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Biomedical subjects

C Abad

Publications and source records attributed to C Abad.

At least 73 records · Page 4Linked to original sources
PubMed1995

HPLC demonstration that an all Trp-->Phe replacement in gramicidin A results in a conformational rearrangement from beta-helical monomer to double-stranded dimer in model membranes.

We have taken advantage of our previously reported high performance liquid chromatographic (HPLC) strategy to investigate the conformational behavior of the optically reversed gramicidin M (gM-), an analog of gramicidin A with all tryptophans replaced by phenylalanines, in different model membranes. It is quantitatively demonstrated for the first time that once inserted in the lipid environment, gM- (unlike the native peptide) undergoes a conformational transition from beta-helical monomers to thermodynamically stable double-stranded dimers. This transition is faster the higher the incubation temperature and can be neatly observed in both small unilamellar phospholipid vesicles and lysophospholipid micelles. The results of this study are discussed in the light of presently available data from other techniques, in the framework of the current efforts to understand structure-function relationships of linear gramicidins.

Chromatography, High Pressure Liquid↗
PubMed1995

Interfacial activation-based molecular bioimprinting of lipolytic enzymes.

Interfacial activation-based molecular (bio)-imprinting (IAMI) has been developed to rationally improve the performance of lipolytic enzymes in nonaqueous environments. The strategy combinedly exploits (i) the known dramatic enhancement of the protein conformational rigidity in a water-restricted milieu and (ii) the reported conformational changes associated with the activation of these enzymes at lipid-water interfaces, which basically involves an increased substrate accessibility to the active site and/or an induction of a more competent catalytic machinery. Six model enzymes have been assayed in several model reactions in nonaqueous media. The results, rationalized in light of the present biochemical and structural knowledge, show that the IAMI approach represents a straightforward, versatile method to generate manageable, activated (kinetically trapped) forms of lipolytic enzymes, providing under optimal conditions nonaqueous rate enhancements of up to two orders of magnitude. It is also shown that imprintability of lipolytic enzymes depends not only on the nature of the enzyme but also on the "quality" of the interface used as the template.

Animals↗
PubMed1995

Congenital aneurysm of the sinus of Valsalva dissecting into the interventricular septum.

The case of a 57-year-old man with a congenital aneurysm of the right sinus of Valsalva dissecting into the interventricular septum is presented. The patient had a previous heart block and aortic insufficiency. The diagnosis was made by echocardiography and cardiac catheterization. Open-heart surgery was performed, closing the entrance of the aneurysm and replacing the aortic valve. The patient survived surgery and is in New York Heart Association functional class II 3 years after surgical repair. Other cases of this uncommon congenital heart disease are reviewed.

Aortic Aneurysm↗
PubMed1995

Acute infectious mitroaortic endocarditis in association with acute aortic dissection. Surgical management of an unusual combination of diseases.

A 58-year-old man with acute mitral and aortic endocarditis suffered an acute ascending aortic dissection. The patient had a double valve replacement, combined with replacement of the ascending aorta with a Dacron graft and sealing and closure of the proximal and distal aortic segments with surgical glue. Six months after the operation the patient is doing well with normal function of both valve prostheses and aortic vascular graft.

Acute Disease↗
PubMed1995

Coronary artery bypass surgery for patients with left main coronary lesions due to Takayasu's arteritis.

Two patients with documented Takayasu's arteritis and severe left main coronary lesion were operated on. The first patient was a 17-year-old boy operated with a double saphenous vein coronary artery bypass graft in 1982, the patient survived 12 years but died suddenly due to associated aortic insufficiency. The second case was a 46-year-old female patient who was successfully operated on.

Adolescent↗
PubMed1995

Arteriosclerotic histologic evaluation of the internal mammary artery in patients undergoing coronary artery bypass grafting.

During 1991, 52 patients undergoing myocardial revascularization had a biopsy of the distal internal left mammary artery (IMA) taken. There were 48 male and 4 female patients with a medium age of 58 years. Arteriosclerotic involvement of the IMA was assessed according to the scale of Kay. Using this index, grade 0 corresponds to a normal artery without atherosclerosis, grade 1 represents minimal disease, grade 2 a narrowing of less than 25% of the lumen, grade 3 narrowing between 25 and 50%, and grade 4 narrowing of 50% or greater of the lumen. Of the 52 IMA examined, the arteries with degree 0, 1, 2, 3, and 4 were: 19 (36.5%), 20 (38.4%), 9 (17.6%), 4 (7.6%) and zero. Thirty-three arteries (63.4%) had some degree of atherosclerosis. Considering the arteries with some atherosclerotic narrowing, 13 (25%) of the whole group had this pathological alteration. The IMA has a low but consistent incidence of arteriosclerosis involvement. Preoperative angiographic investigation of the IMA could be routinely performed.

Adult↗
PubMed1995

Total aortic arch replacement by a cryopreserved aortic homograft.

The case is presented of a 60-year-old man with previous surgery on the transverse aorta and a pseudoaneurysm of the aortic arch and hemoptysis. The patient was operated upon with cardiopulmonary bypass and cerebral perfusion. The aortic arch was resected preserving a cuff of the aorta containing the three supra-aortic trunks. A bronchial fistula was closed with a pediculated flap of the native arch. A long segment of cryopreserved human aorta (ascending, arch and upper descending thoracic aorta) was inserted in the orthotopic position. The aortic cuff with the supra-aortic vessels was re-inserted onto the allograft. The patient is asymptomatic 2 months after the operation. Aortic homografts are a good alternative in cases with suspected infection or contamination, like this one. Other conditions, such as infected aneurysms, infected grafts, aorto-esophageal fistula and aorto-gastrointestinal fistula, are potentially good candidates for homografting. We believe that this case is the first report of a complete substitution of the aortic arch with a human cryopreserved homograft.

Aorta, Thoracic↗
PubMed1995

Removal of infected dual chambered transvenous pacemaker and implantation of a new epicardial dual chambered device with cardiopulmonary bypass: experience with seven cases.

Seven patients with infected transvenous dual chambered pacemakers have undergone removal of the device using cardiopulmonary bypass. There were four women and three men with a mean age of 58 years. Six patients had localized infection in the generator pocket (mean of 4.6 previous unsuccessful operations for surgical sterilization). Four infections were due to Staphylococcus epidermidis, two to Staphylococcus aureus, and one patient presented septicemia caused by Staphylococcus epidermidis and Pseudomonas aeruginosa. The atrial and ventricular transvenous electrodes were removed under direct vision using cardiopulmonary bypass. A new dual chambered epicardial pacemaker was implanted. The procedure was well-tolerated, and all patients are infection free with working pacemakers after a mean follow-up of 25.4 months.

Cardiopulmonary Bypass↗
PubMed1994

Gln5 selectively monodansylated substance P as a sensitive tool for interaction studies with membranes.

Substance P (SP) is a neuropeptide endowed with several important biological activities both in the central and peripheral nervous system. Taking advantage of the presence of glutamine residues in SP, the peptide was labelled with the fluorescent probe monodansylcadaverine using the transglutaminase (TGase)-reaction in order to study interactions between SP and model or natural membranes. Although it was verified that both adjacent glutamines of the peptide can act as substrate for TGase in a consecutive reaction, conditions were optimized to selectively label Gln5. This fluorescent SP analogue was found to adopt environment-dependent conformations similar to those of the natural peptide and proved to be functionally active on guinea pig trachea. Fluorescence spectroscopy was used to demonstrate the potential use of dansylated SP in studies involving interactions with membranes.

Amino Acid Sequence↗
PubMed1994

Characterization of acylating and deacylating activities of an extracellular phospholipase A2 in a water-restricted environment.

The behavior of porcine pancreatic phospholipase A2 (ppPLA2) in monophasic low-water media has been explored, for the first time, in a systematic manner. It has been investigated how a number of variables can modulate both acylating and deacylating activities of the enzyme, and several interesting, unexpected results are presented. Among the most relevant, when placing ppPLA2 in the water-restricted environment, are the following: (i) it displays a remarkable alteration of its specificity toward the substrate polar head relative to all-water medium; (ii) it is quite severely inhibited by lysophosphatidylcholine (LPC), which has important implications, particularly concerning its acylation activity; and (iii) it exquisitely discriminates between saturated and unsaturated long-chain fatty acids when esterifying them with LPC. Finally, it is also illustrated how these results can be exploited to optimize the catalytic performance of the enzyme in nonaqueous medium and obtain a nearly 30-fold increase in the yield of phosphatidylcholine synthesis with respect to previously reported data.

Acylation↗
PubMed1993

Outlet strut fracture of a 23-mm Björk-Shiley 70 degrees convexo-concave aortic valve.

The following brief report describes a fatal complication of a case of outlet strut fracture in a 23-mm Björk-Shiley 70 degrees convexo-concave aortic valve. The valve ruptured 6 years after the operation; diagnosis was made at post-mortem examination. In addition to the high risk of rupture of patients with large-size mitral 60 degrees and 70 degrees convexo-concave Björk-Shiley valves, small-size 70 degrees aortic valves can also present with this complication.

Adult↗