Biomedical subjects

C Bravo

Publications and source records attributed to C Bravo.

At least 37 records · Page 2Linked to original sources

PubMed2000

Woven vascular microsurgical prostheses in our experimental practice.

The authors have been concerned for six years with the development of woven microsurgical prostheses in experiments on laboratory rats, beagle dogs and domestic white pigs. In rats, in 224 experiments employing 38 types of prostheses with an inner diameter of 2 mm, a reliable prosthesis was selected, described as No. 36, with a 100% patency after insertion of a 1 cm long portion into a defect in the abdominal aorta in 40 experiments. The follow-up of this type of prosthesis lasted 12 months. In large animals this type of prosthesis was implanted into a defect of the radial artery and cephalic vein in dogs and into the femoral artery and the artery of a vascular pedicle of groin and lateral thigh flap. These experiments on large animals are not yet complete and will be the subject of a separate paper.

Animals↗

PubMed1999

[Reimplantation lesion in the postoperative period of lung transplantation. Incidence, predictive factors, prognosis and outcome. The Lung Transplantation Group of Vall d'Hebron University General Hospital].

BACKGROUND: Reimplantation disease (RD) is a postoperative complication in lung transplantation. It is defined as hypoxemia (PaO2/FiO2 ratio < 150 mmHg), radiologic infiltrates and decrease of lung compliance. The aim of the study was to analyze the incidence, predictive factors, prognosis and outcome of the patients with RD. PATIENTS AND METHOD: 49 patients submitted to lung transplantation (June 1991-December 1996) were admitted in our intensive care unit (ICU). Donor and recipient conditions, surgical parameters and outcome in ICU were analyzed. Mann-Whitney, Kruskall-Wallis, Fisher, Pearson and ANOVA-Friedman tests were used for statistical analysis according to the different variables. RESULTS: 49% of the patients (29/49) developed RD, which was influenced neither by lung disease, nor by the kind of transplantation or by ischemia time. All patients with a long surgical time developed RD, versus only 41% in those where surgery was undertaken in a shorter period of time, OR: 2.8 (1.5-5.7; p = 0.0016). The patients with RD improved showing a PaO2/FiO2 ratio of 176 and 235 mmHg at 24 and 48 h respectively (ANOVA, p < 0.00001). The patients with RD needed 14 days of mechanical ventilation versus 7 days in those without RD (p = 0.013). There were no statistically significant differences in stay and mortality in ICU. CONCLUSIONS: RD is a common complication in the postoperative phase of lung transplantation. It is present in almost all the patients with long surgical time. Almost all of them improve, with the same survival but a longer period of mechanical ventilation.

APACHE↗

PubMed1999

Inhibition and uncoupling of oxidative phosphorylation by nonsteroidal anti-inflammatory drugs: study in mitochondria, submitochondrial particles, cells, and whole heart.

The effects of the anti-inflammatory drugs diclofenac, piroxicam, indomethacin, naproxen, nabumetone, nimesulide, and meloxicam on mitochondrial respiration, ATP synthesis, and membrane potential were determined. Except for nabumetone and naproxen, the other drugs stimulated basal and uncoupled respiration, inhibited ATP synthesis, and collapsed membrane potential in mitochondria incubated in the presence of either glutamate + malate or succinate. Plots of membrane potential versus ATP synthesis (or respiration) showed proportional variations in both parameters, induced by different concentrations of nimesulide, meloxicam, piroxicam, or indomethacin, but not by diclofenac. The activity of the adenine nucleotide translocase was blocked by diclofenac and nimesulide; diclofenac also slightly inhibited mitochondrial ATPase activity. Naproxen did not affect any of the mitochondrial parameters measured. Nabumetone inhibited respiration, ATP synthesis, and membrane potential in the presence of glutamate + malate, but not with succinate. NADH oxidation in submitochondrial particles also was inhibited by nabumetone. Nabumetone inhibited O2 uptake in intact cells and in whole heart, whereas the other five drugs stimulated respiration. These observations revealed that in situ mitochondria are an accessible target. Except for diclofenac, a negative inotropic effect on cardiac contractility was induced by the drugs. The data indicated that nimesulide, meloxicam, piroxicam, and indomethacin behaved as mitochondrial uncouplers, whereas nabumetone exerted a specific inhibition of site 1 of the respiratory chain. Diclofenac was an uncoupler too, but it also affected the adenine nucleotide translocase and the H+-ATPase.

Adenosine Triphosphate↗

PubMed1999

Preregistration study on the safety and contraceptive efficacy of a progesterone-releasing vaginal ring in Chilean nursing women.

The contraceptive efficacy and safety of a progesterone-releasing vaginal ring (PVR) manufactured in Chile were compared to that of the Copper T 380A IUD (T-Cu) in nursing women enrolled at three Chilean clinics. A total of 285 volunteers chose to use the PVR and 262 the T-Cu. Plasma progesterone levels attained with the ring decreased from 25 to 14 nmol/L from month 1 to month 3 of use. Ring replacement was scheduled every 3 months. Volunteers continued in the study until weaning or completing the continuous use of four PVRs. No pregnancies occurred in 2320 and 2183 woman-months of exposure with the PVR and the T-Cu, respectively. Lower continuation rates in the first 6 months because of problems with use and a longer lactational amenorrhea were observed in the PVR than in the T-Cu group. Breast-feeding performance and infant growth were similar in both groups. These results confirm the high efficacy and safety of the PVR for nursing women and have led to the registration of the PVR by Chilean health authorities.

Adult↗

PubMed1999

A Y form of hammerhead ribozyme trapped by photo-cross-links retains full cleavage activity.

The conformation in solution of a small bipartite I-III hammerhead ribozyme has been deduced from the photo-crosslinks formed between cleavable ribo-deoxysubstrates appropriately substituted with the probe deoxy-4-thiouridine and ribozyme residues. The ribozyme-substrate complex is able to adopt a Y-like structure with stems I and II in close proximity in the presence of 400 mM Na+ only. Indeed, a cross-link joining stem I (1.6) to loop II (AL2.4) forms in significant amount under these conditions. This cross-linked complex furthermore elicits, upon Mg2+ addition, a catalytic activity similar to that exhibited by the complexes cross-linked at the distal ends of either stem I or stem III or of the non-substituted bipartite complex. This shows that the reaction mechanism is fully compatible with a strong structural constraint between stems I and II and that sodium ions at high concentration (400 mM) are able to promote a proper folding of hammerhead ribozymes. None of the multiple cross-links formed within the ribozyme core (probe in position 16.1 or 1.1) was found catalytically active. The cross-link patterns nevertheless indicate a higher flexibility of the core in Na+ than in Mg2+. While most of the cross-links can be accommodated by the Y solution structure, some of them (16.1 to U4 and 2.1) definitely can not, suggesting that additional alternative inactive conformations exist in solution.

Buffers↗

PubMed1999

Determining and understanding the control of flux. An illustration in submitochondrial particles of how to validate schemes of metabolic control.

Two complementary methods were used to determine how the rate of respiration and that of ATP hydrolysis were controlled in rat liver submitochondrial particles. In the first, 'direct control analysis' method, respiration was titrated with malonate, antimycin or cyanide at 20, 30 and 37 degrees C, to determine the flux control exerted by succinate dehydrogenase, cytochrome bc1 complex and cytochrome c oxidase, respectively. Together, the three respiratory complexes only controlled the flux by about 50%, leaving the other 50% of flux control to the H+ leak. In the second, 'elasticity based' method, the elasticity coefficients of the respiratory chain or the H+-ATPase and the H+ leak towards the H+ gradient were determined. Then, the flux control coefficients were calculated using the connectivity and summation laws of metabolic control theory. The correspondence between the flux control coefficients determined in the two ways validated the two methods. This allowed us to use the second method to analyse what was the kinetic origin of the observed distribution of control. Control of ATP hydrolysis by the ATPase decreased with increasing ATPase activity; hence, the control exerted by the H+ leak increased with increasing ATPase activity, due to a diminishing elasticity towards the H+ gradient. Reverse electron transport was mainly controlled by the ATPase; the sum of flux control coefficients of succinate dehydrogenase, NADH-CoQ oxidoreductase, and H+-ATPase yielded a value greater than one, indicating that the H+ leak exerted a significant negative control on this pathway.

Adenosine Triphosphatases↗

PubMed1998

Functional and aesthetic consequences in the forearm after harvesting the Chinese flap.

We have evaluated the donor site after harvesting the chinese flap in 40 patients operated at the Clinic of Plastic and Aesthetic Surgery of Brno between 1989 and 1994. We conclude that: 1--The hand function is not oustandly altered after harvesting the flap, but in our study 11 patients (27.5%) indicated that they have some limitation or impairment of their hand function. 2--Tolerance to forearm deformity is considerable, but it depends on degree of the defect for which the flap is transferred: 25 patients (62.5%) would like to elect a different flap. 3--It is necessary to think about cosmetic consequences of the chinese flap and consider other possibilities of the flap choice. Secondary defect may be for the patient a problem even several years after operation.

Adolescent↗

PubMed1997

The mitochondrial membrane permeability transition induced by inorganic phosphate or inorganic arsenate. A comparative study.

The membrane permeability transition (MPT) induced by Ca2+ and Pi or Asi was studied in rat kidney mitochondria. Membrane potential, Ca2+ transport and swelling were used to monitor the MPT. Asi promoted a faster and more extensive collapse of membrane potential, Ca2+ release and swelling than Pi. The MPT induced by Pi was fully blocked by Mg(2+)+ADP, spermine+ADP, Mg(2+)+ cyclosporin A (CSA), and ADP+CSA. In contrast, the MPT induced by Asi was only prevented, although not completely, by CSA+Mg2+ or ADP+CSA. Asi, but not Pi, was able to cause collapse of membrane potential in the presence of Sr2+. Carboxyatractyloside (CAT) produced collapse of membrane potential at a lower concentration in the presence of Asi+Ca(2+)+ADP than with Pi+Ca(2+)+ADP. The addition of Pi+Ca2+ to [14C]-ADP loaded mitochondria brought about a greater ADP release than Asi+Ca2+. The ADP release was CAT-sensitive with Pi but it was only partially blocked by Asi. The diminution of external pH did not inhibit the MPT induced by Pi or Asi. The results of this study suggest that the adenine nucleotide translocase does not have an essential role in the MPT induced by Asi+Ca2+.

Adenosine Diphosphate↗

PubMed1997

On the protection by inorganic phosphate of calcium-induced membrane permeability transition.

The role of inorganic phosphate as inhibitor of mitochondrial membrane permeability transition was studied. It is shown that in mitochondria containing a high phosphate concentration, i.e., 68 nmo/mg, Ca2+ did not activate the pore opening. Conversely, at lower levels of matrix phosphate, i.e., 38 nmol/mg, Ca2+ was able to induce subsequent pore opening. The inhibitory effect of phosphate was apparent in sucrose-based media, but it was not achieved in KCI media. The matrix free Ca2+ concentration and matrix pH were lowered by phosphate, but they were always higher in K+-media. In the absence of ADP, phosphate strengthened the inhibitory effect of cyclosporin A on carboxyatractyloside-induced Ca2+ efflux. Acetate was unable to replace phosphate in the induction of the aforementioned effects. It is concluded that phosphate preserves selective membrane permeability by diminishing the matrix free Ca2+ concentration.

Animals↗

PubMed1997

Dopaminergic influence on cardiovascular responses to exercise stress in hypertensive subjects.

Ten hypertensive subjects were studied at the Vargas Medical School in Caracas, Venezuela. They were submitted to submaximal treadmill exercises according to Bruce's protocol under treatment with dopaminergic drugs (metoclopramide, bromocriptine). Before and during submaximal exercises, metoclopramide caused a hypotensive effect accompanied by an increased heart rate, which was blocked by the administration of bromocriptine. We conclude that a probable dopaminergic modulatory influence takes place during exercise.

Blood Pressure↗

PubMed1997

Empiric treatments impair the diagnostic yield of BAL in HIV-positive patients.

OBJECTIVE: To investigate the influence of empiric treatments prior to fiberoptic bronchoscopy (FOB) on the diagnostic yield of BAL in HIV-positive patients with respiratory symptoms. METHOD: We studied 123 consecutive FOBs with BAL in HIV-positive patients; 101 of these patients (82%) had received previous antimicrobial treatment from 1 to 60 days. Diagnostic yield of BAL for Pneumocystis carinii, Mycobacterium tuberculosis, and bacterial pneumonia was compared between patients with and without previous empiric treatments. RESULTS: A diagnosis was obtained in 85 patients (69%), of whom 17 (20%) had multiple infections. Diagnostic yield was higher in patients without previous treatment, 91% (20/22) compared with 64% (65/101), p < 0.03. Diagnostic yield was also higher for bacterial pneumonia: seven isolations from 22 patients not receiving previous empiric treatment (32%), compared with 11 of those who had (11%; p < 0.02). The duration of empiric treatment against P carinii in patients in whom it was isolated was significantly shorter than in those in whom P carinii was not detected (3.5 +/- 1.8 days compared with 5.2 +/- 2.4 days; p = 0.003). FOB permitted a change in treatment in 62% of patients with a final diagnosis. CONCLUSION: This study demonstrates that empiric treatments prior to FOB significantly impair the diagnostic yield of BAL in detecting common pathogens in HIV-infected patients with respiratory symptoms.

AIDS-Related Opportunistic Infections↗

PubMed1996

Folding of the HDV antigenomic ribozyme pseudoknot structure deduced from long-range photocrosslinks.

A trans-acting system has been designed in order to explore the three-dimensional structure of the anti-genomic HDV ribozyme. In this system, the substrate (SANT) is associated by base-pairing to the catalytic RNA (RzANT) forming helix H1. RzANT is able to cleave specifically the RNA substrate as well as a deoxysubstrate analogue containing a single ribocytidine at the cleavage site (position -1). This demonstrates that such deoxysubstrate analogues are valuable tools for structural studies of this ribozyme domain. They form however weak complexes with RzANT which is due in part to their ability to fold as stable hairpins unlike the RNA substrate. Using a set of full deoxy or of mixed deoxy-ribo substrate analogues site-specific substituted with the photoaffinity probe deoxy-4-thiouridine, ds4U, at a defined position, we were able to determine a number of long range contacts between the substrate and the ribozyme core. In particular, crosslinks between substrate position -1 and position -2 with residues C15, G19 and C67, thought to be involved in the ribozyme catalytic site, were detected. A three dimensional model of the antigenomic ribozyme system, derived from the structure proposed by Tanner et al. [Current Biol (1994) 4, 488-498] for the genomic system was constructed. Apart from residue deletion or insertion, only minor accommodations were needed to account for all photocrosslinks but one which is attributed to an alternative hybridization of the substrate with the ribozyme. This study therefore further supports the structure proposed by Tanner et al. for the pseudoknot model.

Base Sequence↗

PubMed1996

On the mechanism by which 6-ketocholestanol protects mitochondria against uncoupling-induced Ca2+ efflux.

This work shows that 6-ketocholestanol (kCh) inhibits the effect of carbonyl cyanide-m-chlorophenyl hydrazone (CCP) on mitochondrial Ca2+ efflux. Such an effect proved to be caused by diminution of membrane fluidity, therefore, it is affected by the incubation temperature. Furthermore, kCh reversed CCP-induced Ca2+ efflux depending on the accumulation of phosphate. It is also shown that kCh enhances the effect of carboxyatractyloside on membrane permeability transition.

Animals↗

PubMed1996

Experimental osteochondritis dissecans--the role of cartilage canals in chondral fractures of young rabbits.

Skeletal immature rabbits were used to study the pathogenesis of Osteochondritis Dissecans (OCD). Both histological studies and a radiographical examination were utilized after sagittal and coronal surgical chondral fractures were made in the femoral condyles cartilage. Serial microangiographies were performed in rabbits between 0 and 84 days after the chondral fractures were made. Analyses of the histology and microradiography findings suggest in either a coronal or sagittal direction, that avascular lesions like an experimental OCD occur as a sequence of chondral injury. A fracture in a wide pedicle of a stable cartilaginous flap with abundant cartilage canals heals in the usual way. However, a fracture in an unstable fragment with a small isthmus devoid of cartilage canals and of nutritious vessels, probably doesn't heal completely and a fragment closely resembling OCD is instead formed. An experimental OCD depends on the slender hinge of the flap and on the lack of stability in a rabbit's non-ossified epiphyseal cartilage. The damage to the cartilage canals and the rupture of vessels in the canals by a chondral fracture and the disturbance in the revascularization in the healing process by abnormal mechanical forces are thus most likely considered to be the main factor for OCD production.

Animals↗

PubMed1996

Modulation of matrix Ca2+ content by the ADP/ATP carrier in brown adipose tissue mitochondria. Influence of membrane lipid composition.

The role of the adenine nucleotide translocase on Ca2+ homeostasis in mitochondria from brown adipose tissue was examined. It was found that in mitochondria incubated with 50 microM Ca2+, ADP was not needed to retain the cation, but it was required for strengthening the inhibitory effect of cyclosporin on membrane permeability transition as induced by menadione. In addition, carboxyatractyloside was unable to promote matrix Ca2+ release, even though it inhibits the ADP exchange reaction. However, when the Ca2+ concentration was increased to 150 microM carboxyatractyloside did induce Ca2+ release, and ADP favored Ca2+ retention. Determination of cardiolipin content in the inner membrane vesicles showed a greater concentration in brown adipose tissue mitochondria than that found in kidney mitochondria. It suggested that the failure of the adenine nucleotide translocase to influence membrane permeability transition depends on the lipid composition of the inner membrane.

Adenosine Diphosphate↗

PubMed1995

[Antibacterial effects of antiseptics in vitro and in an experiment in vivo].

The effect of topical antiseptics routinely used in the Department of plastic and aesthetic surgery was tested against bacteria commonly infecting burns and major skin defects. In vivo, the effect on Staphylococcus aureus and Pseudomonas aeruginosa was examined, in vitro also on Proteus mirabilis. A very good effect on tested microorganisms was observed with 0.1% Persteril, Peruvian balsam and Dermazin crm. (Lek, Ljubljana). Gentian violet in a 0.5% concentration and 3% boric acid were not effective on Pseudomonas aeruginosa, 0.05% permanganate and 2% Jodonal were moreover not effective against S. aureus.

Animals↗

PubMed1995

[The use of fibrinogen-thrombin via endoscope in the treatment of massive hemoptysis].

We assessed the efficacy of fibrinogen-thrombin instillation through the fiberoptic bronchoscope to treat massive hemoptysis in patients to whom embolization of bronchial arteries was not available, was contraindicated or had failed. The fibrinogen-thrombin solution used was Tissucol, which in addition to 2% fibrinogen and 4 U/ml of thrombin, also contained factor XIII an aprotinin. The fibrinogen-thrombin solution was instilled with the aid of the Duplojec system and a 70 cm x 2 mm 4-way catheter. In 53 of the 628 fiberoptic bronchoscopies performed during the study, the indication was hemoptysis > or = 150 ml/12 h. Of these, bronchoscopic instillation of fibrinogen-thrombin was indicated in 5 cases because bronchial artery embolization was impossible. The point of bleeding was located by bronchoscopy in all cases and fibrinogen-thrombin instillation controlled hemoptysis immediately and throughout the follow-up period, which ranged 4 to 10 months. Morning expectoration of blood (< 10 ml) was observed in only 1 patient in the 3 days after treatment. The mean time taken for bronchoscopic exploration was 3 minutes (range, 2-7). In all cases fiberoptic bronchoscopy was performed without complications that might have required the procedure to be suspended. We conclude that the local use of fibrinogen-thrombin or fibrin glue instilled through the fiberoptic bronchoscope to the point of bleeding is a simple, fast and cheap way to control massive hemoptysis on a short and long-term basis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

[Effects of the most frequently used solutions and ointments in routine surgical practice].

The authors tested the effect of local antiseptics commonly used at the Clinic of Plastic and Aesthetic Surgery in Brno on bacteria which most frequently infect extensive skin defects. The experiments were carried out in vitro and in vivo in a group of experimental animals. In vivo the effect on Staphylococcus aureus and Pseudomonas aeruginosa was investigated, in vitro also the effect on Proteus mirabilis. The authors found that 0.1% Persteril, Peru balsam, and Dermazine ung./Lek Co./exerted a very favourable effect on the tested microorganisms. A weaker effect was recorded after Vishnevsky balsam and 0.5% Rivanol. 0.5% gentian violet and 3% boricacid had no effect on P. aeruginosa, 0.05% permanganate and 2% Jodonal had no effect on staphylococci.

Animals↗