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Biomedical subjects

A Medina

Publications and source records attributed to A Medina.

At least 55 records · Page 3Linked to original sources
PubMed2000

Transcatheter occlusion of complex atrial septal defects.

Percutaneous device occlusion of secundum atrial septal defects (ASDs) is becoming an accepted alternative to surgical closure. This method allows us to evaluate patients with complex conditions for treatment. From a total of 70 patients with ASD evaluated for percutaneous closure, we selected for analysis 28 who had complex conditions. The mean age was 36+/-23 yr (range, 4-72). Six had heart failure, and of these six, three had atrial fibrillation. At cardiac catheterization, the pulmonary pressure was 47+/-24 mm Hg, and the QP/QS was 1.7+/-0.4; two patients had bidirectional shunt and systemic pulmonary pressure. Two patients received a buttoned device and 26 an Amplatzer septal occluder. The groups of patients with complex conditions were separated into the following groups. Group I (n = 4) underwent combined treatment of associated anomalies. Two patients had pulmonary stenosis, one had mitral stenosis, and one had an aortic root-left atrium fistula. They were treated in or during with the same procedure by combined transcatheter techniques (balloon valvuloplasty and fistula occlusion) before ASD occlusion. Group II (n = 9) had multiple defects (cribiform or two separate holes). They were treated with a single device in five instances and with two separate devices in four cases. Group III (n = 14) had large (32+/-3 mm) single defects. Nine of them underwent successful implantation using a device 33+/-3 mm in diameter; in the remaining five patients the device was removed because of instability. Group IV (n = 3) had residual defects after previous partial device occlusion. All three defects were successfully occluded with a second device. No movement or interference with the first device was observed. Group V (n = 6) had severe pulmonary hypertension (86+/-16 mm Hg). Immediately after ASD occlusion we observed significant relief in these patients (67+/-14 mm Hg; P<0.01). There were no major complications; all 23 patients with successful implants were discharged without symptoms 2-7 days later; one patient with atrial fibrillation recovered sinus rhythm. The follow-up (8+/-5 mo) Doppler echo study showed complete ASD occlusion in 22 patients and a peak pulmonary pressure of 30+/-14 mm Hg. We conclude that transcatheter occlusion of ASDs is an effective and safe treatment for patients with complex anatomic or physiopathologic conditions, as evaluated by short-term follow-up.

Adolescent↗
PubMed2000

Xenopus frizzled 7 can act in canonical and non-canonical Wnt signaling pathways: implications on early patterning and morphogenesis.

Here we report the cloning of a Xenopus frizzled transmembrane receptor, Xfz7, and describe its expression pattern during early embryogenesis. Xfz7 mRNA is provided maternally and zygotic transcription peaks in gastrula stages. At that time, transcripts are preferentially localized to the marginal zone and become restricted to distinct regions of the tadpoles in tailbud stages. Overexpression of Xfz7 in embryos perturbs the morphogenesis of trunk and tail, blocks convergence-extension movements in animal caps induced with activin and dorsal lip explants and decreases cadherin-mediated cell adhesion. Xfz7 can interact specifically with Xwnt-8b and signal in the canonical, dorsalizing Wnt pathway. Overexpression of Xfz7 does not trigger the Wnt-1-type pathway but acts in a non-canonical Wnt or morphogenetic-effector pathway involving the activation of protein kinase C (PKC). Xfz7 seems to be involved in different aspects of Wnt signaling during the course of embryogenesis.

Animals↗
PubMed2000

Mitral valve replacement with small-sized tilting-disc mechanical prostheses may lead to moderate stenosis.

BACKGROUND: Analyzing the hemodynamics of small-sized tilting-disc mechanical prostheses implanted in the mitral position. METHODS EXPERIMENTAL DESIGN: this is a retrospective study. The mean follow-up of patients was 114+/-27 months (range 68-152 months). SETTING: departments of Cardiovascular Surgery and Cardiology in a general community hospital Patients: this study includes 9 survivors of 17 patients undergoing mitral valve replacement with this type of device between May, 1982 and July, 1991. INTERVENTIONS: all subjects underwent mitral valve replacement with size 25 mm Sorin tilting-disc mechanical prostheses. MEASURES: all patients underwent transthoracic echocardiography. Five consenting patients also underwent transoesophageal echocardiography. The following parameters were measured: peak gradient, mean gradient, peak velocity, mean velocity, pressure half-time and Doppler area. RESULTS: The ejection fraction was 50% or more in all patients. The following mean results were obtained: peak gradient: 17.4+/-2.5 mmHg; mean gradient: 8.2+/-0.6 mmHg; peak velocity: 2.1+/-0.1 m/sec; mean velocity: 1.43+/-0.06 m/sec; pressure half-time: 135.9+/-29.7 msec; Doppler area: 1.7+/-0.3 cm2. CONCLUSIONS: Valve replacement with Sorin 25 mm tilting-disc mechanical prostheses appears to originate a moderate degree of mitral stenosis and, therefore, we do not recommend their use if at all possible.

Adult↗
PubMed2000

Combined percutaneous atrial septal defect occlusion and pulmonary balloon valvuloplasty in adult patients.

Severe pulmonary stenosis in association with a large atrial septal defect is uncommon. When these 2 conditions are present, significant left-to-right shunt is often prevented by the outflow obstruction, which protects the pulmonary bed until adulthood. This report shows our initial experience of percutaneous treatment of both congenital malformations, either staged or combined in the same procedure, in 2 adult patients whose treatments yielded effective atrial septal defect occlusion and right ventricular pressure relief that persisted at mid-term follow-up. Although these opposite procedures (opening and closing) have been applied as isolated methods of treatment, this preliminary experience appears to demonstrate the feasibility and effectiveness of a combined percutaneous treatment.

Adult↗
PubMed2000

Percutaneous balloon-expandable stents for sealing of acute aortic dissection.

Acute aortic dissection is a highly lethal disease. When dissection involves only the descending aorta and there are no ischemic complications, medical management may be the treatment of choice. However, a high risk of expansion or rupture of the dissection remains. When renal or limb ischemic complications do appear, surgery has been the only option, despite high mortality and morbidity. Percutaneous placement of stents for sealing an acute aortic dissection might be an alternative to surgical treatment. We treated 2 patients with acute type B aortic dissection by stent-fixation of the proximal and distal descending aorta. In both patients, there was evidence of persistent flap fixation at midterm follow-up.

Acute Disease↗
PubMed2000

Synergistic effect between apolipoprotein E and angiotensinogen gene polymorphisms in the risk for early myocardial infarction.

BACKGROUND: Several studies based on different populations worldwide have described an association between cardiovascular diseases and genetic variations in the apolipoprotein E (A:POE), angiotensinogen (A:GT), angiotensin receptor type 1 (A:T1R), and angiotensin-converting enzyme (A:CE) genes. In addition, there is growing evidence of an interaction between hypercholesterolemia and the renin-angiotensin system in the risk for hypertension and atherosclerosis. METHODS: To determine whether the DNA polymorphisms in A:POE (epsilon2, epsilon3, and epsilon4 alleles), A:GT (M235T), A:T1R (1166 A:/C:), and ACE (I:/D:) are associated with early onset of myocardial infarction (MI), we genotyped 220 patients and 200 controls <55 years of age. Patients and controls were males from the same homogeneous Caucasian population. Data concerning hypertension, diabetes, and tobacco consumption were recorded. The lipid profiles of patients and controls were also determined. RESULTS: APOE, ACE, AGT, and AT1R allele and genotype frequencies did not differ between patients and controls. None of these polymorphisms was related to the biochemical values in patients or controls. The frequency of individuals who were both APOE epsilon4 allele carriers and AGT-TT homozygotes was significantly higher in patients than in controls (11% vs 3.5%; P: = 0.0037). In patients, the frequency of epsilon4 carriers was significantly higher (P: <0.00001) in those who were AGT-TT (46%) than those who were AGT-MT/MM (14%). Mean cholesterol was significantly higher in AGT-TT + APOE epsilon34/44 patients than in the TM/MM + epsilon34/44 or TT + epsilon23/33 genotypes (P: = 0. 029). CONCLUSIONS: Our data suggest a synergistic effect between the APOE and AGT polymorphisms and early MI. The increased risk could be mediated in part through higher cholesterol concentrations among individuals who are AGT-TT + APOE epsilon4 allele carriers.

Adult↗
PubMed2000

The spermatozoon morphology of Solea senegalensis (Kaup, 1858) (Teleostei, Pleuronectiformes).

The spermatozoon of Solea senegalensis (Kaup, 1858) consists of an acrosome-less ovoid head, a short midpiece containing several irregular mitochondria embedded in the cytoplamic mass, and a long tail with two lateral fins and a conventional 9 + 2 axoneme. The centrioles are housed in a deep nuclear fossa and are both orientated in the same longitudinal axis of the spermatozoon. The overall structure of this spermatozoon conforms to the sperm type considered to be plesiomorphic in the neopterigians (type I sperm). The likely apomorphic (coaxial) orientation of the centrioles defines the spermatozoal morphology of the Soleidae investigated thus far and separates them from the other known pleuronectiform spermatozoa.

Animals↗
PubMed1999

Comparison of clinical and genetic variables of cardiac events associated with loud noise versus swimming among subjects with the long QT syndrome.

Acute auditory stimuli and swimming activities are frequently associated with syncope, aborted cardiac arrest, and death in the long QT syndrome (LQTS). We investigated the clinical and genetic findings associated with cardiac events precipitated by these arousal factors. The study population involved 195 patients with an index cardiac event associated with a loud noise (n = 77) or swimming activity (n = 118). Patients with events associated with loud auditory stimuli were older at their index event and were more likely to be women than patients who experienced events during swimming-related activities. Patients with an index event associated with loud noise were likely to have subsequent events related to auditory stimuli; patients with an index event associated with swimming were likely to have recurrent events related to swimming or physical activities. Family patterning of auditory and swimming and/or physical activity-related events was evident. Genotype analyses in 25 patients revealed a significant difference in the distribution of index cardiac events by genotype (p <0.001), with all 19 patients with swimming-related episodes associated with LQT1 genotype and 5 of 6 patients with auditory-related events associated with LQT2 genotype. The clinical profile and genotype findings of patients with LQTS who experience cardiac events related to acute auditory stimuli are quite different from those who experience events accompanying swimming activities.

Acoustic Stimulation↗
PubMed1999

Angiographic anatomy of the inferior right atrial isthmus in patients with and without history of common atrial flutter.

BACKGROUND: Although most ablative procedures undertaken for common atrial flutter target the inferior right atrial isthmus, comparative studies of the morphology of this area are lacking. Our study examines its angiographic anatomy, making correlations with postmortem specimens, to provide a better understanding of the anatomic substrate of this arrhythmia. METHODS AND RESULTS: The gross morphological features and dimensions of the area between the orifice of the inferior caval vein and the attachment of the septal leaflet of the tricuspid valve were determined from angiograms made in 23 patients with documented atrial flutter and 30 control subjects. For comparison, we studied 20 normal heart specimens. When viewed in right anterior oblique projection, 2 morphologically distinct areas were identified. In the specimens, the inferior isthmus measured a mean length of 30+/-4 mm, not significantly different from the dimensions obtained from angiograms of control subjects. The mean length of the isthmus, however, was greater in patients with common atrial flutter than those without (37+/-8 versus 28+/-6 mm). Patients with atrial flutter and structural heart disease had an even longer isthmus than those with flutter alone (39. 6+/-8 versus 33+/-7 mm). Compared with those without flutter, the atrial diameter was also larger in patients with flutter (57.6+/-9 versus 48.5+/-6 mm). Reevaluation carried out at follow-up 10+/-2 months after ablation did not show any reduction in atrial size, although contractility improved. CONCLUSIONS: The inferior isthmus and right atrium in patients with common atrial flutter were significantly larger than those in a control population.

Adult↗
PubMed1999

Simple and complex stent strategies for bifurcated coronary arterial stenosis involving the side branch origin.

Coronary lesions located in major bifurcations constitute a challenge for the use of stents. Although the occlusion of a side branch covered by a stent is infrequent, the maintenance of a patent, stenosis-free bifurcation may result in a complex procedure. Between September 1994 and April 1998, 70 patients were treated by stent implantation for coronary bifurcation stenosis. The side branch always had a diameter >2 mm. The pairs of treated arteries were: left anterior descending (LAD)/diagonal artery in 32 patients, circumflex/obtuse marginal in 26, right coronary/posterior descending artery in 5, and LAD/circumflex in 7. We applied 2 different techniques of stent implantation: (1) deployment of 1 stent in the parent vessel covering the takeoff of the side branch and subsequent angioplasty of the side branch across the metallic structure (group A, n = 47 patients), and (2) implantation of 1 stent at the ostium of the side branch and complete reconstruction of the entire bifurcation with additional implantation of 1 or 2 stents at the parent vessel (group B, n = 23 patients). There were no significant differences between groups at baseline variables. Procedural success was similar in both groups: 42 (89%) in group A versus 21 (91%) in group B. However, major cardiac events at 18 months follow-up were higher in group B (event-free probability 44% vs 75%, p <0.05). Selected patients with coronary stenosis at major bifurcations can be treated with an acceptable rate of primary and late success. Complex techniques providing radical stent reconstruction of the bifurcation seems to provide no advantages over the simpler stent jail followed by ostial side branch balloon dilation.

Aged↗
PubMed1999

Immediate and follow-up findings after stent treatment for severe coarctation of aorta.

Experimental studies have shown that stents implanted at the aorta become incorporated within the aortic wall and can be further expanded in growing animals. Few clinical studies have shown that the stent repair of severe coarctation of aorta provides excellent initial results, and little is known on the follow-up of these patients. We assessed the immediate and follow-up results obtained in a series of 48 patients (mean age 14+/-12 years) with severe coarctation of the aorta who were treated by Palmaz stent implantation; 30 of them (63%) underwent angiographic follow-up studies at a mean of 25+/-11 months after treatment. Quantitative serial analysis of the aortogram (baseline, after treatment, and at follow-up) was performed. Significant relief (mean residual gradient 3+/-4 mm Hg) was always obtained after stent implantation. The isthmus, when hypoplastic (60%), was always expanded with the stent. One associated aneurysm became occluded after the implant. Complications included aortic disruption, stent migration, and decreased or absent femoral pulses. At angiographic follow-up, the stent remained always in place, without recoil. In 22 patients (73%), there were no detectable neointimal proliferation at late angiogram; however, 8 patients (27%) had some degree of intimal thickening (1 to 5 mm), causing mild restenosis in 3 patients treated at early age, and nonsignificant lumen reduction in 5. The serial aortogram analysis revealed a minor but significant increase in nonstented aortic diameters that seemed related to the normal growth of children. No need for stent reexpansion was observed at 2-year follow-up (mean). Two patients (7%) developed late small aneurysm formation at the stented wall; both were occluded by the insertion of coils through the stent orifices. We conclude that stent treatment for severe coarctation of aorta provides excellent immediate and long-term results in young adults and children. However, at early age, restenosis by intimal growth may develop.

Adolescent↗
PubMed1999

Hepatic expression of growth hormone receptor/binding protein and insulin-like growth factor I genes in uremic rats. Influence of nutritional deficit.

The molecular basis for GH resistance in chronic renal failure is unknown. It may partly reside in a decreased number of hepatic GH receptors and subsequently reduced IGF-I synthesis. To investigate the hepatic expression of GH receptor/binding protein (GHBP) and IGF-I genes in chronic renal failure, mRNA levels and the concentrations of its splicing variants were measured by Northern Blot in male 5/6 nephrectomized rats (NX, n = 9), aged 26 +/- 1 days, and three groups of sham-operated rats: (1) fed ad libitum (SAL, n = 9); (2) pair-fed with NX (SPF, n = 7); and (3) pair-fed with NX in terms of protein ingestion but calorically supplemented up to the intake of SAL (SPF+, n = 8). NX rats had severe renal failure, serum urea nitrogen 106 +/- 11 mg/dl (mean +/- SEM), and were growth retarded. GH receptor/GHBP gene expression was detected as two bands of 4.7 and 1.2 kb, respectively. The amount of mRNA was lower (P < 0.0001) in NX than SAL, either when both bands were considered together or separately. No differences were found between NX, SPF, and SPF+. Serum GHBP concentrations were higher (P < 0.01) in NX rats than the other groups. For the IGF-I gene, two bands of 7.5 and 1.8-0.8 kb were identified. Expression of IGF-I gene was reduced (P < 0.05) in NX in comparison with SAL, this reduction being more marked for the 7.5 kb transcript (amount of mRNA equal to 56.6 +/- 2.6 vs 84.8 +/- 6.2% of values found in SAL rats). There were no differences between NX and SPF. Normalization of caloric intake in SPF+ resulted in partial recovery of the 7.5-kb band and did not modify the 1.8-0.8 kb mRNAs. Circulating IGF-I levels were no different among the four groups. These data confirm that expression of liver GH receptor/GHBP and IGF-I genes is markedly decreased in uremic rats. Nutritional deficiency and not uremia itself seems to be the main causal factor, with protein deficit playing a major role.

Animals↗
PubMed1999

[The influence of sex on the performance of dobutamine echocardiography for the diagnosis of ischemic cardiopathy].

OBJECTIVE: To compare the usefulness of dobutamine-atropine stress echocardiography in the diagnosis of coronary artery disease among men and women. METHODS: We have consecutively studied 137 men and 99 women without a previous history of coronary artery disease who underwent dobutamine-atropine stress echocardiography and coronary angiography afterwards. RESULTS: Significant coronary artery disease was detected in 102 men and 42 women (74% and 42% respectively; p < 0.001). 64% of the women had single-vessel versus 45% of the men (p < 0.05). Dobutamine-atropine stress echocardiography was positive in 78 men and 35 women. Sensitivity, specificity and diagnostic accuracy of the test were 72%, 88% and 76% for men and 69%, 89% and 83% for women (p = NS). Positive predictive value was higher in men (95% in men versus 83% in women; p < 0.05) and negative predictive value was significantly greater in women than in men (79% versus 52%; p < 0.01). CONCLUSION: Sensitivity, specificity and diagnostic accuracy of dobutamine-atropine stress echocardiography is not affected by gender. Positive predictive value is higher in men and negative in women owing to the differences in both sexes of the prevalence of coronary artery disease.

Aged↗
PubMed1999

The effect of albumin on astrocyte energy metabolism is not brought about through the control of cytosolic Ca2+ concentrations but by free-fatty acid sequestration.

Albumin is an important serum protein that under normal circumstances is not present in the brain. However, during development, under hypoxia, or after breakdown of the blood-brain barrier, albumin is found in the brain, where it is able to regulate energy metabolism. In this work the mechanism through which albumin regulates astrocyte metabolism was investigated. Our results show that albumin strongly increases (more than 100%) the flux of glucose and lactate through the pyruvate dehydrogenase-catalyzed reaction in astrocytes from primary culture. However, albumin only slightly stimulated other metabolic pathways, such as the tricarboxylic acid cycle or the pentose phosphate shunt, indicating that it exerts its effect specifically on the reaction catalyzed by pyruvate dehydrogenase. Although albumin increased cytosolic Ca2+ concentrations in astrocytes, our results show that the increase in pyruvate dehydrogenase activity promoted by albumin is not due to the enhancement of Ca2+ concentrations. Indeed, highly purified albumins failed to increase the Ca2+ concentration but did enhance lactate oxidation. In agreement with this, the effect of albumin on lactate oxidation was not abolished after Ca2+ depletion. Instead, the presence of fatty acids inhibited lactate oxidation and counteracted the effect of albumin, suggesting that albumin activates pyruvate dehydrogenase by binding free fatty acids and/or their CoA-derivatives.

Albumins↗
PubMed1998

Novel LQT-3 mutation affects Na+ channel activity through interactions between alpha- and beta1-subunits.

The congenital long-QT syndrome (LQT), an inherited cardiac arrhythmia characterized in part by prolonged ventricular repolarization, has been linked to 5 loci, 4 of which have been shown to harbor genes that encode ion channels. Previously studied LQT-3 mutations of SCN5A (or hH1), the gene that encodes the human Na+ channel alpha-subunit, have been shown to encode voltage-gated Na+ channels that reopen during prolonged depolarization and hence directly contribute to the disease phenotype: delayed repolarization. Here, we report the functional consequences of a novel SCN5A mutation discovered in an extended LQT family. The mutation, a single A-->G base substitution at nucleotide 5519 of the SCN5A cDNA, is expected to cause a nonconservative change from an aspartate to a glycine at position 1790 (D1790G) of the SCN5A gene product. We investigated ion channel activity in human embryonic kidney (HEK 293) cells transiently transfected with wild-type (hH1) or mutant (D1790G) cDNA alone or in combination with cDNA encoding the human Na+ channel beta1-subunit (hbeta1) using whole-cell patch-clamp procedures. Heteromeric channels formed by coexpression of alpha- and beta1-subunits are affected: steady-state inactivation is shifted by -16 mV, but there is no D1790G-induced sustained inward current. This effect is independent of the beta1-subunit isoform. We find no significant effect of D1790G on the biophysical properties of monomeric alpha- (hH1) channels. We conclude that the effects of the novel LQT-3 mutation on inactivation of heteromeric channels are due to D1790G-induced changes in alpha- and beta1-interactions.

Cell Line↗
PubMed1998

Identification of a new SCN5A mutation, D1840G, associated with the long QT syndrome. Mutations in brief no. 153. Online.

The long QT syndrome (LQT) is an inherited cardiac disorder that can cause sudden cardiac death among apparently healthy young individuals due to malignant ventricular arrhythmias. LQT was found to be caused by mutations in four genes LTQ1, LQT2, LQT3 and LQT5, and linkage was reported for an additional locus, LQT4, on chromosome 4q25-27. We have studied a large (n=131) LQT-affected Jewish kindred and identified tight linkage between the LQT-affected status and LQT3 (lod score 6.13, with an estimated recombination fraction of zero). We identified a new point-mutation, A to G substitution at nucleotide 5519 of the SCN5A gene, changing the aspartate 1840 to glycine, D1840G. This is a non-conservative change of an amino acid completely conserved in sodium channels from Molusca to human. The mutation was identified in all affected individuals (n=23), and not identified in all the unaffected family members (n=40), and not in 200 chromosomes of healthy control individuals. The mutation was identified in 3/12 individuals with equivocal phenotype, thus, providing an accurate dignostic tool for all family members. This mutation is currently being used in a cellular electrophysiological model, to characterize the function of the mutated sodium channel in this syndrome.

Amino Acid Substitution↗