Biomedical subjects

A Robles

Publications and source records attributed to A Robles.

At least 55 records · Page 3Linked to original sources

PubMed1990

Operative findings after percutaneous pulmonary balloon dilatation of the right ventricular outflow tract in tetralogy of Fallot.

Since 1983 percutaneous balloon dilatation of the right ventricular outflow tract has been performed as an alternative to surgical palliation in selected cases of tetralogy of Fallot at the Royal Liverpool Children's Hospital. From 31 December 1984 to 31 December 1988, 27 of these patients underwent subsequent surgical correction. Age at operation ranged from 7 to 58 months (median 2.7 years). The mean interval between balloon dilatation and correction was 15.6 months (range 3-39 months). Two patients had a systemic pulmonary shunt operation performed before dilatation and a further five required one afterwards. Overall 20 (74%) patients had some anatomical alteration as the result of balloon dilatation, while in seven (26%) there was no discernible change in the right ventricular outflow tract. There was no consistent relation between the ratio of balloon size to pulmonary annulus diameter and the morphological findings. Balloon dilatation may obviate the need for systemic-pulmonary shunt at the expense of some structural damage, particularly to the posterior cusp. The present data suggest that dilatation does not bring about growth of the annulus to such an extent that transannular patch is no longer needed at intracardiac repair.

Catheterization↗

PubMed1990

Evidence suggesting a role for platelet-activating factor (PAF) in experimental nephrotic syndrome.

Sprague-Dawley rats injected with a single dose of adriamycin at 7.5 mg/kg/day developed an important and persistent proteinuria from day 14. Animals treated from day 0 to 3 weeks with PAF-receptor antagonists (BN 52021 or alprazolam) did not present (p less than 0.0005) the adriamycin-induced proteinuria or only to a very low extent. Furthermore, epithelial glomerular cells presented in these animals a normal aspect, while in rats injected with adriamycin, but not treated, the epithelial cells showed effacement of foot processes and intensive degenerative changes. By contrast, rats treated with steroids or cyclosporin did not present a significant reduction in proteinuria or improvements in epithelial cell lesions. Rats injected with adriamycin also presented an increase in the number of inflammatory infiltrating cells, chiefly la(+)-reactive cells (OX6+ cells), macrophages (ED1+ cells) and T-cytotoxic/suppressor cells (OX8+ cells). Concomitant administration of PAF-receptor antagonists induced a significant reduction in the number of these cells. Glomerular cells from normal control rats incubated with adriamycin incorporated 3H-acetate into a polar lipid with biological and migratory characteristics on thin-layer chromatography similar to synthetic PAF. On the whole, our data suggest a role for PAF in the pathogenesis of experimental nephrotic syndrome induced by adriamycin.

Acetates↗

PubMed1989

Truncus arteriosus with interrupted aortic arch: successful correction in a neonate.

Truncus arteriosus (type II) with interrupted aortic arch (type B) was successfully repaired at 11 days of age using anterior translocation of the pulmonary arteries, resection of the ductus arteriosus, and direct anastomosis between the descending aorta and truncus. This technique permitted wide reconstruction of the aortic arch and minimized the number of suture lines. It also positioned the right ventricle-pulmonary artery conduit anteriorly, which may simplify its subsequent replacement.

Abnormalities, Multiple↗

PubMed1989

[The development of the anti-phospholipase A2 antibody response in horses inoculated with venom for the production of polyvalent antisnake serum in Costa Rica].

The development of antibody response against phospholipase A2 activity of Bothrops asper venom was studied in a group of adult and healthy horses used in the production of the polyvalent antivenom at the Instituto Clodomiro Picado. Simultaneously, the general condition of the animals during the immunization schedule was also studied. There was a great individual variability in the immune response, although most of the horses studied reached the highest neutralizing titer after injection of doses of venom of 30 mg and 50 mg. On the other hand, in horses that had been previously immunized and were infected for a second immunization, the highest antibody titer was observed 16-22 days after inoculation. There were only mild alterations in the general condition of the horses as a consequence of venom inoculation. However, local abscesses, fistulae and fibrosis were observed at the site of venom injection. On the basis of the conspicuous individual variability observed, it is proposed that the immune response in horses used in the production of antivenom must be evaluated on individual basis, instead of working with pools of serum samples.

Animals↗

PubMed1988

Dual mechanism of phosphatidylinositol hydrolysis by substance P in brain.

The treatment of cerebral cortex slices with substance P caused alterations in the phospholipid levels. A significant loss of phosphatidylinositol in a dose-dependent manner was observed. In contrast, the levels of the major phospholipids, phosphatidylcholine and phosphatidylethanolamine, were enhanced by the peptide. The effect of substance P on the fatty acid composition of phospholipids was also studied. The most relevant event was the decrease in the content of both stearic and arachidonic acids of phosphatidylinositol. This decrease was more evident at the lowest substance P concentration tested (65 pM). These results are consistent with the phosphatidylinositol breakdown caused by substance P in some tissues. Furthermore, our data indicate that this breakdown is selective depending on the peptide dose. Thus, in the presence of very low doses of substance P (65 pM) a preferential degradation of 1-acyl(predominantly stearoyl)-2-arachidonoylglycerophosphoinositol molecular species occurs, whereas high doses of the peptide (0.65 microM) induce a generalized hydrolysis of phosphatidylinositol without showing any preference towards molecular species rich in arachidonic acid. Hence we describe for the first time a dual, dose-dependent mechanism for phosphatidylinositol hydrolysis by substance P, suggesting the possibility that either phospholipase A2 or phospholipase C activation is involved.

Animals↗

PubMed1988

Insulin action on brain microvessels; effect on alkaline phosphatase.

The effects of insulin on brain alkaline phosphatase activity have been examined. Insulin inhibited the activity of alkaline phosphatase on brain microvessels in in vitro experiments. The inhibition observed was of the non-competitive type. These observations indicate that the hormone is able to induce neurochemical modifications revealed in this case as changes in the phosphate transfer enzymes in brain microvessels.

Alkaline Phosphatase↗

PubMed1988

Long-term performance of 555 aortic homografts in the aortic position.

Long-term results with 555 aortic homografts used for isolated aortic valve replacement (AVR) between 1964 and 1986 were analyzed to assess valve performance and the time-related onset of valve-related events. The total follow-up was 2,931 patient-years. Twenty years after operation, overall survival was 51.6 +/- 8.1%, freedom from valve-related death was 67.1 +/- 8.9%, freedom from primary tissue failure was 12.4 +/- 4.8%, freedom from infective endocarditis was 82.7 +/- 4.3%, freedom from surgical technical failure was 88.1 +/- 2.3%, and freedom from all complications including valve-related death was 9.0 +/- 3.5%. The incidence of thromboembolism was 0.034% per patient-year (one potential event). Long-term results after homograft insertion for aortic stenosis were significantly better than those after insertion for aortic incompetence. It is concluded that the good quality of life and the median life expectancy, which extends more than 20 years after operation, make the homograft an excellent choice for AVR.

Actuarial Analysis↗

PubMed1988

The Ross operation: the autologous pulmonary valve in the aortic position.

Aortic valve replacement (AVR) with a pulmonary valve autograft (PVA) was first reported by Donald N. Ross (DNR) in 1967. The expectation of this procedure was to avoid degenerative changes seen in other biological tissue valves such as calcification, attenuation, and rupture of the leaflets. Recent reports by the original investigator's group have confirmed the lack of degenerative changes in PVA. To corroborate their conclusions, the fate of 12 patients undergoing AVR with PVA by one of us (LGL) has been ascertained. From March 1969 to June 1971, 12 patients underwent AVR with PVA. The right ventricular outflow tract (RVOT) was reconstructed with an aortic homograft valved conduit. The mean age was 42.7 years (range 21 to 52 years). The mean follow-up for 11 hospital survivors is 12.4 years. Three PVA have been replaced; one following infective endocarditis at 13 years, and two at 15 and 73 months due to technical malalignment. There was no evidence of PVA degeneration during histological examination of these explanted PVAs. Six patients are alive and retain the original PVA at 12 years (55%). This analysis corroborates the conclusions of the DNR report and strongly suggests an immunological mechanism in the process of calcification of other biological tissue valves. The Ross operation is advocated for AVR in young patients as valve durability is of paramount importance especially in this group.

Adult↗

PubMed1988

Morbidity following the Ross operation.

Aortic valve replacement (AVR) with a pulmonary valve autograft (PVA) was first reported by Donald N. Ross in 1967. The expectation of this procedure was to avoid degenerative changes seen in other biological tissue valves such as calcification, attenuation, and rupture of the leaflets. Recent reports by the original investigator's group have confirmed the lack of degenerative changes in PVA. To corroborate their conclusions, the fate of 12 patients undergoing AVR with PVA by Dr. Gonzalez-Lavin has been ascertained. From March 1969 to June 1971, 12 patients underwent AVR with PVA. The right ventricular outflow tract (RVOT) was reconstructed with an aortic homograft valved conduit. The mean age was 42.7 years (range 21 to 52 years). The mean follow-up for 11 hospital survivors is 12.4 years. Three PVAs have been replaced; one following infective endocarditis at 13 years, and two at 15 and 73 months due to technical malalignment. There was no evidence of PVA degeneration during histologic examination of these explanted PVA. Six patients are alive and retain the original PVA at 12 years (55%). This analysis corroborates the conclusions of Dr. Ross and strongly suggests an immunological mechanism in the process of calcification of other biological tissue valves. The Ross operation is believed to be the preferred method of AVR in young patients.

Adult↗

PubMed1988

Early and late results of aortic root replacement with antibiotic-sterilized aortic homograft.

Between November 1972 and November 1986, 108 patients aged 5 to 73 years had complete replacement of the aortic root with an aortic homograft into which the coronary arteries were implanted. The main indications were (1) a tunnel type of aortic obstruction involving a hypoplastic ring, (2) a para-aortic annular abscess, (3) prosthetic valve dysfunction, mainly a previous aortic homograft, and (4) aortic stenosis with a small aortic anulus. Eighty-four patients (78%) had previous aortic valve operations. Concomitant cardiac procedures were done in 34 patients (32%). The 30-day mortality rate was 14% (15 patients). The cumulative follow-up period was 180.3 patient-years. The late mortality rate was 6.1% per patient-year (11 patients). The patients were not given anticoagulants postoperatively, but the entire group has been completely free from thromboembolism. The actuarial 5-year survival rate including operative deaths was 72%. The freedom from valve-related death at 5 years after operation is 86% and freedom from reoperation at 5 years is 96%. The use of homografts for replacement of the aortic valve and root in patients with complex lesions affecting these structures has shown encouraging early and late results, with regard to both survival and valve performance.

Actuarial Analysis↗

PubMed1988

Two decades' experience with aortic valve replacement with pulmonary autograft.

Aortic valve replacement with a pulmonary autograft was performed on 241 patients between June 1967 and October 1986 at National Heart Hospital, Guy's Hospital, Middlesex Hospital, Harley Street Clinic, and Italian Hospital in London by one of the authors (D.N.R.). The longest follow-up is 18 years 7 months, and the cumulative total follow-up is 1130 patient-years (pt-yr). The overall 30-day mortality rate is 6.6% (16 patients), with no deaths after 1976, and the late mortality rate is 1.7%/pt-yr (19 patients). The actuarial survival rate is 57.3% +/- 9.6% at 19 years. No anticoagulation has been used and there have been no thromboembolic episodes. The incidence of bacterial endocarditis is 1.2%/pt-yr (14 patients), and its actuarial event-free rate is 74.2% +/- 8.1% at 19 years. Reoperation because of failure of the pulmonary autograft was performed on 36 patients, 27 of whom needed valve replacement. The incidence of pulmonary autograft replacement is 2.5%/pt-yr, and its actuarial event-free rate is 48.5% +/- 13.7% at 19 years. For reconstruction of the right ventricular outflow tract, 186 aortic homografts, 26 pulmonary homografts, 16 autologous fascia lata valved conduits, 7 autologous pericardial conduits with or without a valve, and 6 xenograft valved Dacron conduits were used. Thirty-one patients were reoperated on, mostly because of degeneration of this material. Pulmonary rather than aortic homografts are now favored for reconstruction of the right ventricular outflow tract Because of its satisfactory long-term result without the need for anticoagulation, as well as its safety as an established surgical procedure, this operation can be recommended to a wider range of patients.

Actuarial Analysis↗

PubMed1987

Role of platelet-activating factor in adriamycin-induced nephropathy in rats.

The effect of steroids, heparin and specific PAF-acether antagonists (BN 52021 and triazolobenzodiazepines) on proteinuria and renal histological changes induced in rats by adriamycin was studied. Adriamycin evoked a marked proteinuria that was unaffected by methylprednisolone and slightly reduced by heparin. In contrast, adriamycin-injected rats treated with PAF-acether antagonists had a low proteinuria, if any, and no ultrastructural glomerular alterations. These data suggest that PAF-acether could play a major role in the occurrence of proteinuria and that PAF-acether antagonists might provide a new therapeutic approach in certain human nephropathies.

Animals↗

PubMed1987

Substance P induces alterations on cerebral lipids involved in membrane fluidity.

This study was undertaken to examine the variations in rat brain of cholesterol, phospholipid and phospholipid fatty acid composition induced by substance P. The cholesterol content was increased by substance P; concomitantly, an increase of the ratio cholesterol/phospholipid was observed. These changes do not appear to be responsible of the stimulation observed in Na+,K+-ATPase activity by substance P action. Phospholipid fatty acid analysis revealed that the peptide induced a decrease in both linoleic and arachidonic acids content.

Animals↗

PubMed1987

Alterations in brain lipid composition caused by vanadate.

In an attempt to investigate the effect of sodium meta vanadate on membrane lipids in rat brain, in vivo and in vitro experiments were carried out. Intraperitoneal administration of vanadate (10 and 16 mumole/100 g) caused increase in cholesterol levels, whereas phospholipid levels were much less modified. These alterations brought about a significant increase in the ratio cholesterol/phospholipid. Concomitantly, an increase of both linoleic and docosahexanoic acids was observed, whereas arachidonic acid level was diminished. In all in vivo experiments the most effective dose on the parameters studied was 16 mumole/100 g. On the other hand, when vanadate (10(-3)-10(-5)M) was added in in vitro experiments a similar pattern of variation was obtained in cholesterol and phospholipid levels; however the variations were much less evident, 10(-3)M being the most effective dose. Likewise in the in vivo experiments, vanadate seems to act by increasing the levels of linoleic and docosahexanoic acids and by decreasing the arachidonic acid level. In contrast, the docosahexanoic acid level remained unchanged in in vitro experiments. These results suggest that both the brain delta 6 desaturase and extracerebral docosahexanoic acid synthesis are modified by vanadate. In conclusion, the present study indicates that vanadate is able to modify the cerebral lipid metabolism by altering the ratio cholesterol/phospholipid which in turn could lead to alterations in the membrane fluidity.

Animals↗

PubMed1987

Oral cholecystography and sonography of gallbladder in cholecystectomy patients.

In comparing the diagnostic specificity and sensitivity of oral cholecystography with that of sonography in 479 patients in a community hospital, the oral cholecystogram, when used with a double dose of contrast agent, showed greater specificity (1.00) and sensitivity (0.99) than the sonogram (0.54 and 0.94, respectively). Because of lower cost, the oral cholecystogram should be used as the initial diagnostic study when cholelithiasis is suspected, unless specific contraindications exist.

Adolescent↗

PubMed1986

Somatostatin effects on the cyclic AMP system and lipid metabolism in mouse brain.

The effect of somatostatin on cyclic AMP-protein kinase system and lipid metabolism was studied in mouse brain. Subcutaneous injection of the peptide decreased the cyclic AMP and cyclic GMP levels (70% and 60% respectively) as well as protein kinase and triglyceride lipase activities (30%). Cyclic AMP binding protein activity was not affected. Experiments carried out with [14C]acetate as precursor of lipids seem to indicate that somatostatin blocks the fatty acid turnover. On the other hand, the general decrease of 32P incorporation into all phospholipids by somatostatin suggests that the peptide interferes with the precursor uptake into phospholipids. The findings reported here indicate that somatostatin has a role on brain metabolism and further add more data in support for its neuromodulating action.

Acetates↗

PubMed1986

Glutamate-elicited stimulation of acetylcholinesterase activity in cerebellar slices from newborn rats.

Bath application of glutamate at two concentration ranges, 10(-6)-10(-8) and 1-3 X 10(-3) M, effectively increased acetylcholinesterase activity in cerebellar slices obtained from 8-day-old rats. No such effect was seen in cerebellar slices of 7-week-old rats or cerebral slices of either 7-week or 8-day-old rats. Glutamic acid diethyl ester blocked the glutamate effect at both of these concentration ranges, suggesting that quisqualate-sensitive glutamate receptors are involved in regulation of acetylcholinesterase activity in early postnatal cerebellum. Since bath application of cyclic GMP at 10(-7)-10(-9) M increased the acetylcholinesterase activity in cerebellar slices of 8-day-old rats, it is possible that glutamate-dependent regulation of acetylcholinesterase activity is mediated by cyclic GMP. The observation that adenosine deaminase blocked the effect of glutamate completely at 10(-6)-10(-8) M and partially at 1-5 X 10(-3) M further suggests that release of adenosine is a link from enhanced cyclic GMP activity to activation of acetylcholinesterase.

Acetylcholinesterase↗

PubMed1985

Alterations in rat lipid metabolism following ecdysterone treatment.

The influence of ecdysterone on the lipid metabolism in liver and adipose tissue from rat was investigated using 14C-acetate and 32P-orthophosphate as precursors. Ecdysterone produced an increase in 14C-acetate incorporation into triglycerides. A concomitant decrease in free fatty acids and diglycerides was observed. The effect of ecdysterone on triglyceride lipase activity was investigated and a significant decrease was found. Ecdysterone produced a significant increase in the specific activity of phosphatidylethanolamine and phosphatidylserine in liver. On the contrary, the specific activity of phosphatidylcholine was reduced. In adipose tissue, the most evident effect observed was the increase of specific activity of phosphatidylcholine. These results contribute to knowledge of the heterophylic action of ecdysterone.

Acetates↗