[Implantable defibrillators in the management of malignant ventricular tachyarrhythmias. Experience at the Arrhythmia National Center]

BACKGROUND

Implantable defibrillators are the most effective means to prevent sudden death in patients with malignant ventricular tachyarrhythmias. The availability of this type of devices is limited in Chile, due to their high price.

AIM

To report the first patients treated with implantable defibrillators in our hospital.

PATIENTS AND METHODS

Nine males and one female aged 13 to 65 years old are reported. Three presented with ventricular fibrillation (presenting out of the hospital in three) and the rest had ventricular tachycardia resistant to drugs or radiofrequency ablation.

RESULTS

All implants were performed using intracardiac electrodes. The generator was implanted in the pectoral region in nine and in the abdomen in one. A successful defibrillation was obtained with less than 15 J in four patients, with 20 J in three and with 24 J in three. There were no complications during the procedure. After a 12 months follow up, four patients have been treated by the implantable device. One of these subjects had a ventricular fibrillation in two occasions. One patient died of a bronchopneumonia two years after the implant.

CONCLUSIONS

Implantable defibrillators are an effective therapy for the treatment of malignant ventricular arrhythmias with a high risk of sudden death.

Transcription and weak expression of HLA-DRB6: a gene with anomalies in exon 1 and other regions

HLA-DRB6 is one of the human major histocompatibility complex (MHC) genes present in DR1, DR2, and DR10 haplotypes (approximately 26% of individuals). It shows several anomalies in human and non-human primates, including exon 2 stop codons (non-randomly grouped between codons 74 and 94) and a promoter region, and an exon 1 coming from an inserted retrovirus. It has been shown that not only chimpanzee but also human Mhc-DRB6 lack the usual 3' untranslated (UT) polyadenylation signal, and in the present work it was found that the human DRB6 gene coming from an HLA-DR2 haplotype is effectively transcribed after transfection in mouse L cells, and that HLA-DRB6 molecules may be expressed on the cell surface. DRB6 transcription level is remarkably lower in human than in chimpanzee. Moreover, their exons 1 (both taken from the 3'LTR region of a mammary tumor retrovirus) are also different; this shows that these viral insertions may be an important mechanism for different evolutionary changes in orthologous genes of different species. The pathways by which DRB6 molecules may be expressed on the membrane are unclear but other examples of truncated protein expression have also been described, even within the human major histocompatibility complex (i. e., in HLA-G). Finally, the presence of mature HLA-DRB6 mRNA molecules supports the notion that splicing may take place even in the absence of a canonical 3'UT polyadenylation signal.

Effect of dexamethasone therapy on the neonatal ductus arteriosus

Patent ductus arteriosus (PDA) is believed to be a contributing factor in the etiopathogenesis of bronchopulmonary dysplasia (BPD). We studied the effects of early dexamethasone therapy on persistent ductal patency and the role of PDA in the etiopathogenesis of BPD during the course of a randomized double-blind trial of dexamethasone to prevent BPD. Infants, who weighed between 700 and 999 g, had severe RDS, and had been given surfactant, were randomized to receive a 12-day course of dexamethasone (n = 13) or placebo (n = 17) starting within the first 12 hours of postnatal life. The diagnosis of PDA was made clinically and was confirmed by cardiac ultrasound. The incidence of clinically significant ductus in infants who weighed less than 1000 g was 23% in the dexamethasone-treated group, as compared with 59% in infants who were given placebo. This difference was marginally significant, p = 0.05, odds ratio 0.21, 95% confidence interval 0.04-1.05. None of the infants in the dexamethasone group had recurrence of PDA after indomethacin therapy as compared with three infants in the placebo group. Dexamethasone significantly reduced the number of days infants required ventilator and supplemental oxygen as compared with infants who received placebo. Dexamethasone, as compared with placebo, also reduced the incidence of BPD, p = 0.025, odds ratio 0.08, 95% confidence interval 0.01-0.58. Dexamethasone may reduce the incidence of PDA in premature infants who weigh less than 1000 g at birth and thereby reduce the incidence of BPD.

[Low energy transcatheter atrial defibrillation in one patient with refractory atrial fibrillation]

Most cases of atrial fibrillation are converted with antiarrhythmic medications or external electric defibrillation. However, in some refractory patients, an internal transcatheter defibrillation must be attempted. We report a 50 years old male with an atrial fibrillation of one year duration that was refractory to pharmacological treatment and in whom external cardioversion was unsuccessful. After the application of a bifasic shock of 10 joules between a catheter in the right atrium and another one located at the coronary sinus, the patient was converted to sinus rhythm. At two months of follow up, the patient continues in sinus rhythm.

Protective Effect of Broccoli, Onion, Carrot, and Licorice Extracts against Cytotoxicity of N-Nitrosamines Evaluated by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium Bromide Assay

The protective effect of nine fruit and vegetable aqueous (H(2)O) and ethanolic (EtOH) extracts against the cytotoxicity of N-nitrosodimethylamine (NDMA), N-nitrosopyrrolidine (NPYR), N-nitrosodibutylamine (NDBA), and N-nitrosopiperidine (NPIP) was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The fruit extracts under investigation did not show a protective effect against any N-nitrosamines tested. Four vegetable extracts exhibited a protective effect (to 100% of survival) and a stimulation of cellular proliferation (>100% of survival) in decreasing order against NDMA and NPYR: broccoli(EtOH) > onion(H2O) > carrot(EtOH) > onion(EtOH) > licorice(H2O). Decreasing orders against NDBA and NPIP were, respectively, broccoli(EtOH) > licorice(H2O) > carrot(EtOH) > onion(EtOH) and broccoli(EtOH) > carrot(EtOH) > licorice(H2O) > onion(EtOH). Thus, broccoli(EtOH) extract (19-20 mg/mL) showed greater protective effect and stimulation of cellular proliferation (160% of survival) against all N-nitrosamines studied than the other vegetable extracts tested.

Mhc-E polymorphism in Pongidae primates: the same allele is found in two different species

Mhc-E intron 1, exon 2, intron 2, and exon 3 from pygmy chimpanzee (Pan paniscus), chimpanzee (Pan troglodytes), gorilla (Gorilla gorilla) and orangutan (Pongo pygmaeus) have been sequenced; six new Mhc-E alleles have been obtained but sequence changes are only placed either in introns or in synonymous exonic bases. One pygmy chimpanzee Mhc-E DNA sequence is identical to another sequence from chimpanzee; the fact that no variation is found also at the intronic level suggests that these two species of chimpanzee may have recently separated and/or that both of them might only represent subspecies. Mhc-E phylogenetic trees separate two evolutionary groups: Pongidae, including humans, and Cercopithecinae; this is also found by studying another non-classical class I gene, Mhc-G. The Mhc-E alleles' invariance at the protein level supports that strong selective forces are operating at the Mhc-E locus, as has also been found in both Cercopithecinae and humans. These allelic and evolutionary data suggest an altogether different functionality for HLA-E (and also HLA-G) compared with classical class I proteins: i.e., sending negative (tolerogenic) signals to NK and T cells.

Nontraumatic bilateral diaphragmatic myopathy: an unusual disturbance

Bilateral diaphragmatic paralysis (BDP) is an uncommon entity among neuromuscular diseases. We present a young female with no triggering factors who developed progressive dyspnea with respiratory failure. Further studies led to the diagnosis of BDP.

Interleukin-1beta does not increase synaptic inhibition in hippocampal CA3 pyramidal and dentate gyrus granule cells of the rat in vitro

Effects of interleukin-1beta (bath-applied; 500 pM) on rat hippocampal CA3 pyramidal and dentate granule cells were studied using intracellular microelectrode recording in vitro. In both cell types membrane input resistance, resting membrane potential and action potential amplitude remained stable throughout. No change was seen in postsynaptic potentials in granule cells. After blocking excitatory synaptic transmission in CA3 pyramids interleukin-1beta was found to consistently decrease synaptic inhibition by about 30%.

Inhibition of follicular growth by two different oral contraceptives (monophasic and triphasic) containing ethinylestradiol and gestodene

OBJECTIVE

To evaluate the inhibition level of ovarian follicular growth produced by a triphasic oral contraceptive (OC) containing ethinylestradiol and gestodene vs. the level produced by a monophasic OC containing the same components.

METHODS

A randomized, blind, cross-over trial was performed in a sample of 56 women. The follicular diameters were measured in 56 cycles under triphasic contraceptive treatment, and the other 56 under monophasic contraceptive treatment, using vaginal ultrasound. The statistical analysis was performed using the Student's t test.

RESULTS

The mean follicular diameter under monophasic OC treatment was found to be 8.16 mm (standard deviation 4.5), and while under triphasic OC treatment was found to be 7.44 mm (standard deviation 2.8) (p > 0.05). In 17 out of 112 cycles (15%), a certain degree of follicular activity was found (follicular diameter more than 10 mm), 10 cycles under monophasic OC and 7 cycles under triphasic OC.

CONCLUSIONS

The triphasic OC provides good inhibition of follicular growth and excellent contraceptive efficacy.

[Maximum static respiratory pressures in adults. The reference values for a Mediterranean Caucasian population]

The aim of this study was to establish reference values for PImax and PEmax for the Mediterranean adult population. Male and female individuals between 18 and 83 years old meeting the criteria for consideration as references and residing in the metropolitan area of Valencia were assigned by decades to six subgroups, each containing at least 20 men and 20 women. PEmax was obtained from the point of maximum expiration (residual volume) and PImax was the point of maximum inspiration (total lung capacity). The cohort, which finally included 264 subjects (129 men and 135 women), was separated a priori by sex for data analysis. The following types of variables were studied: sociological (employment, educational level and exercise), biometric (age, height and weight) and spirometric results. A linear correlation analysis was performed for each pair of variables and a Kolmogorov-Smirnov test of normality was performed. In order to check the accuracy of PImax and PEmax readings, intra-individual variability was determined by performing three consecutive procedures over 3 days in 39 randomly selected individuals (18 men and 21 women). Significant inter-day and inter-test effects for respiratory pressures were thus ruled out. Predictive equations were worked out using a simple linear model including all predictive variables and eliminating weaker variables in a stepwise manner. Mathematical goodness of fit was assessed by a coefficient for multiple determinations (R2); also determined were the estimated standard error and statistical significance. We also compared observed and estimated values and the behavior of residual values in terms of their independence, normality and homoscedasticity. Reference limits were established by defining percentiles. The equations finally arrived at for men were as follows: PImax (-cmH2O) - 1.03 x Age + 0.59 x Weight + 133.07, PEmax (cmH2O) - 1.31 x Age + 263.12. The equations for women were PImax (-cmH2O) - 0.64 x Age + 125.18, PEmax (cmH2O) - 0.57 x Age + 0.65 x Weight + 116.26. Agreement with the usual references (the Black and Hyatt equations) was analyzed.

[Long-term effects of nasal continuous positive airway pressure on ventilatory patterns of patients with obstructive sleep apnea syndrome]

We studied 20 patients with obstructive sleep apnea syndrome (OSAS) prospectively, before and after administering continuous positive airway pressure through a nasal mask (CPAPn) at night for 10 months, with the aim of determining the effects of ventilatory pattern of long-term treatment with CPAPn in OSAS patients. The following data were collected for all patients: anthropometric variables, lung function test results, arterial gasometric readings at rest, oxygen alveolar-arterial differential [Dif(A-a)O2)], central respiratory function variables at rest and during hypercapnic stimulus. Mean duration (range) of treatment with CPAPn was 12.5 (10-18) months. We observed a significant increase in PaO2 (p = 0.01) and a decrease in PaCO2 (p = 0.02) with slight variations in body weight and no changes in lung mechanics or in Dif(A-a)O2. The ventilatory pattern at rest showed an increased in VE and in respiratory frequency (p = 0.0003 and p = 0.033, respectively) with non significant changes in VT. The VT/Ti ratio increased (p = 0.015) and P0.1 decreased slightly (p = 0.025). We found no significant changes in the CO2 response slopes of VE or P0.1. In conclusion, CPAPn improves hypoxemia and hypercapnia in OSAS patients, above all by increasing baseline basal ventilation. The exact mechanisms implicated are poorly understood, but our data suggest a certain direct or indirect effect on respiratory muscles, reducing muscle fatigue, thus favoring greater availability during sleep.

[Primary pulmonary hypertension: treatment with prostacyclin before lung transplantation]

We report our experience with two patients diagnosed of primary pulmonary hypertension who later received lung transplants, with treatment with short-acting pulmonary vasodilators (epoprostenol) provided as a bridge to transplantation. Continuous intravenous perfusion at a dose of 6 ng/kg/min was provided to the first patient, a 19-year-old man, for 26 days. An initial dose of 4 ng/kg/min followed by 6 ng/kg/min was given to the second patient, a 49-year-old woman, for 6 months. Symptoms were drastically reduced in both patients, significantly improving their quality of life.

A competitive enzyme-linked immunosorbent assay for detection of bovine milk in ovine and caprine milk and cheese using a monoclonal antibody against bovine beta-casein

A competitive ELISA (enzyme-linked immunosorbent assay) was performed to detect and quantify bovine milk in ovine and caprine milk and cheese using a monoclonal antibody (AH4 MAb) against bovine beta-casein. Ovine or caprine milk and cheese containing bovine milk were added simultaneously with the AH4 MAb to the wells of a microtiter plate that had been previously sensitized with commercial bovine beta-casein. The bovine caseins in milk or cheese samples compete with the bovine beta-casein bound to the plate for the AH4 MAb binding sites. Further immunorecognition of AH4 MAb bound to the bovine beta-casein immobilized onto the plate was attained with rabbit anti-mouse immunoglobulin conjugated to peroxidase. Subsequent enzymic conversion of the substrate showed clear differences in absorbance values during assay of mixtures of ovine and caprine milk and cheese containing various amounts of bovine milk. The competitive ELISA developed in this work allows the quantitative detection of bovine milk in ovine and caprine milk and cheese samples in the range of 0.5 to 25% of substitution.

Virulence factors-pathogenicity relationships for Aeromonas species from clinical and food isolates

The presence of virulence factors in 96 Aeromonas strains isolated from food and clinical samples was studied. Neither cytotoxic activity and hydrophobicity, not the presence of pili or an extra surface layer made it possible to establish differences between food and clinical strains. Statistical studies showed that cytotoxin production was associated with a positive Voges-Proskauer reaction, inability to ferment arabinose and a positive lysine decarboxylation. Therefore, when comparing cytotoxic clinical and food strains with lysine decarboxylation phenotype, there was a significant difference (p < 0.05) between the two groups. The association of a cytotoxin production and lysine decarboxylation character should thus be considered as a possible virulence marker.

Allelic diversity at the primate Mhc-G locus: exon 3 bears stop codons in all Cercopithecinae sequences

Twenty-seven major histocompatibility complex (Mhc)-G exon 2, exon 3, and exon 2 and 3 allelic sequences were obtained together with 12 different intron 2 sequences. Homo sapiens, Pan troglodytes, Pan paniscus, Gorilla gorilla, Pongo pygmaeus, Macaca fascicularis, Macaca mulatta, and Cercopithecus aethiops individuals were studied. Polymorphism does not follow the classical pattern of three hypervariable regions per domain and is found in all species studied; exon 3 (equivalent to the alpha 2 protein domain) shows stop codons in the Cercopithecinae group but not in the Pongidae and human groups. Dendrograms show that cotton top tamarin (Saguinus oedipus) Mhc-G sequences are closer to Homo sapiens and Pongidae than to Cercopithecinae, probably due to the stop codons existing at exon 3 of the latter. There is a clear trans-species evolution of allelism in Cercopithecinae and also in exon 2 of all the other apes studied, but a generation of allelism within each species may be present on exon 3 sequences. This discrepancy may be due to the preferential use of exon 2 over exon 3 at the mRNA splicing level within each species in order to obtain the appropriate functional G product. Mhc-G intron 2 shows conserved motifs in all species studied, particularly a 23 base pair deletion between positions 161 and 183 which is locus specific, and some of the invariant residues, important for peptide presentation, conserved in classical class I molecules from fish and reptiles to humans were not found in Mhc-G alleles; the intron 2 dendrogram also shows a particular pattern of allelism within each species. In summary, Mhc-G has substantial differences from other classical class I genes: polymorphism patterns, tissue distribution, gene structure, splicing variability, and probably an allelism variability within each species at exon 3. The G proteins may also be different. This indicates that the Mhc-G function may not be peptide presentation to the clonotypic T-cell receptor.