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Biomedical subjects

A Steele

Publications and source records attributed to A Steele.

At least 19 recordsLinked to original sources
PubMed1992

Leaching of hydrogen peroxide from bleached bovine enamel.

Accurately weighed bovine enamel slabs were individually immersed in 2 ml of 35% hydrogen peroxide for 1, 3, 5, 30, or 60 min. A control group was obtained by individual immersion of bovine enamel slabs in 2 ml of saline for 60 min. All samples were washed, dried, acid-etched with 37% phosphoric acid for 60 s, then washed and dried again. Two milliliters of double-distilled water were used for individual sample leaching. Leaching was done for 1, 5, 10, 20 min, or 7 days for the experimental groups and for 7 days for the control group. The samples of one of the experimental groups were leached for a second time for 1 min. A total of 112 samples was used in this study. Hydrogen peroxide was spectrophotometrically identified and quantified in all leaching solutions based on the oxidation reaction of leuco-crystal violet buffer solution by hydrogen peroxide, a reaction catalyzed by horseradish peroxidase. The results revealed a significant difference in the quantity of leached peroxide between bleached samples (irrespective of the duration of leaching) and control, saline-treated ones. No difference was observed in the quantity of leached peroxide between releached samples and control, saline-treated ones. However, these were small, random, and numerically insignificant. Statistically significant differences were also noted among some of the experimental groups. They were thought to hold no clinical significance. The results suggested that upon immersion, the complete leaching of peroxide from bleached enamel occurs rapidly.

Animals↗
PubMed1991

Interleukin 4 receptor targeted cytotoxicity: genetic construction and in vivo immunosuppressive activity of a diphtheria toxin-related murine interleukin 4 fusion protein.

The interleukin 4 (IL 4) receptor is expressed on various cells of the immune system, including T and B lymphocytes, macrophages and mast cells. We have constructed a recombinant protein, DAB389-mIL 4, that is composed of the enzymatically active and membrane translocation domains of diphtheria toxin fused to murine IL 4. We demonstrate that this fusion toxin selectively inhibits protein synsthesis in eukaryotic cells which express the murine IL 4 receptor. The cytotoxic potency of this fusion toxin is shown to be directly proportional to the reported number of IL 4 receptors on the surface of target cells. Since the action of DAB389-mIL 4 can be blocked with either excess mIL 4 or antibody to mIL 4, we conclude that its entry into target cells is mediated through the mIL 4 receptor. A mutant form of DAB389-mIL 4, DA(197)B389-mIL 4, in which the fragment A-associated ADP-ribosyltransferase is inactive, is not cytotoxic to murine IL 4 receptor-bearing cells. Finally, we demonstrate that DAB389-mIL 4 administered subcutaneously to DBA/2 mice results in suppression of delayed-type hypersensitivity (DTH); whereas, the non-toxic DA(197)B389-mIL 4 fails to dampen the DTH response.

Animals↗
PubMed1991

Plasma levels of an endogenous Na(+)-K+ pump inhibitor in relation to haemodynamic data in cardiopathic patients.

1. Despite the fact that numerous studies provide evidence for the existence of an endogenous inhibitor of the cell membrane Na(+)-K+ pump in plasma, little is known about the relationships between this factor and the main haemodynamic parameters. 2. In order to shed some light on this, we attempted to correlate haemodynamic parameters, measured during heart catheterization in a group of 22 cardiopathic subjects, with plasma digitalis-like activity levels, determined by two different procedures. 3. The ability of plasma to inhibit a human renal Na(+)-K(+)-ATPase showed an inverse correlation with cardiac index and a direct correlation with peripheral resistance. Plasma cross-reactivity with digoxin antibodies correlated directly with left atrial pressure. 4. These results furnish confirmation of a number of theoretical assumptions which attribute to the digitalis-like factor the ability to modify the contractility of the cardiovascular system.

Adult↗
PubMed1990

Cataract surgery.

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Cataract Extraction↗
PubMed1990

The gastric acid conundrum in peptic ulcer.

According to the traditional view, gastric acid and pepsin are a sine qua non for ulcer development. Acid suppression, however, is far from being the only successful therapeutic approach, and similar healing rates are achieved by drugs with substantially different mechanism of action antacids, H2-antagonists, antimuscarinics, cytoprotective and site-protective agents-thus denoting a multifactorial pathogenesis. Even with the antisecretory compounds, the relationship between gastric acid and ulcer healing gives rise to perplexity: antacids prove effective at widely varying doses; pirenzipine and H2-blockers, which are clinically equieffective, differ considerably in antisecretory efficacy; H2-antagonist studies on early vs late postprandial dosing, yield contradictory clinical results; morning and bedtime single administration of H2-antagonists prove equiactive on ulcer healing, leading to a appraisal of the alleged importance of nocturnal acidity. Ulcer sealants such as colloidal bismuth and sucralfate prove as effective as H2-antagonists despite their total lack of antisecretory activity, thereby reapparently under-mining the primary pathogenetic role of acid. However, with the spectacular 100% healing rates achieved by the proton-pump blocker, omeprazole, the wheel has come full circle, and gastric acid appears to re-emerge as a primary element in pathogenesis. Specific therapy, based on the predominant pathogenetic factor involved, is likely to be a feasible proposition, but, at present, remains little more than a remote possibility.

Gastric Acid↗
PubMed1989

Drug treatment of functional dyspepsia. A meta-analysis of randomized controlled clinical trials.

The results of therapeutic trials in functional dyspepsia (FD), a frequently encountered condition, are contradictory. Our aim, then, was to produce a pooled estimate, or meta-analysis, of a series of short-term randomized placebo-controlled clinical trials on the pharmacological treatment of FD with antisecretory and gastrokinetic drugs. We retrieved trials for analysis purposes by consulting computerized data bases and by scanning published reviews, Current Contents, and references cited in the individual studies. We also requested bibliographical updates from the medical departments of the manufacturers of the drugs used in the various trials. Of 74 trials retrieved by these means, 23 proved eligible for meta-analysis on the basis of six selection criteria defined a priori. Results were expressed in terms of "therapeutic success" (TS), which includes "symptom-free patients," patients with "significant improvement in symptoms," "excellent results," and so on. The differences in TS rates between the various drugs and placebo were calculated in each trial as the algebraic difference together with the respective 95% confidence interval (95% C.I.); the pooling of results of all eligible trials was done using Cochran's weighted method. With antisecretory drugs, the mean difference in TS rates versus placebo was +20% (95% C.I.: 14-24%). The therapeutic gain for the respective antisecretory agents was 25% (95% C.I.: 14-36%) in the case of pirenzepine and 18% (95% C.I.: 12-24%) in the case of H2 antagonists. Meta-analysis of trials with gastrokinetic drugs also showed superior efficacy of these agents compared with placebo, with a mean difference in TS rates of +46% (95% C.I.: 40-52%).(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical Trials as Topic↗
PubMed1989

High plasma levels of a ouabain-like factor in normal pregnancy and in pre-eclampsia.

Recent reports have described high levels of one or more substances which cross-react with digoxin antibodies in the serum of women with pre-eclampsia. We measured plasma ouabain-like activity and intraerythrocyte sodium and potassium concentrations, in addition to performing routine hypertensive laboratory tests, in 13 normotensive non-pregnant subjects, 15 normotensive pregnant women and 16 pre-eclamptic women (gestational age: 33-36 weeks). Plasma ouabain-like activity, measured as plasma-induced variations in ouabain binding to human erythrocytes, proved significantly higher in both groups of pregnant subjects as compared to normotensive non-pregnant women, and a significant difference was also found between pre-eclamptic and normotensive pregnant women, the former exhibiting higher plasma ouabain-like activity. No differences in intracellular sodium and potassium levels were detected among the three groups studied. Though there is reason to believe that the high plasma levels found both in normal and hypertensive pregnancy may depend on placental production, we are not in a position to define with any degree of certainty what the mechanism or mechanisms are that regulate ouabain-like factor production.

Adult↗
PubMed1989

Plasma ouabain-like activity in essential hypertensive patients and in subjects with primary aldosteronism.

Plasma from 37 essential hypertensive patients, from 11 subjects with primary aldosteronism and from 23 normotensive subjects was tested for ouabain-like activity. Despite a very substantial overlap, hypertensive patients (both essential and secondary) showed significantly higher levels of a ouabain-like plasma factor compared to normotensive controls. No substantial differences could be detected, however, between the two forms of hypertension; in particular, no significant changes were observed in the low-PRA subgroup. Our results are hardly compatible with the hypothesis that this substance may be of crucial importance in the development either of essential hypertension or of primary aldosteronism.

Adolescent↗
PubMed1989

Platelet intracellular free Ca2+ after incubation with plasma from hypertensive patients.

Variations in intracellular free calcium were measured in platelets from normal donors, incubated with plasma from hypertensive patients and from control subjects to test the hypothesis that a circulating factor might induce an increase in calcium concentration. Before incubation, plasma was heat-inactivated or ultrafiltered. Incubation both with heat-inactivated and ultrafiltered plasma failed to result in any significant modifications in intracellular free calcium. Similarly, no significant increase was observed after incubation with ouabain at concentrations ranging from 10(-7) to 10(-4) M. No significant differences were observed between platelets incubated with plasma from hypertensive as compared with control subjects. These findings are not consistent with the hypothesis that the increase in intracellular free calcium observed in platelets of hypertensive patients may be due to a plasma ouabain-like factor.

Adult↗
PubMed1988

Effects of indomethacin on the acid-base balance and hemodynamics of chronically instrumented pregnant sheep.

Maternal and fetal responses to maternal intravenous administrations of indomethacin (0.5 mg/kg over 3 min) were evaluated in 10 experiments performed on 6 ewes at gestational ages of 107-139 days. Maternal and fetal aortic blood samples were obtained at frequent intervals over 2 h from the start of infusion. Significant maternal effects were (1) an increase in blood pressure (5 min) and (2) a decrease in heart rate (5, 15, 30 min). Fetal effects included (1) an increase in pH (5, 15 min) and (2) tachycardia (45, 60, 90, 120 min). At the dosage and duration administered, these maternal and fetal hemodynamic and fetal acid-base changes occurred independently of any effect upon uterine blood flow.

Acid-Base Equilibrium↗
PubMed1988

Demyelination and axonal degeneration in Lewis rat experimental allergic neuritis depend on the myelin dosage.

We describe the clinical and pathologic features of experimental allergic neuritis in Lewis rats inoculated with varying doses of myelin, ranging from 0.5 to 20 mg. The clinical scores were assessed daily. On days 18 and 19 or 28 postimmunization, the rats were perfused with fixative and samples of cervical and lumbar roots and sciatic nerves were processed and embedded in Epon. Tissues were examined by light and electron microscopy and the degree of edema, inflammation, demyelination, and axonal degeneration was assessed quantitatively. We found that the severity of clinical and pathologic experimental allergic neuritis correlated positively with the dose of myelin used for immunization. High dose tolerance was not observed. Demyelination prevailed in nerve roots and increased with higher doses of antigen. Accompanying axonal degeneration was seen only with high doses of myelin. The pathology of sciatic nerves differed. Sciatic nerves of rats immunized with 0.5 and 1 mg of myelin were either normal or showed perivenular lymphocytic infiltrates and demyelination, but nerves from rats with higher immunizing doses of myelin showed increasingly severe axonal degeneration. The axonal degeneration in nerve roots paralleled the degree of inflammation and demyelination and may have been a nonspecific product of the inflammatory reaction. However, the much more severe axonal destruction seen in sciatic nerves with high myelin doses was probably due to other pathogenetic mechanisms.

Animals↗
PubMed1985

Screening for wart virus infection in normal and abnormal cervices by DNA hybridisation of cervical scrapes.

Cervical scrapings from 78 women attending a sexually transmitted diseases (STD) clinic, family planning clinic, and colposcopy clinic were assayed for human papillomavirus type 6 (HPV-6) by DNA hybridisation. Results of hybridisation were compared with clinical, colposcopic, and cytological findings. Scrapings from 2 of the 4 women with genital warts gave positive results with the HPV probe. No HPV-6 DNA was detected in scrapings from 18 women attending an FPC whereas scrapings from 2 of 19 STD clinic patients with normal colposcopic and cytological examination were positive-this means that DNA hybridisation detected wart virus infection where previously none was suspected. HPV-6 DNA was detected in about 10% of cervical scrapings from women with cervical intraepithelial neoplasia (CIN) both before and after treatment. Indeed in 2 patients in whom viral DNA persisted after laser therapy, it was associated with local recurrence of neoplasia. This non-invasive technique is suitable for use as a screening test for HPV infection. In this study it identified women who have a high risk of developing CIN and in whom close cytological and colposcopic surveillance is indicated.

Animals↗
PubMed1985

Coronary ostial bar.

This article describes an unusual minor coronary artery anomaly. An intimal-lined fibromuscular bar was found bisecting a right coronary ostium. Possible origin and clinical relevance of the lesion are discussed.

Adult↗
PubMed1975

Proflavine photodynamic viral inactivation in herpes simplex keratitis.

We used the photodynamic inactivation technique with proflavine as the photoactive dye to treat herpetic epithelial keratitis in a preliminary study of patients who had idoxuridine toxicity or resistance. A comparative study with idoxuridine in treating dendritic ulcerations of the cornea showed a good therapeutic effect. But the investigation was suspended when adverse reactions, consisting of a generalized epithelial keratitis and an anterior uveitis, possibly of phototoxic origin, developed in a few patients receiving treatment. The ulcers treated by photodynamic inactivation apparently healed by a process of "debridement" followed by subsequent re-epithelialization.

Acridines↗