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Biomedical subjects

A Ortiz

Publications and source records attributed to A Ortiz.

At least 163 records · Page 9Linked to original sources
PubMed1992

Interaction of retinol and retinoic acid with phospholipid membranes. A differential scanning calorimetry study.

The influence of retinol and retinoic acid, two retinoids of major interest, on the main gel to liquid-crystalline phase transition of different phospholipid membranes has been studied by means of differential scanning calorimetry. Both compounds exerted perturbing effects on the phase transition of membranes composed of dipalmitoylphosphatidylcholine or dipalmitoylphosphatidylethanolamine. At concentrations up to 42.5 mol% of retinoid in the membrane, the delta H was not much affected with respect to the pure phospholipid, indicating a rather slight interaction. As the concentration of retinol was increased the Tc transition temperature decreased. A fluid-phase immiscibility was observed for the system DPPC/retinol at concentrations between 0 and 33 mol%. Almost ideal phase diagrams were obtained for the mixture DPPE/retinol. At concentrations of 33 mol% and higher retinol was able to induce phase separations in DPPC membranes, but not in DPPE. The effect of retinoic acid was much weaker, the Tc and delta H remaining almost unaltered and equal to that of the pure phospholipid up to concentrations of 30 mol%, at neutral pH. Retinoic acid exerted a pH-dependent effect. As the pH decreased, and therefore increased the extent of protonation of retinoic acid, the pertubation of the membrane induced by this compound was less. A strong effect, both on Tc and delta H, was observed at pH 10, where the retinoic acid moiety will be mainly unprotonated and the negative charge will generate repulsive forces thus destabilizing the membrane. The mixture DPPC/retinoic acid presents a region of fluid-phase immiscibility. At low pH, when the retinoic acid moiety was fully protonated, this fluid-immiscibility region extended from 0 to 36 mol% of retinoic acid, but its size decreased with increasing pH, and at pH 10 it was only found from 0 to 3 mol%. These results are discussed in terms of the possible retinoid/phospholipid interactions and the disposition of the retinoid moiety in the bilayer.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1992

Loss and recovery of activities of alpha+ and alpha isozymes of (Na(+) + K+)-ATPase in cortical focal ischemia: GM1 ganglioside protects plasma membrane structure and function.

Alterations in cellular membrane structure and the subsequent failure of its function after CNS ischemia were monitored by analyzing changes in the plasma membrane marker enzyme (Na(+) + K(+)-ATPase. The levels of two isozymes of (Na(+) + K(+)-ATPase, alpha+ and alpha, which have distinct cellular and anatomical distributions, were studied to determine if differential cellular damage occurs in primary and peri-ischemic injury areas. The efficacy of monosialoganglioside (GM1) treatment was assessed, since this glycosphingolipid has been shown to reduce ischemic injury by protecting cell membrane structure/function. Using a rat model of cortical focal ischemia, levels of both ATPase isozyme activities were assayed in total membrane fractions from primary ischemic tissue (parietal cortex) and three peri-ischemic tissue areas (frontal, occipital, and temporal cortex) at 1, 3, 5, 7, and 14 days after ischemia. No significant loss of either isozyme's activity occurred in any tissue area at 1 day after ischemia. At 5 days, in the primary ischemic area, both isozyme activity levels decreased by 70-75%. The alpha+ enzyme activity loss persisted up to 14 days, while a 17% recovery in alpha activity occurred. In the three peri-ischemic tissue areas, enzyme activity losses ranged from 42%-59% at 3 days after ischemia. A complete restoration of both isozyme activities was seen at 14 days. After three days of GM1 ganglioside treatment there was no loss of total (Na*+) + K(+)-ATPase activity in the three peri-ischemic areas, and a significantly reduced loss in the primary infarct tissue. An autoradiographic analysis of brain coronal sections using 3H-ouabain supports the enzymatic data and GM1 effects. Reductions in 3H-ouabain binding in all cortical layers at 3 days after ischemia were visualized. GM1 treatment significantly reduced these 3H-ouabain binding losses. In summary, time-dependent quantitative changes in activity levels of ATPase isozymes (alpha+ and alpha) reflect the different degree of membrane damage that occurs in primary vs. peri-ischemic tissues (e.g., irreversible vs. reversible membrane damage), and that ischemia affects cell membranes of all neural elements in a largely similar fashion. GM1 ganglioside was found to reduce plasma membrane damage in all CNS cell types.

Animals↗
PubMed1992

Reversible achalasia-like motor pattern of esophageal body secondary to postoperative stricture of gastroesophageal junction.

Two cases are presented of benign stenosis of the cardia secondary to fibrosis following antireflux surgery in which the patients developed a motor alteration in the esophageal body similar to that of achalasia of the cardia. There was a complete absence of contractions in one patient, which had developed over a long period of time, and a vigorous pattern in the other patient, which had evolved over a short period. In both cases, after surgical treatment of the stenosis, normal motility in the esophageal body returned.

Adult↗
PubMed1992

Long-term results of Nissen fundoplication in reflux esophagitis without strictures. Clinical, endoscopic, and pH-metric evaluation.

The present paper evaluates the efficiency of Nissen fundoplication as an antireflux technique in a series of 51 patients with different grades of esophagitis. Follow-up time averaged 6.6 years. The evaluation includes a clinical assessment, endoscopic study, and 24-hr pH monitoring. The results reveal an acceptable rate of recurrences, with clinical (9.8%) being less frequent than endoscopic (13.7%) or pH-metric (19.6%) recurrences. Side effects appeared in 37.3% of the patients (mainly inability to belch or vomit, and postprandial fullness), which were mild and transitory in most cases. Nissen fundoplication proved effective in controlling long-term gastroesophageal reflux, as over 80% of the patients presented an excellent-to-good clinical situation, without or with minimal digestive consequences.

Adult↗
PubMed1992

1,2-Dioleoylglycerol promotes calcium-induced fusion in phospholipid vesicles.

The effect of 1,2-dioleoyglycerol (1,2-DOG) on the promotion of Ca(2+)-induced fusion of phosphatidylserine/phosphatidylcholine (PS/PC) vesicles was studied. 1,2-DOG is able to induce the mixing of membrane lipids at concentrations of 10 mol% without mixing of vesicular contents. At concentrations of 20 mol% or higher, 1,2-DOG promotes fusion, lipid and content mixing, of LUV composed of an equimolar mixture of PS and PC, which otherwise are unable to fuse in the presence of Ca2+. Fusion was demonstrated by fluorescence assays monitoring mixing of aqueous vesicular contents and mixing of membrane lipids. Studies by Fourier transform infrared spectroscopy provided evidence for a fusion mechanism different to that of Ca(2+)-induced fusion of pure PS vesicles. Final equilibrium structures were characterized by 31P-NMR and freeze-fracture electron microscopy. Ca(2+)-induced fusion of 1,2-DOG containing vesicles is accompanied by the formation of isotropic structures which are shown to correspond to structures with lipidic particle morphology. The possible fusion mechanisms and implications are discussed.

Calcium↗
PubMed1992

Imported fire ant immunotherapy: effectiveness of whole body extracts.

The purpose of this study was to determine if whole body extract (WBE) immunotherapy for imported fire ant (IFA) hypersensitivity is effective. This evaluation was carried out by retrospectively interviewing 76 patients with a history of generalized allergic reactions to IFA stings and positive skin tests to IFA-WBE. The study groups consisted of 65 patients on immunotherapy and 11 similar patients who were not treated for various reasons. In addition, an IFA sting challenge was performed in 30 volunteers of the 65 patients on immunotherapy. The retrospective review showed that of the 65 patients on immunotherapy there had been 112 subsequent field-sting episodes in 47 patients. Only one sting episode in this group (2.1%) produced an anaphylactic reaction. Six of the 11 patients not on immunotherapy have had subsequent field re-sting episodes, and each has had a systemic reaction. Repeat skin testing on 31 of the 65 patients in the immunotherapy group showed persistent positive responses in five (16%), but each was at a lower dilution than initially. Responses of the other 26 of the 31 patients who had skin testing had become negative. The four untreated patients who were available for skin testing continued to have positive responses at comparable dilutions on skin testing. Sting challenges carried out on 30 volunteers from the 65 patients (all from the 31 who had repeat skin tests) on immunotherapy resulted in only local reactions.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaphylaxis↗
PubMed1992

Familial IgA nephropathy associated with bilateral sensorineural deafness.

Alport's syndrome is the most frequent disorder with familial nephritis and deafness, but other types of nephropathy have been occasionally associated with hereditary hearing loss. The familial occurrence of IgA nephropathy has been well documented. We report a family with hereditary, bilateral, sensorineural deafness spanning four generations. Three of five members with deafness had microscopic hematuria. Renal histology of the two deaf members undergoing biopsy showed mesangial glomerulonephritis with mesangial IgA deposits, without ultrastructural abnormalities of the glomerular basement membranes. Familial nephritis with deafness should not be equated with the diagnosis of Alport's syndrome.

Deafness↗
PubMed1992

Postsurgical management of the patient undergoing radical prostatectomy.

Radical prostatectomy is a useful procedure for the treatment of prostate cancer limited to the gland; however, failure may occur as a result of the immediate or delayed complications of surgery, or to disease recurrence related to incomplete tumour excision. Seventy-nine radical prostatectomies were performed between April 1985 and August 1991 in patients with prostate cancer (primarily stage B1) who averaged 63 years of age. Immediate post-operative complications included vesicocutaneous fistulae, cystic lymphangiomas, abdominal wall abscesses, extraperitoneal haematoma, acute cholecystitis, and enterocutaneous fistula. Massive pulmonary embolism accounted for 2 deaths. Of the 77 surviving patients followed up for an average of 34 months, 79.2% (61) were continent, 15.6% had stress-related incontinence or severe incontinence and 5.2% were lost to follow-up. Sexual potency was preserved in 13 of the 33 patients (39%) who were pre-operatively potent. A favourable outcome as defined by no recurrence was seen in 69 patients (87.3%). Four patients (5.1%) are living with recurring prostatic cancer and 1 patient has died of the disease 46 months after surgery.

Aged↗
PubMed1992

Effect of recombinant human growth hormone in a postpediatric hemodialysis patient with delayed growth.

We present an 18-year-old patient who has been on renal replacement therapy since the age of 11. He had growth retardation and delayed puberty, with a bone age of 13.6 years. Treatment with human recombinant growth hormone (rhGH) resulted in a clearcut increase in height and lean body mass. We emphasize that rhGH treatment could be tried even at a postpediatric age, provided bone radiology suggests that further growth is possible.

Adolescent↗
PubMed1992

Can pH recordings suggest defective esophageal peristalsis in patients with gastroesophageal reflux?

The data provided by 24-h pH monitoring in 40 patients with gastroesophageal reflux, divided in three groups in accordance with esophageal motor pattern, were compared. Patients with hypomotility had significantly greater reflux rates than those with normal motility or hypermotility, if we consider both total time with pH < 4 and time with pH < 4 corresponding to episodes of > 5 min duration. We conclude that when 24-h pH monitoring shows very high reflux rates, basically corresponding to episodes lasting > 5 min, we should suspect the presence of defective esophageal peristalsis, which must be confirmed with a manometric study.

Adolescent↗