The rise and falls of introns.

There has been a lively debate over the evolution of eukaryote introns: at what point in the tree of life did they appear and from where, and what has been their subsequent pattern of loss and gain? A diverse range of recent research papers is relevant to this debate, and it is timely to bring them together. The absence of introns that are not self-splicing in prokaryotes and several other lines of evidence suggest an ancient eukaryotic origin for these introns, and the subsequent gain and loss of introns appears to be an ongoing process in many organisms. Some introns are now functionally important and there have been suggestions that invoke natural selection for the ancient and recent gain of introns, but it is also possible that fixation and loss of introns can occur in the absence of positive selection.

Genes without frontiers?

For bacteria, the primary genetic barrier against the genetic exchange of DNA that is not self-transmissible is dissimilarity in the bacterial DNA sequences concerned. Genetic exchange by homologous recombination is frequent among close bacterial relatives and recent experiments have shown that it can enable the uptake of closely linked nonhomologous foreign DNA. Artificial vectors are mosaics of mobile DNA elements from free-living bacterial isolates and so bear a residual similarity to their ubiquitous natural progenitors. This homology is tightly linked to the multitude of different DNA sequences that are inserted into synthetic vectors. Can homology between vector and bacterial DNA enable the uptake of these foreign DNA inserts? In this review we investigate pUC18 as an example of an artificial vector and consider whether its homology to broad host-range antibiotic resistance transposons and plasmid origins of replication could enable the uptake of insert DNA in the light of studies of homology-facilitated foreign DNA uptake. We also discuss the disposal of recombinant DNA, its persistence in the environment and whether homologies to pUC18 may exist in naturally competent bacteria. Most DNA that is inserted into the cloning site of artificial vectors would be of little use to a bacterium, but perhaps not all.

Mitochondrial pseudogenes: evolution's misplaced witnesses.

Nuclear copies of mitochondrial DNA (mtDNA) have contaminated PCR-based mitochondrial studies of over 64 different animal species. Since the last review of these nuclear mitochondrial pseudogenes (Numts) in animals, Numts have been found in 53 of the species studied. The recent evidence suggests that Numts are not equally abundant in all species, for example they are more common in plants than in animals, and also more numerous in humans than in Drosophila. Methods for avoiding Numts have now been tested, and several recent studies demonstrate the potential utility of Numt DNA sequences in evolutionary studies. As relics of ancient mtDNA, these pseudogenes can be used to infer ancestral states or root mitochondrial phylogenies. Where they are numerous and selectively unconstrained, Numts are ideal for the study of spontaneous mutation in nuclear genomes.

Genomic gigantism: DNA loss is slow in mountain grasshoppers.

Several studies have shown DNA loss to be inversely correlated with genome size in animals. These studies include a comparison between Drosophila and the cricket, Laupala, but there has been no assessment of DNA loss in insects with very large genomes. Podisma pedestris, the brown mountain grasshopper, has a genome over 100 times as large as that of Drosophila and 10 times as large as that of Laupala. We used 58 paralogous nuclear pseudogenes of mitochondrial origin to study the characteristics of insertion, deletion, and point substitution in P. pedestris and Italopodisma. In animals, these pseudogenes are "dead on arrival"; they are abundant in many different eukaryotes, and their mitochondrial origin simplifies the identification of point substitutions accumulated in nuclear pseudogene lineages. There appears to be a mononucleotide repeat within the 643-bp pseudogene sequence studied that acts as a strong hot spot for insertions or deletions (indels). Because the data for other insect species did not contain such an unusual region, hot spots were excluded from species comparisons. The rate of DNA loss relative to point substitution appears to be considerably and significantly lower in the grasshoppers studied than in Drosophila or Laupala. This suggests that the inverse correlation between genome size and the rate of DNA loss can be extended to comparisons between insects with large or gigantic genomes (i.e., Laupala and Podisma). The low rate of DNA loss implies that in grasshoppers, the accumulation of point mutations is a more potent force for obscuring ancient pseudogenes than their loss through indel accumulation, whereas the reverse is true for Drosophila. The main factor contributing to the difference in the rates of DNA loss estimated for grasshoppers, crickets, and Drosophila appears to be deletion size. Large deletions are relatively rare in Podisma and Italopodisma.

Frequent assimilation of mitochondrial DNA by grasshopper nuclear genomes.

Multiple copies of mitochondrial-like DNA were found in the brown mountain grasshopper, Podisma pedestris (Orthoptera: Acrididae), paralogous to COI and ND5 regions. The same was discovered using the ND5 regions of nine other grasshopper species from four separate subfamilies (Podisminae, Calliptaminae, Cyrtacanthacridinae, and Gomphocerinae). The extra ND5-like sequences were shown to be nuclear in the desert locust, Schistocerca gregaria (Cyrtacanthacridinae), and probably so in P. pedestris and an Italopodisma sp. (Podisminae). Eighty-seven different ND5-like nuclear mitochondrial pseudogenes (Numts) were sequenced from 12 grasshopper individuals. Different nuclear mitochondrial pseudogenes, if descended from the same mitochondrial immigrant, will have diverged from each other under no selective constraints because of their loss of functionality. Evidence of selective constraints in the differences between any two Numt sequences (e.g., if most differences are at third positions of codons) implies that they have separate mitochondrial origins. Through pairwise comparisons of pseudogene sequences, it was established that there have been at least 12 separate mtDNA integrations into P. pedestris nuclear genomes. This is the highest reported rate of horizontal transfer between organellar and nuclear genomes within a single animal species. The occurrence of numerous mitochondrial pseudogenes in nuclear genomes derived from separate integration events appears to be a common phenomenon among grasshoppers. More than one type of mechanism appears to have been involved in generating the observed grasshopper Numts.

Study of muscular and ventricular function in dynamic cardiomyoplasty: a ten-year follow-up.

BACKGROUND: The basic physiologic principle underlying cardiomyoplasty is long-term electrostimulation of a latissimus dorsi muscle (LDM) wrapped around the heart to obtain a phasic activity that could be integrated with ventricular kinetics. The aim of cardiomyoplasty is to prolong survival and to improve the quality of life of patients with severe chronic and irreversible myocardial failure by improving systolic contraction and correcting diastolic dysfunction. METHODS: To evaluate the long-term outcome of cardiomyoplasty, we investigated 82 patients electively undergoing this procedure in-our hospital. All patients had severe chronic heart failure that did not respond to optimal medical treatment. Patients had a mean age of 50 +/- 12 years (84% males). The cause of heart failure was ischemic (55%), idiopathic cardiomyopathy (34%), ventricular tumor (6%), and other (5%). The mean follow-up was 4.3 years. RESULTS: The mean New York Heart Association functional class improved after operation from 3.2 to 1.8. Average radioisotopic left ventricular ejection fraction increased from 17% +/- 6% to 28% +/- 3% (p < 0.05). Stroke volume index increased from 35 +/- 9 to 46 +/- 8 ml/beat/m2 (p < 0.05). The heart size remained stable at long term (evaluated by echo and computed tomography scanning). After cardiomyoplasty the number of successive hospitalizations resulting from congestive heart failure was reduced to 0.4 hospitalizations/patient/year (before operation 2.5, p < 0.05). Computed tomography scans showed at long-term a preserved LDM structure in 82% of patients who underwent operation. Survival probability at 7 years was 54% for the totality of patients, and 66% for patients who underwent operation in New York Heart Association functional class 3. Five patients underwent heart transplantation after cardiomyoplasty (mean delay 29 months), principally as a result of the natural evolution of their underlying heart disease, without major technical difficulties. CONCLUSIONS: Our 10-year clinical experience demonstrates that cardiomyoplasty increases ejection fraction, improves functional class, and ameliorates quality of life. Ventricular volumes and diameters remain stable long term. LDM structure is maintained long term if electrostimulation is performed avoiding excessive myostimulation. Patient selection is the most important determinant for early and late outcome. Late death in patients undergoing cardiomyoplasty is principally due to sudden death. Our future aim is to incorporate a cardioverter-defibrillator in the cardiomyostimulator, thus improving long-term results. Cardiomyoplasty may delay or prevent end-stage heart failure and the need for heart transplantation.

[Mid-term results of cardiomyoplasty]. / Résultats à moyen terme de la cardiomyoplastie.

Cardiomyoplasty (CMP) is a technique of circulatory assistance using a pediculated latissimus dorsi muscle wrapped around the heart and electrically stimulated during systole. Sixty-four patients, aged 15 to 69 years (average 50.8 +/- 13 years) with cardiac failure underwent CMP between January 1985 and July 1993. The causes of cardiac failure were : ischaemic heart disease (39 cases), dilated cardiomyopathy (18 cases), cardiomyopathy following valvular heart disease (2 cases), cardiac tumours (4 cases) and congenital heart disease (1 case). Twenty-four patients underwent an associated surgical procedure. Intra and postoperative intra-aortic balloon pumping was required in 27 cases. Hospital mortality (before latissimus dorsi stimulation) was 20.3% (13/64 cases). Evaluation of the survivors 12 months after surgery showed an improvement in functional class (1.,5 versus 3.3 before CMP ; p < 0.05), in isotopic ejection fraction (27 +/- 3% versus 17 +/- 6%, p < 0.05) and cardiac index (2.87 +/- 0.63 l/min/m2 versus 2.38 +/- 0.41 l/min/m2, p < 0.05). There was no significant change in cardiac filling pressures. The number of hospital admissions for congestive cardiac failure in operated patients was 0.4 per patient per year, compared with 2.5 per patient per year (p < 0.05) before CMP. The preoperative predictive factors for late mortality were: permanent functional Class IV (NYHA), severe cardiac dilatation (cardio-thoracic ratio greater than 0.60; left ventricular end diastolic dimension > 75 mm), an isotopic left ventricular ejection fraction < 15%, severe biventricular cardiac failure and irreversible pulmonary hypertension. The actuarial 4 year survival rate was 68.3%.(ABSTRACT TRUNCATED AT 250 WORDS)

[Cardiac failure caused by cardiomyopathy disclosing pheochromocytoma. Perioperative treatment]. / Défaillance cardiaque par cardiomyopathie révélatrice d'un phéochromocytome. Traitement péri-opératoire.

A case of cardiomyopathy secondary to an unrecognised pheochromocytoma is reported. It was cured by successful outset with congestive cardiac failure with an ejection fraction of 11%. Following medical treatment including a beta-blocker and converting enzyme inhibitors, the situation remained so disturbing that cardiac transplant was envisaged. It was nevertheless decided to first remove the tumour, with mechanical circulatory assistance cover if necessary. Surgical excision proved to be relatively easy. Cardiac failure disappeared clinically within a few days, though a degree of myocardial impairment revealed by paraclinical investigations persisted after ten months. The pathophysiology, beneficial effect of beta-blockers and the SvO2 usefulness blood during the perioperative period are discussed. The prognosis of the cardiomyopathy, considered up to the present to be uncertain, new seems favourable once it is possible to completely excise the tumour.

Dynamic cardiomyoplasty at seven years.

Since January 1985, the date of the first dynamic cardiomyoplasty, until April 1992, 52 patients with end-stage heart disease were operated on in our institution. Mean preoperative New York Heart Association functional class was 3.3 and ventricular ejection fraction 16% +/- 3%. Associated procedures in 23 patients comprised ventricular aneurysm resection (10), valve surgery (9), coronary artery bypass (8), and tumor resection (3). Thirty-eight patients had a ventricular reinforcement, 13 a ventricular substitution, and 1 an atrial reinforcement using the left latissimus dorsi muscle. Preassist mortality rate before full latissimus dorsi muscle stimulation was 7 of 13 patients (54%) in the 1985 to 1987 period and 5 of 39 (12%) in the 1988 to 1992 period. The causes of death were heart failure (4), multiorgan failure (4), septicemia (2), ventricular fibrillation (1), and sudden death (1). Multivariate analysis of factors influencing hospital mortality showed that age, cardiac suture technique, associated surgical procedures, biventricular heart failure, and hemodynamic instability plus inotropic drug support were predictors of unfavorable outcome. All patients were followed up for from 2 months to 7 years (mean 21 months). Postassist mortality rate was 8 of 40 (20%). Causes of death included heart failure (5), ventricular fibrillation (1), myocardial infarction (1), and gastric bleeding (1). Preoperative risk factors influencing long-term mortality were permanent New York Heart Association functional class IV, biventricular heart failure, atrial fibrillation, cardiothoracic ratio greater than 60%, and ejection fraction less than 15%. Actuarial survival at 7 years was 70.4% (preassist mortality excluded). Surviving patients were in a mean New York Heart Association functional class of 1.8 (preoperatively 3.3, p < 0.05). The average ejection fractions (rest/stress) were 25%/28% at 1 year, 26%/30% at 2 years, and 23%/28% at 3 years. Average cardiothoracic ratios were 57% +/- 3% at 1 year, 56% +/- 2% at 2 years, and 57% +/- 2.5% at 3 years. Catheterization obtained in 20 patients showed no significant changes at rest in capillary wedge pressure, pulmonary artery pressure, and diastolic left ventricular pressure when compared with preoperative pressures. Average ejection fractions increased from 24% to 30.6%. Maximal oxygen consumption increased from 12.8 +/- 3.5 to 18.6 +/- 4 ml/min per kilogram. The number of rehospitalizations resulting from congestive heart failure was reduced to 0.4 hospitalizations per patient per year (preoperatively 2.4, p < 0.05). In 62% of the patients, pharmacologic therapy was diminished after the operation. Three patients required orthotopic heart transplantation 6 months, 4 years, and 5 years after cardiomyoplasty.

Dynamic cardiomyoplasty for long-term cardiac assist.

The principle of cardiomyoplasty is long-term electrostimulation of a latissimus dorsi muscle (LDM) wrapped around the failing heart. Technically, this procedure consists of placing the left LDM flap around the heart via a window created by partial resection of the 2nd or 3rd rib, and subsequent muscle electrostimulation in synchrony with ventricular systole. The aim of cardiomyoplasty is to support ventricular function in ischemic or dilated cardiomyopathies, or to partially replace the ventricular myocardium after large aneurysm or tumor resections. Our clinical experience at Broussais Hospital involves 44 patients. The functional class and quality of life improved after cardiomyoplasty. Improvement of the ventricular performance and limitation of cardiac dilatation were demonstrated over the long-term. The actuarial survival at 6 years was 71%. Risk factors influencing perioperative mortality were: age > 65 years, associated surgical procedures, pulmonary vascular hypertension, and patients hemodynamically unstable or on inotropic drug support. Preoperative risk factors influencing the long-term mortality were: permanent NYHA functional class 4, cardiothoracic ratio > 0.60, LV ejection fraction < 15%, bi-ventricular heart failure, and atrial fibrillation. Cardiomyoplasty does not preclude the use of future orthotopic heart transplantation.

Intra-operative transoesophageal echocardiography after mitral repair--specific conditions and pitfalls.

The aim of this study was to determine the specific conditions and pitfalls of immediate assessment of the reconstructed mitral valve in open chest patients. Sixty-two patients had a mitral reconstruction controlled by transoesophageal echocardiography and colour Doppler (TEE) from the moment when cardiac activity restarted under extracorporeal circulation (ECC), until complete rewarming of the patient and weaning off the by-pass. The following conditions altered the imaging quality: (1) dried probe in the oesophagus or air bubbles, (2) non-aspirated air from the stomach, (3) small or empty left atria, (4) invagination of the left atrial appendage, (5) trapped air in the posterior pericardium, (6) spontaneous contrast. Transient mitral regurgitation disappeared completely in 12/62 patients: five had temporary impairment of LV function, two had reduced filling of the heart, one had left ventricular outflow obstruction exacerbated by isoproterenol and nitroglycerin, two had ventricular ectopic rhythms, and two epicardial pacing. Only one of the 62 patients had persistent significant MR which required a second run of ECC. We conclude that mitral regurgitation after mitral valve repair is closely related to the quality of LV function. A decision to reoperate should eliminate the possible pitfalls, and take into consideration the specific conditions of immediate postoperative cardiac function.

[Cardiomyoplasty. Experimental bases, operative technic, indications]. / Cardiomyoplastie. Bases expérimentales, technique opératoire, indications.

Dynamic cardiomyoplasty aims at restoring ventricular contractility by means of a skeletal muscle sutured around the heart. It consists of transferring a latissimus dorsi muscle flap onto the heart through a window created in the thoracic wall by partial resection of the second rib. The skeletal muscle may be used to reinforce the ventricular systole in ischemic or dilated cardiomyopathy, or to replace the myocardium after resection of a large aneurysm or an extensive tumour. The electronic pacing material includes an implantable cardiomyostimulator, muscle stimulating electrodes and R wave detecting electrodes. Muscular pacing begins 2 weeks after the operation, this being the time required for adhesions to be formed between the heart and the muscle. A progressive and sequential electrostimulation procedure results in the transformation of glycolytic muscle fibres that are fatigue-sensitive into fatigue-resistant oxidative fibres. The purpose of this biomechanical cardiac assistance system, where cardiac surgery is combined with plastic surgery and biomedical engineering, is to prolong life and improve its quality in patients with severe heart failure.

Comparative evaluation of aortic valve replacement with Starr, Björk, and porcine valve prostheses.

Three groups of 100 consecutive patients with aortic valve disease who were operated on between 1974 and 1978 underwent long-term evaluation. There were 100 aortic valve replacements with porcine bioprosthetic valves (group I), 100 with Starr valves (group II), and 100 with Björk valves (group III). There were no significant differences in the preoperative clinical conditions of the patients in the three groups. Cumulative follow-up was 1688 patient-years. Incidence of valve-related death at 8 years was 4 +/- 2.3% in group I, 13 +/- 3.6% in group II, and 13 +/- 3.8% in group III (p less than .05). At 8 years 95 +/- 2.8% of the patients in group I were free of thromboembolism, compared with 81 +/- 4.8% of those in group II and 84 +/- 4.2% of those in group III (p less than .002). The actuarial risk of a reoperation at 8 years was 16 +/- 6% in group I, 5 +/- 2% in group II, and 2 +/- 1.6% in group III (p less than .025 group I vs group III). At 8 years 98 +/- 1.2% of the patients in group I were free of anticoagulant-related complications, compared with 88 +/- 3.8% of those in group II and 86 +/- 3.9% of those in group III (p less than .005). We conclude that at 8 years porcine bioprosthetic valves performed better than mechanical valves, taking into consideration thromboembolism, anticoagulant-related hemorrhage, and valve-related death.

[Direct atriopulmonary anastomosis (modified Fontan) for single ventricle and its equivalents]. / Anastomose atrio-pulmonaire directe (Fontan modifié) pour ventricule unique et ses équivalents.

The modified Fontan procedure is being used in an increasing number of complex cyanotic cardiac lesions with pulmonary stenosis. Seven patients aged 11 to 24 years (average 17.5 years) underwent surgery by a technique derived from the Fontan procedure: direct atriopulmonary anastomosis without a tube or valve. The tricuspid valve when patent was closed with a patch. The diagnoses were: single ventricule (4 cases), Taussig-Bing anomaly (2 cases) and tricuspid atresia (1 case). All patients had associated pulmonary stenosis with low pulmonary vascular resistances. The great vessels were in L-malposition in 3 cases. The hospital mortality was nil. Transient atrial fibrillation was observed in 2 cases and was well tolerated clinically. The follow-up period ranges from 2 months to 4 years (average 2.3 years). All patients are acyanotic with no signs of right-sided failure and in sinus rhythm. Control cardiac catheterisation and angiography were performed in 6 cases and showed good function of the anastomosis and a mean atrial pressure of 14 mmHg. Direct atriopulmonary anastomosis offers a very acceptable surgical solution to certain forms of single ventricle or equivalent with low pulmonary pressures. The short and medium term results seem to be better than those of intraventricular repair.

[Emergency in neo-natal surgery. High risks in forty-one cases (author's transl)]. / L'urgence en chirurgie cardiaque du petit enfant. Etude des facteurs de gravité à propos de 41 cas.

41 babies were operated upon in emergency in the cardiac surgery department. 11 of them were submitted to open heart surgery and 30 were operated without extra corporeal circulation. Amongst them, there were 21 coarctations of thoracic aorta either isolated or associated with other cardiac malformations. 13 of them, presented a pericardial effusion, and the mean age was 3 months. First of all, the notion of emergency in cardiac surgery of the new-born is stressed. Then, premedication and technic of anaesthesia are shortly described. The authors insist on the frequency of lethal cardiac fibrillation occurring at the opening of pericardium in case of coarctations of aorta complicated by pericardial effusion. Prevention of this accident is possible if at the beginning of anaesthesia the baby lies in a proclive position. On the opposite, bradycardia occurring at the opening of the pericardium or during pulmonary artery banding have a good prognosis. Lastly, the authors insist on the high risk of this surgery in the baby (25 p. cent of mortality) and 80 p. cent under 6 months of age and the high mortality of iterative operations.