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Biomedical subjects

F J Belda

Publications and source records attributed to F J Belda.

At least 19 recordsLinked to original sources
PubMed1991

[Evaluation of 2 culture systems for the isolation of opportunistic mycobacteria].

The increment of infections produced by opportunist environmental mycobacteria (OEM) raises the question about the appropriateness of the conventional culture methods since they were initially designed to isolate M. tuberculosis. In this study we have comparatively evaluated the yield of a conventional culture (Löwenstein-Jensen) with respect to that of Middlebrook 7H12 (Bactec) in 396 selected samples in which OEM were isolated. Samples with commensal flora were previously subjected to a chemical homogenization-decontamination process with alkaline N-acetyl-cysteine. All cultures were sown with standard inoculates obtained from centrifugate material. The 7H12 culture showed a more rapid detection (mean: 17-18 days) and a greater effectiveness in the isolation of eventually pathogenic mycobacteria than the conventional Löwenstein-Jensen culture. The 7H12/LJ ratio for the species with high clinical relevance was: 1.3 for M. kansasii, 1.0 for M. marinum, 1.8 for M. scrofulaceum, 1.3 for M. xenopi, 1.5 for M. avium-intracellulare, 0.5 for M. chelonae, and 2.0 for M. fortuitum.

Bacteriological Techniques↗
PubMed1984

Structural changes in mitochondrial F1-ATPase induced by the removal of loosely bound nucleotides.

Mitochondrial F1-ATPase from beef heart, forms aggregates when it is depleted of loosely bound nucleotides by repeated precipitation in ammonium sulfate. Polyacrylamide gradient gel electrophoresis, in non dissociating conditions shows that the aggregate formed is a dimer (708,000 daltons). The aggregation is attributed to a conformational change of the protein as a consequence of the elimination of the nucleotides from the low affinity binding sites. This structural alteration seems to be reversible because, after addition of ATP, the aggregation is not observed on polyacrylamide gels but the catalytic properties remain unchanged. This conformational change alters the accessibility of protein sulfhydryl groups to 5,5' - dithiobis(2-nitrobenzoic acid). All these observations emphasize the importance of protein nucleotide interactions to the conformation of the mitochondrial F1-ATPase.

Animals↗
PubMed1983

A kinetic study of the interaction between mitochondrial F1 adenosine triphosphatase and adenylyl imidodiphosphate and guanylyl imidodiphosphate.

1. The presence of 5'-adenylyl imidodiphosphate, a non-hydrolysable analogue of ATP, in the solution used to assay the soluble bovine heart mitochondrial F1-ATPase produced slow competitive inhibition. If the enzyme was preincubated with the inhibitor before the substrate, MgATP, was added, a partial re-activation was obtained. 2. The slow inhibitory process showed first-order rate kinetics, and therefore it seems likely that a conformational change of the enzyme occurs following a faster binding process. A reaction scheme is suggested. At pH 7.8 the rate constant for the inhibition reaction was calculated to be 6.7 X 10(-2)s-1 and that for the re-activation 3.8 X 10(-3)s-1, with Keq. 17.6, indicating that the inhibited enzyme-inhibitor complex will be favoured over the non-inhibited enzyme-inhibitor complex. 3. The presence of 5'-guanylyl imidodiphosphate in the solution used to assay F1-ATPase produced rapid competitive inhibition, which was then slowly reversed until a steady state was reached. This might be explained by a rapid but reversible shift of the inhibition pathway induced by this non-hydrolysable analogue of ATP. A complex rate constant for the displacement of the inhibitor by the substrate of 7.6 X 10(-3)s-1 was calculated. 4. The results are discussed in the light of other recent observations about binding of 5'-adenylyl imidodiphosphate to F1-ATPase and with reference to the binding-site-change mechanism of hydrolysis of ATP by F1-ATPase.

Adenosine Triphosphate↗
PubMedDate not supplied

[Application of high frequency jet ventilation during microsurgery of the larynx under suspending laryngoscopy].

OBJECTIVES: This study describes the results obtained with high frequency jet ventilation (HFJV) in 19 patients who underwent laryngeal microsurgery under suspending laryngoscopy. MATERIAL AND METHODS: After premedication and anesthetic induction with propofol (Diprivan R, ICI-Farma), we performed an endotracheal intubation (28F tube) under succinyl-choline facilitation. Conventional ventilation was started at a rate of 14-16 cpm with a minute volume of 8-10 l, and a FiO2 of 0.4 (air-oxygen). The endotracheal tube was replaced by an insufflation catheter of 2 mm internal diameter and HFJV was initiated at a rate of 100 cpm, inspiratory time equal to the 33% of the total cycle, generator pressure of 2.5-3.6 kg/cm2, and similar FiO2. We used an Ergojet CVT (Temel SA) respirator that allowed continuous monitoring of the injector released volume during each cycle (Vjet) as well as the air way pressure. Anesthesia was maintained with continuous propofol perfusion. RESULTS: During HFJV there were no significant hemodynamic alterations and surgeons considered that the condition of the surgical field was excellent. Air way pressure was maintained at low levels in all cases, although brief hypertensive episodes occurred during laryngeal manipulation. Oxygenation was satisfactory in all except one patient with chronic obstructive pulmonary disease. Conventional ventilation and HFJV did not induce significant differences in alveolar ventilation nor in PaCO2. However, during HFJV oxygenation and ventilatory levels suffered a high degree of interindividual variability. This phenomenon could be due to the existence of variable degrees of gas reflux during insufflation. CONCLUSIONS: We conclude that HFJV is a very useful technique for anesthesia in laryngeal microsurgery. However, an appropriate monitoring of ventilatory dynamics and a detailed knowledge of the influences of patient's characteristics on HFJV are required.

Adult↗
PubMedDate not supplied

[Results of functional analysis on an obstructive model of the lung using an Ergojet CVT high-frequency jet respirator. Comparison with the normal pattern].

This paper expands a previous study on functional analysis of high frequency jet (HFJV) "Ergojet CVT" ventilation module inserted in Ergotronic 3 (Temel SA) respirator. The analysis was made on a pulmonary monoalveolar model with a compliance of 50 ml/cmH2 = and a resistance of 20 cmH2O/l/se simulating an obstructive pattern. Results were also compared with those obtained in a previous study on normal lung. HFJV was applied using a jet with or without additional gas input (VE) at respiratory rates of 90, 120, 150, 180, 210, 240, 270, and 300 per minute varying in each frequency the releasing pressure of the jet (PG 1, 2, and 3 kg/cm2) and the inspiratory time (Ti 30 to 50%) giving rise to a total of 96 different situations. In each of these conditions we measured the air way pressure (Paw) and the alveolar pressure (PA) and we calculated the tidal volume (VT) and the trapped volume (VAT). These measurements were correlated with those monitored by the respirator and those obtained in the normal lung. Results show that the VT is composed almost exclusively by the jet volume (VTjet), being only of consideration the VE with a Ti of about 33% and a PG of 2 to 3 kg/cm2. When the normal pattern was compared with the obstructive one, a small reduction in VT (average of 15%) and a marked increase in peak Paw (average of 75%) were observed. The use of a Ti of 50% has no clinical interest due to the large VAT that it produces.(ABSTRACT TRUNCATED AT 250 WORDS)

High-Frequency Jet Ventilation↗
PubMedDate not supplied

[Functional analysis of the high frequency jet respirator on a normal lung model. Ergojet CVT].

In this paper the results of the functional analysis of the Ergojet CVT, which is the high-frequency jet ventilation (HFJV) module of the Ergotronic 3 ventilator (Temel S.A.) are described. For a better understanding a detailed description of the module has been included. The functional analysis was performed on a standard lung model of normal compliance and resistance (C: 50 ml/cmH2O and R: 8 cmH2O.1-1.seg-1). High frequency jet ventilation was applied using the jet with and without additional gas entrainment, at frequencies of 90, 120, 150, 180, 210, 240, 270 and 300 rpm; for each frequency changes were made on the driving pressure (Pdriv: 1-2-3 kg.cm-2) and the inspiratory time (Ti: 33-50%). The combination of these parameters produced 96 different ventilatory circumstances. In each of them, airway and alveolar pressures (Paw and PA) were measured. Tidal and alveolar gas-trapped volumes (VT and Vtrap) were calculated from the previous PA measurements. These values were compared with those displayed by the ventilator. Following the results of the functional analysis of the Ergojet CVT, the VT delivered by the jet is the primary determinant of the VT, being little de increment due to the entrainment of gas. In the normal lung model, an adequate VT is obtained until frequencies of 240 rpm, using a Pdriv of 3 kg.cm-2. Vtrap, as in conventional ventilation, depend on VT and Te. The Pdriv and Ti, can be adequatelly combined in order to obtain a minimal Vtrap. Peak Paw depends on VT and Paw min on Vtrap.(ABSTRACT TRUNCATED AT 250 WORDS)

Biophysical Phenomena↗