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D R Appleton

Publications and source records attributed to D R Appleton.

At least 37 records · Page 2Linked to original sources
PubMed1989

A protocol for the routine measurement of lactate and pyruvate in cord blood.

The influence of the site of sampling and the delay in sample collection on cord blood concentrations of lactate and pyruvate were investigated. A delay in sample collection of greater than 1 min after cord clamping could invalidate the results obtained. Samples from umbilical artery had higher lactate values (mean 3.13 mmol/l) than paired vein samples (mean 2.32 mmol/l) but there were no significant differences in lactate values between different sites sampled within the umbilical vein. A calculation was devised to circumvent the need to take cord blood samples immediately after delivery.

Blood Specimen Collection↗
PubMed1988

A protective effect of sulindac against chemically-induced primary colonic tumours in mice.

Sulindac, a non-steroidal anti-inflammatory drug, has been reported to lead to tumour regression in cases of human polyposis coli. We have investigated the effects of this drug on the growth of 1,2-dimethylhydrazine (DMH)-induced mouse colonic tumours. In one experiment, DMH and oral sulindac were administered concurrently to a group of mice for a period of up to 24 weeks, while a control group of animals received DMH only for the same period. Sulindac caused a significant reduction in both the number of mice with colonic tumours and the number of tumours per mouse. In a second experiment, two groups of mice which had already been treated with DMH for 17 weeks received either sulindac or not for 78 days. In this experiment sulindac had no effect. These results demonstrate that sulindac has a protective effect against the chemical induction of colonic tumours in mice, but does not cause the regression of established tumours.

1,2-Dimethylhydrazine↗
PubMed1988

Verapamil sensitizes normal and neoplastic rodent intestinal tissues to the stathmokinetic effect of vincristine in vivo.

A morphological method has been developed allowing measurement of the effect on intestinal epithelia of vincristine. In routinely prepared tissue sections the proportion of mitotic events progressing beyond metaphase is counted by microscopy. When estimated over a range of doses of vincristine this post-metaphase index (PMI) can be used to compare the sensitivity of differing intact tissues. Intestinal tumours were induced in rats by chemical carcinogenesis. Administration of vincristine in the presence or absence of verapamil was performed in these tumour-bearing animals. Sections were prepared from colonic and small-bowel tumours and from normal mucosa. The results show that verapamil increases the sensitivity of the tissues studied to vincristine. A dose dependent effect of verapamil on vincristine sensitisation was demonstrated in colonic tissues. These findings indicate a shared pharmacological property between the resistance of primary tumour tissue and the multidrug-resistance phenotype.

Animals↗
PubMed1988

Analysis of data in nephrology. V. Contingency tables.

The first article in this series dealt with 2 x 2 contingency tables. We now return to contingency tables and discuss those formed by a dichotomous response variable and a discrete, but not dichotomous, explanatory variable. The logit transform is introduced.

Data Interpretation, Statistical↗
PubMed1988

Analysis of data in nephrology. II. When to use the t-test.

This is the second of a series of six articles describing how to choose the most appropriate statistical method to test for relationships between two variables. When the response variable is continuous and the explanatory variable is dichotomous, the t-test is often used. The article indicates when this is really appropriate and when the test should be modified or replaced by another.

Data Interpretation, Statistical↗
PubMed1988

Analysis of data in nephrology. III. Survival analysis and analysis of variance.

In this article discussion is continued of the case where the response variable is continuous and the explanatory variable is discrete. Two particular situations are covered: the response variable survival time and the explanatory variable dichotomous: and the response variable continuous (but not survival time) and the explanatory variable discrete (but not dichotomous).

Analysis of Variance↗
PubMed1988

Analysis of data in nephrology. VI. The generalised linear model.

This is the last of six articles describing how to choose the appropriate statistical test to look for relationships between two variables. It shows that when the response variable is dichotomous and the explanatory variable is continuous it may not be appropriate to carry out a t-test. Some comments are made on extending the tests considered to more complex situations.

Analysis of Variance↗
PubMed1987

A trophic effect of epidermal growth factor (EGF) on rat colonic mucosa in organ culture.

The development of an organ-culture system for rat colonic mucosa has enabled a direct assessment of the effect of epidermal growth factor (EGF) on cell division. An augmented mitotic index (AIm) has been employed to identify changes in cell proliferation. Explants of colonic mucosa from four animals were maintained in a medium containing serum for five days. On the fifth day of culture, half of the explants received fresh medium containing EGF (40 ng/ml) and the remainder (controls) fresh medium only. At 6, 12, 24 and 48 hr thereafter groups of both experimental and control explants received the metaphase-arresting drug vincristine (4 micrograms/ml) for 3 hr prior to fixation. The proportions of vincristine-arrested metaphases within the explants were determined. Analysis of the data indicates that when serum is present exogenous EGF exerts a trophic effect which increases with time (P less than 0.001). In a second experiment colonic explants from four animals were maintained for five days in a serum-free medium and were then divided into groups, each of which received one of a range of concentrations of EGF. The AIm was determined for each group after 36 hr. It was found that increasing concentrations of EGF produce a small but significant increase in cell proliferation (P less than 0.01). This effect, however, was less pronounced than that seen when serum was present. These results suggest that EGF has a trophic action on the colon and interacts with additional factors found in serum.

Animals↗
PubMed1987

Sugars consumption of Northumbrian children aged 11-14 years.

In order to investigate the relationships between diet and tooth decay the authors recently completed the first longitudinal study of diet and dental caries increment in children. 405 children initially aged 11.5 years each recorded their intake of foods and drinks for a total of 15 days over a period of 2 years. This is a review of some of the findings.

Child↗
PubMed1986

A cytokinetic study of small-intestinal and colonic mucosa after resection of 70% of the small intestine.

Pulse-labelling with tritiated thymidine and a fraction of labelled mitoses experiments have been performed in order to investigate the proliferative changes induced at various sites in the hyperplastic small-intestinal mucosa of rats previously subjected to resection of 70% of the small intestine. Proliferative activity in the colon was also studied. In the distal ileum there is a significant reduction in cell cycle time (Tc) of cells at all levels within the crypt and the growth fraction falls. In the jejunum and proximal ileum the crypts contain an increased number of proliferating cells, but as the size of the maturation zone is also increased, there is no significant alteration in the relative number of proliferating cells per crypt. Nor does the distribution of proliferating cells in these crypts seem to alter. There is no general reduction in Tc at these sites, but there does appear to be a significant reduction in Tc on the part of the cells in the stem-cell zone at the crypt base. In neither proximal nor distal colon was there any significant proliferative change apparent after small-intestinal resection.

Animals↗
PubMed1986

Interpreting the correlation coefficient when one of the variables is discrete.

The effect on the correlation coefficient of discretizing data was investigated in two ways. First, the theoretical effect of dichotomizing data was calculated, and it was shown that the resulting correlation coefficient is considerably less than that between the underlying bivariate normally distributed variables. Second, computer simulations were performed of a model in which a continuous variable (measured with some error) gives rise to a counting variable through a mechanism in which the count is zero below a certain threshold value for the continuous variable and then increases linearly as the continuous variable increases. It was shown that the correlation coefficient between the observed values of the continuous and counting variables decreased as (a) the measurement error increased, (b) the slope of the relationship decreased, and (c) the number of counts decreased. It is concluded that caution is required when interpreting correlation coefficients when one or both of the variables consist of a few (say only four or five) discrete scores.

Computer Simulation↗
PubMed1986

Dietary sources of energy, protein, fat and fibre in 375 English adolescents.

The aim of this report of the dietary sources of energy, protein, fat and fibre in 375 English adolescents aged 11-14 years is to contribute to the development of health education. Each child recorded their dietary intake five times over a 2-year period using a 3-day diary with interview. Food tables (Paul & Southgate, 1978) were used to calculate nutrient intake. The results are the mean of all 15 days intake. Potatoes (chips and crisps) were the largest single source of energy but 'meat' was the main source of protein and fat, other important sources of fat were the spreading fats, milk, chips and crisps. Chips were the main source of fibre but white bread, crisps and baked beans also contributed similar proportions of fibre. Some differences between the sexes and social classes were observed; the lower social class children appeared to have more undesirable eating habits.

Adolescent↗
PubMed1986

A comparison of crypt-cell proliferation in rat colonic mucosa in vivo and in vitro.

The successful development of a long-term organ culture system has made it possible to perform experiments on rat colonic mucosa in vitro. However, the effect of trauma or the withdrawal of trophic influences in culture may result in the disturbance of proliferation within the tissue. In this paper we describe an investigation designed to characterise the culture system by a comparison of the proliferative parameters in vitro with those in vivo. Stathmokinetic experiments were performed in vivo and in vitro to estimate cell birth rate. Mitotic indices were also calculated. The in vivo birth rate (7.8 +/- 0.8 cells/1000 cells/hour) and the in vitro birth rate for the whole explant (7.7 +/- 0.5 cells/1000 cells/hour) were found to be similar. A study of crypts in the centre and at the edge of the cultured explants, however, indicated that proliferation at the two sites differed markedly, the birth rate at the edge (7.5 +/- 0.9 cells/1000 cells/hour) being approximately twice that at the centre (3.2 +/- 0.9 cells/1000 cells/hour). Provided that this topological difference in proliferation within the explant is recognised the in vitro model, in particular the basal level found at the centre, may still be regarded as a valid system for studying tissue responses to carcinogens and trophic factors.

Animals↗