Biomedical subjects
Publications and source records attributed to L Ballerini.
Three different devices were used to close secundum-type atrial septal defects in 28 patients. The "Amplatzer" is associated with an easier and shorter procedure than are the "Sideris Buttoned Device" and the Microvena "Angel Wings" devices.
The contribution of endothelin to the genesis of neointimal development in collared rabbit carotid arteries, a widely accepted model of atherosclerosis, was investigated. Three sets of rabbits were studied. In the first group, a non-occlusive, biologically inert silastic collar was positioned around the right carotid artery of the rabbit. In another group, the application of the collar was accompanied by endothelial denudation via a Fogarty arterial balloon catheter, while the third group of animals underwent only endothelial denudation. After two weeks, intimal hyperplasia of a similar degree was observed in all groups. The administration of the nonselective ET(A)/ET(B) receptor antagonist Bosentan, significantly reduced both the neointimal area and the intima/media area ratio in all groups. However, the beneficial effects of Bosentan were less pronounced in balloon injured vessels than in collared ones. The results of the present study indicate that i) endothelin has a key role in the development of intimal hyperplasia following arterial collaring, ii) the contribution of endothelin to intimal hyperplasia is greater in collared arteries that in balloon injured ones, and iii) the nonselective ET(A)/ET(B) receptor antagonists are potential tools for the prevention of intimal hyperplasia.
In this paper, we report on the use of stents in the treatment of late-onset post-Mustard systemic venous obstruction in three patients with clinical signs of obstructive caval syndrome. After unsuccessful balloon dilation, Palmaz-Schatz stents were implanted at the veno-atrial junction. Further dilation has been achieved using high-pressure balloons. Vessel diameter increased from 4.4+/-1.8 to 13+/-1.7 mm (P < 0.05) and the trans-stenotic pressure gradient dropped from 8+/-6 to 0 mmHg (P < 0.01), with clinical improvement. After 26+/-4 months of non-invasive follow-up, no signs of recurrent stenosis were observed. Stent implantation is effective in the treatment of systemic venous obstruction after Mustard operation.
Organotypic cocultures of dorsal root ganglia and spinal cord from embryonic rats provides direct access to spinal interneurons in a culture system in which the cytoarchitectural organization of the spinal cord slice is maintained. This preparation was used to investigate the possible induction of rhythmic behaviour at different times of development in vitro. Spontaneous rhythmic bursts induced by coapplication of strychnine (1 microM) and bicuculline (20 microM) were observed with patch-clamp recordings from ventral interneurons. Ventral horn interneurons consistently developed a very regular pattern of activity which was superimposed on a background of sustained synaptic activity. The pattern of the spontaneous bursting following application of strychnine and bicuculline showed a developmentally regulated difference in frequency between two distinct stages of in vitro development.
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The cellular mechanisms underlying rhythmic bursts induced in the isolated neonatal rat spinal cord by bath application of strychnine and bicuculline (which block glycine- and gamma-aminobutyric acid-A-receptor-mediated inhibition, respectively) were probed with pharmacological tools. Such spontaneous bursts were recorded either intracellularly from lumbar motoneurons or extracellularly from ventral roots. As previously described, these network-driven events consisted of large-amplitude depolarizations arising abruptly from baseline with a highly regular period (on average 28 s). Burst episodes (lasting on average 7 s) comprised several oscillations and appeared synchronously on flexor and extensor motoneuron pools of both sides of the spinal cord. Their diffuse location made convenient to use bath-applied substances in the attempt to selectively block distinct membrane processes operating through the network. Application of apamin (0.4 microM) shortened both cycle period and burst duration without changing their regular rhythmicity. Similar results were obtained with carbachol (10 microM). Cs+ (4 mM) reversibly hyperpolarized the motoneuron membrane potential and largely increased burst duration, which was characterized by a long series of repetitive oscillatory waves. Cycle period and rhythmicity remained unaltered. Ouabain (10 microM), strophanthidin (4 microM), or K(+)-free solutions disrupted rhythmic bursting, which was fragmented into irregularly occurring paroxysmal activity mixed with short depolarizing events, still developing simultaneously on both sides of the spinal cord. Bursting activity eventually ceased after approximately 30-40 min of application of ouabain or strophanthidin. Prolonged washout of strophanthidin or K(+)-free solutions reestablished regular bursting patterns, whereas no recovery from ouabain was observed. At the time of strong depression of bursting, it was still possible to evoke bursts by single electrical pulses applied to the segmental dorsal root. Antidromic spikes of motoneurons could still be evoked by ventral root stimulation. These results demonstrate that, in a spinal bursting network mainly made up by excitatory processes, blockers of slow Ca(2+)-dependent K+ currents, such as apamin or carbachol, or of the slow inward rectifier, such as Cs+, did not suppress rhythmicity, suggesting that these conductances simply contributed to control cycle period and/or burst duration. Conversely, pharmacological blockers of the electrogenic Na+ pump such as ouabain, strophanthidin, or K(+)-free solutions severely disrupted all characteristics of rhythmic bursting. It is proposed that the operation of the electrogenic Na+ pump of premotoneurons was a crucial element for rhythmic bursting.
INTRODUCTION: The stent has demonstrated to be a useful device in the prevention of postangioplasty coronary restenosis and it is expected to have a favourable effect as an alternative or complementary treatment of stenotic lesions in arteries or veins associated with congenital defects. The aim of this study is to analyze our experience in this setting. MATERIAL AND METHODS: From February 1992 to March 1996, 28 stenting procedures were performed in 26 patients (mean age: 8.6 +/- 0.7 years; mean weight: 26.2 +/- 3 kg). In 12 patients, stenting was single, and a iliac Palmaz stents were always used. Stenting location was: pulmonary artery branches in 17 patients, right ventricular outflow in 2 patients, in the junction of right atrium with pulmonary artery in 2 patients, systemic veins in 2 patients and in post Mustard intratrial channel stenosis in 2 patients. 25 patients had previously undergone at least one surgical procedure. RESULTS: The stenotic diameter of the treated lesions increased significantly after the procedure (4.4 +/- 0.3 mm before stenting vs 11.6 +/- 0.3 mm after stenting, p < 0.0001) and the transtenotic gradient decreased from 38.1 +/- 5 to 12 +/- 3.8 mmHg. Those changes were associated with a diminution of right ventricular pressure (81.6 +/- 3 vs 56.7 +/- 6 mmHg, p < 0.0001) in patients with pulmonary branch stenosis without septal defects. There was no mortality among the percutaneously treated patients and only one patient needed surgery. Nevertheless, one patient died after bilateral intraoperative stenting. CONCLUSION: The treatment of proximal or distal stenotic lesions in the pulmonary tree, systemic veins, and obstructed intraatrial channels with stents, can replace or complement conventional balloon angioplasty. It also offers a useful and effective alternative to surgery, when it is impossible or carries a risk.
Spontaneous rhythmic bursting induced by coapplication of strychnine (1 microM) and bicuculline (20 microM) was observed with electrophysiological recording from pairs of lumbar ventral roots (usually L5) in an isolated preparation of the neonatal rat spinal cord. Bursting was insensitive to exogenously applied GABA or glycine, confirming that it was attributable to block of glycine and GABAA receptor-mediated inhibition. NMDA accelerated bursting in a dose-dependent manner. Complete coronal spinal transection at L3 or L6 level did not block bursting recorded from L5 or L2 roots, respectively. Gradual cutting of the cord along the midline through a sagittal plane preserved bursting activity in both disconnected sides but led to loss of synchronicity. Once the spinal cord was fully separated into left and right halves, regular bursting persisted on each side with no phase-coupling between the two preparations. Section along a frontal plane to remove dorsal horns and much of the central canal area did not affect burst frequency or left-to-right synchronicity, whereas it reduced burst duration. A quadrant preparation containing mainly a single ventral horn displayed enhanced burst frequency while bursts became very short events. Bath application of 5-hydroxytryptamine (30 microM) or NMDA (5 microM) increased burst frequency and decreased burst duration in all types of preparation except the isolated quadrants, in which brief bursts were accelerated but not shortened by these chemical agents. These results suggest that bursting induced by strychnine and bicuculline apparently relied on distinct mechanisms for burst triggering and intraburst structure. The first required a relatively smaller neuronal network that was confined to a ventral quadrant. Intraburst structure was dependent on a larger circuitry comprising either both ventral horns or one side of the spinal cord including more than two segments.
A case of idiopathic right pulmonary artery aneurysm with pulmonary valve insufficiency simulating a mediastinal teratoma occurred in an asymptomatic 13-year-old boy. The key to correct diagnosis was pulmonary angiography. The patient was successfully treated with surgery.
1. The effects of blocking gamma-aminobutyric acid- and glycine-mediated synaptic transmission by bicuculline and strychnine on the neonatal rat isolated spinal cord were investigated by intracellular recording from motoneurons with the use of current-clamp and voltage-clamp techniques and by extracellular recording from homologous ventral roots of the L5 segment. 2. Bicuculline per se evoked irregular bursts of motoneuron membrane potential, often comprising individual events fused together. Strychnine alone did not elicit spontaneous bursting in the large majority of preparations. Simultaneous application of bicuculline and strychnine consistently induced regular rhythmic bursts (frequency approximately 2 per min, duration approximately 7 s), comprising a rapid depolarization followed by large-amplitude oscillations. 3. Burst frequency, duration, and intraburst oscillation time course were independent of motoneuron membrane potential. Burst and oscillation amplitude decreased with membrane depolarization and, under voltage-clamp conditions, inverted polarity near 0 mV. 4. The regular bursts produced by bicuculline and strychnine were blocked by 6-cyano-7-nitroquinoxaline-2,3-dione, tetrodotoxin, or Cd2+. 5. N-methyl-D-aspartate antagonists [R-5-aminophosphonovalerate or 3-((RS)-2-carboxypiperazine-4-yl)-propyl-1-phosphonate (CPP)] reversibly blocked or slowed down bursting induced by bicuculline and strychnine. Addition of cyclothiazide to the bicuculline and strychnine solution increased bursting frequency while preserving the regular burst structure; under these conditions bursts became insensitive to CPP. 6. In the presence of bicuculline and strychnine, 5-hydroxytryptamine (5-HT) increased burst frequency and decreased burst duration in a dose-dependent fashion. 7. In the presence of bicuculline and strychnine, L5 ventral roots developed synchronous rhythmic activity with a time course similar to that recorded from individual motoneurons. The rhythmic activity was accelerated by 5-HT on both roots, in accordance with observations on single motoneurons. 8. Rhythmic bursts thus appear to result from large, synchronous synaptic events generated by a network modulated by 5-HT and highly sensitive to variations in efficacy of glutamatergic synaptic transmission. These results show that in the rat spinal cord highly patterned motor output can occur despite block of inhibition.
Congenital stenosis and/or hypoplasia of the pulmonary veins(s) is a rare cardiac malformation, whose treatment is difficult and not well defined, so conditioning an extremely poor prognosis. In fact, balloon angioplasty and surgery proved to be ineffective during a mid-term follow-up, thus not significantly modifying the natural history of this cardiovascular malformation. Although heart-lung transplantation is thought by someone to be the sole reliable treatment for congenital stenosis of the pulmonary vein(s), a recently available therapeutic option, the endovascular "stent" implantation during cardiac catheterization prompted to hope for a better outlook for these patients. However, this procedure is far from being an easy approach, due to technical problems that cause a high rate of failure and major complications. We report on two cases of pulmonary vein stenosis successfully treated by endoluminal "stent" implantation during open heart surgery, and suggest, and suggest that this safe and effective approach might be an alternative therapeutic option in the definitive or palliative treatment of this congenital cardiovascular malformation.
The clinical, histologic, histochemical, immunohistochemical, and ultrastructure studies of a primary neoplasia of the myocardium with onset in a 14-year-old boy led to the conclusion that this was a benign neoplasia of myocardial origin, apparently not previously described. The authors propose to call this entity "myocardial rhabdomyoma with rhabdomyoblastic moiety".
Intracellular recording was used to study the effect of cyclothiazide, a selective blocker of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor desensitization, on lumbar motoneurons of the rat isolated spinal cord. Cyclothiazide (25 microM) enhanced the responses to AMPA in a tetrodotoxin-insensitive fashion, without affecting those produced by N-methyl-D-aspartate or gamma-aminobutyric acid. Excitatory postsynaptic potentials (EPSPs) evoked by dorsal root stimulation were strongly potentiated in amplitude while paired-pulse depression (produced by applying pairs of pulses at 2 s interval) of the EPSP was decreased. In the presence of cyclothiazide the frequency of spontaneous synaptic events was greatly increased and network-driven bursting activity developed with eventual loss of electrical excitability. The present results suggest that pharmacological block of AMPA receptor desensitization led to strong excitation of motoneurons and indicate a physiological role of desensitization in protecting these nerve cells from overactivity.
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Single trunk anomalous origin of both coronary arteries from the pulmonary artery is a rare congenital cardiac anomaly. We report on 2 cases of its association with aortic coarctation, the diagnosis of which in living patients is very difficult. We think that the possibility of this anatomic arrangement should always be considered in patients with isolated aortic coarctation whose clinical condition seems impaired rather than improved after an apparently successful coarctectomy.
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BACKGROUND: Pulmonary balloon valvuloplasty is the treatment of choice of pulmonary valve stenosis, but early results and long-term follow-up in a numerous and homogeneous pediatric population are poorly known. MATERIAL AND METHODS: From April 1984 to April 1994, 202 valvuloplastic procedures were performed in 197 patients (age 52.5 +/- 150 months). Hemodynamic data were analysed according with valvular morphology and patient's age at procedure. During a follow-up period of 50 +/- 38 months, clinical and instrumental data were collected. RESULTS: After pulmonary valvuloplasty RV pressure decreased from 86 +/- 28 to 41 +/- 21 mm Hg (p < 0.001), transvalvular pressure gradient from 67 +/- 27 to 24 +/- 14 mm Hg (p < 0.001) and RV/LV pressure ratio from 1.01 +/- 0.29 to 0.53 +/- 0.19 (p < 0.001). Overall success rate was 95% (187/197 patients). Pulmonary valve dysplasia and/or annulus hypoplasia significantly influenced the efficacy of the procedure and/or the recurrence of valvar stenosis (18.8% vs 2.7%, p < 0.01). During the follow-up period, clinical examination was unremarkable, and transvalvular pressure gradient did not change (23 +/- 9 vs 24 +/- 6 mm Hg at discharge, p = NS). Freedom from restenosis was 98% at 3 years and 96% at 5 and 10 years. CONCLUSIONS: Pulmonary balloon valvuloplasty is a safe, effective and possibly definitive treatment for isolated pulmonary valve stenosis in infants and children. Age at valvuloplasty does not influence the success of the procedure, as opposed to valvular dysplasia and/or annulus hypoplasia that positively relate to the need of surgical valvotomy and/or the recurrence of stenosis during a long-term follow-up. In conclusion, prognosis of the majority of infants and children after a successful valvuloplasty is excellent during a long-term follow-up period.