Search PubMed⌕ Search

Biomedical subjects

J McCarthy

Publications and source records attributed to J McCarthy.

At least 91 records · Page 5Linked to original sources
PubMed1995

Probing the presumed catalytic triad of selenium-containing peroxidases by mutational analysis of phospholipid hydroperoxide glutathione peroxidase (PHGPx).

Single and double site mutants affecting the presumed catalytic centre of the selenoenzyme PHGPx were subjected to functional analysis. The rate constants k+1 and k'+2, for the oxidation and the regeneration of the ground state enzyme were estimated, respectively. Moreover, the alkylation rate of the reactive centre by iodoacetate (kinact.) was also analysed. The substitution of the catalytically competent selenocysteine 46 by cysteine (PHGPxcys46) decreased k+1 and k'+2 by about three orders of magnitude, although leaving unaffected kinact.. Furthermore, mutations of PHGPxcys46 involving the other residues of the triad decreased both kinact. and k+1, thus highlighting the involvement of Gln 81 and Trp 136 in the dissociation/activation of the nucleophilic cysteine thiol. In general, substitutions of Gln 81 or Trp 136 by acidic residues in PHGPxcys46 most dramatically depressed the k+1 values, because they practically prevented the dissociation of the thiol group, while neutral or positively charged residues in these positions allowed an intermediate dissociation and induced a corresponding reactivity of the thiol. Our data, for the first time, reveal that the presumed triad of selenocysteine, glutamine and tryptophan residues represents a novel type of catalytic centre, whose integrity is essential for the full catalytic function of glutathione peroxidases.

Animals↗
PubMed1995

Circumvallate placenta: sonographic diagnosis.

We prospectively identified 12 patients who had a shelf at the margin of the placenta consistent with the diagnosis of circumvallate placenta. Ten patients were followed to delivery and three placentas were sent for pathologic analysis. Circumvallate placenta was diagnosed by gross inspection in all three but was confirmed by microscopic analysis in only two. One of these patients had placental abruption and cesarean delivery for fetal distress at 27 weeks. Circumvallate placenta is another cause of uterine band, sheet, or shelf. The finding can be associated with a normal obstetric outcome but may predispose to placental complications.

Abruptio Placentae↗
PubMed1994

Tubular nephrotoxicity after cardiac surgery utilising cardiopulmonary bypass.

Markers of renal tubular injury were examined in 21 patients (16 male, 5 female, mean age 57.4 years) undergoing cardiac surgery utilising cardiopulmonary bypass. Postoperative urine outputs were very high (200-250 ml/h at 1-2 h), decreasing to 100 ml/h by 6 h. Although creatinine clearances did not vary significantly in the postoperative period (P = 0.16), significant changes were noted in the urinary concentrations of three tubular markers relative to creatinine concentration (P < 0.001). Urinary beta 2-microglobulin increased from negligible levels (median 0.01 mg/mmol creatinine) to peak at 4 h (median 4.55 mg/mmol), in part due to interference with its reabsorption by the plasma volume expander Haemaccel. Concentrations of the brush border antigen adenosine deaminase binding protein increased 6-fold, from a median of 5.03 arbitrary units (AU)/mumol to 31.2 AU/mumol at 48 h. The lysosomal enzyme N-acetyl-beta-D-glucosaminidase increased nearly 4-fold, from 0.68 units/mmol to 2.64 units/mmol at 48 h. Our results suggest that cardiac surgery utilising cardiopulmonary bypass is associated with acute tubular injury which can occur in the absence of overt changes in creatinine clearance.

Acetylglucosaminidase↗
PubMed1994

Detection and direction discrimination performance with flicker gratings in peripheral vision.

Detection and direction discrimination experiments were conducted with luminance and flicker gratings. The flicker gratings had bars made up of static random pixels interspersed between other bars with flickering random pixels. All experiments were carried out in peripheral vision with grating images centered at 8 deg eccentricity in the superior retina. Detection of flicker gratings (i) was independent of pixel size, (ii) declined with spatial frequency in the range 1-4 c/deg, and (iii) improved with stimulus area (number of grating cycles). Detection performance with a flicker grating was comparable to that obtained with a low-contrast (0.01) luminance grating, and the results suggest that the spatial structure of a flicker-domain stimulus is based upon signals which are weak compared to the maximum signals attainable with a luminance-domain stimulus. With the detectability of flicker and luminance gratings equated, d' for discriminating the direction of motion of a luminance grating increased with step size (1/12 to 1/4 cycle) whereas direction discrimination performance with a flicker grating remained unchanged and at chance levels. Under the conditions tested, there was no evidence that the motion of a flicker-domain stimulus could be processed peripherally. Constraints on alternative models of motion processing are discussed.

Contrast Sensitivity↗
PubMed1994

Retrospective analysis of the utility of video-assisted thoracic surgery in 100 consecutive procedures.

One hundred consecutive video-assisted thoracic surgery (VATS) procedures, diagnostic (n = 54) and therapeutic (n = 46), in 90 patients over a 2-year period are reviewed. Hospital mortality was 2%. Conversion to formal thoracotomy was required in 3%, and re-exploration for bleeding in 1%. Seven patients required intensive care unit facilities postoperatively. The technique described was safe and there was minimal postoperative morbidity. Diagnostic VATS was of particular use in cases of indeterminate pulmonary masses (Sensitivity of 96%), anterior mediastinal masses and in immunocompromised patients. Video-assisted thoracic surgery may now be the treatment of choice for recurrent pneumothoraces and it demonstrated potential for development in a variety of other benign thoracic disorders. This method had a limited role in the management of empyaema with a 60% conversion rate to formal thoracotomy. Pulmonary resections were feasible but its role in the treatment of malignancy is questioned.

Adolescent↗
PubMed1994

The closet and the ethics of outing.

Because social circumstances have changed, the question of outing has assumed an importance unknown in a time when homosexuality was a guarded secret. This essay describes the evils of the closet in terms of its affronts to the worth of gay men and lesbians. While outing might appear as a repudiation of the closet, this essay argues that not all outing is justified. On the other hand, the article also rejects those arguments that criticize outing as a violation of privacy as well as arguments that defend outing as no violation of others' rights.

Ethics↗
PubMed1994

Video-assisted thoracic surgery for delayed pericardial effusion post-CABG.

Delayed-onset pericardial effusion following coronary artery bypass grafts can give rise to significant morbidity in its presentation and in its management by traditional surgical techniques. A video-assisted thoracoscopic technique to create a pericardial window, with the advantage of a minimally invasive approach combined with excellent visualization in such a patient is described.

Coronary Artery Bypass↗
PubMed1994

Reconstruction of major segmental loss of the proximal femur in revision total hip arthroplasty.

Reconstruction of major proximal femoral segmental defects is one of the most difficult challenges in revision total hip arthroplasty (THA). One technique that has been successful is the use of a modular, long-stemmed prosthesis, cemented to an allograft proximal femur and press-fit to the host bone. Since July 1989, the authors have used this technique in 30 hips (29 patients). The trochanteric slide approach was used in all cases. Sixty pounds of weight bearing was encouraged for six weeks, then full weight bearing as tolerated. The mean follow-up period was 22 months (range, two to 46 months). All but two grafts united to the host bone clinically and radiographically. Complications included five dislocations, one graft-host nonunion, one graft resorption, and one deep infection requiring resection arthroplasty. The latter patient was subsequently reconstructed successfully using the same technique. Although the follow-up period is short, the authors have been encouraged by the early success of these allograft-prosthetic composites. Advantages of this approach include rapid return to weight bearing, physiologic loading of the distal femur, and reconstitution of vital proximal bone stock.

Adult↗
PubMed1993

Video assisted thoracic surgery.

Using video thoracoscopic techniques in 30 patients over a twelve month period we have been able to perform 33 procedures that would have been previously performed by thoracotomy, with its associated morbidity. We have found the applications of this procedure to be diverse, being both diagnostic (n = 16) and therapeutic (n = 17). The diagnostic procedures were associated with a high diagnostic yield and allowed accurate staging. The therapeutic procedures were associated with minimal morbidity and short hospital stay. Our experience indicates an established and expanding role for Video Assisted Thoracic Surgery.

Adolescent↗
PubMed1993

Maternal serum screening for fetal Down syndrome in the United States: a 1992 survey.

OBJECTIVE: Our purpose was to determine the status of screening for fetal Down syndrome in the United States in 1992. STUDY DESIGN: Information was sought from laboratories participating in two proficiency testing programs. RESULTS: The 301 responding laboratories (98%) annually provided services to 2,113,000 pregnant women. Of these laboratories, 242 provided Down syndrome screening (1,924,000 pregnant women); 55% used alpha-fetoprotein levels alone, 30% used alpha-fetoprotein, unconjugated estriol, and human chorionic gonadotropin combined, and 14% used alpha-fetoprotein and human chorionic gonadotropin combined. All laboratories used clinically validated analytes. Nearly all screened at appropriate gestational ages, used a validated algorithm, and used risk as the screening variable. However, many laboratories, especially smaller ones, were unable to monitor their performances adequately. CONCLUSION: Since 1988 maternal serum screening for Down syndrome has approximately doubled, and other analyte measurements have been added in nearly one fourth of the screened pregnancies. Most laboratories appear to be performing adequately, although there is room for improvement.

Chorionic Gonadotropin↗
PubMed1993

Effects of extracellular matrix components on cell locomotion.

The extracellular matrix (ecm), which is composed of collagens, glycoproteins, and proteoglycans, has emerged as an important regulator of cell locomotion. This review describes some of the mechanisms by which the ecm may regulate locomotion, focusing primarily on cell extension and lamellae formation. Ecm-receptor interactions form an important part of cell recognition of ecm. Such interactions can result in altered cell adhesion, signal transduction, and cytoskeletal organization, all of which impact on cell locomotion. It is important to note that although the effects of single ecm components have been studied, generally, the cell is likely to perceive ecm in vivo as a macromolecular complex. It will fall to future work to define how complexes of ecm regulate cell behavior. Because of our own particular research bias, we focus on reviewing the role of fibronectin, integrins, chondroitin sulfate, hyaluronan, and hyaluronan receptors in the regulation of cell locomotion and examine their effect on adhesion, signal transduction, and cytoskeletal integrity. Cytoskeleton assembly mechanisms, particularly those that might be regulated by the ecm, are also described. These events are summarized in a working model of ecm-promoted locomotion.

Animals↗