Biomedical subjects
Publications and source records attributed to C Abad.
We present the case of an isolated rupture of the common carotid after a non-penetrating trauma of the neck. The patient was diagnosed by auscultation, ultrasound examination and arteriography and subsequently operated. A carotid segment was resected and reconstructed by an interposed vascular graft. We comment on the mechanisms of carotid artery blunt trauma, diagnostic methods and surgical options in this uncommon situation.
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The cases of two girls with 4 and 7 years of age presented. They had a patent ductus and an aortic coarcation which were subsequently surgically repaired. After the operation paraplegia was diagnosed. With rehabilitation they are able to walk, however paraparexis persist. Anatomy of the arterial irrigation of the spinal cord is reviewed and also the pathophysiology and mechanisms of medullar ischemia.
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We have investigated the conformational adaptability of gramicidin A incorporated into reverse micelles of sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/isooctane/water, a so far unexplored "host" membrane-mimetic model system for this peptide. A high-performance liquid chromatographic strategy previously developed for the study of gramicidin in phospholipid vesicles and normal micelles [Bañó et al. (1989) FEBS Lett. 250, 67; Bañó et al. (1991) Biochemistry 30, 886] has been successfully extended to this system. The method has permitted the separation of peptide conformational species, namely, double-stranded dimers and monomers, and an accurate quantitation of their proportion in the inverted micellar environment. It has been demonstrated that, once inserted in the micelle, the double-stranded dimers undergo a dissociation process toward a thermodynamically stable monomeric configuration, whose monomerization rate constant (k1) is dependent in a bell-shaped manner on the water:surfactant mole ratio, w0. A tight correlation between k1 and the double-stranded dimer backbone conformation has been found from the comparison of chromatographic and circular dichroism data. In addition, fluorescence experiments indicate that the peptide tryptophans are in a rather nonpolar environment, with a restricted accessibility to water-soluble quenchers such as acrylamide.
In an extension of our previous work (Bañó, M. C., Braco, L., and Abad, C. 1991. Biochemistry. 30:886-94), the kinetics of dissociation of gramicidin A double-stranded dimers into beta 6.3-helical monomers in small unilamellar vesicles prepared following different protocols, were investigated using in combination circular dichroism (CD) and high-performance liquid chromatography (HPLC). The analysis of the data from both techniques according to a two-component model strongly supports that any given CD pattern of gramicidin incorporated in the phospholipid bilayer can be deconvoluted essentially as a linear combination of the reference subspectra calculated for the double-stranded dimer and the helical monomer. An HPLC-based, semi-empirical approach is proposed for the simulation of gramicidin CD curves in the model membrane used, and it is shown that the congruence between theoretical and experimental spectra is very satisfactory.
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The aortoduodeonal fistula is a rare condition and has high mortality. We report five retrospective cases of digestive hemorrhage due to an aortoduodenal fistula (4 secondary and 1 primary) between 1986 and 1990. Three of them died. Attention is called to the importance of clinical suspicion and the main diagnostic methods in early diagnosis such as oral endoscopy. We also enhance the importance of emergency surgery for survival.
The 26-amino acid linear, amphiphilic peptide melittin was enzymatically modified with the fluorescent probe monodansylcadaverine using guinea pig liver transglutaminase and a fluorescent derivative of stoichiometry 1:1 was obtained. Reversed-phase and size-exclusion high-performance liquid chromatographic modes were tested in order to resolve the labelled peptide and native species. The influence of several operational variables was analysed and the elution conditions were optimized so that a satisfactory resolution could be achieved in both instances in a rapid, easy manner. Both chromatographic modes offer the possibility of accurate monitoring of the time course of the enzyme-mediated conversion and more interestingly, can be applied to the semi-preparative purification of the labelled peptide.
We have investigated the conformation of gramicidin A reconstituted in different phospholipid environments, small unilamellar vesicles, extensive bilayers, and micelles, by exploiting a recently proposed experimental approach based on high-performance liquid chromatography [Bañó et al. (1988) J. Chromatogr. 458, 105; Bañó et al. (1989) FEBS Lett. 250, 67]. The method allows the separation of conformational species of the peptide, namely, antiparallel double-stranded (APDS) dimers and beta 6.3-helical monomers, and quantitation of their proportions in the lipid environment. Various experimental parameters (e.g., nature of organic solvent, time of incubation in organic solvent, lipid-to-peptide mole ratio, time of sonication, and temperature) commonly involved in sample preparation protocols have been analyzed independently. The results show how the peptide conformation in model membranes is exquisitely dictated by the particular nature of the reconstitution protocol. In addition, we have elucidated the nature of the slow conformational transition of gramicidin toward the channel configuration that takes place upon incubation of the model membranes. This transition has been characterized as a temperature-dependent conversion from APDS dimeric to beta 6.3-helical monomeric forms. Analysis of kinetic data permits an accurate calculation of the rate constant for this process at different temperatures in phospholipid vesicles and micelles. Finally, an explanation is proposed for the laboratory-to-laboratory variation in the observed spectral patterns of inserted gramicidin.(ABSTRACT TRUNCATED AT 250 WORDS)
Melittin, a C-terminal glutamine peptide, incorporated the fluorescent probe monodansylcadaverine (DNC) when catalysed by guinea-pig liver transglutaminase and Ca2+, as determined by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). A 1:1 adduct DNC-melittin was identified in which a single glutamine residue out of two, i.e. Gln25, acts as acyl donor. Incubation of melittin with transglutaminase in the absence of DNC originated high molecular mass complexes indicative that the peptide lysine residue can act as an acyl acceptor. The DNC-melittin was about 3 times more active in the lysis of red cell membranes than native melittin. Fluorescence study of the labelled melittin in the submicromolar range where it is active on cells showed that while totally exposed to solvent in methanol solution, both Trp and dansyl groups are buried in buffer solution. This strongly suggests that DNC-melittin is self-associated and indeed more active than the native melittin in the same conditions.
Over a 7-year-period, 25 patients had delayed sternal closure after open heart operations out of 34 patients whose sternum was not closed. The indications were extreme cardiac dilatation and uncontrollable mediastinal hemorrhage. This represented a 1.79% incidence in the overall open heart surgical experience at our unit. Sternal closure was performed at a mean of 2.64 days after the initial operation. Eighteen patients (52.9%) left the hospital alive and well, representing a 72% survival rate among patients undergoing delayed sternal closure. No mediastinal or fatal infection developed and only 1 patient had late superficial wound infection after delayed sternal closure. We conclude that delayed sternal closure is an effective method to treat severe complications after cardiac operations.
A 3-month-old boy with tuberous sclerosis was diagnosed of biventricular heart tumor by means of 2D-echocardiogram. Three masses of tumor were excised from the right ventricle with the aid of cardiopulmonary bypass. Pathologic examination disclosed a cardiac rhabdomyoma. The boy is symptoms-free after 5 years of the operation. An echocardiogram taken at this time showed no-evidence of heart tumor. Pathology, diagnostic methods and surgical indications are commented. A review of selected surgically resected cases is also presented.
A case of left atrial hemangioma with papillary endothelial hyperplasia in a 42-year-old man is reported. With the aid of cardiopulmonary bypass, the tumor was resected, and the patient is well 22 months after operation. The clinical symptoms at initial examination, operative procedure, and pathological findings are reported, and the diagnostic and therapeutic approaches to cardiac tumors are described briefly. A review of surgically treated hemangiomas is also given.
A novel HPLC methodology for the study of gramicidin A reconstituted in model membranes has been tested in comparison with circular dichroism data. It is shown that this chromatographic technique not only corroborates most of the recent spectroscopic results but allows one to explain them in terms of mass fractions of different actual conformational species of GA in the phospholipid assemblies. In particular, the dependence of the inserted peptide configuration on the organic solvent and other parameters involved in the 'history' of the sample preparation and handling has been analyzed by HPLC in two phospholipid model systems: small unilamellar vesicles and micelles. Moreover, a slow conformational transition of GA towards a beta 6.3-helical configuration, accelerated by heat incubation, has been also chromatographically visualized and quantitatively interpreted.
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A primary fibrosarcoma was removed from the left atrium in a 58-year-old woman. We comment on the rareness of this cardiac neoplasm, the usefulness of two-dimensional echocardiogram in the clinical diagnosis of all cardiac tumors, and also the necessity for surgical treatment.
A new high-performance size-exclusion chromatographic strategy is reported for the analysis of the hydrophobic self-associating peptide gramicidin A, incorporated into artificial phospholipid vesicles (liposomes). The method is based on the direct injection of a few microlitres of the gramicidin A-containing liposome suspension into the column, which is eluted with a non-polar solvent, such as tetrahydrofuran. The type and amount of information which can be derived from this methodology have been evaluated. Using this chromatographic approach, a correlation has been unambiguously shown to exist between the organization of the peptide in the vesicles and a number of variables involved in the method of preparation of liposomes. Finally, a gramicidin A conformational transition has been monitored in the phospholipid vesicles which proved to be dependent on the class of phospholipid present in the liposome.