Biomedical subjects

I Gordon

Publications and source records attributed to I Gordon.

At least 19 recordsLinked to original sources

PubMed1992

Effect of posture on regional ventilation in children.

Little information has been published concerning the pattern of regional ventilation in children, yet many differences in lung and chest wall mechanics in childhood, supported by clinical observation, have led to the hypothesis that the pattern of regional ventilation seen in children may not be the same as in adults. Forty-three children and 16 adult volunteers underwent Krypton (Kr) 81m radionuclide ventilation lung scans in the supine and right and left decubitus postures. In children aged 2-10 years mean fractional ventilation to the right lung (VfR) was 46.1%. This fell to 36% when dependent and rose to 56.1% in the uppermost position. Redistribution of ventilation away from the dependent towards the uppermost lung was seen in all children. In children aged 10-18 years VfR was 57.2% (supine), 48.0% (dependent), and 62.9% (uppermost). An identical pattern was seen in children with normal or abnormal pulmonary function tests (peak expiratory flow rate, and FEV1: FVC ratio). In subjects over 18 years of age a different pattern was seen: mean VfR was 52.4% (supine), rising to 53.4% (dependent), and falling to 48.9% (uppermost). Postural redistribution of ventilation, as assessed by Kr81m ventilation imaging, changes late in the second decade of life. This will have clinical consequences in the management of children with unilateral lung disease.

Adolescent↗

PubMed1992

Urinary endothelin (ET1) in complete ureteric obstruction in the miniature pig.

Segmental renal scarring occurs in experimental obstructive uropathy in the multipapillary porcine kidney, and segmental abnormalities in renal perfusion are likely to be responsible. This preliminary study examines the urinary excretion of the potent locally active vasoconstrictor endothelin 1 (ET 1) in a pig model of renal obstruction and subsequent relief. Significant urinary excretion of ET 1 from the postobstructive kidney was found to occur after longstanding obstruction. Preglomerular arteriolar stenosis may be the cause of the renal ischaemia in obstruction that is at first reversible but later becomes irreversible if the stimulus persists. ET 1 may be implicated in the pathogenesis of this injury.

Animals↗

PubMed1992

Vesico-ureteric reflux in the damaged non-scarred kidney.

Renal damage without scarring is a rare manifestation of reflux nephropathy, and is infrequently reported in the literature. A retrospective review of a large series of patients with urinary tract disorders at the hospital for Sick Children, Great Ormond Street, identified 12 patients with vesico-ureteric reflux (VUR) with no evidence of scarring but with renal damage as assessed using technetium 99m dimercaptosuccinic acid (99mTc-DMSA) scan. There were 9 simplex kidneys, the differential function was between 33% and 43% (mean 38%). On follow-up to date (mean 6.7 years) all kidneys show stable differential function with neither improvement nor deterioration. Only 8 children had a urinary tract infection. Renal damage without evidence of a focal scar associated with VUR may be a manifestation of growth arrest possibly due to glomerular damage. The sensitivity of 99mTc-DMSA may reveal the permanent nature of the renal damage.

Child↗

PubMed1992

The evaluation of paediatric renal transplants using resistive index and renal blood flow.

Six children (aged 1.3-6.9 years) were examined with serial duplex Doppler sonography and diethylenetriaminepenta-acetic acid (DTPA) isotope renography in the post-renal transplant period. The resistive index (RI) was derived from sonographic studies and the renal blood flow (RBF) calculated from the isotope scans. The clinical status of the child and the corresponding plasma creatinine level were assessed together with these two parameters. The RIs ranged from 40% to 100% and the RBF from 0% to 16.8%. There were six rejection episodes in four patients. A significant fall in RBF mirrored a rise in plasma creatinine on each occasion, but there was no significant change in RI recorded. There were two graft losses, both associated with renal venous thrombosis. In both cases no significant RBF could be detected on DTPA renography. In one patient, the RBF remained low throughout a period of primary non-function associated with acute tubular necrosis, and increased as primary function was established and the plasma creatinine fell. Throughout this period there was no significant change in the RI. From our preliminary data RBF reflects graft dysfunction more accurately than does the RI.

Child↗

PubMed1992

Effective portal insulin delivery with enzyme-protected capsules in pancreatectomized pigs.

1. Plasma concentrations of insulin, C-peptide, glucagon and glucose were measured in surgically pancreatectomized pigs given insulin into the colon directly and in enteric peptidase-resistant (methacrylic acid copolymer-encapsulated) form. 2. Following introduction of insulin-containing capsules, plasma insulin concentration rose from 2.7 +/- 0.1 microU/ml to 110.9 +/- 51.9 microU/ml in the portal vein, and from 2.6 +/- 0.1 microU/ml to 26.9 +/- 7.3 microU/ml in the systemic circulation. Corresponding portal and systemic values after direct (non-encapsulated) insulin instillation were 28.2 +/- 15.9 microU/ml to 44.8 +/- 13.0 microU/ml and 7.5 +/- 2.6 microU/ml to 15.2 +/- 2.5 microU/ml respectively. Insulin concentrations peaked at 75 min in the group as a whole and between 60-90 min in individual animals. Absorption was most pronounced in pigs given aprotinin (a trypsin inhibitor) with insulin. 3. Plasma portal vein glucose concentrations fell from 76.2 +/- 8.9 mg/dl to 31.1 +/- 3.2 mg/dl 150 min after encapsulated insulin administration. Corresponding systemic glucose levels were 84.5 +/- 11.0 mg/dl and 37.0 +/- 1.4 mg/dl. 4. Colonic administration of insulin in methacrylic acid coated capsules results in peak portal and systemic insulin levels 60-90 min after administration. Co-administration of aprotinin enhances the fraction of insulin absorbed.

Animals↗

PubMed1992

What proportion of isotope injected does the child receive in dynamic renal scanning?

Because of significant difficulties encountered in the manipulation of data from 99Tcm-DTPA and 99Tcm-mercaptoacetyltriglycine (MAG3) renogram studies, it was decided to try to improve the percentage dose of radioisotope injected and thus the number of counts obtained by using a minimum dose volume of 1 ml for all injections. This resulted in an improvement in the percentage dose injected. However, difficulties were still encountered in the younger children. 18.7% of children aged less than 3 months, received less than 50% of the injected dose, showing little or no improvement using the newer method. The difficulty of injecting small babies seems the most obvious reason. During the interpretation of the findings in paediatric radioisotope studies, it is important to remember that not all children may have received an adequate percentage dose to constitute a reliably diagnostic study.

Child↗

PubMed1992

Can technetium-99m-mercaptoacetyltriglycine replace technetium-99m-dimercaptosuccinic acid in the exclusion of a focal renal defect?

The presence of focal renal damage dictates different management of a child with urinary tract infection (UTI) compared with children who have normal kidneys. Technetium-99m-dimercaptosuccinic (DMSA) has a high sensitivity in the detection of a focal defect, and allows estimation of differential function. The introduction of 99mTc-MAG3 with high renal extraction suggests that this may be useful in children with UTI but its role remains speculative. Fifty-nine children with previous UTI underwent both 99mTc-DMSA and MAG3 within 4 wk of each other. Differential function and assessment of the images were undertaken. There is close correlation (R2 = 0.97) between the differential function. Analysis of the 99mTc-DMSA and functional MAG3 images showed that the functional image had a specificity of 88% and a sensitivity of 88% in the detection of a focal parenchymal defect. Technetium-99m-MAG3 in the clinical setting of a child with UTl allows accurate assessment of differential function and a high probability of detecting a focal renal abnormality.

Adolescent↗

PubMed1992

Can dynamic krypton-81m imaging separate regional ventilation and volume?

This study explores the assumption that 81mKr static images represent regional ventilation. Dynamic acquisition of 81mKr ventilation images permits creation of time-activity curves and the possible separation of the confounding influences of ventilation and volume. By using a two-compartment gas mixing lung phantom, the results demonstrate that both total and tidal 81mKr are closely related to regional ventilation. In 61 children and 15 adult volunteers, there was good agreement between fractional ventilation assessed by total and tidal 81mKr. The dynamic steady-state ventilation image can be analyzed to separate tidally exchanged and resident 81mKr. This may allow regional ventilation to be distinguished from regional volume.

Adolescent↗

PubMed1991

Laser-assisted versus mechanical recanalization of femoral arterial occlusions.

A randomized clinical trial was performed to test the hypothesis that a laser-heated probe is superior to standard techniques to reopen occluded femoral arteries. Twenty patients were treated with a standard guidewire and balloon dilation method. In a second group of 20 patients, the laser probe was initially used as a nonheated mechanical device. If the probe was unsuccessful in mechanically reopening the artery, an Argon laser was activated to heat the probe. The mean length of occlusion was 15.9 +/- 10.3 cm. The success rate for the laser probe was 15 of 20 (75%), which was not significantly different from the standard method, 19 of 20 (95%). Most of the success in the laser-probe group was due to the probe's mechanical properties. The laser probe was successful as a cold, mechanical device in 13 of 15 (87%) arteries. It was necessary to heat the probe in 5 patients. When heated, the laser probe assisted recanalization in 2 but perforated the artery in 3 cases. The results of this randomized trial do not support the hypotheses behind the use of the thermal laser probe. The laser probe functions primarily as a mechanical device. The thermal activation does not significantly improve the success rate without increasing the risk of perforation. This small additional benefit does not justify the large cost of current thermal laser devices. This controlled study also demonstrates a higher success rate in long occlusions than previous reports of mechanical balloon recanalization. This is due to a combination approach of retrograde and anterograde probing of the occluded segment.

Adult↗

PubMed1991

A chromosomal study of workers with long-term exposure to radio-frequency radiation.

OBJECTIVE: To examine whether an increased level of chromosome damage occurs in the stimulated lymphocytes of radio-linemen after long-term but intermittent exposure to radio-frequency radiation (RFR) during the course of their work. DESIGN AND PARTICIPANTS: Chromosome studies were performed on blood samples from 38 radio-linemen matched by age with 38 controls, all of whom were employed by Telecom Australia. The radio-linemen had all worked with RFR in the range 400 kHz-20 GHz with exposures at or below the Australian occupational limits, and the controls were members of the clerical staff who had no exposure to RFR. Two hundred metaphases from each subject were studied and chromosome damage was scored by an observer who was blind to the status of the subjects. RESULTS: The ratio of the rate of aberrant cells in the radio-linemen group to that in the control group was 1.0 (95% confidence interval, 0.8-1.3). There were no statistically significant differences in the types of aberrations that were scored. CONCLUSION: Exposure to RFR at or below the described limits did not appear to cause any increase in chromosomal damage in circulating lymphocytes.

Chromosome Aberrations↗

PubMed1991

Behavioral and biochemical studies in rats following prenatal treatment with beta-adrenoceptor antagonists.

Increased motor activity and poor performance in the active avoidance test were observed in the offspring of rats treated with dl-propranolol or sotalol during pregnancy, but not with atenolol and d-propranolol. All substances were administered in drinking water from days 8-22 of gestation. A significant increase in the density of muscarinic acetylcholine receptors in the hippocampus was found for dl-propranolol and sotalol, at 35 and 20 days of age, respectively. Twenty-day-old pups born to dl-propranolol-treated rats exhibited a non-significant decrease in the number of beta-adrenoceptors in the frontal cortex. Assuming that all the beta-adrenoceptor antagonists tested had access to the developing fetal brain, the effect of dl-propranolol and sotalol on behavior could stem from central beta 2-adrenoceptor blockade. In view of the lack of behavioral changes after atenolol, a beta 1-selective adrenoceptor antagonist, it is suggested that the clinical use of beta 1-selective adrenoceptor antagonists during pregnancy might be safer for the fetus than beta 2-adrenoceptor antagonists.

Administration, Oral↗

PubMed1991

Paediatric nuclear medicine.

Until the 1980s no serious attempts were made to develop paediatric nuclear medicine, as for various reasons many centres were reluctant to perform radionuclide examinations on children. Then two books were published on paediatric nuclear medicine in 1984 and 1985, respectively. In 1987, a group of physicians formed an informal club of paediatricians and nuclear medicine specialists in an effort to improve the relationship and cooperation between these specialties. Carrying out nuclear medicine examinations on children requires a completely different approach than on adults. Suggestions are made and tips given, and the specific problems involved are discussed in detail.

Child↗

PubMed1991

Renal injury in complete ureteric obstruction. A functional and morphological study.

This preliminary study examined reno-vascular injury sustained by the multipapillary porcine kidney in acute and chronic complete ureteric obstruction. In combination with measurement of upper tract pressure, regional function was assessed by [99mTc]-dimercaptosuccinic acid (DMSA) uptake and qualitative renal perfusion, by resin casting of the arterial tree prior to scanning electron microscopy (SEM). In acute obstruction, segmental defects were noted in the renal poles on both [99mTc]-DMSA scanning and casting. On SEM there was a polar afferent arteriolar vasodilatation after 30 min of obstruction and, subsequently, a segmental reduction in cortical perfusion. In kidneys that had been obstructed for 20 days, we observed a marked reduction in outer cortical perfusion coincident with afferent arteriolar vasoconstriction. The pathogenesis and significance of segmental injury to the multipapillary kidney in obstructive uropathy is discussed.

Animals↗

PubMed1991

Antenatal diagnosis of renal pelvic dilatation--the natural history of conservative management.

Seventy children with an antenatal diagnosis of unilateral renal pelvic dilatation underwent Tc 99 m DTPA diuretic renograms. There were 16 kidneys with moderate function, and 54 with good function, 31 underwent pyeloplasty, all had a renal pelvis greater than 12 mm diameter on ultrasound. Thirty nine children with good function were treated conservatively. Long term follow up has demonstrated that conservative management for PUJ dilatation with a good functioning kidney may be justified but a randomised control study is required.

Dilatation, Pathologic↗

PubMed1991

Reproducibility of renal blood flow estimation in the miniature pig using 99Tcm-DTPA: introducing semiautomatic processing.

This study examines the reproducibility of renal blood flow measurement (RBF) in nine miniature pigs using 99Tcm-DTPA renography, and introduces a new algorithm useful in data processing. Renal blood flow can be estimated using three arterial regions of interest (ROI), the left ventricle (LV), the right lung (RL) and the aorta. Using the LV ROI, left kidney RBF was 9.08 (S.D. 1.69) and right RBF was 10.87 (S.D. 2.26). Reproducibility was assessed by performing renograms on successive days in nine pigs and was found to be best for LV [S.D. of change 0.32 for the left kidney (LK) and 0.74 for the right kidney (RK)] followed by RL (0.77 for LK and 0.75 for RK) and worst for aorta (1.47 for LK and 1.78 for RK).

Algorithms↗

PubMed1991

Estimation of glomerular filtration rate in the miniature pig by kidney uptake on the gamma camera.

Measurement of glomerular filtration rate (GFR) by the renal uptake of 99Tcm-diethylene triamine penta-acetic acid (99Tcm-DTPA) in the miniature pig was compared to that by plasma disappearance of 99Tcm-DTPA using multiple blood samples. Nineteen animals were examined under identical conditions. There was a highly significant relationship between the two tests, r = 0.88, P less than 0.001, although the uptake method gave consistently higher results than those obtained from plasma disappearance. Reproducibility of the uptake method was also assessed in this group of animals by performing two consecutive renograms. Confidence limits of 95% were +/- 7.5% or 0.7 ml min-1 kg-1. The test is useful for the serial examination of single kidney GFR on follow-up renography but is unlikely to replace disappearance techniques as a more accurate means of GFR estimation.

Animals↗

PubMed1991

Imaging in urinary tract infection.

The relationship of vesicoureteric reflex (VUR) and renal scarring was studied in 94 children (188 kidneys) with proved urinary tract infection in a district general hospital. There were 61 girls and 33 boys, with nine girls and 17 boys aged less than 1 year, 31 girls and nine boys aged between 1 and 5 years, the remaining 28 children were over 5 years of age. All children had a micturating cystourethrogram and a 99mTc (technetium) dimercaptosuccinic acid (DMSA) scan. Forty two of the 188 kidneys were scarred and 70 of the kidneys had VUR. Only 37.1% of the kidneys with reflux were scarred but 61.9% of the scarred kidneys had VUR. In children of less than 1 year, 48% of kidneys with VUR were scarred whereas 70.6% of scarred kidneys had reflux. In children between 1 and 5 years of age only 36.4% of kidneys with VUR were scarred but 63.2% of scarred kidneys had VUR. There is good correlation between the detection of a scarred kidney on DMSA and the presence of vesicoureteric reflux. However the detection of reflux particularly in children over 1 year of age shows poor correlation with renal scarring. This suggests that the primary imaging in children over 1 year of age presenting with a urinary tract infection should be of the kidney: a cystogram should be performed only if the DMSA scan is abnormal.

Age Factors↗

PubMed1991

A prospective study in the Australian petroleum industry. I. Mortality.

This paper reports the mortality experience of employees of the Australian petroleum industry from 1981 to 1989. Two surveys by personal interview incorporated more than 15,000 employees representing 92% of the eligible population. Subjects were included in the analysis after completing five years of service in the industry. At the time of this report the cohort does not include sufficiently large numbers of women for useful analysis; results presented are restricted to men. By 31 December 1989, 76,529 person-years of observation had accumulated for male mortality with 241 deaths. The standardised mortality ratio (SMR) analysis showed a favourable mortality experience for most causes with overall cancer rates slightly lower than those of the national population. Whereas deficits were seen in some cancer sites, notably lung cancers (SMR 0.5, 95% confidence interval (95% CI) 0.3-0.8), mortality for lymphohaematopoietic cancers, notably leukaemia (SMR 1.6, 95% CI 0.6-3.4) suggested increased risk. The SMR for cancers of the pleura was 3.9 (95% CI 0.8-11). Two of the three cases seen had previous employment, however, in industries with likely exposure to asbestos.

Australia↗