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Biomedical subjects

M P O'Neill

Publications and source records attributed to M P O'Neill.

10 recordsLinked to original sources
PubMed1995

The use of PCR to isolate a putative ABC transporter from Saccharopolyspora erythraea.

A gene (ertX) encoding a putative ABC transporter was cloned from the erythromycin producer Saccharopolyspora erythraea, using PCR. The primers were based on regions of homology from ABC transporters which confer resistance to macrolide antibiotics. While ertX encodes a protein with a strong degree of similarity to other macrolide ABC transporters from streptomycetes and staphylococci, it did not confer resistance to erythromycin, tylosin, spiramycin, oleandomycin, josamcin, chalcomycin or midecamycin when subcloned into sensitive streptomycete hosts. Southern blot analysis suggested that ertX did not constitute part of the erythromycin gene cluster as identified to date.

ATP-Binding Cassette Transporters↗
PubMed1995

Laser-feedback measurements of turtle basilar membrane motion using direct reflection.

In mammalian hearing, the frequency-dependent spatial pattern of movement in the basilar membrane/organ of Corti complex forms the basis of frequency discrimination. This is not necessarily the case in lower vertebrates; the turtle, for example, has an electrical resonance mechanism in its auditory receptor cells that varies in best frequency from cell to cell. But how much, if any, of the frequency separation by the turtle is done mechanically by the basilar membrane complex? Attempts to find an investigative approach that avoided placing objects on the basilar membrane led to the rediscovery of laser-feedback interferometry. Laser-feedback interferometric investigations of the vibrational amplitude and phase of the turtle basilar membrane in response to imposed nanometer displacements of the eardrum reveal that the membrane reflects the broadly-tuned middle-ear filter characteristics. Phase-angle measurements of the basilar membrane as a function of frequency, and the best frequency of the obtained amplitude tuning curves, did not vary as a function of position within each specimen. Input-output functions of the basilar membrane were generally linear. The middle ear demonstrates a negative gain of 2-6 while the central region of the basilar membrane has a positive gain of 4-18 dependent on location and biological variability.

Acoustic Stimulation↗
PubMed1995

Pulse-spray pharmacomechanical thrombolysis of thrombosed hemodialysis access grafts: long-term experience and comparison of original and current techniques.

OBJECTIVE: Pulse-spray pharmacomechanical thrombolysis is an evolving method for the treatment of vascular occlusions in which a highly concentrated fibrinolytic agent is injected as a high-pressure spray directly into thrombus. The purpose of this retrospective study was to analyze our long-term experience with this technique for the treatment of clotted hemodialysis grafts and to compare the efficacy and safety of the original and current methods. SUBJECTS AND METHODS: Over 6 years, 284 cases of dialysis graft thrombosis were considered suitable for treatment with pulse-spray thrombolysis. The original technique involved the injection of highly concentrated urokinase directly into a clot through two crisscross catheters with multiple side holes. The current technique includes early fragmentation of residual clot with a balloon catheter, intrathrombic injection of heparin, mechanical treatment of a lysis-resistant clot at the arterial anastomosis, and routine administration of aspirin. After thrombolysis, underlying obstructions were treated with balloon angioplasty, atherectomy, or stents. The technical success, immediate clinical success, and frequency of complications for the entire population were analyzed. In addition, the results for 36 cases treated with the original technique were compared with the results for 37 recent cases treated with the current technique. RESULTS: Of 284 cases considered suitable for treatment, thrombolysis was not done in eight cases because the venous anastomosis could not be crossed. Thrombolysis was discontinued in two cases because of extravasation of contrast material. The technical success for all grafts considered for treatment was 96%; 92% of treated grafts remained patent for at least 24 hr. Major complications occurred in 1% of cases, and minor complications occurred in 9% of cases. The clinical efficacies of the original and current techniques were 86% and 92%, respectively. The mean thrombolytic agent infusion time was reduced from 44 +/- 20 min to 23 +/- 13 min (p < .001). The overall procedure time for the recently treated subgroup was 67 +/- 26 min. There was no significant difference in the frequencies of major and minor complications between the treatment subgroups. CONCLUSION: Pulse-spray pharmacomechanical thrombolysis is a reliable, rapid, and safe method for recanalization of occluded dialysis grafts. The current technique has been proven as safe and effective as the original technique but offers the advantage of a significant reduction in the time required for the infusion of thrombolytic agent.

Anastomosis, Surgical↗
PubMed1993

Models for growth, decline and regrowth of the dendrites of rat Purkinje cells induced from magnitude and link-length analysis.

This study examines Purkinje neurons of rats aged 1, 10, 18 and 28 months to investigate growth and decline in the magnitude of the dendritic tree, i.e. the number of exterior links (terminal segments) per cell. Growth in the mean number of exterior links was observed from 1 to 10 months, decline at 18 months and regrowth at 28 months. At 10, 28, and especially at 18 months, the cell size frequency distribution indicates two groups of cells, one of small and the other of large sized cells. The study also examines the relationship of age to lengths of topologically defined links of various types. For each age group we find that exterior links are longer than interior links (non-terminal or intermediate segments). Analysis of the geometric mean lengths of subtypes of exterior and interior links at maturity (10 months) indicates that they follow a Fibonacci series of link lengths, such that mean lengths of topologically defined types of mean exterior links are either about 13 or 8 microns long, while interior links are about 5 microns long. A sequential growth model for adding exterior links is suggested to illustrate a style of growth which could account for the various mean link lengths and the Fibonacci ratio (1.618) between their lengths. Interior link lengths are also dependent on the generation of exterior links from the sides of pre-existing interior links. If the Strahler branching ratio, Rb, should increase owing to growth of terminals from interior links, then mean interior link length would decline. During a period of regression, mean exterior link lengths become shorter and mean interior link lengths become longer. Changes in mean interior link length are much less affected by changes in Rb during regression than is the situation during growth. Finally, the changes in link lengths dictate that the ratio of mean exterior to mean interior link length increases during growth phases from 1 to 10 and 18 to 28 months, and declines during regression from 10 to 28 months. The lowest values of the ratio of mean exterior to mean interior lengths are found at 1 month. This is the period of most intense growth. During this period, the rate of development of new exterior links outbalances the rate at which the links increase in length.

Aging↗
PubMed1982

Effect of preanaesthetic medication on anaesthesia with ICI 35, 868.

The effect of three commonly used premedicants and a control on anaesthesia with ICI 35, 868 is described. Two randomized studies were performed--one a group study of induction characteristics at 2 mg kg-1 and the other a detailed study in patients undergoing minor gynaecological surgery with an induction dose of 1.5 mg kg-1 and maintenance with incremental doses plus 66% nitrous oxide in oxygen. Premedication had little effect on the already good induction characteristics. Only heavy opiate premedication produced reliable induction at 1.5 mg kg-1, but with an increase in side-effects. Diazepam appears to be the premedicant of choice, although the overall frequency of pain on injection has not been affected by premedication.

Adolescent↗
PubMed1982

A comparative study of enflurane and halothane in children.

Equipotent concentrations of enflurane and halothane inhaled by children caused substantial hypotension and respiratory depression, these changes being more pronounced with the former agent. Plasma catecholamine levels were unaltered indicating that enflurane, like halothane, elicits little sympatho-adrenal response. Induction of anaesthesia and recovery times were largely comparable but earlier and more frequent use of narcotic analgesics was required after enflurane anaesthesia.

Anesthesia, Inhalation↗
PubMed1982

Recovery from intravenous anaesthesia. Comparison of disoprofol with thiopentone and methohexitone.

Using the endpoints of spontaneous opening of eyes, giving date of birth, sitting up unaided and normal pegboard time, recovery from 2 and 3 mg/kg disoprofol was compared with that from 4 and 6 mg/kg thiopentone and 1.5 mg/kg methohexitone in groups each of 10 unpremedicated patients. The study method differentiated between recovery from the two doses of disoprofol and thiopentone at the first two endpoints only. A between-drug comparison showed early recovery was slightly faster with thiopentone than with equivalent doses of the new drug while no differences were detected between the recovery from equivalent doses of methohexitone and thiopentone. The differences found in this study are felt to be of no clinical significance and recovery from anaesthesia with disoprofol would not be expected to be any slower than that from equivalent doses of thiopentone.

Adult↗
PubMed1982

A comparative study of the haemostatic properties and cardiovascular effects of adrenaline and ornipressin in children using enflurane anaesthesia.

In a randomized, double-blind trial, haemostatic and cardiovascular effects of ornipressin and adrenaline were compared in 30 children requiring surgery for "bat-ear" deformity. Mean total blood loss was 14.3 ml with ornipressin and 11.7 ml with adrenaline, this difference being insignificant. There was a significant and progressive reduction in mean heart rate in children who received ornipressin, from 134 to 116 bpm (P less than 0.05), and a significant rise from 127 to 134 bpm (P less than 0.05) with adrenaline. Mean systolic pressure was unaltered by ornipressin but was significantly increased from 97 to 105 mmHg (P less than 0.05) in children receiving adrenaline. Ornipressin is as effective a haemostatic agent as adrenaline and the rises in heart rate and systolic pressure associated with adrenaline, which are factors known to predispose to the onset of ventricular dysrhythmias, do not occur with ornipressin.

Adult↗
PubMed1982

Lorazepam premedication for labour.

Fifty primigravidae were given either lorazepam (2 mg) or identical dummy tablets in early labour, in a randomized double-blind fashion. Analgesia (standardized at pethidine 100 mg) was given as required, and pain relief was assessed by visual analogue scale. Analgesia was significantly better in those mothers who had received lorazepam. There was a higher incidence of respiratory depression at birth in the infants in this group, although this was not statistically significant. Patients given lorazepam were all satisfied with their analgesic regimen compared with half of those given an inactive tablet. There was a higher incidence of amnesia for labour in the active group. There is a need for a similar study of the effects of other drugs which are given to supplement pethidine in labour.

Adolescent↗