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Biomedical subjects

M Alvarez

Publications and source records attributed to M Alvarez.

At least 343 records · Page 19Linked to original sources
PubMed1989

Selective second-trimester termination of the anomalous fetus in twin pregnancies.

Selective termination of the affected fetus was performed during the second trimester in 17 pregnancies in which one twin was diagnosed to be anomalous. The affected twin had a chromosomal aneuploidy in 14 cases, neural tube defect in two cases, and an inborn error of metabolism in one case. With increasing operator skill and improvement in technique, a striking improvement occurred in pregnancy outcome in the last 11 patients as compared with the first six. In four of the first six cases, the entire pregnancy was lost. Among the last 11 patients, on the other hand, no pregnancy was lost. All 11 women delivered healthy, viable infants; eight delivered at term and three delivered between 31-35 weeks. Of the various techniques used, we found intracardiac injection of potassium chloride to be the most effective, but it should not be used in monochorionic twin gestations.

Abortion, Induced↗
PubMed1988

Gastrointestinal arterial fibromuscular dysplasia of childhood.

An unusual case of a progressive, noninflammatory stenosing vasculopathy, arterial fibromuscular dysplasia is presented. The distinctive features of this particular case include onset in early childhood with a predominant involvement of the gastrointestinal system, sparing of the renal arteries, lack of hypertension, and no cutaneous features of progressive systemic sclerosis. We discuss the clinical history over a decade and the pathologic features, including routine and electron microscopic findings of biopsy and autopsy tissues, and review the literature.

Adolescent↗
PubMed1987

Mesenchymal tissue of the interventricular septum. Structural and ultrastructural study.

Light and electron microscopic studies of frontal and sagittal sections of embryonic chick hearts (Stages 25, 28-29), reveal mesenchymal tissue in the cephalic portion of the interventricular septum. The endocardium of this cephalic portion contains reoriented and invaginated cells with pseudopodia; in addition there are cells immediately subjacent to the endocardium. Similar cellular events take place during the formation of mesenchymal tissue in the atrioventricular and conotruncal regions. In these regions the mesenchymal tissue originates by means of an endocardial activation process. The structural characteristics of the formation of the cephalic portion of the interventricular septum suggest that local mesenchymal tissue is contributed by the endocardium. However, based upon the close anatomic relationship observed by us between the mesenchymal tissues of the atrioventricular canal, conotruncal region and the cephalic portion of the interventricular septum; we do not discard a contribution by migration of cells from atrioventricular and conotruncal regions to the interventricular septum.

Animals↗
PubMed1987

Origin of mesenchymal tissue in the septum primum: a structural and ultrastructural study.

A structural, ultrastructural and histochemical study in chick embryos indicates that the septum primum mesenchymal tissue originate between 3 and 5 days of development and that their origin may be related to an activation of endocardial cells that cover the septum primum. By day 3, endocardial cells display migratory appendages, cell hypertrophy and an increase in secretory and mitotic activity. In later stages (day 4) hypertrophic endocardial cells undergoing division seem to delaminate and translocate toward the subendocardial space to give rise to free mesenchymal-type cells. These results suggest that the endocardium makes up the bulk of the septum primum mesenchymal tissue as has been demonstrated during mesenchymal tissue formation in the atrioventricular canal and outflow tract. Before and during mesenchymal tissue formation an accumulation of extracellular matrix components like proteoglycans can be visualized using tannic acid. These extracellular components might be related to the promotion of cellular events described during endocardial activation. The fusion of the septum primum with the atrioventricular (AV) endocardial cushions which would obliterate the foramen primum, occurs between mesenchymal tissues. Therefore, any alteration in the normal development of these mesenchymal tissues could be related to pathological cases of persistent atrial communications. Light microscopy preliminary observations of embryonic mouse heart indicate that septum primum mesenchymal tissue formation occurs similarly between mouse and chick embryos.

Animals↗
PubMed1987

Influence of the mesenchymal microenvironment on myocardial and endocardial cell behaviour in experimental interaction with chick limb mesenchyme.

In an attempt to clarify the possible influence of the mesenchymal microenvironment in the differentiation of myocardial and endocardial cells, an "in vivo" transplantation experiment was performed in which the ventricular region of the heart (chick or quail) was placed in close association to the mesenchyme of the anterior chick limb to create an experimental interaction between myocardium and foreign mesenchyme. The results showed that after 48 h of tissue interactions the ventricular myocardium is incorporated into the mesenchyme of the anterior chick limb, changing its organization and cytological appearance. The myocytes tend to dissociate, exhibiting a less organized myofibrillar pattern. In addition, abundant extracellular matrix components made up of granular and fibrillar material were observed associated with the myocardial and the mesenchymal cell membranes as well as distributed in their surrounding microenvironment. The endocardium became discontinuous, due to detachment of the cells and emitted multiple pseudopodia and filopodia. These observations indicate that the mesenchyme from the anterior chick limb modifies the cellular behaviour and organization of the neighbouring myocardium and endocardium with which it interacts. We suggest that this might occur through participation of extracellular matrix components such as glycosaminoglycans, fibronectin and collagen which are known to act as macromolecular mediators in cell to cell interactions, cell migration and differentiation.

Animals↗
PubMed1987

Structure-activity relationships among di- and tetramine disulfides related to benextramine.

The synthesis and irreversible alpha-blocking activity in the rat vas deferens of a series of tetra- and diamine disulfides 2-38, structural analogues of benextramine (BHC), are described. All compounds containing a central cystamine moiety displayed an irreversible alpha-adrenergic blockade at concentrations ranging from 10(-4) to 6 X 10(-6)M. Potency was increased in cystamines N,N'-disubstituted with 6-aminohexyl groups, especially when the outer nitrogen atoms bear arylalkyl substituents or are enclosed in a ring. However, N,N,N',N'-tetrasubstituted cystamines were poor blockers. Structural specificity in the outer portion of the tetramine disulfide is low, since many types of substituents gave rise to potent alpha-blockers. Even replacement of the outer amines with nonbasic ethers or amides was observed to maintain irreversible alpha-blockade.

Adrenergic alpha-Antagonists↗
PubMed1987

Prenatal diagnosis of fetal brain tumors.

Two cases of congenital brain tumors were detected during routine antepartum sonography at the Mount Sinai Medical Center Perinatal Ultrasound Unit. In both cases, diagnosis was made during the third trimester at 31 and 33 weeks, respectively. In one of these patients, no intracranial abnormalities were noted on a sonogram performed in conjunction with genetic amniocentesis at 18 weeks gestation. The histologic diagnosis of both tumors was glioblastoma multiforme grade III. Previous reports describing the prenatal sonographic diagnosis of intracranial tumors have been in cases with fetal intracranial teratomas.

Adult↗
PubMed1986

Young men with high blood pressure report few recent life events.

Men who had high, medium and low blood pressure at age 18 (compulsory screening for military service in Stockholm) were examined ten years later at age 28. Interviewers, having had no information regarding past or present blood pressure, interviewed them about life events experienced during the year preceding the examination. Men with high blood pressure at rest reported fewer life events for the past year than other men. Furthermore, high plasma adrenaline levels at rest were associated with few reported life events.

Adolescent↗