Biological signals of cardiac hypertrophy

Chronic increases in haemodynamic load modify the expression of cardiac genes, leading to a new phenotype better adapted to the new functional demand. Several mechanisms such as the global activation of genes, the modulation of single genes and/or differential expression of multigene families may account for these modifications. Changes in gene expression of isomyosin shift are permanent and have been associated with modifications of the physiological properties of cardiac muscle. The exact cellular and molecular mechanisms which either do or do not initiate and maintain these changes in cardiac expression remain to be elucidated. Recent technical advances in cellular and molecular biology provide a foundation for understanding those cellular mechanisms that control cardiac muscle growth. This is a review of some transient changes in gene expression induced by mechanical overload such as the expression of cellular oncogenes, heat shock protein and alpha-skeletal actin genes. The biological functions of these genes are not yet precisely defined, some of them could interfere in the process of myocyte hypertrophy.

Botulinum toxin treatment of cranial-cervical dystonia, spasmodic dysphonia, other focal dystonias and hemifacial spasm

In the past five years, 477 patients with various focal dystonias and hemifacial spasm received 3,806 injections of botulinum A toxin for relief of involuntary spasms. A definite improvement with a global rating greater than or equal to 2 on a 0-4 scale, was obtained in all 13 patients with spasmodic dysphonia, 94% of 70 patients with blepharospasm, 92% of 13 patients with hemifacial spasm, 90% of 195 patients with cervical dystonia, 77% of 22 patients with hand dystonia, 73% of 45 patients with oromandibular dystonia, and in 90% of 21 patients with other focal dystonia who had adequate follow up. While the average duration of maximum improvement lasted about 11 weeks after an injection (range seven weeks in patients with hand dystonia to 15 weeks in patients with hemifacial spasm), some patients benefited for over a year. Only 16% of the 941 treatment visits with follow up were not successful. Except for transient focal weakness, there were very few complications or systemic effects attributed to the injections. This study supports the conclusion that botulinum toxin injections are a safe and effective therapy for patients with focal dystonia and hemifacial spasm.

Myocardial adaptation to creatine deficiency in rats fed with beta-guanidinopropionic acid, a creatine analogue

A creatine analogue, beta-guanidinopropionic acid (GPA), was fed to 12 young rats for several weeks. Another 12 animals were kept in the same conditions and age matched. Six pairs of animals were used to measure some energetic and mechanical parameters of the isovolumic perfused heart and to measure the accumulation of the phosphorylated form of GPA (GPAP) by 31P-nuclear magnetic resonance (NMR) spectroscopy. As a result of GPAP accumulation, phosphocreatine and ATP content decreased by 90 and 40%, respectively, and mechanical performance was impaired. Six other pairs of animals were used to assess the mechanical performances of Triton X-100-skinned fibers and the myosin isoenzyme distribution. It was found that the maximal force, Ca and ATP sensitivities, and myofibrillar creatine kinase efficacy of creatine-depleted hearts were similar to control values. There was, however, a decrease in the rate of cross-bridge cycling, and the isoenzymic expression of myosin was changed from the fast myosin V1 to the slower forms V2 and V3. In all animals, hypertrophy was observed in both right and left ventricles. We conclude that rat hearts subjected to a slow and persistent decrease in creatine and phosphocreatine respond with both quantitative and qualitative changes. These alterations, which most probably lead to an improvement in the economy of cardiac contraction, are nonetheless not sufficient to maintain maximal force.

Effect of thyroid hormone on the accumulation of mRNA for skeletal and cardiac alpha-actin in hearts from normal and hypophysectomized rats

Skeletal alpha-actin gene products are coexpressed with cardiac alpha-actins in cardiac tissue of adult humans, cows, and pigs; in prenatal rats; and during hypertrophy due either to increased hemodynamic load or the administration of alpha-adrenergic agonists. Because there is preferential synthesis of the beta-myosin heavy chain in each case, it has been suggested that the synthesis of skeletal alpha-actin in cardiac tissue is linked to that of beta-myosin heavy chain. To test this hypothesis, thyroid hormone, which causes cardiac hypertrophy with preferential synthesis of alpha-myosin heavy chain, was administered to normal and hypophysectomized rats. Animals were sacrificed from 2 to 24 hr after the injection of either 1 or 5 micrograms of hormone per 10 g of body weight. The relative amount of mRNA for skeletal and cardiac alpha-actin was measured by using the technique of primer extension. Thyroid hormone caused a rapid increase in the amount of skeletal alpha-actin mRNA relative to controls, more than 7 times in hearts from normal animals and 15 times in hearts from hypophysectomized animals. A small increase in cardiac alpha-actin mRNA also occurred. The rapid increase in transcripts for skeletal alpha-actin under conditions where the isoform of myosin heavy chain that is being synthesized is primarily alpha demonstrates independent patterns of activation of the actin and myosin heavy chain multigene families during cardiac growth in mammals.

Botulinum toxin injections for cervical dystonia

We followed 205 of 232 patients with medically intractable cervical dystonia for at least 3 months and up to 4 years, during which time they received 1,074 injections in 505 visits. One hundred forty-five of the 205 patients (71%) improved substantially (global rating greater than or equal to 2; from 0 = no response to 4 = marked improvement in severity and function) after 1 or more visits. Of the 89 patients who reported pain, 68 (76%) had almost complete relief of their pain. While most patients noted improvement within the 1st week after injection, some had a latency of up to 8.5 weeks. Duration of maximum benefit lasted up to 12.5 months in some, but the average was 11.2 weeks. Only 58 of 205 (28%) patients, seen in 76 of 505 visits (15% of all visits), had complications, primarily mild dysphagia (35 patients) or neck weakness (17 patients). We conclude that botulinum toxin is a safe and effective therapy for most patients with cervical dystonia.

Function of the sarcoplasmic reticulum and expression of its Ca2(+)-ATPase gene in pressure overload-induced cardiac hypertrophy in the rat

The reduction in Ca2+ concentration during diastole and relaxation occurs differently in normal hearts and in hypertrophied hearts secondary to pressure overload. We have studied some possible molecular mechanisms underlying these differences by examining the function of the sarcoplasmic reticulum and the expression of the gene encoding its Ca2(+)-ATPase in rat hearts with mild and severe compensatory hypertrophy induced by abdominal aortic constriction. Twelve sham-operated rats and 31 operated rats were studied 1 month after surgery. Eighteen animals exhibited mild hypertrophy (left ventricular wt/body wt less than 2.6) and 13 animals severe hypertrophy (left ventricular wt/body wt greater than 2.6). During hypertrophy we observed a decline in the function of the sarcoplasmic reticulum as assessed by the oxalate-stimulated Ca2+ uptake of homogenates of the left ventricle. Values decreased from 12.1 +/- 1.2 nmol Ca2+/mg protein/min in sham-operated rats to 9.1 +/- 1.5 and 6.7 +/- 1.1 in rats with mild and severe hypertrophy, respectively (p less than 0.001 and p less than 0.001, respectively, vs. shams). This decrease was accompanied by a parallel reduction in the number of functionally active CA2(+)-ATPase molecules, as determined by the level of Ca2(+)-dependent phosphorylated intermediate: 58.8 +/- 7.4 and 48.1 +/- 13.5 pmol P/mg protein in mild and severe hypertrophy, respectively, compared with 69.7 +/- 8.2 in shams (p less than 0.05 and p less than 0.01, respectively, vs. shams). Using S1 nuclease mapping, we observed that the Ca2(+)-ATPase messenger RNA (mRNA) from sham-operated and hypertrophied hearts was identical. Finally, the relative level of expression of the Ca2(+)-ATPase gene was studied by dot blot analysis at both the mRNA and protein levels using complementary DNA clones and a monoclonal antibody specific to the sarcoplasmic reticulum Ca2(+)-ATPase. In mild hypertrophy, the concentrations of Ca2(+)-ATPase mRNA and protein in the left ventricle were unchanged when compared with shams (mRNA, 93.8 +/- 10.6% vs. sham, NS; protein, 105.5 +/- 14% vs. sham, NS). in severe hypertrophy, the concentration of Ca2(+)-ATPase mRNA decreased to 68.7 +/- 12.9% and that of protein to 80.1 +/- 15.5% (p less than 0.001 and p less than 0.05, respectively), whereas the total amount of mRNA and enzyme per left ventricle was either unchanged or slightly increased. The slow velocity of relaxation of severely hypertrophied heart can be at least partially explained by the absence of an increase in the expression of the Ca2(+)-ATPase gene and by the relative diminution in the density of the Ca2+ pumps.(ABSTRACT TRUNCATED AT 400 WORDS)

Altered sarcoplasmic reticulum Ca2(+)-ATPase gene expression in the human ventricle during end-stage heart failure

A decrease in the myocardial level of the mRNA encoding the Ca2(+)-ATPase of the sarcoplasmic reticulum (SR) has been recently reported during experimental cardiac hypertrophy and failure. To determine if such a deficit occurs in human end-stage heart failure, we compared the SR Ca2(+)-ATPase mRNA levels in left (LV) and right ventricular (RV) specimens from 13 patients undergoing cardiac transplantation (6 idiopathic dilated cardiomyopathies; 4 coronary artery diseases with myocardial infarctions; 3 diverse etiologies) with control heart samples using a rat cardiac SR Ca2(+)-ATPase cDNA probe. We observed a marked decrease in the mRNA for the Ca2(+)-ATPase relative to both the 18S ribosomal RNA and the myosin heavy chain mRNA in LV specimens of patients with heart failure compared to controls (-48%, P less than 0.01 and -47%, P less than 0.05, respectively). The LV ratio of Ca2(+)-ATPase mRNA to 18S RNA positively correlated with cardiac index (P less than 0.02). The RV ratio correlated negatively with systolic, diastolic and mean pulmonary arterial pressures (P less than 0.02, P less than 0.02, and P less than 0.01, respectively). We suggest that a decrease of the SR Ca2(+)-ATPase mRNA in the myocardium plays an important role in alterations of Ca2+ movements and myocardial relaxation reported during human end-stage heart failure.

Atrial natriuretic factor gene expression in rat ventricle during experimental hypertension

Activation of atrial natriuretic factor (ANF) gene expression has been reported in the rat ventricle in several models of hemodynamic overload, including hypertension. However, nothing is known about the potential trigger(s) and the time course of this activation during the development of hypertension. We measured aortic blood pressure, left ventricular hypertrophy (LVH), and left ventricular ANF mRNA concentration (LV ANF mRNA) in a first group of rats (study A) killed at 5 and 18 h and 2, 4, 6, 9, 15, and 30 days after suprarenal coarctation of the abdominal aorta. Coarctation induced a progressive rise in aortic blood pressure and left ventricular mass. We observed a biphasic accumulation of ANF mRNA in the left ventricle with a peak at day 4 averaging 20 times the control value long before stable hypertension and hypertrophy were achieved, followed by a decrease until day 9. This decrease was followed by a new rise, which stabilized around 10 times the control value seen during stable hypertension and hypertrophy. In a second group of rats killed at days 4 and 30 (study B), we determined, in addition to the previous parameters, left ventricular end-diastolic pressure (LVEDP), plasma renin (PRC), and plasma ANF concentrations. LVEDP and PRC were markedly increased at day 4, but at day 30, during stable hypertension and hypertrophy, these parameters returned to control values, whereas plasma ANF was increased. Using immunocytochemistry, we looked in a third group of rats (study C) for the presence of the immunoreactive peptide at days 4 and 30.(ABSTRACT TRUNCATED AT 250 WORDS)

[Left ventricular accumulation of messenger ribonucleic acid coding for the natriuretic atrial factor in various experimental models of cardiac hypertrophy in rats]

Cardiac hypertrophy secondary to chronic hemodynamic overload is associated with an increase in the ventricular concentration of the messenger ribonucleic acid (mRNA) coding for the atrial natriuretic factor (ANF). We have compared, in male Wistar rats (10 week old, 200-220 g), using dot blot hybridization and a specific oligonucleotide probe, the left ventricular concentration of ANF mRNA (LV ANF mRNA) in 4 models of chronic hemodynamic overload inducing various patterns of left ventricular hypertrophy (LVH): a model of volume overload, the aortocaval fistula (ACF, n = 15); a model of pressure overload, coarctation of the abdominal aorta (CoA, n = 13) and 2 models of mixed overload, aortic regurgitation (AR, n = 7) and myocardial infarction (INF, n = 18). A month after surgery, LVH was 49 p. 100 for AR, 41 p. 100 for Co A and 21 p. 100 for ACF. Instead of a severe infarction, LVH was 6 p. 100 in INF demonstrating a marked hypertrophy of the non infarcted myocardium. For each model, LV ANF mRNA was compared to that in a corresponding group of sham-operated control rats and expressed as the percentage of ANF mRNA concentration in the pooled atria of the controls. In the 4 control groups LV ANF mRNA was 1 +/- 0.5 p. 100 that in the corresponding atria and the sham-operated animals were thus pooled in a single group (n = 19). In the 4 models of LVH, LV ANF mRNA markedly increased as compared to controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization and expression of the rat heart sarcoplasmic reticulum Ca2+-ATPase mRNA

Sarcoplasmic reticulum Ca2+-ATPase cDNA clones have been isolated from an adult rat heart cDNA library and the nucleotide sequence of the Ca2+-ATPase mRNA determined. The sequence has an open reading frame of 997 codons. It is identical to a cDNA isolated from a rat stomach cDNA library and 90% isologous to the rabbit and human slow/cardiac cDNAs. Nuclease S1 mapping analysis indicates that this sequence corresponds to the main Ca2+-ATPase mRNA present in heart and in slow skeletal muscle and that it is expressed in various proportions in smooth and non-muscle tissues, together with another isoform which differs from the cardiac form in the sequence of its 3'-end.

Nonsynchronous accumulation of alpha-skeletal actin and beta-myosin heavy chain mRNAs during early stages of pressure-overload--induced cardiac hypertrophy demonstrated by in situ hybridization

The development of cardiac hypertrophy secondary to pressure overload is accompanied by isoformic changes of contractile proteins such as myosin and actin. 35S-Labeled complementary RNA (cRNA) probes and in situ hybridization procedures were used for analysis of the regional distribution of newly formed transcripts from alpha-skeletal actin (alpha-sk-actin) and beta-myosin heavy chain (beta-MHC) genes during the early stages of pressure overload. The study was performed in 25-day-old rats submitted to a thoracic aortic stenosis and killed after surgery at times ranging from 4 hours to 3 days. Neither alpha-sk-actin nor beta-MHC messenger RNA (mRNA) was detected in the hearts of normal and sham-operated animals. However, alpha-sk-actin mRNA accumulated throughout the entire left ventricle as early as 4 hours after aortic stenosis, and by 12 hours was also detected in the left atrium. In contrast, beta-MHC mRNA was hardly detectable before day 1, and by days 2-3 was mainly restricted to the inner part of the left ventricle and around the coronary arteries. The absence of spatial and temporal coordination in the accumulation of alpha-sk-actin and beta-MHC mRNAs indicates that different signals and/or regulatory mechanisms are implicated in the induction of the two genes in response to hemodynamic overload.

Atrial natriuretic factor messenger ribonucleic acid and peptide in the human heart during ontogenic development

We have investigated the level of expression of the atrial natriuretic factor (ANF) gene in the human heart during ontogenic development by determining the concentrations of ANF messenger ribonucleic acid (ANF mRNA), of immunoreactive ANF (IR ANF) and of receptor reactive ANF (RR ANF), in myocardial samples of the various heart chambers. We found the level was high and almost identical in the left and right ventricles in utero. It gradually decreased during ontogenic development to reach the low adult levels, with a more rapid decrease in the right than in the left ventricle after birth. In the atria, ANF gene expression was high as early as the 13th week of gestation, was higher in the right than in the left atrium, and appeared little affected by ontogenic development.

Saccadic tracking of a periodic target motion in the cat

Cats were tested for their ability to follow a dot target which periodically jumps horizontally from side to side. They can learn to perform saccadic tracking of various stimulus frequencies, and often they produce saccades predicting the target displacements. The preferred stimulus frequency for response to synchronize was in the 0.5-Hz range. Cats tend to undershoot the target. They also tend to adopt a strategy of locking predominantly to one direction of displacement, but they can be trained to reverse this preferred side or to lock to both sides. Saccades to the preferred side are more accurate, and longer and slower in comparison to saccades to the other side, thus demonstrating a velocity-accuracy trade-off phenomenon in the cat responses. Saccadic characteristics as expressed by the main sequence are apparently a stable property independent of the stimulus frequency.

Comparison of Sinemet CR4 and standard Sinemet: double blind and long-term open trial in parkinsonian patients with fluctuations

"Wearing-off" effect, the most common form of levodopa-induced fluctuations, seems to be related to the short plasma half-life of the drug. More sustained plasma levodopa levels may be achieved with a new controlled-release formulation of carbidopa/levodopa, Sinemet CR4. We studied 20 patients, 12 men and 8 women, with Parkinson's disease complicated by "wearing-off" phenomenon. Mean age was 61.1 +/- 8.1 years, duration of symptoms 8.3 +/- 2.4 years, and the Hoehn-Yahr stage 3.0 +/- 0.9. In a 12-week double-blind study, the average number of tablets administered per day decreased from 5.7 +/- 1.2 to 3.8 +/- 0.7 when Sinemet CR4 (50/200) was substituted for the standard Sinemet (25/100) (p less than 0.001). However, this was at the expense of reducing the "on" time (without dyskinesia) from 9.3 +/- 4.6 to 7.5 +/- 4.3 (p less than 0.05), although the total "on" time did not significantly change. In a long-term follow-up of 18 patients, the "on" time with dyskinesia and morning dystonia significantly increased (p less than 0.05). There was no significant change in the total daily dosage of levodopa, but the daily number of doses and tablets significantly decreased (p less than 0.001). Despite increased dyskinesia, most patients preferred taking fewer tablets and have elected to continue taking Sinemet CR4 instead of standard Sinemet. Sinemet CR4 seems to offer a new and effective strategy for the management of levodopa-related fluctuations.

Characterization of the atrial natriuretic peptide clearance receptor using a vaccinia virus expression vector

A recombinant vaccinia virus has been used to direct the expression of the atrial natriuretic peptide clearance receptor (ANP C-receptor) in mammalian cell lines normally deficient in this protein. The recombinant receptor binds 125I-ANP-(102-126) in a specific and saturable manner and carboxyl-terminal truncated and internal-deleted ANP analogs bind to this site with high affinity. Following the covalent attachment of 125I-ANP-(102-126) to the recombinant ANP C-receptor, the protein exhibits an electrophoretic mobility identical to that of the native ANP C-receptor of cultured vascular cells. Expression of the ANP C-receptor in heterologous cells does not affect ANP-stimulated cyclic GMP accumulation, confirming previous reports that this novel ANP receptor subpopulation is not coupled to cyclic GMP metabolism. Furthermore, specific antisera, generated by inoculating rabbits with living recombinant virus, block 125I-ANP binding to the ANP C-receptor but do not inhibit ANP stimulation of cyclic GMP, supporting the existence of two receptor subpopulations that are functionally and immunologically distinct.

D-amino acid-substituted atrial natriuretic peptide analogs reveal novel receptor recognition requirements

The introduction of D-amino acid residues into peptide hormones has been traditionally utilized in structure-activity studies to probe the conformational requirements of ligand-receptor interactions. A study was undertaken to examine the effect of D-amino acid substitutions into the atrial natriuretic peptide molecule on interactions with distinct subpopulations of specific membrane-associated receptors of bovine aortic smooth muscle cells. Competitive binding analysis revealed that each of 15 synthetic D-amino acid-substituted analogs showed comparable affinities for C-ANP receptors, a class of specific receptors which have been proposed to mediate the sequestration and metabolic clearance of ANP. The relative affinities of all 15 analogs did not differ more than 10-fold. In contrast, the interaction of the ANP analogs with a second receptor pool (B-ANP receptors), which is coupled to the stimulation of particulate guanylate cyclase, varied over a 1000-fold range of potency consistent with expectations for a receptor that displays rigorous conformational specificity. The indiscriminant selectivity of C-ANP receptors for D-amino acid-substituted ANP analogs is unprecedented for hormone receptors involved in biological signal transduction. These results, when coupled with the inability to correlate any direct in vitro biological effect associated with C-ANP receptor occupancy supports the hypothesis that the C-ANP receptor protein is a novel transport protein involved in the metabolic clearance of ANP.

Suicide attempts and resuscitation dilemmas

The conventional psychiatric opinion that suicide is a manifestation of psychiatric illness may not apply to circumstances in which suicide or the refusal of life-sustaining medical treatment results from the rational decisions of autonomous individuals. As medical technology advances, questions about the prolongation of life and the discontinuation of medical treatment have become commonplace in the medical setting. In this context, contradictions may exist between the principle of patient autonomy and that of physician responsibility. Dilemmas about treatment decisions that emerge from these conflicting perspectives are highlighted in this article. We report two cases of attempted suicide in the context, respectively, of (1) terminal illness and (2) advanced age. Some of the complex psychiatric, ethical, and legal issues related to the case reports are addressed.

Effect of latissimus dorsi dynamic cardiomyoplasty on ventricular function

In our approach to dynamic cardiomyoplasty, which consists of wrapping a skeletal muscle around the heart and stimulating the former in synchrony with heart contractions to augment ventricular contractility, we have transferred a latissimus dorsi muscle flap to the heart by way of a partial resection of the second rib and subsequently suturing the muscle flap around the ventricles. The muscle flap is stimulated by a Cardio-Myostimulator burst-pulse generator (Medtronic SP 1005) connected to intramuscular electrodes. In preclinical animal research, the latissimus dorsi muscle flap was shown to maintain adequate contractile force and to increase its fatigue resistance by gradual conversion of glycolytic-fatigue-sensitive-to-oxidative-fatigue-resistant muscular fibers (100%). Histochemical and biochemical studies of chronically stimulated muscles showed a total transformation of muscle fast myosin to slow myosin with characteristics similar to those of myocardium. Electron microscopy showed preserved myofibrillar cytoarchitecture and increased mitochondrial density in the cell. At 9 months, cardiac output and ultrasonic Doppler studies showed a significant increase in ventricular function (cardiac output, +21%; peak blood velocity, +40% -80%; and stroke volume, +98% -102%) during muscle stimulation. In the clinical situation, long-term (range of follow-up interval, 4-42 months) beneficial cardiac effects of cardiomyoplasty have been documented in eight patients with various pathologies (ventricular tumor, left ventricular aneurysm, ischemic disease, and dilated cardiomyopathy). Our current understanding of this process is that dynamic cardiomyoplasty acts in two ways: 1) it promotes more vigorous systolic contraction, and 2) it appears to limit heart dilatation.