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J Barra

Publications and source records attributed to J Barra.

54 records · Page 3Linked to original sources
PubMed1988

Diploid mouse embryos constructed at the late 2-cell stage from haploid parthenotes and androgenotes can develop to term.

Male and female gamete nuclei are required to ensure the full-term development of the mouse embryo. Differential expression of the two genomes has been proposed as the basis for this requirement. In order to investigate whether some interactions between the paternal and the maternal genomes are essential before or at the time of the activation of the embryonic genome, we have constructed diploid embryos from haploid parthenotes and androgenotes at the late 2-cell stage. These embryos developed to term into normal offsprings. This shows that the male and the female genomes can be activated separately and are still able to ensure complete development when put together in cytoplasm synchronized with the nuclei. These experiments also show that the egg cytoplasm does not need any male contribution before the late 2-cell stage.

Animals↗
PubMed1988

[Action of the paternal genome at the beginning of embryonic development].

Recent experiments using nuclear transfer between mouse embryos shows that the parental genomes are not equivalent: both of them must be present at least in a part of the blastomeres to allow full term development of the embryo. The paternal genome is preferentially involved in the development of trophoectodermic cells and appears to be eliminated from the primitive ectoderm when kept alone in androgenetic cells aggregated with normal ones. Differences of expression between parental genomes affect not only the X chromosome, but also several autosomes as evidenced by genetic analysis using meiotic non-disjunction. The nature of the imprinting mechanism that leads to the modification of parental homologous chromosomes is unknown. From experiments involving a particular strain of mice called DDK it appears that the egg cytoplasm may exert a specific action not only on the male pronucleus at the one-cell stage, but also on the paternal contribution of the diploid nucleus of the embryo at the 2-cell stage; a paternal developmental effect on the cytoplasm of one-cell stage embryo can also be demonstrated. These results show that nucleocytoplasmic interactions regulate early paternal gene expression differently from the maternal one.

Animals↗
PubMed1988

[Constrictive and stiffening effects of parasympathetic blockade on the pressure response of the aorta to angiotensin in the conscious dog ].

The elastic response of the thoracic aorta to increasing steps of angiotensin was studied in chronic instrumented conscious dogs with and without parasympathetic blockade by atropine. A pressure microtransducer and two ultrasonic crystals diametrically opposed and fixed in the adventitia enabled to determine the mean and systolic-diastolic changes of pressure (P) and diameter (D). By computing these measurements two representative indexes of dynamic elastic modulus in vivo were calculated; the elastic modulus of Peterson (Ep) Ep = delta P/D.D and the incremental elastic modulus (Ei) Ei = 0.75 EP/gamma, gamma being the ratio of the thickness to the external radius. A positive correlation (p less than 0.01) was obtained between pressure and diameter variations in the presence or absence of atropine but the slope of these relationship were lower with atropine than in controls. The slope of the positive correlations observed between Peterson and incremental elastic modulus and the increase in mean arterial pressure in response to angiotensin (p less than 0.01) was higher in the presence of atropine (p less than 0.05). These observations indicate that in response to angiotensin mediated high blood pressure, the cholinergic blockade of muscarinic receptors with atropine induce a contraction and increasing rigidity of the aorta.

Angiotensin II↗
PubMed1985

Right ventricular function in healed myocardial infarction in man. A cineangiographic assessment.

To evaluate the frequency of right ventricular dysfunction following recovery from myocardial infarction (MI) and the relationship of segmental right ventricular (RV) wall motion abnormalities to left ventricular (LV) function or location of coronary arterial stenosis, biplane right and left ventricular cineangiograms were obtained in 100 consecutive patients (4 +/- 3 months post MI). Thirty (group A) had anterior MI and significant stenosis or obstruction of left anterior descending artery (LAD). The remaining 70 patients had inferior MI. They were divided into three groups according to the site of the main coronary stenosis or obstruction and corresponding LV akinesia: right coronary artery (RCA) proximal to the acute marginal artery (RMA), (group B: 32 patients), RCA distal to the RMA (group C: 18 patients), left circumflex artery (LCF), (group D: 18 patients). RV and LV end-diastolic volume index (EDV), end-systolic volume index (ESV), stroke volume (SV) and ejection fraction (EF) have been determined. RV segmental wall motion was assessed in RAO and LAO projection by determining the percentage of systolic shortening (+ delta R) along 11 hemiaxes. Mean axial shortening (delta R) of the RV inferior and free walls were considered. When compared with that in 10 normal subjects, RV end-diastolic volume (RVEDV), RV end-systolic volume (RVESV) were increased and RV ejection fraction (RVEF) was lower in patients with anterior or inferior MI. Inferior delta R exhibited comparable sequential changes in the three groups of inferior MI and similar LVEF alteration.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

[Surgical treatment of patent ductus arteriosus in adults].

The surgical treatment of patent ductus arteriosus (PDA) in adults as in children, usually comprises section and suture, but a certain number of technical precautions must be taken. The aortic wall is often fragile due to atheromatous lesions which are more common with increasing age. Associated hypertension may add to the fragility. Controlled medicated hypotension and reinforcement of sutures with a piece of pericardium may be useful in reducing the risk of haemorrhage. It is sometimes necessary to use partial femoro-femoral cardiopulmonary bypass circuit. The presence of an aneurysm at the aortic end of a calcified ductus necessitates the same precautions. When PDA is complicated by pulmonary hypertension, the surgical indication can only be considered when the left-to-right shunt remains voluminous and when pulmonary artery pressures fall significantly during catheter or peroperative trials of closure. The operative risk in these cases increases with age. Cardiopulmonary bypass may also be very useful in these cases. Secondary repermeabilisation of an operated ductus, and cases complicated by endocarditis require an endopulmonary approach under cardiopulmonary bypass because of the fragility of the ductus region and difficulty in controlling haemorrhage. This technique is also preferred when an associated intracardiac malformation is to be corrected. Between 1965 and 1981, 37 patients were operated in the department of thoracic and cardiac surgery at the Pitié Hospital. The ages ranged from 20 to 65 years with a mean of 34 years. Cardiopulmonary bypass was necessary in 5 cases, (partial in 4, and total in 1 case of endoaortic closure).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1981

Surgical treatment of ventricular tachycardia guided by ventricular mapping in 23 patients without coronary artery disease.

Twenty-three patients with resistant ventricular tachycardia not related to coronary artery disease underwent surgical treatment guided by ventricular mapping. The patients were grouped according to radiological and anatomical findings. Group 1 (13 patients) had arrhythmogenic right ventricular dysplasia. Group 2 (3 patients) had left ventricular aneurysm. Group 3 (2 patients) had nonobstructive myocardiopathy. Group 4 (5 patients) had normal-appearing hearts. At operation all patients underwent ventricular mapping when in sinus rhythm and during ventricular tachycardia. The rationale of operation was ventriculotomy or cryosurgery at the site of origin of ventricular tachycardia or exclusion, resection, or undermining of arrhythmogenic areas where delayed potentials were observed. Four patients died during the perioperative period, 3 of low-output failure and 1 from bleeding. Ventricular tachycardia recurred immediately after operation in 4 patients, 3 of whom died during the perioperative period. Ventricular tachycardia recurred late in 5 patients. Three had only episodic, unsustained runs of tachycardia. Two were well controlled by drugs. All patients with ventricular tachycardia situated over the free wall of the ventricles had inducible ventricular tachycardia and had good surgical results. Three out of 5 patients with ventricular tachycardia situated in the septum had poor surgical results. Septal ventricular tachycardia needs a better surgical approach to the septum and a suitable surgical concept.

Adult↗
PubMed1981

[Myxomas of the right atrium. Apropos of 3 cases. Review of the literature].

The authors report 3 cases of right atrial myxoma and review 88 other cases in the literature managed by surgery. The first personal case, in a 74 year old patient, illustrate the dramatic consequences of tumour engagement in the tricuspid orifice, in this instance cardiac arrest during catheterisation justifying emergency surgery. The second case exemplifies the diagnostic value of echocardiography: the correction of an erroneous diagnosis of pericarditis. The third case shows that some forms may be totally asymptomatic, the tumor being diagnosed on clinical examination and confirmed by echocardiography. In their review of the literature, the low overall incidence of primary cardiac tumours, of which myxoma is the most common, is emphasised. A right atrial localisation is found in only 25% cases. 88 surgical reports have been published since Bahnam's original attempt at surgical cure under cardiopulmonary bypass. Myxoma may occur at any age but it usually presents between the ages of 30 and 60. Some familial forms have been reported. The presenting symptoms are protean but usually point to an obstacle in the right heart chambers. They may be summarized as follows: 1. Isolated right ventricular failure without left heart disease may be observed in large tumours (reported in 50% of cases). 2. Simulating pericarditis (25% of cases) with a low grade pyrexia (25% of cases). 3. Paroxysmas of cardio respiratory distress of variable severity (a few cases). Clinical examination, chest x-ray and ECG are not diagnostic but do show non-specific changes which are of value in drawing attention to the heart and leading to echocardiography. This confirms the diagnosis by showing abnormal mobile echos in the right atrium prolapsing into the right ventricle in diastole. Angiography serves only to confirm these appearances. Surgery is the treatment of choice, and preferably with the shortest possible delay. It offers definitive cure at a minimal risk to the patient.

Adult↗
PubMed1978

The role of phosphodiesterase in aggregation of Dictyostelium discoideum.

The role of cAMP phosphodiesterase in the cAMP-mediated aggregation of the cellular slime mould Dictyostelium discoideum was investigated with a morphogenetic mutant defective in phosphodiesterase production. Mutant cells become capable of aggregating normally when incubated in the presence of exogenous phosphodiesterase isolated from Idictyostelium or rat brain. Direct contact between enzyme and the cell membrane is not required for this phenotypic suppression. The aggregateless character of this strain presumably results from an over-accumulation of cAMP in the extracellular medium since aggregation can be induced in the absence of added phosphodiesterase under conditions facilitating diffusion of the nucleotide. This suggests that phosphodiesterase is not involved in the generation or recognition of cAMP signals, but that the enzyme is essential in the control of the cAMP signal-to-noise ratio.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1977

[Synergism between aggregation mutants of Dictyostelium discoideum].

The cells of an aggregateless mutant of Dictyostelium discoïdeum, agip 235, can cooperate with other aggregateless or wild strains to form differentiated aggregates. A soluble mediator liberated by the coaggregating cells seems responsible for the development of agip 235. In most cases, the development of mutant agip 235 stops at the aggregation stage; however, its coaggregation with the mutant 518 results in cosporulation, with the production of viable spores of each genotype, effecting a phenotypic suppression of both mutations.

Cell Aggregation↗
PubMedDate not supplied

An X-linked recessive mutation producing cleft palate, crooked tail, and polydactyly in mice.

Palate-tail-digits abnormality (ptd) is a new X-linked recessive mutation affecting the morphogenesis of the mouse. It maps proximal to Tabby. Hemizygous males and homozygous females exhibit skeletal malformations of the tail, polydactyly of the hind feet, and in about 60% of the cases a cleft palate. A very high level of postnatal mortality is observed even among the mutants without a cleft palate.

Abnormalities, Multiple↗
PubMedDate not supplied

Surgical treatment of acute dissection of the aorta superimposed on pre-existing aneurysm of the ascending aorta. Total replacement of the ascending aorta with reimplantation of the coronary arteries. A report on five cases.

Five cases of acute dissection of the ascending aorta superimposed on a pre-existing aneurysm, including two with propagation of the dissection into the coronary arteries, were treated by total replacement of the ascending aorta utilizing a valve containing tube graft and reimplantation of the coronary arteries. Diverse techniques such as the use of an intermediate tube for reconnecting the coronary arteries, correction of the coronary dissection by reapproximation of the two layers or with bypass grafting, support of the distal aortic suture line with Teflon felt and fistulization of the periprosthetic space to the right atrium, greatly simplified the treatment of these lesions, permitting survival of four out of five patients, who are in excellent health one, four, and seven years respectively after surgery.

Adult↗