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D J Murray

Publications and source records attributed to D J Murray.

At least 19 recordsLinked to original sources
PubMed1999

A grouping interpretation of the modality effect in immediate probed recognition.

In a series of experiments on immediate probed recognition for eight 3-digit numbers, it was shown that if the target modality involved auditory components and the effect of the similarity of the modality of the probe to that of the targets was controlled, unequivocal evidence was obtained for an auditory superiority effect (modality effect) for hit rates for the final items of the list. Moreover, false-alarm rates were significantly lower following targets with an auditory component than they were following silently seen targets. It is argued that this pattern of hits and false alarms is consistent with the idea that targets that have an auditory component yield memory representations that are better grouped as units than are those for targets that are only silently seen; in particular, if a new probe has a first digit that accidentally matches the first digit of a target item, it is more likely that the subject will mistakenly identify this new probe as old (give a false alarm) if the target has only been partially encoded because it was only silently seen.

Auditory Perception↗
PubMed1999

Charpentier (1891) on the size-weight illusion.

This paper offers background for an English translation of an article originally published in 1891 by Augustin Charpentier (1852-1916), as well as a summary of it. The article is frequently described as providing the first experimental evidence for the size-weight illusion. A comparison of experiments on the judged heaviness of lifted weights carried out by Weber (1834) and by Charpentier (1891) supports the view that Charpentier's work deserves priority; review of other experimental studies on the size-weight illusion in the 1890s suggests that the idea that the illusion depended on "disappointed expectations," especially with respect to speed of lift, became dominant almost immediately following the publication of Charpentier's paper. The fate of this and other ideas, including "motor energy," in 20th-century research on the illusion is briefly described.

France↗
PubMed1998

A partial matching theory of the mirror effect in immediate probed recognition.

A set of experiments on immediate probed recognition of digit triples is reported in which the variables were list length (five, six, seven, or eight triples), the probability that a probe was old (.33, .5, or .67), and whether the digit triples were presented with an auditory component or articulatory suppression. Previous work had suggested that the false alarm (FA) rate in this paradigm was lower when auditory information was available than when it was not; this observation had led to the development of the partial matching theory of immediate probed recognition, according to which FAs could arise not only as a result of unlucky guesses but also when new probes shared a first digit in common with a partially retained target triple. It was argued that partial memory representations were less likely following auditory presentation than following articulatory suppression. Partial matching theory is contrasted with the rational response theory, according to which all FAs are unlucky guesses; partial matching theory gave a better account of the present experimental data than did rational response theory. However, a logical relationship between the two theories was suggested, a consequence of which was that rational response theory could be modified to include partial matching in such a way as to account for mirror effects, not only in unusually difficult immediate probed recognition tasks, but also in the more commonly studied mixed test list paradigm involving words of high or low frequency.

Adult↗
PubMed1997

Transfusion management in pediatric and adolescent scoliosis surgery. Efficacy of autologous blood.

STUDY DESIGN: A retrospective review of consecutive pediatric and adolescent patients who required posterior spinal fusion to correct scoliosis. OBJECTIVES: To 1) measure the participation of pediatric patients in predeposit programs for autologous and directed blood donation 2) to assess the success of autologous predonation in preventing allogeneic blood use, 3) to determine whether transfusion indications differed between patients who received allogeneic blood and those who received autologous blood, and 4) to assess factors that predict transfusion requirements during scoliosis surgery. SUMMARY OF BACKGROUND DATA: Authors of recent studies in adults have questioned whether transfusion of autologous blood is a cost-effective therapy when compared with the less-expensive alternative--transfusion of allogeneic blood. In children, the efficacy of autologous blood has not been assessed in a large population of surgical patients. In adults, the frequency of patient participation, the success of autologous donors in avoiding allogeneic transfusion, and the proportion of collected autologous units used during the perioperative period are measures used to establish the efficacy of autologous predonation programs. METHODS: Hospital and clinic records for each patient who underwent posterior spinal fusion from September 1, 1989 through September 1, 1994 were reviewed. Blood bank consultation, autologous donation records, anesthesia records, surgical reports, and hospital records were reviewed. Seventy percent of patients (164 of 243) participated in autologous donation. RESULTS: More than 90% of autologous donors successfully avoided receiving allogeneic blood. Patients with idiopathic scoliosis (n = 168) were more likely to participate in autologous donation (n = 144) and to avoid allogeneic blood (n = 135). Patients with neurologic causes of scoliosis more commonly used allogeneic or directed donation (56 of 75 patients). Nineteen patients with neuromuscular causes of scoliosis participated in autologous donation, but more than one half of this group (10 of 19 patients) required allogeneic blood in addition to autologous units. CONCLUSIONS: Using measures of efficacy similar to those reported in studies of adults, autologous blood was found to be more effective in meeting the transfusion needs of pediatric patients who required posterior spinal fusion than in meeting those needs in adult surgical patients in previous studies.

Adolescent↗
PubMed1997

Heparin detection by the activated coagulation time: a comparison of the sensitivity of coagulation tests and heparin assays.

OBJECTIVE: Laboratory and point-of-care coagulation tests are frequently obtained to determine the presence of heparin after surgical procedures. The objective of this study was (1) to compare the sensitivity of the activated coagulation time (ACT), activated partial thromboplastin time (aPTT), protamine titration (Hepcon; HMS Medtronic, Hemotec, Englewood, CO), and thromboelastography (TEG) with heparin anticoagulation and (2) to determine how frequently residual heparin is present in the 24-hour period after heparin neutralization in cardiopulmonary bypass (CPB) patients. DESIGN: A prospective study. SETTING: A tertiary care university teaching center that performs more than 15,000 surgical procedures per year. PARTICIPANTS: Vascular surgical (n = 17) and CPB (n = 29). INTERVENTIONS: In vascular surgical patients, coagulation tests (ACT, protamine titration [Hepcon], and TEG) were obtained before and 90 minutes after heparin (50 to 60 U/kg IV) and compared with heparin concentration determined by factor Xa inhibition assay. In cardiac surgical patients, ACT and heparin concentrations were measured after anesthesia induction, during CPB, after protamine neutralization, and 3 as well as 6 hours after CPB. In addition to heparin concentrations and ACT measures, platelet counts, fibrinogen levels, and bleeding times were determined before and 3 and 24 hours after CPB. MEASUREMENTS AND MAIN RESULTS: Ninety minutes after heparin, significant heparin concentrations were present in all vascular surgical patients, but ACT was elevated in only 4 of 17 patients. Protamine titration (Hepcon) correlated with the factor Xa inhibitory assay for heparin (r2 = 0.76). All 17 patients had an abnormal TEG (mean "R" time = 81 +/- 39 minutes) and a marked elevation of aPTT (135 +/- 35 sec [normal 22 to 33 seconds]) 90 minutes after heparin. In CPB patients, ACT did not correlate with heparin assays. After protamine neutralization of heparin in CPB patients, ACT returned to baseline despite the presence of heparin in 3 of 29 patients (0.22, 0.18, and 0.33 U/mL). CONCLUSIONS: ACT was less sensitive to residual heparin anticoagulation than aPTT, TEG, and whole blood heparin assay. The whole blood heparin assay (Hepcon) provided sensitive and specific data about the presence of residual heparin. Despite the limitation of ACT in detecting heparin, the investigators found that residual heparin was not common in the period after uncomplicated CPB.

Aged↗
PubMed1997

The psychophysics of J-R-L Delboeuf (1831-1896).

Delboeuf's writings on psychophysics are little known nowadays. The object of this paper is to describe the psychological contributions of this eminent Belgian psychologist of the second half of the 19th century. A true pioneer of experimental psychology, his work on psychophysics began in 1865 at the University of Gand (Ghent) but was not published until 1873 and following years. His work in this area is characterised on the one hand by the adoption of a logarithmic law relating sensation strength to stimulus strength, but which differed from that of Fechner; and on the other hand by the utilisation of a psychophysical technique based on brightness contrast (now called the 'bisection method'). Even though, Delboeuf was classified by Fechner in his later writings as an opponent of his beliefs. Delboeuf was nevertheless one of his least-virulent critics and the only psychologist of that era to have adopted a logarithmic law. Delboeuf's work is not only of historic interest; his original ideas possess sufficient interest for present-day psychophysicists to reexamine them.

Belgium↗
PubMed1996

Postoperative care following single-stage laryngotracheoplasty.

Single-stage laryngotracheoplasty (SSLTP) provides a method of correcting mild-to-moderate laryngotracheal stenosis while avoiding the risks of prolonged laryngeal stenting. Pediatric patients are orally intubated for 5 to 7 days postoperatively to ensure an adequate airway while edema resolves and healing begins. During this period, continuous neuromuscular blockade has been advocated in infants and young children to avoid endotracheal tube trauma to the fresh graft and potentially life-threatening accidental decannulation. Pulmonary atelectasis is the most common morbidity associated with prolonged neuromuscular blockade. Neuromuscular weakness also may follow prolonged paralysis and prolong hospitalization. This paper compares the postoperative course of 17 patients who underwent 18 SSLTP procedures by the senior author. The first 8 patients received continuous neuromuscular blockade in the early postoperative period. To reduce perceived morbidity, the last 9 patients were managed with a protocol that incorporated daily 4- to 8-hour "interruptions" of paralysis. Seven patients tolerated this protocol modification. As a group, these patients had less postoperative pulmonary atelectasis prior to extubation (p < .05) and were extubated sooner than patients receiving continuous neuromuscular blockade (p<.05) without compromising the surgical success of the procedure. Intermittent paralysis permitted for more accurate assessment of pain control and protected against accidental drug accumulation. Although self-extubation did not occur, diligent nursing care with adequate sedation and analgesia is necessary to avoid the risk of accidental extubation.

Child↗
PubMed1995

Ligation of CD38 suppresses human B lymphopoiesis.

CD38 is a transmembrane glycoprotein expressed in many cell types, including lymphoid progenitors and activated lymphocytes. High levels of CD38 expression on immature lymphoid cells suggest its role in the regulation of cell growth and differentiation, but there is no evidence demonstrating a functional activity of CD38 on these cells. We used stroma-supported cultures of B cell progenitors and anti-CD38 monoclonal antibodies (T16 and IB4) to study CD38 function. In cultures of normal bone marrow CD19+ cells (n = 5), addition of anti-CD38 markedly reduced the number of cells recovered after 7 d. Cell loss was greatest among CD19+ sIg- B cell progenitors (mean cell recovery +/- SD = 7.2 +/- 11.7% of recovery in control cultures) and extended to CD19+CD34+ B cells (the most immature subset; 7.6 +/- 2.2%). In contrast, CD38 ligation did not substantially affect cell numbers in cultures of normal peripheral blood or tonsillar B cells. In stroma-supported cultures of 22 B-lineage acute lymphoblastic leukemia cases, anti-CD38 suppressed recovery of CD19+ sIg- leukemic cells. CD38 ligation also suppressed the growth of immature lymphoid cell lines cultured on stroma and, in some cases, in the presence of stroma-derived cytokines (interleukin [IL] 7, IL-3, and/or stem cell factor), but did not inhibit growth in stroma- or cytokine-free cultures. DNA content and DNA fragmentation studies showed that CD38 ligation of stroma-supported cells resulted in both inhibition of DNA synthesis and induction of apoptosis. It is known that CD38 catalyzes nicotinamide adenine dinucleotide (NAD+) hydrolysis into cyclic ADP-ribose (cADPR) and ADPR. However, no changes in NAD+ hydrolysis or cADPR and ADPR production after CD38 ligation were found by high-performance liquid chromatography; addition of NAD+, ADPR, or cADPR to cultures of lymphoid progenitors did not offset the inhibitory effects of anti-CD38. Thus, anti-CD38 does not suppress B lymphopoiesis by altering the enzymatic function of the molecule. In conclusion, these data show that CD38 ligation inhibits the growth of immature B lymphoid cells in the bone marrow microenvironment, and suggest that CD38 interaction with a putative ligand represents a novel regulatory mechanism of B lymphopoiesis.

ADP-ribosyl Cyclase↗
PubMed1995

Analysis of changes in coagulation factors after postoperative blood loss in burn and non-burn patients.

A prospective study of the postoperative kinetics of coagulation factors was undertaken in 23 burn patients and in six non-burn patients. All procedures resulted in a large volume blood loss. Fibrinogen, platelets and factors V, VIII and IX were measured serially. Burn patients returned all parameters to preoperative levels by 48 h postoperation, while non-burn patients showed a slower rate of return of platelets and factor V. This study suggests that burn patients may safely undergo re-operation at 48 h intervals for successive wound debridements if clinically necessary.

Adolescent↗
PubMed1995

Anesthesia for magnetic resonance imaging in children: a low incidence of protracted post-procedure vomiting.

STUDY OBJECTIVE: To determine the incidence and severity of vomiting in pediatric patients who have had inhalation anesthesia for magnetic resonance imaging (MRI). DESIGN: A retrospective study of consecutive pediatric patients who had anesthesia for MRI. SETTING: A large university hospital with an integrated clinic facility. PATIENTS: 234 children who required an MRI under general anesthesia over a 30 month period (July 1989 to February 1992). MEASUREMENTS AND MAIN RESULTS: The duration of inhalation anesthesia was 105 +/- 33 minutes. Following anesthesia, the time to oral intake was 92 +/- 69 minutes. Eighteen patients (9%) experienced one or more episodes or emesis. In 14 of the 18 patients, vomiting occurred once and did not delay the intake of oral fluids or the discharge time from clinic when compared with the rest of the patients. Only one patient had frequent vomiting (more than three episodes), and all vomiting resolved spontaneously without anti-emetic therapy in less than eight hours following anesthesia. CONCLUSIONS: Protracted post-procedure vomiting is an infrequent complication of inhalation anesthesia for MRI. Inhalation anesthesia may be a less important cause of postoperative vomiting than factors such as the type of operative procedure, use of opioids, or presence of postoperative pain.

Anesthesia, Inhalation↗
PubMed1995

Packed red cells in acute blood loss: dilutional coagulopathy as a cause of surgical bleeding.

The purpose of this study was: 1) to define coagulation abnormalities in patients who receive red cell concentrates rather than whole blood for large volume blood loss (greater than 0.5 blood volume); and 2) to determine when coagulation abnormalities lead to increased bleeding in the massively transfused surgical patient. We studied 32 ASA physical status I or II patients (mean age 15.6 +/- 2.3 yr) who lost more than 50% of their blood volume during elective posterior spinal stabilization. Crystalloid solutions and packed red cell concentrates were used to replace blood and fluid losses. Invasive hemodynamic measures, urinary output, and serial hematocrit determinations were used to help maintain a constant intravascular volume and confirm the estimates of blood loss. The quality of hemostasis was assessed during operation. In 15 of the 32 patients, surgical hemostasis remained effective throughout posterior spinal fusion. A coagulation profile (prothrombin time [PT] and activated partial thromboplastin time [aPTT], platelet count, and fibrinogen) was measured at the conclusion of operation in these patients. In 17 patients, increased surgical bleeding as a result of decreased clot formation and increased bleeding from the wound was present. In these 17 patients at the time increased bleeding was diagnosed, hemostatic tests (PT, aPTT, fibrinogen, platelet count, and coagulation factor assays V, VIII, and IX) were obtained.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Pancreatic duct obstruction treated with percutaneous antegrade insertion of a metal stent: report of two cases.

Expanding metal stents were used to treat symptomatic pancreatic duct obstruction in two patients with chronic pancreatitis. Both patients initially underwent percutaneous external pancreatic duct drainage and then had metal stents inserted for internal drainage. Both patients remained asymptomatic, and the stents were patent during short-term follow-up periods of 6 and 9 months, respectively. Percutaneous insertion of metal stents, which can be performed to treat pancreatic duct obstruction after a trial of external drainage has been shown to relieve the patient's symptoms, should be considered as an alternative to endoscopic stent placement or surgical drainage.

Aged↗
PubMed1992

Comparative hemodynamic depression of halothane versus isoflurane in neonates and infants: an echocardiographic study.

The purpose of this study was to measure and compare the relationship of cardiovascular depression and dose during equal potent levels of halothane and isoflurane anesthesia in neonates (n = 19) (16.7 +/- 6.9 days) and infants (n = 54) (6.1 +/- 3.1 mo). Seventy-three children had heart rate, arterial blood pressure, and pulsed Doppler pulmonary blood flow velocity as well as two-dimensional echocardiographic assessments of left ventricular area and length recorded just before anesthesia induction. Anesthesia was induced by inhalation of increasing inspired concentrations of halothane or isoflurane in oxygen using a pediatric circle system and mask. During controlled ventilation, halothane and isoflurane concentrations were adjusted to maintain 1.0 MAC and then 1.5 MAC (corrected for age), and echocardiographic and hemodynamic measurements were repeated. A final cardiovascular measurement was recorded after intravenous administration of 0.02 mg/kg of atropine. All measurements were completed before tracheal intubation and the start of elective surgery. In neonates, 1.0 MAC concentrations of halothane and isoflurane decreased cardiac output (74% +/- 16%), stroke volume (75% +/- 15%), and ejection fraction (76% +/- 15%) similarly from awake levels. Decreases in cardiac output, stroke volume, and ejection fraction with halothane and isoflurane were significantly larger at 1.5 MAC (approximately 35% decreases from awake values) than at 1.0 MAC. Heart rate decreased significantly during 1.5 MAC halothane anesthesia (94% +/- 4%) but remained unchanged during isoflurane anesthesia. In infants, 1.0 MAC halothane and isoflurane decreased cardiac output (83% +/- 12%), stroke volume (78% +/- 12%), and ejection fraction (74% +/- 12%) when compared with awake measures.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗
PubMed1992

Application of digital signal processing to hearing aids: a critical survey.

An audiologic rationale for the application of digital signal processing techniques to hearing aids is developed. These techniques enable complex processing beyond that possible in presently available analog aids. A critical survey of algorithms for filtering, nonlinear processing, noise reduction, speech enhancement, and feedback reduction is presented. The paper concludes with a discussion of practical considerations for implementation.

Algorithms↗
PubMed1991

The additive contribution of nitrous oxide to isoflurane MAC in infants and children.

The purpose of this study was to determine the contribution of nitrous oxide to isoflurane MAC in pediatric patients. MAC was determined in 47 infants and small children (mean ages 16.6 +/- 6.7 months) during isoflurane and oxygen anesthesia (n = 11) and isoflurane and nitrous oxide anesthesia (25% nitrous oxide [n = 12], 50% nitrous oxide [n = 12], and 75% nitrous oxide [n = 12]). After assigning patients to one of four groups, anesthesia was induced with increasing inspired concentrations of isoflurane in oxygen. After anesthetic induction and tracheal intubation, ventilation was controlled (carbon dioxide partial pressure = 32 +/- 5 mmHg), and nitrous oxide was added to the inspired gas mixture to achieve end-expired nitrous oxide concentrations of 0, 25, 50, or 75%. Inspired and expired gas samples were obtained from a distal sampling port in the tracheal tube. The response to skin incision in each patient was assessed at a previously selected end-tidal concentration of isoflurane. The MAC of isoflurane was determined in each group using the up-and-down method described for evaluating quantal responses. The mean duration of constant end-tidal concentrations prior to skin incision was 14 +/- 7 min (range 6-46 min). The ratio of expired to inspired nitrous oxide and isoflurane concentrations during the period of constant end-tidal concentrations was 0.96 +/- 0.01 and 0.93 +/- 0.03 respectively. The MAC of isoflurane in oxygen was 1.69 +/- 0.13 vol% (mean +/- standard deviation).(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗