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Biomedical subjects

G Knight

Publications and source records attributed to G Knight.

At least 37 records · Page 2Linked to original sources
PubMed1994

Observations in Australia of the use of glass ionomer cement restorative material.

The aim of this study was to evaluate, with the aid of a questionnaire distributed to selected groups of dentists, the use of glass ionomer cement in different types of proximal restorations and further to evaluate any complications observed with the use of GIC. Few dentists responded in the 'Often' category regarding the observation of secondary caries or gingival inflammation in association with GIC fillings compared with about three-quarters of the dentists who reported on posterior composite resin restorations. Tunnel cavities had been prepared and restored by 54 per cent of the dentists, simple proximal restorations in primary molars by 89 per cent and 'sandwich' restorations by 69 per cent. Few dentists with at least two years experience with tunnel restorations observed biological complications, but fracture of the marginal ridge was reported in the 'Often' category by 12 per cent. Among the dentists with at least five years experience with proximal restorations in primary molars 59 per cent of the operators mentioned more complications with these than with amalgam restorations. Biological complications were not a great problem with glass ionomer/composite laminates but wear or dissolution of the proximal GIC surface was recorded in the 'Often' section by 14 per cent of those placing them.

Australia↗
PubMed1991

Mitozantrone and prednimustine in the treatment of advanced breast cancer--a toxic regimen with low activity.

The combination of mitozantrone and prednimustine has been reported to elicit response rates of around 50% in patients with advanced breast cancer. In the present trial, either three or nine courses of this combination were given to previously untreated patients with advanced breast cancer. Mitozantrone was given at 12 mg/m2 on day 1 and prednimustine was given orally at 130 mg/m2 on days 1-5; treatment was repeated every 4 weeks. A total of 34 patients were treated; the performance status was 0-1 in 29 subjects and 2 in 5 cases. Locoregional disease only was present in 13 patients; 9 showed lung involvement; 8, liver; 3, bone; and 1, stomach involvement. A total of 10 subjects had received no prior hormone therapy. The median disease-free interval from the time of initial diagnosis was 24 months (range, 0-144 months). In all 14/23 patients exhibited an oestrogen receptor level of greater than 20 fmol. Grade 1 nausea and vomiting occurred in 16 patients and that of grade 2-3, in 11 subjects; nausea was prolonged for greater than 10 days in 7 cases. Grade 4 neutropenia occurred in 2 patients. The response rate was 21% (95% confidence interval, 8%-38%). The combination of mitozantrone and oral prednimustine is toxic and displays low activity.

Adult↗
PubMed1991

Development of impactor size-selective dust samplers at the Elliot Lake Laboratory.

The Elliot Lake Laboratory designs and uses impactor size selectors for respirable and other dust samplers both in the laboratory and in mines. Advantages of the selectors are compact size, reproducibility of size-selection performance based on the high precision of drill manufacture and use, flexibility in design and layout, and manufacturing ease in a machine shop. The major problems in design and performance were secondary deposition of dust and overloading with coarse dust. Secondary deposition modified the calculated size selection and either limited the spacing between adjacent orifices or orifices and other features or required a final calibration. Overloading of the coarse dust deposition zone led to changes in size-selection characteristics as the dust load increased, giving a definite limit to acceptable dust collection quantities. The use of multiple stages increased the coarse dust-holding capability manyfold. All the dust samplers developed at the Elliot Lake Laboratory used two or more successive stages to increase dust-holding capacity.

Dust↗
PubMed1990

Maternal smoking habits and Down's syndrome.

Two series of pregnancies were studied to investigate the relationship between maternal smoking and the risk of fetal Down's syndrome. In the first series, ascertained in the 1960s, in which smoking habits were determined after the outcome of pregnancy was known, the proportion of smokers (47 per cent) among the 461 women whose pregnancies ended in the birth of an infant with Down's syndrome was similar to that in the 461 controls (46 per cent) who had pregnancies affected by other congenital disorders. In the second series, ascertained between 1973 and 1984, smoking habits were determined by measurement of cotinine in antenatal serum samples that were routinely collected and stored or, if a serum sample was not available, from information in the antenatal notes. In this series, the proportion of smokers (14 per cent) among the 91 women who had pregnancies associated with Down's syndrome was lower than that among 413 controls (19 per cent), though this was not statistically significant. Collectively, our results provide no evidence for an association between fetal Down's syndrome and smoking. Other published studies found a deficit of smokers among women who had pregnancies associated with Down's syndrome. This may be partly due to some studies not taking adequate account of maternal age (older women are more likely to have had a Down's syndrome pregnancy but are less likely to be smokers) and partly due to the greater tendency for positive findings to be published than negative ones.

Adult↗
PubMed1988

Localization of vitamin D3-responsive alkaline phosphatase in cultured chondrocytes.

Alkaline phosphatase activity appears to be altered when chondrocyte cultures are incubated with 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3). This study examined whether the hormone-responsive enzyme activity is associated with alkaline phosphatase-enriched extracellular membrane organelles called matrix vesicles. Confluent, third passage cultures of rat costochondral growth cartilage (GC) or resting zone chondrocytes (RC) were incubated with 1,25-(OH)2D3 or 24,25-dihydroxyvitamin D3 (24,25-(OH)2D3) and enzyme specific activity was assayed in the cell layer or in isolated matrix vesicle and plasma membrane fractions. Alkaline phosphatase-specific activity in the matrix vesicles was enriched at least 2-fold over that of the plasma membrane and 10-fold over that of the cell layer. Matrix vesicle alkaline phosphatase was stimulated by 1,25-(OH)2D3 in GC cultures and by 24,25-(OH)2D3 in RC cultures. The cell layer failed to reveal these subtle differences. 1,25-(OH)2D3 increased GC enzyme activity but the effect was one-half that observed in the matrix vesicles alone. No effect of 1,25-(OH)2D3 on enzyme activity of the RC cell layer or of 24,25-(OH)2D3 on either GC or RC cell layers was detected. Thus, response to the metabolites is dependent on chondrocytic differentiation and is site specific: the matrix vesicle fraction is targeted and not the cells per se.

24,25-Dihydroxyvitamin D 3↗
PubMed1988

Maternal serum thyroid antibodies in early pregnancy and fetal Down's syndrome.

Thyroid antibodies were measured in mid-trimester antenatal serum samples from 77 pregnancies affected by fetal Down's syndrome and 385 unaffected control pregnancies. Using a haemagglutination technique, thyroglobulin antibodies were detected in 5.2 per cent of cases (4) and 2.9 per cent of controls (11), and thyroid microsomal antibodies were detected in 22 per cent (17) and 15 per cent (59), respectively. Using an enzyme-linked immunosorbent assay (ELISA) for thyroglobulin antibodies and a cut-off level of 50 KIU/l, positive results were found in 25 per cent of cases (19) and 22 per cent of controls (84). Using an ELISA for thyroid microsomal antibodies and the same cut-off level, the proportions were 52 per cent (40) and 39 per cent (149), respectively. While not statistically significant, the differences were consistent with the previously reported increased levels of thyroid antibody found in non-pregnant women who had had pregnancies associated with Down's syndrome.

Antibodies↗
PubMed1988

A measure of treatment satisfaction designed specifically for people with insulin-dependent diabetes.

The psychometric properties of a diabetes-specific treatment satisfaction scale were examined with responses from 128 adults with insulin-dependent diabetes who had used one of three treatment options for a period of 12 months. The reliability of the seven-item measured was found to be satisfactory (Cronbach's Alpha = 0.76) and factor analyses indicated three useful sub-scales (Perceived General Management; Perceived Compatibility with Lifestyle; Perceived Frequency of Hypo/hyperglycaemia). Use of the treatment satisfaction measure in a feasibility study of continuous subcutaneous insulin infusion (CSII) demonstrated the measure's ability to distinguish between three treatment groups (CSII, intensified conventional therapy and conventional therapy). People choosing to use CSII reported significantly greater improvements in satisfaction than those choosing either from of conventional therapy (F = 36.6; df 2, 125; p less than 0.001). If used in conjunction with measures of blood glucose control, the Treatment Satisfaction measure offers the opportunity for a more holistic appraisal of outcomes in studies evaluating and comparing treatments for insulin-dependent diabetes.

Adolescent↗
PubMed1987

Changes in the factor VIII complex in diabetic ketoacidosis: evidence of endothelial cell damage?

Factor VIII-related antigen and von Willebrand factor are synthesised by and released from vascular endothelium. Acute increases in the plasma concentration of these proteins may reflect endothelial cell damage. We have thus measured the plasma concentration of factor VIII-related antigen and von Willebrand factor, together with procoagulant factor VIII, during the course of acute diabetic ketoacidosis in seven patients. In addition, evidence for qualitative changes in the factor VIII complex was sought. Plasma factor VIII-related antigen and von Willebrand factor were markedly increased (plasma factor VIII-related antigen at presentation, median 2.75 U/ml; von Willebrand factor 2.95 U/ml) and returned toward normal with clinical and biochemical resolution (plasma factor VIII-related antigen at clinical recovery, median 1.80 U/ml; von Willebrand factor 2.05 U/ml). Plasma procoagulant factor VIII followed a similar pattern, but levels were less elevated (plasma procoagulant factor VIII, at presentation, median 1.6 U/ml; at clinical recovery, 1.2 U/ml). Crossed immunoelectrophoresis and sodium dodecyl sulphate-acrylamide electrophoresis with autoradiographic identification of multimeric structure revealed no evidence of structurally abnormal factor VIII-related antigen in diabetic ketoacidosis. However, an extra peak on crossed immunoelectrophoresis ("pre-peak") was a feature in the acute phase ketoacidotic plasma in six subjects, and may represent aggregated factor VIII. Changes in plasma factor VIII are a feature of diabetic ketoacidosis and, whilst not specific to this condition, may be the result of endothelial cell damage.

Adult↗
PubMed1987

Size distribution of airborne dust in Labrador iron mines.

The size distribution of the total airborne dust and its components approximates a straight line on a plot of log mass undersize against log aerodynamic size. The quartz component distribution has a reasonably constant slope, is close to the distributions found in other mines and mills, and follows the normal breakage laws. The results for the iron component suggest that the top size present is similar to that of quartz and that the slope is also similar. The slopes for total dust by weight are not as steep as for quartz and suggest a bimodal distribution consisting of a coarser mineral fraction mixed with a finer fraction from other sources, such as combustion products, that are often found. The slopes for manganese are sometimes much less than for iron or quartz and suggest that manganese is associated with a more crushable rock. The one finding of chromium suggests that it is associated mostly with very fine particles and, therefore, may have been dispersed as fume from an operation such as welding.

Air Pollutants, Occupational↗
PubMed1987

Comparison of dust samplers: statistical analysis techniques.

Statistical analyses comparing pairs of dust samplers were carried out using five models, a straight line through the origin, linear with intercepts, logarithmic, a logarithmic (weight + constant), and a fifth forced through the origin. The fourth and fifth models combined the arithmetic portion of the error, associated with weighing and handling, with the geometric portion, associated with sampling and the dust cloud variations, into a unified geometric form. It was shown that some of the assumptions on which the least squares method of regression analysis are based were not met and that corrections had to be made. In most cases no significant difference was found between the corrected regression lines and the expected physical relation, a straight line through the origin. In the exceptions physical reasons were found to support the nonlinearity found in statistical analysis. It is suggested that the best estimate of the relation between two dust samplers can be obtained by a least squares determination of the straight line through the origin using transformed variables. A method is given for determining values of the constants. The application of this statistical method to comparisons between dust samplers not measuring the same parameter of the dust cloud is discussed with an example. The considerations in assessing historical dust measurements are outlined.

Air Pollutants↗
PubMed1987

Comparison of respirable dust samplers for use in hard rock mines.

Five respirable dust size selectors and eleven filter holders were compared, some at two flow rates. These included horizontal elutriators, impactors, metal cyclones and nylon cyclones. The comparisons were carried out both in the laboratory and in mines. The respirable dust on the filters was assessed by weighing, and where relevant, by X-ray diffraction for quartz with the use of a direct-on-filter method. The results obtained showed that the relation between most pairs of samplers could be represented by a straight line through the origin and that the personal samplers collecting more dust--the CAMPEDS impactor and the B.C.I.R.A. cyclone--gave higher reproducibility in the low dust concentrations found in many hard rock mines. The samplers based on the nylon cyclone were less suitable for hard rock mines containing a substantial proportion of quartz, though satisfactory in coal mines with their higher dust control standards.

Air Pollutants↗
PubMed1987

Glycaemic control in diabetic patients transferred from therapy with animal insulins to human crystalline zinc insulin of recombinant DNA origin: a multicentre study.

87 stable insulin-dependent diabetic patients from 6 diabetic clinics within the UK were transferred from their existing once or twice daily regimen of subcutaneous animal insulin to a similar regimen of human insulin of recombinant DNA origin in neutral soluble and crystalline zinc suspension formulations. Seven point blood glucose profiles, glycosylated haemoglobin concentrations and insulin dose were examined, in each patient, before and after 6 weeks therapy with human insulins. The 67 patients on twice daily insulin showed no significant change in mean blood glucose values or glycosylated haemoglobin but required a significantly higher dose of human crystalline zinc suspension than their previous long-acting animal insulin. In contrast the 17 patients on a once daily regimen experienced a significant deterioration in glycaemic control without a significant change in insulin dose or glycosylated haemoglobin. Three patients on twice daily insulin withdrew shortly after transfer to human insulin. The combination of human soluble and crystalline zinc suspension appears to be a more satisfactory substitute for animal insulin when used in a multi-dose regime rather than on a once daily basis.

Animals↗