGISTRATION

NCT03375918.

PROTOCOL VERSION

1.0 (November 10, 2020).

Using whole-exome sequencing to identify inherited causes of autism

Despite significant heritability of autism spectrum disorders (ASDs), their extreme genetic heterogeneity has proven challenging for gene discovery. Studies of primarily simplex families have implicated de novo copy number changes and point mutations, but are not optimally designed to identify inherited risk alleles. We apply whole-exome sequencing (WES) to ASD families enriched for inherited causes due to consanguinity and find familial ASD associated with biallelic mutations in disease genes (AMT, PEX7, SYNE1, VPS13B, PAH, and POMGNT1). At least some of these genes show biallelic mutations in nonconsanguineous families as well. These mutations are often only partially disabling or present atypically, with patients lacking diagnostic features of the Mendelian disorders with which these genes are classically associated. Our study shows the utility of WES for identifying specific genetic conditions not clinically suspected and the importance of partial loss of gene function in ASDs.

The extracellular matrix and the cytoskeleton in heart hypertrophy and failure

Cell characteristics and phenotype depend on the nature of the extracellular matrix, the type and organization of integrins and cytoskeleton. The interactions between these components are poorly known at the myocyte level and during cardiac remodeling associated with cardiac hypertrophy and heart failure. We analyze here the nature and organization of extracellular matrix (ECM) proteins, cytoskeleton and integrins and their regulation by growth factors, such as angiotensin II, in normal myocyte growth and in pathological growth (hypertrophy) of the myocardium and heart failure.

Extracellular matrix and growth factors during heart growth

The effects of growth factors on tissue remodeling and cell differentiation depend on the nature of the extracellular matrix, the type and organization of integrins, the activation of metalloproteinases and the presence of secreted proteins associated to the matrix. These interactions are actually poorly known in the cardiovascular system. We describe here: 1) the main components of extracellular matrix within the cardiovascular system; 2) the role of integrins in the transmission of growth signals; 3) the shift in the expression of the components of the extracellular matrix (fibronectin and collagens) and the stimulation of the synthesis of metalloproteinases during normal and hypertrophic growth of the myocardium; 4) the effects of growth factors, such as Angiotensin II, Fibroblast Growth Factors (FGF), Transforming Growth Factor-beta (TGF-beta), on the synthesis of proteins of the extracellular matrix in the heart.

Effect of pressure overload on angiotensin receptor expression in the rat heart during early postnatal life

The development of cardiac hypertrophy during neonatal life and in adults implies different processes. The angiotensin II (Ang II) system is involved in the development of cardiac hypertrophy in adults, but its role in neonates remains unclear. The aim of this study was to estimate the influence of increased hemodynamic load on the developmental pattern of the AT1/AT2 receptor expression in the heart. Two-day-old rats submitted to abdominal aortic constriction (AC) or sham operation were sacrificed 2 h, and 1, 3, and 8 days after surgery. Ang II was evaluated in sera and immunohistology was performed to define the cardiac hypertrophy process. The Ang II receptor subtypes 1 and 2 were quantified at the receptor and mRNA levels by(125)I-Ang II binding and RT-PCR, respectively. Ang II content in sera increased transiently 2 h after surgery in the AC group. In sham-operated, AT1 and AT2 decreased throughout the period studied at both mRNA and receptor levels. However, the AT1 mRNA level decrease was more pronounced than that of AT2 (by 57% and 27%, respectively). AC not only prevented the postnatal decrease in AT mRNA level but resulted in an increase in AT1 mRNA 8 days after surgery (P<0.05). Besides in the AC groups, AT2 mRNA levels but not those of AT1 mRNA were linearly correlated with the left ventricular mass. At the receptor level, a significant transient (1 day after surgery) increase in both AT1 and AT2 was observed. In conclusion, our data demonstrated that imposition of pressure overload soon after birth altered the pattern of AT receptor expression.

Comparison of the effects of fetal cardiomyocyte and skeletal myoblast transplantation on postinfarction left ventricular function

OBJECTIVES

Transplantation of fetal cardiomyocytes improves function of infarcted myocardium but raises availability, immunologic, and ethical issues that justify the investigation of alternate cell types, among which skeletal myoblasts are attractive candidates.

METHODS

Myocardial infarction was created in rats by means of coronary artery ligation. One week later, the animals were reoperated on and intramyocardially injected with culture growth medium alone (controls, n = 15), fetal cardiomyocytes (5 x 10(6) cells, n = 11), or neonatal skeletal myoblasts (5 x 10(6) cells, n = 16). The injections consisted of a 150-microL volume and were made in the core of the infarct, and the animals were immunosuppressed. Left ventricular function was assessed by echocardiography immediately before transplantation and 1 month thereafter. Myoblast-transplanted hearts were then immunohistologically processed for the expression of skeletal muscle-specific embryonic myosin heavy chain and cardiac-specific connexin 43.

RESULTS

The left ventricular ejection fraction markedly increased in the fetal and myoblast groups from 39.3% +/- 3.9% to 45% +/- 3.4% (P =.086) and from 40.4% +/- 3.6% to 47.3% +/- 4.4% (P =.034), respectively, whereas it decreased in untreated animals from 40.6% +/- 4% to 36.7% +/- 2.7%. Transplanted myoblasts could be identified in all animals by the positive staining for skeletal muscle myosin. Conversely, clusters of connexin 43 were not observed on these skeletal muscle cells.

CONCLUSIONS

These results support the hypothesis that skeletal myoblasts are as effective as fetal cardiomyocytes for improving postinfarction left ventricular function. The clinical relevance of these findings is based on the possibility for skeletal myoblasts to be harvested from the patient himself.

Expression of laminin alpha2 chain during normal and pathological growth of myocardium in rat and human

OBJECTIVES

Fibrosis is a classical feature of cardiac hypertrophy. To date changes within the basal lamina during normal and pathological cardiac growth have been poorly investigated. The goal of the present study was to determine if the expression of the muscle specific subunit of merosin (laminin alpha2 chain) together with that of fibronectin (FN) is modified in the diseased human heart. Laminin alpha2 chain expression was also investigated during physiological and pathological cardiac growth in the rat.

METHODS

In ten normal human hearts and ten hearts with idiopathic dilated cardiomyopathy (IDCM), the laminin-alpha2 and FN mRNA levels were quantified by slot-blot using total RNA and the protein distribution was analysed using an immunofluorescence approach. In Wistar rats, laminin alpha2 and FN mRNA expression was analyzed using RNase protection assay (RPA) and slot-blot assays.

RESULTS

The amount of laminin alpha2 mRNA did not vary in normal and pathological human hearts whereas it was significantly decreased in renovascular hypertensive rats (-20%) P<0.05 versus normal tissue). The amount of fibronectin mRNA increased in IDMC patients (x2, P<0.05 versus normal tissue), but was unchanged in hypertensive rats. A negative correlation was found between the cardiac laminin-alpha2 level and the age of the patients whatever the cardiac status. During postnatal development in the rat, a similar decrease in cardiac laminin-alpha2 level was observed between 3 and 30 weeks of age. Finally, the immunofluorescent approach failed to detect any alteration in laminin alpha2 distribution within the human myocardium.

CONCLUSION

These data indicate that an imbalance between myocyte hypertrophy and the level of laminin-alpha2 might contribute to alterations in sarcolemmal properties, which occur during the development of cardiac hypertrophy and its transition to cardiac failure.

Thyroid hormones differentially modulate enolase isozymes during rat skeletal and cardiac muscle development

During muscle development, an isozymic transition of the glycolytic enzyme enolase occurs from the embryonic and ubiquitous alphaalpha-isoform to the muscle-specific betabeta-isoform. Here, we demonstrate a stimulatory role of thyroid hormones on these two enolase genes during rat development in hindlimb muscles and an inhibitory effect on the muscle-specific enolase gene in cardiac muscle. In hindlimb muscles the ubiquitous alpha-transcript level is diminished by hypothyroidism, starting at birth. On the contrary, the more abundant muscle-specific beta-transcript is insensitive to hypothyroidism before establishment of the functional diversification of fibers and is greatly decreased thereafter. Our data support the hypothesis of a role of thyroid hormones in coordinating the expressions of contractile proteins and metabolic enzymes during muscle development. The subcellular localization of isoenolases, established here, is not modified by hypothyroidism. Our results underline the specificity of action of thyroid hormones, which modulate differentially two isozymes in the same muscle and regulate, in opposite directions, the expression of the same gene in two different muscles.

Self-protection by cardiac myocytes against hypoxia and hyperoxia

Cardiac muscle must maintain a continuous balance between its energy supply and work performed. An important mechanism involved in achievement of this balance is cross talk via chemical signals between cardiac myocytes and the cardiac muscle vascular system. This has been demonstrated by incubating isolated cardiac myocytes in different concentrations of oxygen and then assaying the conditioned media for vasoactive substances on isolated aortic rings and small-resistance arteries. With increasing oxygen concentrations above 6%, cardiac myocytes produce increasing amounts of angiotensin I, which is converted to angiotensin II by the blood vessel. The angiotensin II stimulates vascular endothelial cells to secrete endothelin and increase vascular tone. Below 6% oxygen, cardiac myocytes secrete adenosine, which acts directly on vascular smooth muscle to block the effect of alpha-adrenergic agonists and reduce vascular tone. In an intact heart, the net effect of these 2 regulatory systems would be the maintenance of oxygen concentration within a narrow range at the cardiac myocytes. By acting as oxygen sensors, cardiac myocytes modulate vascular tone according to the needs of the myocytes and reduce potential problems of hypoxia and extensive formation of reactive oxygen species.

Vascular endothelial cell-cardiac myocyte crosstalk in achieving a balance between energy supply and energy use

In isolated perfused hearts, endothelial cells in the coronary arterial vascular system release substances that can alter the contractility of the cardiac myocytes. There are at least two different substances, one that increases and another that decreases the contractility of cardiac myocytes. The rate of release of these endothelial-derived cardioactive substances depends on the oxygen tension in the immediate vicinity of the cardiac myocytes. As the local oxygen tension increases the contractility changes in the same direction. The oxygen sensor in this regulatory system is the cardiac myocyte, which then releases substances that regulate the secretion of endothelin and a relaxant by endothelial cells. The result is a loop involving cross talk between coronary endothelial cells and cardiac myocytes to modulate cardiac contractility in accordance with the oxygen supply to the cardiac myocytes. Preliminary data suggest that the change in contractility is related to a change in structure and position of the cross bridge due to phosphorylation of a protein in the thick filament.

Cellular distribution of Ca2+ pumps and Ca2+ release channels in rat cardiac hypertrophy induced by aortic stenosis

BACKGROUND

The response of ventricular myocytes to pressure overload is heterogeneous and not spatially coordinated. We investigated whether or not the alterations in SERCA and RyR gene expression are homogeneous within the myocardium.

METHODS AND RESULTS

The cellular distribution of mRNAs and proteins encoding the 2 sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) isoforms (SERCA 2a and 2b) and 2 Ca2+ release channels (the ryanodine receptor, RyR, and the IP3 receptor, IP3R) were analyzed by in situ hybridization and immunofluorescence, respectively. Analyses were performed during early (1 and 5 days) and late (1 month) stages of cardiac hypertrophy induced in rat by thoracic aortic stenosis (AS). The results indicated that 1 and 5 days after AS, the cellular distribution of SERCA 2a and RyR2 mRNAs in right ventricle and atrium was similar to controls but the mRNA levels appeared to decrease in some areas of the left ventricle (LV). One month after AS, the distribution of SERCA 2a mRNA and protein became heterogeneous throughout the LV, whereas RyR2 mRNA and protein levels were decreased in a homogeneous manner. SERCA 2b, poorly expressed in both cardiomyocytes and vessels of controls, was increased 4-fold 1 month after AS in coronary arteries only. In both sham (Sh) and AS, SERCA 3 and IP3R mRNAs were mainly found in the vessels.

CONCLUSIONS

In severe hypertrophy, decreased accumulation of SERCA 2a was heterogeneous and not compensated by an induction of SERCA 2b in the cardiomyocytes. Decrease in RyR2 expression was more homogeneous and not compensated by an increased IP3R expression.

Can cellular transplantation improve function in doxorubicin-induced heart failure?

BACKGROUND

Transplantation of fetal cardiomyocytes has been shown to improve function of regionally infarcted myocardium, but its effects on global heart failure are still unknown.

METHODS AND RESULTS

Heart failure was induced in female mice by intraperitoneal injection of doxorubicin (2 mg/kg twice per week over 2 cycles of 2 weeks separated by a 2-week drug-free period). One week after the end of treatment, left ventricular function was assessed by transthoracic echocardiography (baseline). Animals were then randomized into 3 groups: The treated group (n = 12) received an intramyocardial injection of fetal cardiomyocytes (1 x 10(6) in 10 microL) harvested from transgenic mice expressing the gene of beta-galactosidase, the control group (n = 15) received an equivalent volume of culture medium alone, and 10 sham mice had no surgery. Two weeks and 1 month after transplantation, function was again assessed echocardiographically. At baseline, fractional shortening was not significantly different between the 3 groups. It then significantly increased in cell-treated mice at 2 weeks and 1 month after transplantation (P < 0.002 and P < 0.03 versus baseline, respectively), whereas it did not change in untreated animals. Transplanted cells could not be identified by beta-galactosidase activity or presence of Y chromosome (with 1 exception).

CONCLUSIONS

Cellular transplantation can improve function of globally failing hearts by a mechanism that might not necessarily involve the sustained presence of transplanted cells but rather the effects of cardioprotective factors released by them.

[Cellular cardiomyoplasty: state of the art, evaluation, and future possibilities]

Cellular cardiomyoplasty, or the transplantation of myogenic cells into the myocardial tissues, could emerge as a therapeutic alternative in patients with cardiac failure. It depends on several procedures: implantation of cell types, syngenic embryonic cardiomycocytes, allogenic and autogenic cardiac muscle cells. These cells carne into contact with host cardiomyocytes and could contract in a synchronous fashion. Experimental data suggests that this technique could improve global left ventricular function in the post-infarction period or in dilated cardiomyopathy even though the precise mechanism of this improvement is not fully understood. Many difficulties remain, the cell types have an oncogenic potential; syngenic foetal cells are weakly immunogenic but their use is limited by ethical and problems of supply. Therefore, auto-transplantation either of cardiomycocytes obtained by endomyocardial biopsy or of adult skeletal muscle, could be a potential clinical option.

Microvasculature in angiotensin II-dependent cardiac hypertrophy in the rat

The long-lasting effect of angiotensin II (Ang II) on the microvasculature in the rat left ventricle was studied. Immunolabeling of ventricular cryosections combined with morphometric analysis allowed us to (1) distinguish between capillaries and arterioles and (2) precisely evaluate their respective densities in the endomyocardium. Ang II-induced hypertensive cardiac hypertrophy was associated with an 18% decrease in capillary density (P<0.05) and an increase in arteriole density (+54%, P<0.001). Treatments with losartan or PD123319, the respective antagonists of the angiotensin subtype 1 and subtype 2 receptors, prevented the increase in arteriolar density, whereas only losartan, which restored normal arterial pressure, prevented changes in capillary density. Taken together, these results indicate that Ang II-induced cardiac hypertrophy was associated with capillary rarefaction and arteriolar growth, the 2 processes being independently regulated.

Cytoskeleton and mitochondrial morphology and function

It has been well established that the cytoskeleton is an essential modulator of cell morphology and motility, intracytoplasmic transport and mitosis, however cytoskeletal linkage to the organelles has not been unequivocally demonstrated. Indeed, cytoskeleton appears to be essential in determining and modulating gene phenotype as a function of cellular environment. According to recent studies, the organization of the cytoskeleton network together with associated protein(s) could be essential in regulating mitochondrial function and particularly the permeability of the mitochondrial outer membrane to ADP. The aim of this chapter is to summarize the main properties of the cytoskeletal environment of mitochondria and the possible role(s) of this network in mitochondrial function in myocytes.

Study of regulation of mitochondrial respiration in vivo. An analysis of influence of ADP diffusion and possible role of cytoskeleton

The purpose of this work was to investigate the mechanism of regulation of mitochondrial respiration in vivo in different muscles of normal rat and mice, and in transgenic mice deficient in desmin. Skinned fiber technique was used to study the mitochondrial respiration in the cells in vivo in the heart, soleus and white gastrocnemius skeletal muscles of these animals. Also, cardiomyocytes were isolated from the normal rat heart, permeabilized by saponin and the "ghost" (phantom) cardiomyocytes were produced by extraction of myosin with 800 mM KCl. Use of confocal immunofluorescent microscopy and anti-desmin antibodies showed good preservation of mitochondria and cytoskeletal system in these phantom cells. Kinetics of respiration regulation by ADP was also studied in these cells in detail before and after binding of anti-desmine antibodies with intermediate filaments. In skinned cardiac or soleus skeletal muscle fibers but not in fibers from fast twitch skeletal muscle the kinetics of mitochondrial respiration regulation by ADP was characterized by very high apparent Km (low affinity) equal to 300-400 microM, exceeding that for isolated mitochondria by factor of 25. In skinned fibers from m. soleus, partial inhibition of respiration by NaN3 did not decrease the apparent Km for ADP significantly, this excluding the possible explanation of low apparent affinity of mitochondria to ADP in these cells by its rapid consumption due to high oxidative activity and by intracellular diffusion problems. However, short treatment of fibers with trypsin decreased this constant value to 40-70 microM, confirming the earlier proposition that mitochondrial sensitivity to ADP in vivo is controlled by some cytoplasmic protein. Phantom cardiomyocytes which contain mostly mitochondria and cytoskeleton and retain the normal shape, showed also high apparent Km values for ADP. Therefore, they are probably the most suitable system for studies of cellular factors which control mitochondrial function in the cells in vivo. In these phantom cells anti-desmin antibodies did not change the kinetics of respiration regulation by ADP. However, in skinned fibers from the heart and m. soleus of transgenic desmin-deficient mice some changes in kinetics of respiration regulation by ADP were observed: in these fibers two populations of mitochondria were observed, one with usually high apparent Km for ADP and the second one with very low apparent Km for ADP. Morphological observations by electron microscopy confirmed the existence of two distinct cellular populations in the muscle cells of desmin-deficient mice. The results conform to the conclusion that the reason for observed high apparent Km for ADP in regulation of oxidative phosphorylation in heart and slow twitch skeletal muscle cells in vivo is low permeability of mitochondrial outer membrane porins but not diffusion problems of ADP into and inside the cells. Most probably, in these cells there is a protein associated with cytoskeleton, which controls the permeability of the outer mitochondrial porin pores (VDAC) for ADP. Desmin itself does not display this type of control of mitochondrial porin pores, but its absence results in appearance of cells with disorganised structure and of altered mitochondrial population probably lacking this unknown VDAC controlling protein. Thus, there may be functional connection between mitochondria, cellular structural organisation and cytoskeleton in the cells in vivo due to the existence of still unidentified protein factor(s).

Does transplantation of cardiomyocytes improve function of infarcted myocardium?

BACKGROUND

The feasibility of successfully grafting fetal cardiomyocytes into infarcted myocardium is now established, but the functional effects of such a procedure still remain elusive.

METHODS AND RESULTS

Twenty-three female rats underwent 45 minutes of coronary artery occlusion followed by 30 minutes of reperfusion. At this time point, 13 animals received intramyocardial injections of fetal cardiomyocytes (6 x 10(6) cells in 60 microL of culture medium) in the once ischemic area, whereas the 10 control rats were injected with an equivalent volume of culture medium alone. One month after transplantation, left ventricular function was assessed by two-dimensional (2D) and Doppler echocardiography using a short focus 10- to 13-MHz transducer, and a numeric acquisition of 2D images up to 65.5 frames/second. Explanted hearts were then processed for histological assessment of infarct size. The presence of male donor cells into female recipient myocardium was detected by fluorescent in situ hybridization using a deoxyribonucleic acid probe specific for Y chromosome. Cellular transplantation resulted in an improved left ventricular function, as demonstrated by significantly higher 2D ejection fraction and cardiac output (P<.02 and P<.02 versus control hearts, respectively). The histological sections of female recipient myocardium were Y-positive in all but one heart, thereby suggesting that this improvement of function was causally related to the presence of transplanted cells.

CONCLUSIONS

These data suggest that transplantation of cardiomyocytes might be an effective means of improving function of infarcted myocardium.

Trophic effect of human pericardial fluid on adult cardiac myocytes. Differential role of fibroblast growth factor-2 and factors related to ventricular hypertrophy

Pericardial fluid (PF) may contain myocardial growth factors that exert paracrine actions on cardiac myocytes. The aims of this study were (1) to investigate the effects of human PF and serum, collected from patients undergoing cardiac surgery, on the growth of cultured adult rat cardiac myocytes and (2) to relate the growth activity of both fluids to the adaptive changes in overloaded human hearts. Both PF and serum increased the rate of protein synthesis, measured by [14C]phenylalanine incorporation in adult rat cardiomyocytes (PF, +71.9 +/- 8.2% [n = 17]; serum, +14.9 +/- 6.5% [n = 13]; both P < .01 versus control medium). The effects of both PF and serum on cardiomyocyte growth correlated positively with the respective left ventricular (LV) mass. However, the magnitude of change with PF was 3-fold greater than with serum (P < .01). These trophic effects of PF were mimicked by exogenous basic fibroblast growth factor (FGF2) and inhibited by anti-FGF2 antibodies and transforming growth factor-beta (TGF-beta), suggesting a relationship to FGF2. In addition, FGF2 concentration in PF was 20 times greater than in serum. On the other hand, the LV mass-dependent trophic effect, present in both fluids, was independent of FGF2 concentration or other factors, such as angiotensin II, atrial natriuretic factor, and TGF-beta. These data suggest that FGF2 in human PF is a major determining factor in normal myocyte growth, whereas unidentified LV mass-dependent factor(s), present in both PF and serum, participates in the development of ventricular hypertrophy.

Increased expression of fibronectin isoforms after myocardial infarction in rats

Fibronectin is a known chemoattractant for several cell types which play a role in the wound healing process, like fibroblasts, endothelial cells and macrophages. In addition, fibronectin generates a scaffold to which other extracellular matrix components can attach. The possible involvement of fibronectin in the wound healing process after myocardial infarction (MI) was investigated by studying the expression of fibronectin isoforms after induction of a MI in the rat. Deposition of plasma (pFN) and cellular fibronectin (cFN) protein was determined immunohistochemically, using monoclonal antibodies specific for cFN and polyclonal anti-human total FN (tFN antibodies). Expression of the mRNAs of total cFN and the embryonic isoforms EIIIA and EIIIB was investigated, using in situ hybridization (ISH). The ratio between EIIIA containing fibronectin (EIIIA+-FN) mRNA and total cFN mRNA was determined using a semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). cFN protein was present from day 4 until day 35 after infarction and was located around the area of infarction, in the epi- and endomyocardium and in the wall of larger vessels. pFN was found in the infarcted cardiomyocytes 1 day after the induction of the MI. From day 4 on pFN protein deposition was found in the border zone of the infarction and in the wall of larger vessels. pFN immunoreactivity remained present at high levels around the area of infarction and in the vessel wall throughout the entire period of investigation (90 days). From day 35 after the infarction pFN protein was detected in cardiomyocytes of the right ventricle and septum. cFN mRNA, determined by in situ hybridization, was present in the border zone of the infarcted area as early as 1 day after MI, and its expression peaked at 4 days after MI. Four days after MI the mRNA's coding for both the embryonic isoforms EIIIA and EIIIB could also be detected in the same area. Because expression of the EIIIA isoform was more abundant than the EIIIB isoform we only determined the percentage of the EIIIIA containing isoform from total FN. EIIIA+ mRNA was elevated 1 day after MI. We conclude that various fibronectin isoforms including the embryonic isoforms accumulate in the heart after MI. This suggests that these isoforms may play a role in the wound healing process in the left ventricle of the infarcted heart.

Differential roles of AT1 and AT2 receptor subtypes in vascular trophic and phenotypic changes in response to stimulation with angiotensin II

The aim of this study was to investigate the roles of angiotensin II (Ang II) receptor subtypes 1 (AT1) and 2 (AT2) in producing vascular wall hypertrophy and qualitative changes in smooth muscle cell gene expression. Wistar rats were treated for 23 days with osmotic minipumps containing solvent and either Ang II (120 ng.kg-1.min-1) or PD123319 (30 mg.kg-1.d-1), an AT2 receptor antagonist. In addition, rats receiving solvent and either Ang II or PD123319 were given losartan, an AT1 receptor antagonist, in the drinking water (10 mg.kg-1.d-1). Vascular wall hypertrophy and smooth muscle phenotype were characterized by morphometric analysis combined with immunohistochemistry. Ang II-induced hypertension was associated with the development of medial hypertrophy of the aorta and coronary arteries accompanied by reversion of vascular smooth muscle cells (VSMCs) toward an immature phenotype, as shown by the expression of cellular fibronectin and nonmuscle myosin. Losartan treatment, which restored normal arterial pressure, prevented all these changes. PD123319 treatment, which had no effect on blood pressure, prevented only vascular hypertrophy, with no effect on VSMC phenotype. Administration of only losartan to normal rats reproduced the Ang II-induced vascular hypertrophy, with no effect on VSMC phenotype. Taken together, these results suggest that (1) the trophic effect of Ang II on VSMCs is mediated via AT2 receptor subtypes and (2) changes in VSMC phenotypes are triggered mainly through AT1 receptor subtypes.

Prognostic factors for alarm treatment

A review of the literature concerning the use of enuresis alarms highlighted the lack of standardised definitions used to define enuresis and the insufficient understanding of the working mechanisms of alarms. Although first reported in 1904, enuresis alarms were not in routine use until the 1930's. Sensors in the bed or underwear, in conjunction with audible warning devices are the most common types of alarms. The alarm success rate of approximately 75% is independent of the type of alarm and there is a low relapse rate. In predicting alarm response, studies utilizing multivariate analysis techniques are superior to univariate techniques, but no one or combination of predictor variables is currently known to predict outcome accurately enough to alter standard clinical decision making. It is imperative that definitions are standardized and that study protocols are applied uniformly to well-defined populations that have a better potential response to enuresis alarms-the best intervention currently available.

HR 720, a novel angiotensin receptor antagonist inhibits the angiotensin II-induced trophic effects, fibronectin release and fibronectin-EIIIA+ expression in rat aortic vascular smooth muscle cells in vitro

The aim of this study was to evaluate the direct trophic effects of angiotensin II (AII) on rat vascular smooth muscle cells obtained from a single cellular isolate. Cell volume, protein synthesis, fibronectin (FN) release and FN-EIIIA+ mRNA isoform expression were analyzed in parallel. The effects of HR 720, a novel AT1 angiotensin receptor antagonist with some AT2 receptor affinity, were compared with those of selective AT1 antagonist EXP 3174. Both HR 720 and EXP 3174 inhibited in a concentration-dependent manner the maximum increase in cell volume induced by 10(-9) M Sar1-All (IC50 = 0.49 x 10(-9) M and 0.79 x 10(-9) M, respectively). Maximum [3H]leucine incorporation was also achieved at 10(-9) M All. HR 720 blocked the increase in protein synthesis with potency similar to EXP 3174; the respective IC50 values were 1.04 x 10(-9) M and 1.36 x 10(-9) M. All dose-dependently increased FN release, which was also equally inhibited by about 50% with both compounds at 10(-6) M. Furthermore, All enhanced FN-EIIIA+ mRNA in rat vascular smooth muscle cells (VSMC), which indicated a modulation of FN isoform expression which was inhibited by angiotensin II antagonists. In conclusion, All induced parallel and concentration-dependent increases in cell volume, protein synthesis, FN release and FN-EIIIA+ mRNA expression in vascular smooth muscle cells. These effects appeared to be essentially mediated by AT1 receptor stimulation as indicated by the equal inhibitory effects of HR 720 and EXP 3174.

Can grafted cardiomyocytes colonize peri-infarct myocardial areas?

BACKGROUND

Cell transplantation is emerging as a potential means of improving repair of damaged organs. This preliminary study tests the feasibility of grafting allogenic cells into the border zone of a myocardial infarct (MI).

METHODS AND RESULTS

Neonatal cardiomyocytes were obtained from fetuses of female rats 20 days pregnant. They were then injected at three different sites (2 x 10(6) cells per site) into the left ventricular (LV) myocardium of control rats (n = 10) or of rats in which MI had been created by proximal occlusion of the left coronary artery (n = 10). In the latter case, injections were placed along the peri-infarct border zone. Half of each batch of cells was grown in culture to provide a control for cell morphology and viability. Six additional rats were injected with the culture medium alone. Forty-eight hours after injection, LV slices were processed for histological (hematoxylin-eosin) and immunohistological (sarcomeric alpha-actinin transplantation and laminin staining) techniques. Examination of serial sections from injected regions showed that grafted myocytes were harbored into the host LV myocardium in all control animals and at the border zone in 50% of the infarcted rats. Grafted cells were identified by their morphological characteristics and an immunohistological pattern of loose myofibrillar organization similar to that seen in cells concomitantly grown in culture. Injection of the culture medium alone had no effect but allowed us to rule out needle-related injury.

CONCLUSIONS

These initial results suggest the feasibility of transplanting allogeneic cardiomyocytes into the border zone of MI areas, a prerequisite for this approach to successfully improve the function of ischemically damaged hearts.

On the regulation of cellular energetics in health and disease

Very recent experimental data, obtained by using the permeabilized cell technique or tissue homogenates for investigation of the mechanisms of regulation of respiration in the cells in vivo, are shortly summarized. In these studies, surprisingly high values of apparent Km for ADP, exceeding that for isolated mitochondria in vitro by more than order of magnitude, were recorded for heart, slow twitch skeletal muscle, hepatocytes, brain tissue homogenates but not for fast twitch skeletal muscle. Mitochondrial swelling in the hypo-osmotic medium resulted in the sharp decrease of the value of Km for ADP in correlation with the degree of rupture of mitochondrial outer membrane, as determined by the cytochrome c test. Very similar effect was observed when trypsin was used for treatment of skinned fibers, permeabilized cells or homogenates. It is concluded that, in many but not all types of cells, the permeability of the mitochondria outer membrane for ADP is controlled by some cytoplasmic protein factor(s). Since colchicine and taxol were not found to change high values of the apparent Km for ADP, the participation of microtubular system seems to be excluded in this kind of control or respiration but studies of the roles of other cytoskeletal structures seem to be of high interest. In acute ischemia we observed rapid increase of the permeability of the mitochondrial outer membrane for ADP due to mitochondrial swelling and concomitant loss of creatine control of respiration as a result of dissociation of creatine kinase from the inner mitochondrial membrane. The extent of these damages was decreased by use of proper procedures of myocardial protection showing that outer mitochondrial membrane permeability and creatine control of respiration are valuable indices of myocardial preservation. In contrast to acute ischemia, chronic hypoxia seems to improve the cardiac cell energetics as seen from better postischemic recovery of phosphocreatine, and phosphocreatine overshoot after inotropic stimulation. In general, adaptational possibilities and pathophysiological changes in the mitochondrial outer membrane system point to the central role such a system may play in regulation of cellular energetics in vivo.

Pediatric compliance and the roles of distinct treatment characteristics, treatment attitudes, and family stress: a preliminary report

Much research and clinical practice derives from the assumption that there is a set of psychological-social variables that commonly influence medical (non)compliance. This assumption may lead to overly general strategies for managing specific illnesses in children with chronic illness. With this concern in mind, a study was made of health provider ratings of compliance, treatment attitudes, and illness-related family stress for three pediatric cohorts (N = 75, ages 8 to 20 years): boys with hemophilia (n = 31), sickle cell disease (n = 22), or asthma (n = 22). Between-group differences were found on compliance and treatment attitudes (p < .05), with patients with sickle cell demonstrating greater treatment cooperation than their counterparts and boys with hemophilia expressing more positive outlooks on medical advice and about health outcomes (Newman-Keuls test, p < .05). Positive treatment attitudes were associated with specific compliance behaviors for boys with hemophilia (p < .045) but not for other groups.

Accumulation of fetal fibronectin mRNAs after balloon denudation of rabbit arteries

BACKGROUND

Fibronectin (FN), a component of the extracellular matrix, influences cellular migration and differentiation. It is a prominent component of the extracellular matrix of normal arteries and is thought to play an important role in the pathogenesis of restenosis after angioplasty. FN exists in multiple forms that arise from a single RNA transcript that can be alternatively spliced. EIIIA- and EIIIB-containing FN mRNAs predominate in the embryo, whereas in the adult, most of the normal tissue FN lacks these domains. Since few data were available concerning pattern of expression of the different alternatively spliced forms of FN mRNA in arteries after endoluminal injury, we analyzed the expression of EIIIA and EIIIB FN isoforms at different times after experimental angioplasty.

METHODS AND RESULTS

The spatial and temporal alterations in FN expression were studied in an in vivo model of endothelial denudation in the rabbit aorta and iliac artery by a combination of immunochemistry and in situ hybridization methods. Alternatively spliced forms of FN EIIIA and EIIIB were detected in the media and the adventitia of both types of vessels 24 to 48 hours after injury. Two weeks after injury, EIIIA and EIIIB mRNAs were found to accumulate within the luminal layers of the neointima. The cellular form of FN protein was not found until 2 weeks after the injury and accumulated in the inner part of the neointima.

CONCLUSIONS

These data demonstrate that FN upregulation is an early and long-lasting process after arterial injury. These results suggest that the induction of the embryonic FN isoforms may be involved in the restenotic process that follows balloon denudation of arteries.

Fibronectin expression in the cardiovascular system

Fibronectin (FN) is a dimeric glycoprotein found in the extracellular matrix (ECM) of most tissues and serves as a bridge between cells and the interstitial collagen meshwork. It also influences diverse processes including cell growth, adhesion, migration, and wound repair. Multiple FN forms arise by the alternative splicing of a primary transcript originating from a single gene. The spatial and temporal alterations in FN expression in the cardiovascular system have been studied in vitro in cell culture and in vivo during fetal development, hypertrophy, infarction, arterial injury and aging. This review describes characteristics of FN expression in cardiovascular system: 1. the FN phenotype is regulated during development. A high FN mRNA level is related to an early cardiac organogenesis and a progressive decrease that begins at the fetal stage and continues through senescence. During cardiac ontogeny, there is a linear correlation between total FN mRNA accumulation and the relative amounts of FN-EIIIA and EIIIB RNA. This correlation is absent during cardiac growth in the adult. 2. A differential reexpression of the FN isoforms is observed in both myocardium and aorta in different models of hypertension or infarction but with different threshold and time course. Changes in total FN mRNA levels in hypertensive models vary depending on the authors. Nevertheless the differences in the expression of the fetal forms of FN mRNA observed among the various models of hypertension-induced hypertrophy indicate that the process of FN pre-mRNA splicing in the adult myocardium is specifically regulated and depends on the pathological situations and the type of cell.(ABSTRACT TRUNCATED AT 250 WORDS)

Fibronectin expression during physiological and pathological cardiac growth

Fibronectin (FN) is a dimeric glycoprotein found in the extracellular matrix of most tissues that serves as a bridge between cells and the interstitial collagen meshwork and influences diverse processes including cell growth, adhesion, migration, and wound repair. Multiple FN forms arise by the alternative splicing of a primary transcript originating from a single gene. The spatial and temporal alterations in FN expression in the myocardium has been studied in models of cardiac growth in vivo such as fetal development, and hypertrophy secondary to pressure overload. This review focuses on the differential expression of FN isoforms that are observed in different models of cardiac growth. Using a combination of qualitative and quantitative analyses it is shown that in the rat myocardium: (1) the FN phenotype is developmentally regulated, (2) the re-expression of the fetal FN isoforms is observed in different models of cardiac hypertrophy secondary to a sudden or progressive hypertension and (3) the changes in cardiac FN expression affect mostly the coronary artery smooth muscle cells.

Expression of fibronectin during rat fetal and postnatal development: an in situ hybridisation and immunohistochemical study

OBJECTIVE

Fibronectin is a protein of the extracellular matrix with numerous binding sites to the other elements of the matrix and to the cells. The aim of this study was to determine the relative importance of fibronectin isoform expression (FN-EIIIA, FN-EIIIB) during fetal and postnatal development of the rat heart.

METHODS

In situ hybridisation and immunolabelling approaches were used to describe the cellular synthesis of fibronectin and its distribution throughout the rat heart from 11 d postconception until adulthood. The distribution of fibronectin was compared to that of laminin and of alpha type III procollagen.

RESULTS

The accumulation and pattern of distribution of the major fibronectin mRNA isoforms were identical, that is, there was a progressive decrease in their accumulation as a function of time after 11 d postconception, resulting in a complete absence in the adult. The distribution of fibronectin and procollagen type III mRNAs were, however, quite distinct. At the protein level the time course of synthesis and secretion of the locally synthesised fibronectin (c-FN) did not follow fibronectin mRNA expression, the accumulation of the protein being rather poor, except just before birth, where it was found mainly in the coronary vessels.

CONCLUSIONS

During the development of the fetal rat heart fibronectin gene transcription is active and progressively decreases with age, whereas the translation of the mRNAs into their corresponding proteins is always relatively poor. If fibronectin is involved in fetal and postnatal morphogenesis of the rat myocardium, it is the plasma form (p-FN) that is most probably involved in the process of growth and differentiation of the rat heart.

Differential splicing of fibronectin pre-messenger ribonucleic acid during cardiac ontogeny and development of hypertrophy in the rat

BACKGROUND

Fibronectin, an extracellular matrix protein, exists as multiple isoforms expressed in a time- and cell-dependent manner. Since the developmental pattern of fibronectin expression has not been determined in the heart, the first issue of this study was to investigate the expression of total fibronectin mRNA as well as its isoforms during cardiac ontogeny. In adults, pressure overload induces a shift towards the fetal form of proteins expressed by either muscle or nonmuscle cardiac cells. Fetal forms of fibronectin mRNA being found in smooth and nonmuscle cardiac cells soon after imposition of pressure overload, the pattern of fibronectin expression during the development of pathological growth was analyzed to determine whether the two conditions of cardiac growth resulted in an identical pattern of fibronectin expression.

EXPERIMENTAL DESIGN

Total RNA were isolated from rat heart (a) during in utero and postnatal life and (b) at varying periods of time after imposition of a pressure overload induced by coarctation of the thoracic aorta in 25-day-old rats. Fibronectin-EIIIA+ or -EIIIB+ and total fibronectin mRNAs were quantitated by reverse transcription-polymerase chain reactions and dot-blot analysis, respectively.

RESULTS

Fibronectin mRNA, abundant in the 14-day-old fetal heart, rapidly decreased during cardiac physiologic growth (> 5-fold); no changes in the fibronectin mRNA level was observed during the development of pressure-induced cardiac hypertrophy. The percentages of fibronectin transcripts containing EIIIA or EIIIB exons, very high in the early fetal heart (> 45%), harmoniously decreased during cardiac maturation (< 12%). Aortic coarctation resulted in an early, transient (12 to 48 hours) and preferential expression of fibronectin-EIIIA+ mRNA (approximately 40%).

CONCLUSIONS

In rat heart, neither physiologic nor pressure-induced growth requires increased amounts of fibronectin mRNA but the growth conditions specifically modulated the fibronectin pre-mRNA splicing.

In situ mRNA distribution of sarco(endo)plasmic reticulum Ca(2+)-ATPase isoforms during ontogeny in the rat

The Sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) plays a crucial role in maintaining the Ca2+ homeostasis, which itself, controls various essential cellular function. The existence of several SERCA isoforms, encoded by three different genes and produced by alternative splicing of pre-mRNA transcripts, has been established by cDNA cloning. However, the temporo-spatial evolution of their expression during ontogeny was unknown. We have used in situ hybridization to determine the cellular distribution of three of these mRNA isoforms, SERCA 2a, SERCA 2b and SERCA 3 during rat ontogeny and focused our study on the cardiovascular system. We demonstrate that early in embryogenesis, SERCA 3 mRNA is highly expressed in the heart tube and is also present in the yolk sac. In 14-16 days embryos, SERCA 3 mRNA has disappeared from the heart but is expressed in the aorta and in discrete foci of the liver. Later on, its expression in the cardiovascular system is restricted to the arterial endothelium. SERCA 2a mRNA is coexpressed with SERCA 3 mRNA in the heart tube and remains expressed in the cardiomyocytes throughout life. It is transiently expressed in skeletal muscle at the onset of differentiation. In early foetal life, SERCA 2b is expressed in the mesenteric area and thereafter in all cell types at various levels. Our data indicate that (i) expression of SERCA 2b is neither tissue-specific nor developmentally regulated (ii) expression of SERCA 2a and SERCA 3 isoforms is regulated in a cell specific manner during development and suggest that the SERCA 3 gene plays a role in controlling the function of endothelial cells during vasculogenesis.

The sarco(endo)plasmic reticulum Ca(2+)-ATPase mRNA isoform, SERCA 3, is expressed in endothelial and epithelial cells in various organs

The sarco(endo)plasmic reticulum Ca(2+)-ATPase mRNA isoform, SERCA 3, was previously shown to be expressed in a great variety of muscle and non-muscle tissues [(1989) J. Biol. Chem. 264, 18568] but its cellular localization within these organs was unknown. We have used in situ hybridization and RNase protection techniques to demonstrate that SERCA 3 mRNA is expressed in specific cell types, namely the endothelial and epithelial cells.

Arterial smooth muscle cell phenotype in stroke-prone spontaneously hypertensive rats

The aim of this study was to determine the phenotype of smooth muscle cells in the arteries of chronically hypertensive animals and to analyze the effects of treatments known to increase the survival of the animal without a clear effect on its hypertensive state. Stroke-prone spontaneously hypertensive rats (SHRSP) kept on a 1% sodium drinking solution were untreated or treated with one of two diuretics, indapamide (3 mg/kg per day) or hydrochlorothiazide (20 mg/kg per day), from 6 to 13 weeks of age. Phenotype was characterized by the immunolabeling of arteries with antibodies raised against a cellular form (EIIIA) of fibronectin, alpha-smooth muscle actin, and nonmuscle myosin. We demonstrated that phenotypes of smooth muscle cells of the SHRSP differ from those found in Wistar-Kyoto rats. The difference in phenotype is specific for the vessel type: ie, an increased expression of nonmuscle myosin in the aorta and of both EIIIA fibronectin and nonmuscle myosin in the coronary arteries. The two diuretics (1) had no effect on blood pressure, (2) prevented or did not prevent the increase in medial thickness, and (3) prevented changes in both smooth muscle cell phenotype and ischemic tissular lesions. Taken together, the results suggest that in SHRSP the changes in the phenotype of smooth muscle cells and the thickness of arteries are unrelated events. We propose that the maintenance of the contractile phenotype of the arterial smooth muscle cells could be an essential parameter involved in the prevention of the deleterious consequences characteristic of a severe hypertensive state.

Alpha-, beta-MHC mRNA quantification in adult cardiomyocytes by in situhybridization: effect of thyroid hormone

Cardiac myocytes isolated from adult rats and cultured for up to 5 days in a defined serum- and 3,5,3'-triiodothyronine-(T3) free medium were processed for in situ hybridization using [35S]cRNA probes specific for alpha- or beta-myosin heavy chain (MHC) mRNAs. A computer-assisted image analysis system was used to quantitate the hybridization signals within individual myocytes (100 cells/experimental point). The method was validated by comparison with dot-blot quantitation. The mean alpha-MHC mRNA density per cell decreased by 50% (P < 0.01) after 2 days in culture and remained stable thereafter, whereas the relative amount of beta-MHC mRNA did not increase until day 5. Addition of 10(-12) M T3 to the culture medium for 2 or 3 days was sufficient to maintain alpha-MHC mRNA levels similar to the day 0 values, whereas 10(-9) M T3 was necessary to completely inhibit beta-MHC mRNA expression. The independent analysis of myocytes exhibiting different morphological phenotypes with time in culture demonstrated that rounded myocytes contain relatively more alpha-MHC mRNA and were as sensitive to T3 as their rod-shaped counterparts. Their beta-MHC RNA content was similar to that found in rod-shaped cells and was still depressed by T3. In conclusion, we show that 1) physiological doses of T3 are sufficient to maintain in vitro a MHC phenotype close to that observed in vivo in adult, 2) the dose responsiveness of adult myocytes to T3 differs from that reported in neonatal myocytes, and 3) the alpha-MHC mRNA content and the T3 sensitivity of spheroidal myocytes imply that there is no alteration in their state of maturation.

Laminin variants and integrin laminin receptors in developing and adult human smooth muscle

Distribution of laminin variant chains and of laminin-binding beta 1-associated alpha integrin subunits was studied in human arterial and visceral smooth muscle during development using the immunofluorescence method. In aortic media of 10-week-old fetuses (early fetal stage of development), B1, B2, and A chains were found, and at 27 weeks of gestation (late fetal step), in addition, the S chain was revealed. In the major part of adult aortic media, staining for the B1 chain was substituted by staining for the S chain. A reasonable explanation for this is that the basement membrane of arterial SMCs contains the A-B1-B2 laminin trimer at the early fetal stage of development, a mixture of A-B1-B2 and A-S-B2 variants during the late fetal period, and the A-S-B2 form in adult media. In the intimal thickening of adult arteries, staining for A and S chains was decreased, and the B1 chain was detected, thus suggesting coexistence of A-B1-B2 and A-S-B2 variants similar to the fetal aorta. These data led us to propose that maturation of arterial SMCs is accompanied by a switch from expression of A-B1-B2 to A-S-B2 laminin, the only protein variant associated with the differentiated SMC phenotype. The M chain was not detected in fetal and adult arterial smooth muscle. In differentiated visceral SMCs from adult colon, in contrast to arterial medial SMCs, B1, S, B2, and A chains, i.e., both B1 chain- and S chain-containing laminin molecules, were present. Similar to vascular smooth muscle, the expression of A and S laminin chains in SMCs of the intestine was developmentally regulated. Of the four beta 1-associated alpha integrin subunits that have been shown to recognize laminin (alpha 1, alpha 2, alpha 3, and alpha 6), only alpha 1 was revealed during the early fetal stage of development in smooth muscle of the arteries and digestive tract. alpha 3 appeared in aortic media only during the late fetal period. In adult arterial media and smooth muscle of the colon, alpha 1 and alpha 3 were the major potential laminin-binding integrins. The spatial-temporal distribution of laminin variants in developing and adult smooth muscle suggests that a variant laminin (possibly A-S-B2) interacting with its receptor (alpha 1 beta 1 or alpha 3 beta 1) may be important for maintenance of the differentiated SMC phenotype in vivo.

Contractile protein gene expression in serum-free cultured adult rat cardiac myocytes

The effects of two adhesion substrates (serum and laminin) and time in culture on the expression of genes encoding myosin heavy chain (MHC) isoforms and alpha-skeletal actin were analysed in myocytes isolated from adult rat heart and maintained in serum-free culture. Relative messenger ribonucleic acid (mRNA) abundances were quantitated by dot-blot analysis. Gene expression was not influenced by the substrate used. Time in culture induced a decrease in total mRNA abundance and an up-regulation of beta-MHC and alpha-skeletal actin genes. It is proposed that atrophy of adult myocytes is associated with a pattern of gene expression similar to the fetal program.

Diuretic effects on cardiac hypertrophy in the stroke prone spontaneously hypertensive rat

OBJECTIVE

The aim was to compare the effects of two diuretics, indapamide and hydrochlorothiazide, on cardiac hypertrophy in stroke prone spontaneously hypertensive rats (SHR-SP).

METHODS

Six week old SHR-SP, on a 1% sodium chloride water intake, were treated with oral indapamide (3 mg.kg-1 x d-1) or hydrochlorothiazide (20 mg.kg-1 x d-1) over a 44 d period. The hypertrophic process was evaluated by classical indices and by the morphological analysis of myocyte cross sectional area, coronary artery thickness, and immunohistochemical analysis of interstitial fibrosis.

RESULTS

In the untreated SHR-SP on 1% sodium chloride, all animals developed severe hypertension and cardiac hypertrophy when compared to normotensive salt loaded WKY by 13 weeks of age. In salt loaded SHR-SP treated with indapamide or hydrochlorothiazide, systolic blood pressure was moderately decreased by the end of the treatment when compared with untreated SHR-SP, at 259(7) and 245(7) mm Hg respectively, v 300(11) mm Hg, p < or = 0.05. Myocyte enlargement appears to be the main feature involved in the development of cardiac hypertrophy in the SHR-SP. By the end of treatment both indapamide and hydrochlorothiazide prevented the development of cardiac hypertrophy evaluated by heart weight to body weight ratio [4.69(0.07) and 4.61(0.08) respectively, v 5.39(0.13), p < or = 0.001] and myocyte hypertrophy (-33% and -21% of the SHR-SP values, p < or = 0.001). Myocardial interstitial fibrosis and perivascular fibrosis were practically absent in the two treated groups.

CONCLUSIONS

Our results allow the characterisation of SHR-SP cardiac hypertrophy and indicate that the two types of chronic diuretic treatment prevent SHR-SP cardiac hypertrophy with a drug specific efficiency.