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S R Langton

Publications and source records attributed to S R Langton.

At least 19 recordsLinked to original sources
PubMed2000

You must see the point: automatic processing of cues to the direction of social attention.

Four experiments explored the processing of pointing gestures comprising hand and combined head and gaze cues to direction. The cross-modal interference effect exerted by pointing hand gestures on the processing of spoken directional words, first noted by S. R. H. Langton, C. O'Malley, and V. Bruce (1996), was found to be moderated by the orientation of the gesturer's head-gaze (Experiment 1). Hand and head cues also produced bidirectional interference effects in a within-modalities version of the task (Experiment 2). These findings suggest that both head-gaze and hand cues to direction are processed automatically and in parallel up to a stage in processing where a directional decision is computed. In support of this model, head-gaze cues produced no influence on nondirectional decisions to social emblematic gestures in Experiment 3 but exerted significant interference effects on directional responses to arrows in Experiment 4. It is suggested that the automatic analysis of head, gaze, and pointing gestures occurs because these directional signals are processed as cues to the direction of another individual's social attention.

Adult↗
PubMed2000

The mutual influence of gaze and head orientation in the analysis of social attention direction.

Three experiments are reported that investigate the hypothesis that head orientation and gaze direction interact in the processing of another individual's direction of social attention. A Stroop-type interference paradigm was adopted, in which gaze and head cues were placed into conflict. In separate blocks of trials, participants were asked to make speeded keypress responses contingent on either the direction of gaze, or the orientation of the head displayed in a digitized photograph of a male face. In Experiments 1 and 2, head and gaze cues showed symmetrical interference effects. Compared with congruent arrangements, incongruent head cues slowed responses to gaze cues, and incongruent gaze cues slowed responses to head cues, suggesting that head and gaze are mutually influential in the analysis of social attention direction. This mutuality was also evident in a cross-modal version of the task (Experiment 3) where participants responded to spoken directional words whilst ignoring the head/gaze images. It is argued that these interference effects arise from the independent influences of gaze and head orientation on decisions concerning social attention direction.

Adult↗
PubMed1995

The effect of ciprofloxacin on theophylline pharmacokinetics in healthy subjects.

1. The mechanism of the interaction between ciprofloxacin and theophylline was investigated in nine healthy subjects. 2. Subjects were given a single oral dose of theophylline (3.4 mg kg-1), before and after 60 h of ciprofloxacin therapy at a dose of 500 mg twice daily. 3. Ciprofloxacin reduced the oral clearance of theophylline by 19% (-7.73 +/- 6.42 ml kg-1 h-1 (95% confidence limits -12.66, -2.79)). Some subjects (group A, n = 4) showed little decrease in clearance (mean 4.4%; -1.6 +/- 0.7 ml kg-1 h-1 (-2.6, 0.5)), whereas others (group B, n = 5) showed a marked decrease (mean 30%; -12.7 +/- 3.7 ml kg-1 h-1 (-17.2, -8.1)). 4. Comparing groups A and B, the decrease in oral clearance of theophylline in group B could not be ascribed to differences in the AUC of ciprofloxacin. Group A subjects showed only slight inhibition of 1-demethylation (-12.8 +/- 5.5% (-21.5, -4.0)), while group B subjects showed a significantly greater inhibition of 1-demethylation (-49.9 +/- 9.8% (-62.1, -37.7)), 3-demethylation (-44.8 +/- 8.6% (-55.4, -34.1)) and 8-hydroxylation (-27.0 +/- 3.7% (-31.6, -22.4)). 5. The results suggest that inter-individual variability in the inhibition of theophylline metabolism by ciprofloxacin can be attributed to inter-individual differences in the level of CYP1A2 expression and/or in the degree of inhibition of hepatic CYP1A2 and CYP3A4. 6. The interaction between ciprofloxacin and theophylline can be clinically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1992

Kinetic properties of Helicobacter pylori urease compared with jack bean urease.

The urease proteins of the jack bean (Canavalia ensiformis) and Helicobacter pylori are similar in molecular mass when separated by non-denaturing gradient polyacrylamide gel electrophoresis, both having three main forms. The molecular mass of their major protein form is within the range 440-480 kDa with the other two lesser forms at 230-260 kDa and 660-740 kDa. These forms are all urease active; however, significant kinetic differences exist between the H. pylori and jack bean ureases. Jack bean urease has a single pH optimum at 7.4, whereas H. pylori urease has two pH optima of 4.6 and 8.2 in barbitone and phosphate buffers that were capable of spanning the pH range 3 to 10. The H. pylori Km was 0.6 mM at pH 4.6 and 1.0 mM at pH 8.2 in barbitone buffer, greater than 10.0 mM, and 1.1 mM respectively in phosphate buffer and also greater than 10.0 mM in Tris.HCl at pH 8.2. By comparison, the jack bean urease had a Km of 1.3 mM in Tris.HCl under our experimental conditions. The findings show that the urease activity of H. pylori was inhibited at the pH optimum of 4.6 in the phosphate buffer, but not in the barbitone buffer. This was shown to be due to competitive inhibition by the sodium and potassium ions in the phosphate buffer, not the phosphate ions as suggested earlier. Jack bean urease activity was similarly inhibited by phosphate buffer but again due to the effect of sodium and potassium ions.

Fabaceae↗
PubMed1992

Serum phospholipase A2 and lysolecithin changes following myocardial infarction.

We have examined changes in the activities of phospholipase A2 (PLA2) and the concentrations of total choline-phospholipids and lysolecithin, in serum from patients following a myocardial infarction by comparison with patients suffering from unstable angina. A significant increase in PLA2 activity was found after myocardial infarction. The peak increase occurred approximately 36 h after infarction. No significant PLA2 change was found in the patients with unstable angina. Concentrations of lysolecithin, the major metabolite of PLA2 activity, were high in the admission samples from the infarction patients, followed by an overall fall during the first 24 h: the concentrations in the patients with angina were normal. PLA2 and lysolecithin changes post-infarction showed they were involved in processes not occurring in angina.

Aged↗
PubMed1992

Helicobacter pylori associated phospholipase A2 activity: a factor in peptic ulcer production?

AIMS: To examine the potential role of the lipolytic enzyme phospholipase A2, produced by Helicobacter pylori in ulcer formation. METHODS: Phospholipase A2 activity in H pylori was compared with that in 10 commonly occurring pathogenic bacteria. Phospholipase A2 activity and its cytotoxic metabolite, lysolecithin, in the basal gastric aspirates of 12 patients infected with H pylori were compared with those in 12 subjects not infected with H pylori. RESULTS: The phospholipase A2 activity in H pylori was substantially higher than that in most of the other bacteria tested, and the activities of phospholipase A2 and lysolecithin in the basal gastric aspirates of those infected with H pylori were significantly higher than the activities found in the basal gastric aspirates of subjects who were not infected. The lysolecithin proportion of total phospholipids in the gastric aspirates was also much higher in the infected than the non-infected group and a weak positive correlation (0.415) was found between phospholipase A2 and lysolecithin in the infected group. CONCLUSIONS: H pylori has clinically important concentrations of phospholipase A2, an enzyme capable of hydrolysing gastric mucosal phospholipids. The high values of phospholipase A2 and lysolecithin in gastric fluid from subjects with H pylori infections supports the notion that phospholipase A2 is involved in the inflammation and mucosal damage associated with peptic ulcer formation.

Helicobacter Infections↗
PubMed1991

Phospholipase A2 is associated with albumin in patients with acute pancreatitis.

Evidence for the association of serum phospholipase A2 (PLA2) (EC 3.1.1.4) and serum proteins was examined. The effect of this on the PLA2 results from patients diagnosed as having acute pancreatitis was investigated. Two distinct zones of PLA2 activity were found on agarose electrophoresis of purified human PLA2 in the presence of albumin, and in the sera from the acute pancreatitis patients. One of the zones was coincident with albumin. To investigate this finding, a comparison of the PLA2 activity in sera and protein-free ultrafiltrates prepared from the sera of the same patients, showed that PLA2 was not completely ultrafiltered as would be expected from its molecular weight. The PLA2 method used employed a radiolabelled E. coli membrane-phospholipid substrate. It has been previously shown that there is an association between PLA2 and albumin and there is good evidence that albumin interferes with certain methods used for the measurement of PLA2. The recovery of PLA2 activity from the ultrafiltrates of patients' serum was highly variable and it may be that serum proteins, in particular albumin, provide a protective 'buffer' against small increases in PLA2 activity. Inhibitor proteins such as lipocortin which were originally postulated as binding to the enzyme, have been subsequently shown to be substrate-binding agents. However, direct protein effects may be a factor in the inconsistent PLA2 results reported in studies of patients with acute pancreatic disease.

Acute Disease↗
PubMed1991

Lipolytic enzyme and phospholipid level changes in intraoperative salvaged blood.

Autotransfusion is becoming increasingly popular, mainly because it eliminates the risk of disease transmission. One of the techniques available is intra-operative blood salvage and retransfusion with or without washing of the collected blood. The blood collected during this process is subjected to a variety of chemical and physical insults which can alter the normal composition of the plasma by activating plasma and cellular homeostatic mechanisms. In this study, we measured the plasma levels of total phospholipids, lysolecithin and non-esterified fatty acids, and the lipolytic enzymes phospholipase A2 (PLA2) and lipase in the salvaged blood before and after washing. In the unwashed salvaged blood the mean levels of PLA2, non-esterified fatty acids and lysophospholipids increased by 144, 96 and 149%, respectively, while those of total phospholipids and lipase did not change to any extent. All these substances were reduced to well below the patients circulating plasma levels by washing the collected blood. The changes indicate that the lipid profile of salvaged blood is significantly altered and that potentially dangerous substances such as PLA2 and its metabolites, lysolecithin and non-esterified fatty acids, are present in increased amounts. Washing the blood is recommended prior to reinfusion.

Blood Loss, Surgical↗
PubMed1989

Calculated bicarbonate or total carbon dioxide?

To test the relationship pK' = 6.103 + log[HCO3calc] - log[HCO3meas], we used a Corning 168 blood-gas analyzer to analyze 500 blood samples for pH and PCO2, from which we calculated a value for bicarbonate. We also analyzed 500 venous blood samples, collected simultaneously, for potentiometric total carbon dioxide with the Ektachem 700 analyzer. In a similar study of 415 arterial and venous blood samples, we determined total carbon dioxide colorimetrically with the SMA 6/60 analyzer. The coefficients of determination (r2) found for the difference observed between the calculated and measured bicarbonate values vs the pK' in the two studies were 0.86 and 0.96, respectively. The results also confirmed the positive bias caused by organic acids in the Ektachem method for total carbon dioxide. Analysis of the SMA 6/60 results indicated a significant decrease of the pK' in patients classified as having a metabolic acidosis.

Acidosis↗
PubMed1987

Rapid urease test in the management of Campylobacter pyloridis-associated gastritis.

Campylobacter pyloridis colonization of the stomach may be an etiological factor in gastritis and peptic ulceration. Campylobacter pyloridis produces large amounts of urease, and the presence of this enzyme in gastric mucosa usually indicates infection with the organism. In this paper we describe the use of a rapid urease test (CLOtest) to detect C. pyloridis infection in gastric mucosal biopsies. In 141 consecutive endoscopy cases, antral biopsies were taken for culture and histology, and an extra biopsy was inserted into the CLOtest gel. There were 79 patients infected with C. pyloridis, 78 of whom were detected by CLOtest: 75% were positive at 20 min, 92% at 3 h, and 98% at 24 h. There were no false positive results. Eighteen infected patients were rebiopsied after a course of amoxycillin and bismuth subcitrate. Active chronic gastritis resolved in eight of nine who were cleared of the organism, but histological gastritis was unchanged in nine patients who were still infected. CLOtest is a simple, sensitive, and highly specific test that enables the endoscopist to diagnose C. pyloridis infection in the endoscopy room. A negative test after antibiotic therapy correlates with clearance of the bacteria and healing of active gastritis.

Amoxicillin↗
PubMed1985

Clinical validation of dialysable calcium in relation to other methods of serum calcium measurement.

Dialysable calcium (CaD) values were measured by a simple technique not interfered with by protein bound calcium and validation attempted by comparison with concentrations of ionised calcium (CaI) and clinical categorisation. CaD values were also compared with total calcium (CaT) and albumin adjusted calcium (CaA) concentrations. The normal ranges for CaD, CaT, CaA, and CaI were calculated from the results in healthy blood donors. In 50 normal subjects CaD was more highly correlated with CaI than CaT or CaA. The effects of lying down and of venous stasis in 10 normal subjects showed that CaD was slightly influenced by posture only, whereas CaT was noticeably affected by posture and venous stasis; CaA reduced but did not abolish these effects on CaT. The correlation coefficient of CaD and CaI in patients with chronic renal failure was 0.81. CaD was compared with CaT and CaA values in 293 consecutive hospital patients; discrepant results were obtained in 14.3% and 13.0% of cases respectively and there were some clinical grounds for accepting CaD as correct in 86% and 74% of these cases. Measurement of CaD is a simple, reliable method for estimating accurately the calcium concentration free from biologically inactive protein bound calcium.

Adult↗