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Biomedical subjects

S J Walker

Publications and source records attributed to S J Walker.

At least 55 records · Page 3Linked to original sources
PubMed1994

Acute rheumatic fever in Auckland, New Zealand: spectrum of associated group A streptococci different from expected.

Annual specific rates for acute rheumatic fever (ARF) in Auckland children less than 15 years were 22/100,000 for the years 1980 to 1984. From 1984 to 1992 the rates remained relatively constant with an average of 45 (range, 30 to 70) children annually admitted with ARF to the Auckland Children's Hospital. This study examined retrospectively Group A streptococci identified from hospitalized pediatric patients during these 9 years. The total of 2410 isolates included 32 isolates from well-documented cases of ARF and an additional 6 from siblings of cases. Results of M typing indicated that streptococci associated with ARF are generally different from those described overseas and involved types which cause more skin than throat infections in the community.

Adolescent↗
PubMed1993

Electrical current paths in acute pericarditis.

The electrocardiographic changes accompanying pericarditis consist of ST elevation in most of the leads of the 12-lead electrocardiogram. The source of this ST elevation is thought to be local inflammatory changes in the epicardium underlying the inflamed pericardium. The current from this area of ST elevation must return to some unaffected region of the heart and this should be associated with a region of ST depression. This current path from the external epicardial surface has been postulated to flow back into the endocardium through the great vessels and atria. To test this hypothesis, 18 patients with pericarditis were studied by body surface potential mapping and inverse epicardial potential distributions were computed. The resultant maps were compared to those of normal people and patients with acute anterior infraction. Epicardial maps from patients with pericarditis showed a region of current flow into the heart over the great vessels and atria in all 18 patients. This pattern was not seen in normal patients or infarction patients and was consistent with the mechanism resulting in ST elevation in pericarditis being one of current flowing from the epicardium out into the thorax and back into the heart through the great vessels and atria.

Acute Disease↗
PubMed1993

Pituitary corticotroph function during the stress hyporesponsive period in neonatal rats.

Rats undergo a period in early postnatal development during which they exhibit a reduced response to stress (stress-hyporesponsive period, SHRP). SHRP is marked by a reduced capacity to secrete adrenocorticotropin (ACTH) and corticosterone in response to stressful stimuli. To characterize pituitary responsiveness during this period, we examined the release of ACTH from cultured pituitary cells derived from rats at different ages. Corticotrophs were studied from animals before (day 1 postnatally), during (days 6 and 11) and after (days 16, 20 and adult) SHRP. Direct stimulation of dispersed pituitary cells, with increasing concentrations of synthetic corticotropin-releasing factor (CRF; 1 x 10(-12) to 1 x 10(-8) M), produced significant ACTH release at all ages tested. The greatest maximal release was observed for cells isolated from animals at 6 and 11 days of age (in the midst of SHRP). CRF-stimulated ACTH release from cells obtained just prior to (day 1) or immediately following (days 16 and 20) the hyporesponsive period was dramatically reduced (relative to cells from adult animals). SHRP is, therefore, not due to diminished intrinsic corticotroph responsiveness. In fact, pituitary cells derived from animals in SHRP exhibited enhanced ACTH secretion relative to cells from animals outside SHRP. This enhanced secretion was manifested as both an increased basal (unstimulated) release of ACTH as well as an increased maximal release of ACTH at saturating concentrations of CRF.

Adrenocorticotropic Hormone↗
PubMed1992

Comparison of Nissen total and Lind partial transabdominal fundoplication in the treatment of gastro-oesophageal reflux.

Fifty-two patients with gastro-oesophageal reflux disease refractory to medical treatment were randomized to undergo a Nissen total (360 degrees wrap) or Lind partial (300 degrees wrap) transabdominal fundoplication. Each group was comparable in number (26 patients), mean age (47 and 48 years) and sex distribution (eight women). Preoperative and postoperative assessment involved a modified Visick score, 22-h intraoesophageal pH monitoring, endoscopy and manometry. Follow-up was at 6 weeks and between 3 and 33 (mean 13) months. The prevalence of heartburn and regurgitation and the results of pH monitoring improved significantly after both operations (P less than 0.001). At early assessment eight previously asymptomatic patients (31 per cent) from the Nissen group and six (23 per cent) from the Lind group experienced difficulty swallowing. Ten patients (38 per cent) in each group complained of 'gas bloat'. Both complications had improved at late assessment in the majority of patients. No statistically significant advantage could be demonstrated for either operation.

Adult↗
PubMed1992

Supernatural beliefs, natural kinds, and conceptual structure.

This article presents cross-cultural evidence in support of the notion that adults' natural kind concepts are theory based but may be informed by knowledge/belief systems other than the biological. Three groups of subjects from western Nigeria--rural, urban, and elite--participated in the study. Subjects heard stories describing alterations of appearance; that is, one natural kind was made to resemble another in both ritual and nonritual contexts. Subjects then were required to judge the identity of the altered item and to give an explanation for the category judgment. It was predicted that subjects would make more nonpreservation-of-identity category judgments supported by supernatural explanations in the ritual contexts and that subjects' use of supernatural explanations would reflect the extent of their engagement with the supernatural. The first prediction was borne out; the second prediction was only partially supported. Discussion of the results emphasizes the importance of exploring the role of sociocultural factors in conceptual structure.

Adult↗
PubMed1991

Assessment of the response to chemotherapy in oesophageal cancer.

Thirty-eight patients with localised oesophageal carcinoma have been studied by computed tomography (CT) and barium swallow before and after preoperative chemotherapy and the results correlated with the pathological findings in the resected specimen. Overall 48% of patients showed a complete or partial response to chemotherapy on CT, compared with 50% on barium and 94% on pathological examination. This study highlights deficiencies in CT scanning and barium swallow as methods of assessing the regression of tumor bulk following chemotherapy for oesophageal carcinoma. We suggest that strict and specific criteria will have to be laid down before the results of chemotherapy in this disease can be reliably and accurately evaluated.

Aged↗
PubMed1991

A phase II study of 5-fluorouracil, adriamycin and mitomycin-C in adenocarcinoma of the oesophagus.

We have evaluated the effect of 5-fluorouracil 600 mg/m2, doxorubicin ('Adriamycin') 40 mg/m2, and Mitomycin-C 4 mg/m2 (FAM) in two groups of patients with adenocarcinoma of the oesophagus, as either a preoperative or primary treatment. Response was assessed by barium swallow, CT scan, and measurement of metastases where present. Toxicity was as reported for FAM in gastric cancer. In the operated group 8 of 22 patients (36%) showed a partial response following two courses of FAM. Resection was completed in 20 patients, with six hospital deaths (30%). Of the 14 patients who were discharged from hospital, 8 have died (median 8 months) and 6 are alive at 12 to 27 months, with known recurrence in 1. In the non-operated group 6 of 17 patients (35%) showed a response, one complete, following one to six (mean 4.2) courses of FAM. Fifteen patients have died (median 5 months), and 2 are alive and free from disease at 12 and 17 months. Neoadjuvant therapy with FAM in adenocarcinoma of the oesophagus offers no advantage over surgery alone, although with inoperable disease FAM may be of use in palliation.

Adenocarcinoma↗
PubMed1990

Growth of Listeria monocytogenes at refrigeration temperatures.

The growth of three strains of Listeria monocytogenes at refrigeration temperatures (-0.5 to 9.3 degrees C) in chicken broth and/or UHT milk was determined using a rocking temperature gradient incubator. Minimum growth temperatures ranged from -0.1 to -0.4 degree C for the three strains. Lag times of 1-3 d and 3 to greater than 34 d were observed with incubation at 5 and 0 degrees C respectively. Corresponding generation times ranged from 13-24 h at 5 degrees C and 62-131 h at 0 degree C. The type of culture medium had an influence on both the rate and extent of growth. Incubation of cultures at 4 degrees C before inoculation caused a marked reduction in the lag time when compared with cultures which had been previously incubated at 30 degrees C.

Animals↗
PubMed1990

Abnormal gastric adaptive relaxation in patients with gastrooesophageal reflux.

Gastric adaptive relaxation was measured in 15 healthy volunteers (control group) and in 12 patients with symptomatic gastrooesophageal reflux confirmed by 24 hour pH monitoring (reflux group). The control group were: 13 men, two women; median age 30 years, range 22-41; median body weight 70 kg, range 50-79 kg. All were asymptomatic on no medication. The reflux group were: eight men, four women, median age 48 years, range 23-65; median body weight 77 kg, range 60-92 kg. Medication was withheld for 12 hours before the study. Endoscopy showed no abnormality in five patients, oesophagitis in three patients and oesophagitis with hiatus hernia in four patients. Fasted subjects were intubated with a Ryle's tube containing a pressure microtransducer within a flaccid plastic bag (800 ml). Gastric corpus-fundus pressure was recorded during distension of the bag with 460 (20) ml mean (SD) of air over 30 seconds. Pressure indices (median: range) derived from areas under the pressure curves during distension were: control: 12.7 (7.5-17.1) cm H2O; reflux: 9.1 (6.4-13.3) cm H2O, p less than 0.01 (Mann Whitney U test). Similar results were obtained from pressure indices derived from recordings during the immediate postdistension period. No correlation was found between pressure indices and age, sex or body weight. The results indicate that the gastric pressure response to distension is reduced in patients with gastrooesophageal reflux.

Adaptation, Physiological↗
PubMed1990

Importance of the great vessels in the genesis of the electrocardiogram.

The electrocardiogram is the graphic representation against time of the difference in potential between points of the body caused by the current field of the heart. To examine the origin of this current field, a method of transforming body surface electrocardiographic data to the epicardial surface has been developed. The computed epicardial current density distributions in 219 patients with acute inferior myocardial infarction showed that, in 89% of patients, the current flow out of the heart during the ST segment came from two regions, not only from the infarction region but also from a region over the great vessels. This findings suggests that current flows from the ischemic region, through the low-resistance pathway provided by the intracavity blood, out the great vessels, and back to the epicardium. A similar pathway has been hypothesized when ischemia caused endocardial ST elevation, such as during a stress test or with unstable angina. To test this hypothesis, a group of patients with ST depression on the 12-lead electrocardiogram, not associated with ST elevation, was examined with body surface mapping. Ninety-four percent of patients had epicardial current density distributions that showed a region of current flow out of the heart and over the great vessels that was consistent with this hypothesis. This could explain the poor localization of coronary artery disease by electrocardiographic techniques when there is ST depression on the body surface.

Aorta↗
PubMed1990

Cholecystostomy: a safe alternative?

We have studied retrospectively 27 patients undergoing cholecystostomy for acute cholecystitis over the past decade. The mean age of the patients was 60 years, and 17 were female. 'Difficult dissection' was the reason given for cholecystostomy in 18 cases and in the remainder the patients were deemed unfit for cholecystectomy. An operative cholangiogram was performed in only two cases, and none of the patients had a primary common bile duct exploration. Post-operative cholangiograms in 14 patients revealed common bile duct stones in three (21%). Three elderly patients (mean age 79) died in hospital. At a mean follow-up of one year, 26% of patients had come to elective cholecystectomy, and there had been a further three unrelated deaths. We conclude that under difficult circumstances, cholecystostomy may be a safe alternative to cholecystectomy. These patients have a high incidence of choledocholithiasis, and thus we would recommend operative cholangiograms in all patients. However, early ERCP and sphincterotomy may be a safe alternative if this service becomes more widely available.

Acute Disease↗
PubMed1990

Oesophageal carcinoma: the view from East Birmingham.

Oesophageal carcinoma is a bad, but not a hopeless, disease. Overall survival is poor but a 5-year survival rate in the region of 30% can be obtained with surgical resection in properly selected patients. In this review we outline our overall strategy for the management of patients with both localized and advanced disease, based on more than 1500 cases treated over the past 14 years.

Combined Modality Therapy↗
PubMed1989

Prognostic significance of ST potentials determined by body surface mapping in inferior wall acute myocardial infarction.

Electrocardiographic body surface mapping on admission to coronary care has been shown to predict prognosis in a previous study of 100 patients with inferior wall acute myocardial infarction (AMI). A further 98 patients with first inferior wall AMI were now studied by body surface mapping on admission to coronary care to confirm that both the spatial distribution or map pattern of ST-segment potentials and the precise measurement of the maxima and minima are of prognostic significance. Each ST-segment map was compared by correlation coefficient to the average map pattern of the 4 groups derived in a previous study and placed in the group with the highest correlation coefficient. Analysis of these groups against outcome confirmed that the group dominated by a large area of marked anterior ST depression was associated with a high rate of complications and a significantly lower survival free of coronary artery bypass grafting (p less than 0.01). Patients in this group had more extensive and severe coronary artery disease than patients in the other groups. Increasing values of maximal ST depression correlated with mortality and complication rates. The extent by which the magnitude of ST-segment depression exceeded the magnitude of ST-segment elevation correlated with mortality and incidence of left ventricular failure. The results confirm the findings of the original study. Body surface mapping is of prognostic significance in inferior wall AMI.

Adult↗
PubMed1989

Natural history of ST-segment potential distribution determined by body surface mapping in patients with acute inferior infarction.

The authors studied the natural history of the electrocardiographic ST-segment using body surface mapping in 123 patients with acute inferior infarction who were not treated with thrombolytic agents. In 91 patients they compared body surface ST-segment maps recorded at 7.9 +/- 5.4 hours after the onset of acute myocardial infarction with maps recorded at 32.6 +/- 21.6 hours after infarction. In 46% of the patients the ST-segment distribution map pattern was unchanged. Twenty-eight percent of the patients moved to a ST-segment distribution associated with low mortality, and 7% correlated with a normal ST-segment distribution. Patients who started in a group dominated by marked anterior ST-segment depression or who developed this pattern at the time of the late map had a 45% morbidity, compared to 13% for patients who never developed this pattern (p less than 0.005). In a second group of 61 patients they compared maps recorded at 15.0 +/- 15.8 hours after infarction and repeat maps 19.6 +/- 13.0 recorded months later. At follow-up mapping, 44% of the patients correlated with a normal ST-segment distribution, 38% of patients had a low-risk pattern map and in 7% the map pattern was dominated by anterior ST-segment potential depression. The latter patients had a higher morbidity than patients in the other groups, but this did not reach statistical significance. Four of seven patients in this last group had significant angina at the time of follow-up mapping, compared to 2 of 54 patients in the other two groups (p less than 0.001).

Aged↗
PubMed1989

Adrenocorticotropin and corticosterone levels in pre-weanling spontaneously hypertensive rats.

Circulating plasma ACTH and corticosterone levels were measured in spontaneously hypertensive rats (SHR) and the corresponding, normotensive Wistar-Kyoto (WKY) strain at 10 and 20 days of age. In addition, stored levels of ACTH were measured in the pituitary glands of these animals. Circulating corticosterone levels were significantly lower, in both strains, at 10 days than at 20 days. Although the glucocorticoid was undetectable in WKY animals at 10 days, significant levels were observed in age-matched SHR. No difference in corticosterone concentrations was observed between the two strains at 20 days. Circulating ACTH levels did not reflect the values for circulating glucocorticoids. There were no significant differences in the levels of ACTH between strains or between age groups. Moreover, pituitary stores of ACTH between animals of different strains and ages were not found to be significantly different among any of the groups tested. These results demonstrate that there is a difference in circulating corticosterone levels between spontaneously hypertensive and Wistar-Kyoto rats at 10 days postnatally which is not evident just prior to weaning (20 days). This difference is not due to variations in stored or circulating ACTH. Indeed, ACTH levels are high at a time (10 days) when corticosterone is low - thus suggesting that the difference may reside within the responsiveness of the adrenal cortex.

Adrenocorticotropic Hormone↗
PubMed1989

Derived epicardial potentials differentiate ischemic ST depression from ST depression secondary to ST elevation in acute inferior myocardial infarction in humans.

It was hypothesized that in acute inferior wall myocardial infarction, an additional ischemic area in the subendocardium of the noninfarcting territory would produce a selective current dipole between the infarcting and ischemic regions. A resistance network model to calculate epicardial potentials from body surface electrocardiographic potentials was developed and used to examine the hypothesis in 219 patients with acute inferior myocardial infarction. In the learning set of 110 patients, two characteristic dipole patterns were observed, each associated with a high mortality rate in the ensuing 15 months when compared with that in the remaining patients. In the test set of 109 patients, a double-blind analysis of the patterns showed that the 34 patients with a dipole pattern had a collective mortality rate of 35% at 15 months compared with a 15 month rate of 5% in the remaining patients. In the total group of 219 patients, the magnitude of ST segment elevation and both the magnitude and integral of the area voltage of ST depression on the epicardium were significantly correlated with the mortality rate (p less than 0.0002 for all variables against death at 15 months). This study strongly suggests that ST depression due to ischemia can be differentiated from ST depression secondary to the ST elevation in acute inferior infarction by the examination of epicardial potential distributions.

Aged↗