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Biomedical subjects

A Peña

Publications and source records attributed to A Peña.

At least 19 recordsLinked to original sources
PubMed1992

Long-term anorectal function in imperforate anus treated by a posterior sagittal anorectoplasty: manometric investigation.

Thirty imperforate anus patients were investigated by anorectal manometry 5 to 10 years after a posterior sagittal anorectoplasty. Anal resting tone (ART) and anal squeezing pressure (ASP) were subnormal in most patients. Rectal volume (RV) and sensation to balloon distension were within the normal range. Rectoanal reflex inhibition was demonstrated in 9 of 30 patients. Soiling was more common in patients with a very low ART (less than 40 cm H2O) and a low ASP (less than 100 cm H2O). Constipation was more common in patients with a large RV (greater than 150 mL). Still, the correlation to clinical results was incomplete. As regards to the correlation to type of malformation the rectal atresia patients showed near normal results. The vestibular fistula patients were next in results showing rectoanal reflex inhibition in 5/6 patients. There was no difference in the results between bulbar and prostatic fistula patients.

Adolescent↗
PubMed1992

Transanorectal approach for the treatment of urogenital sinus: preliminary report.

The treatment of the urogenital sinus with normal rectum still represents a challenge. A perineal approach with or without a skin flap seems to be effective for those patients with a low implantation of the vagina. However, in patients with a high vaginal implantation, this treatment frequently fails to provide a good, functional vagina due to a narrow, strictured vaginal opening. Based on previous experience in the treatment of more than 80 patients with a persistent cloaca, a posterior sagittal transanorectal approach with a protective colostomy was performed in three patients with urogenital sinus and normal rectum. The pelvis was approached through a midsagittal posterior incision; the coccyx was split and the entire anorectal sphincteric mechanism was divided in the midline. The rectum was bivalved in the midline including both posterior and anterior rectal walls. This provided excellent exposure to the urogenital sinus. The vagina was then fully separated from the urogenital sinus (as described in cases of persistent cloacas), and then mobilized and sutured to the perineum. The rectum and sphincteric mechanism were meticulously reconstructed. A midline incision assures the preservation of anorectal innervation, and provides excellent exposure to the pelvis. Anal dilatations are not necessary to maintain a patent and supple anorectal opening because the rectum has two suture lines, one in front of the other. After the colostomy was closed, all patients had appropriate bowel control for their age; two of them are fully continent for urine and the third one still has a suprapubic cystostomy tube waiting for a repair of an additional urethral malformation.

Anal Canal↗
PubMed1992

Current management of anorectal anomalies.

A significant amount of new information has been obtained concerning the early management of anorectal malformations. The surgical approach also has changed and improved the functional prognosis of children with these defects. Recommendations are made based on a series of 632 cases. A simplified approach to avoid the most common errors in the management of these defects is emphasized. Yet, there are still many children born with severe anatomic deficiencies who cannot expect normal bowel function; however, for this group, a bowel management program is available to help improve their quality of life.

Anal Canal↗
PubMed1991

An energy-dependent efflux system for potassium ions in yeast.

An efflux of potassium ions was demonstrated in mutants of yeast cells lacking a functional high affinity carrier system for monovalent cations. This efflux showed the following characteristics: (a) It was stimulated by the presence of a substrate, either glucose or ethanol. (b) It was stimulated by several cationic organic molecules, such as ethidium bromide, dihydrostreptomycin, diethylaminoethyldextran, and also by trivalent cations, such as Al3+ and lanthanides; this stimulation also depended on the presence of a substrate. (c) K+ efflux was decreased in yeast mutants with decreased ATPase activity, which generated a lower membrane potential. (d) Although the efflux appeared to be of an electrogenic nature, producing hyperpolarization of cells, it was accompanied by the efflux of phosphate, probably as an anion partially compensating for the large amount of cations leaving the cell. (e) K+ efflux was also accompanied by an uptake of protons. (f) The efflux appeared more clearly in cells grown in YPD medium, and not in more complex media nor in the same YPD medium if supplemented with Ca2+ or Mg2+. Efflux of monovalent cations produced by Tb3+ and organic cationic agents was also demonstrated in wild type strains. This efflux system appears to be, at least partially, electrogenic, but seems to be also an exchange system for protons and to function as a symport with phosphate; it may be involved in the regulation of the internal pH of the cell, and appears to be regulated by its link to the energetic status of the cell, probably through the membrane potential.

Calcium↗
PubMed1991

Molecular association enhances the toxic effects of non-substituted monoterpene suspensions on isolated mitochondria.

1. The effects of two, cyclic, non-substituted monoterpenes (betapinene and limonene) were studied on isolated mitochondria. Oxidative phosphorylation was inhibited depending on monoterpene concentration and on monoterpene association (droplet size) in aqueous suspension. 2. In the absence of hydration, both monoterpenes, dissolved in either dimethylformamide (DMF) or dimethylsulphoxide (DMSO), inhibited oxidative phosphorylation through depletion of the transmembrane potential and inhibition of oxygen consumption. Hydration of the monoterpene solutions before addition to mitochondria resulted in milder inhibitory effects. The decrease in inhibition was more pronounced with DMSO than with DMF. 3. The possibility that the biochemical properties of a compound in suspension may depend on molecular association should be considered whenever studies of a hydrophobic compound in an aqueous environment are conducted.

Animals↗
PubMed1991

Effects of K+ and other monovalent cations on yeast mitochondria.

In mitochondria from Saccharomyces cerevisiae and in the presence of ethanol or NADH, K+ or Na+ increased the rate of O2 uptake in states 3 and uncoupled as well as in sonicated mitochondria. The respiratory control, the ADP:O ratio and the synthesis of ATP also increased. ATP hydrolysis by sonicated mitochondria increased depending on the cation added as follows: K+ = NH4+ = Rb+ Na+ Li+. This correlated with the ionic radii of the cations. Monovalent cations increased the activity of: 1) F1F0ATPase which was sensitive to cation size and 2) complex I of the respiratory chain, which seemed to regulate the rate of oxidative phosphorylation, but did not discriminate between K+ or Na+.

Adenosine Triphosphate↗
PubMed1990

Does the distal rectal muscle in anorectal malformations have the functional properties of a sphincter?

Smooth muscle strips from the distal rectum of 11 patients who underwent surgery for imperforate anus and cloacal malformations, were studied in vitro to assess the motility response to electrical field stimulations (EFS) and to pharmacological stimulation with adrenergic and cholinergic agonists. EFS induced a nonadrenergic, noncholinergic inhibition in most strips. Acetylcholine caused either a modest contraction, no response, or a relaxation. Following atropine administration, acetylcholine caused a nonadrenergic and tetrodotoxin-resistant relaxation. The alpha-adrenergic agonist phenylephrine induced contractions in all strips. The response was abolished by alpha-adrenoceptor blockade with phentolamine, but was resistant to atropine and tetrodotoxin. beta-Adrenergic stimulation caused a relaxation that was abolished by propranolol. Function of the distal rectal smooth muscle, resected during correction of anorectal malformations, shows similarities to the function reported previously on normal anal smooth muscle evaluated in vitro.

Adrenergic Agonists↗
PubMed1989

Leucine transport in plasma membrane vesicles of Saccharomyces cerevisiae.

Yeast plasma membrane vesicles were obtained by the fusion of liposomes with purified yeast membranes by means of the freeze thaw-sonication technique. Beef heart mitochondria cytochrome-c oxidase was incorporated into the vesicles. Addition of substrate (ascorbate/TMPD/cytochrome c) generated a membrane potential negative inside, and an alkaline pH gradient inside the vesicle, that served as the driving force for leucine transport. Both delta pH and delta psi could drive leucine transport. When delta pH was increased in the presence of valinomycin and potassium, at the expense of delta psi, leucine uptake increased by 10%.

Animals↗
PubMed1989

Effect of DDE on ionic and fluid movement in rat colon in vitro.

1. The effect of DDE on ionic (Na+ and K+) and fluid movement was studied in rat colon in vitro. 2. DDE (10(-7) M) increased net K+ secretion while inhibited the net flux of Na+ and fluid movement inducing net secretion. 3. DDE added before or after aldosterone caused an inhibition on the net influx of Na+ and fluid movement and potassium secretion. 4. DDE also inhibited (Na+ and K+)-ATPase from the same tissue suggesting that the inhibition of DDE is due to an action of this organochlorine compound on the sodium pump.

Aldosterone↗
PubMed1989

Incorporation of ionic channels from yeast plasma membranes into black lipid membranes.

Recently, patch-clamping of yeast protoplasts has revealed the presence of plasma membrane K+ channels (Gustin, M. C., B. Martinac, Y. Saimi, M. R. Culberston, and C. Kung. 1986. Science (Wash. DC). 233:1195-1197). In this work we show that fusion of purified plasma membranes into planar bilayers allows the study of the yeast channels. The main cationic conductances detected were of 64 and 116 pS, however, larger and smaller conductances have been observed. The two main conductances were sensitive to the K+ channels blockers tetraethylammonium (TEA+) and Ba2+. Bionic experiments indicated that both conductances were K+ selective.

Cell Membrane↗
PubMed1989

The surgical management of persistent cloaca: results in 54 patients treated with a posterior sagittal approach.

This report describes the author's personal experience in the surgical treatment of 54 patients. The approach is called posterior sagittal ano recto vagino urethroplasty (PSARVUP). Forty patients underwent a primary procedure, and 14 a secondary operation. The anatomic variations found were multiple, integrating a wide spectrum of defects. The posterior sagittal approach proved to be a good initial approach, and permitted complete repair of the defect in 47 patients. Seven patients required a laparotomy in addition. The length of the common channel varied from 0.5 to 7 cm. Common channels longer than 3 cm usually required some technical alternative to replace the vagina. In at least 34 cases, the vagina was reconstructed primarily without any additional technical manoeuvres. Different degrees of vaginal and uterine septation were found in 25 of 50 cases. Hydrocolpos was an associated defect in 14 of 49 patients. Sixty-eight percent of the patients had an important associated urological defect. Twenty-six patients were clinically evaluated without medical management, twenty-one of whom had voluntary bowel movements by the age of 3 years, but most of them had minor episodes of soiling. Nineteen patients had a normal sacrum, and five had urinary incontinence that was successfully managed by intermittent catheterization. Seven patients had a very abnormal sacrum, and five of them had urinary incontinence. Twenty patients underwent a late postoperative vaginoscopy, 14 of whom showed an adequate introitus and vagina, whereas five had different degrees of narrowing of the introitus. Six patients had a urethrovaginal fistula. One ureter was accidentally divided and one vagina had complete ischaemic necrosis.

Adolescent↗
PubMed1989

Persistent cloaca and phallic urethra.

During the last 8 years 54 children with a persistent cloaca have been treated by one of us (A. P.). The most common associated anomalies involved the urinary tract, with renal agenesis, renal dysplasia, vesicoureteral reflux and megaureter encountered most frequently. Four patients demonstrated the rare entity of an opening at the tip of a pseudophallus and 2 also had an accessory urethra in association with the cloacal malformation. These children exhibited some form of masculinization of the external genitalia with the accessory urethra or cloacal channel assuming a phallic position in an enlarged clitoris. No adrenal, metabolic or chromosomal abnormalities were detected and virilization was limited to the genitalia. These cases illustrate the greater predilection of these patients to more complex congenital malformations than patients with an isolated cloaca. The posterior sagittal approach has been used effectively for repair of these congenital malformations.

Abnormalities, Multiple↗