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Biomedical subjects

D Machin

Publications and source records attributed to D Machin.

At least 163 records · Page 9Linked to original sources
PubMed1980

The leucocyte alkaline phosphatase activity in mature neutrophils of different ages.

The marrow myeloid precursor cells of a haematologically normal patient were labelled by intravenous injection of tritiated thymidine. Young labelled segmented neutrophils were then released from the marrow into the blood by an injection of cortisol. These PMN had a significantly lower LAP activity than the older blood neutrophils. It is shown that within the morphologic boundaries of the segmented PMN, the cells are still in different stages of cytoplasmic maturation. In addition, labelled and unlabelled neutrophils showed a linear and parallel increase of LAP activity during the 24 h following cortisol injection. This observation suggests that the neutrophil prematurely released in the blood can mature into normal LAP=PMN and more generally that LAP activity of a blood neutrophil increases with time.

Aged↗
PubMed1980

Critical evaluation of lung scintigraphy in cystic fibrosis: study of 113 patients.

A long-term study has been performed on 285 lung perfusion scintigrams obtained from 113 patients with cystic fibrosis. Transverse and longitudinal comparisons with clinical and radiological scores, as well as retrospective analysis of the deceased patients, were the methods used in order to evaluate the importance of the scintigraphic images. It appears that lung scintigraphy is the best index of the regional lung impairment, and contributes, as does a chest radiograph, to the early detection of lung lesions, the two methods being complementary. The survival rate of CF patients reached 0.80 at 9 yr when initial scintigraphy was normal or only moderately impaired, but fell to 0.18 when severe lesions were seen on the first scintigrams.

Cystic Fibrosis↗
PubMed1980

Inhibition of RNA synthesis in murine ependymoblastoma by the combination of amphotericin B and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea.

The aim of this study was to clarify the mechanism of the potentiation by amphotericin B (AMB) of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) antineoplastic effects on s.c. murine ependymoblastoma. The effect of AMB on tumor cell permeability to CCNU labeled on the cyclohexyl moiety was studied. The radioactivity measured in ependymoblastoma 1, 6, 14, and 25 hr after i.m. injection of 10.4 microCi of 1-(2-chlorethyl)-3-[cyclohexyl-1-14C]cyclohexyl-1-nitrosourea per mouse was significantly higher (p less than 0.001) in the tumors of animals treated with AMB (25 mg/kg 10 hr prior to [14C]CCNU) as compared to controls. The effects of AMB and CCNU given separately or in combination on RNA and protein synthesis were studied by measuring the incorporation of [3H]uridine and [14C]leucine, respectively, into RNA and proteins. The administration of AMB (25 mg/kg) or CCNU (10 mg/kg) did not affect the incorporation of [3H]uridine measured 2 hr after the i.p. injection of 40 microCi of labeled precursor per mouse. On the other hand, the incorporation of [3H]uridine was significantly (p less than 0.001) inhibited in animals treated with AMB (25 mg/kg) followed 10 hr later by CCNU (10 mg/kg), as compared to animals receiving CCNU alone. The inhibition, which reached a maximum of about 35% 24 hr after the administration of CCNU, was not observed when AMB was given after CCNU. The inhibition of RNA synthesis was also observed in mice treated with AMB and cyclohexyl isocyanate (5.4 mg/kg), a degradation product of CCNU. Measurements of [14C]leucine incorporation showed that AMB did not increase the inhibition of protein synthesis produced by CCNU. These observations suggest that AMB increases the uptake of a cyclohexyl derivative arising from the degradation of CCNU. The increased uptake of this compound results in inhibition of RNA synthesis. This mechanism could account for the potentiation of the CCNU therapeutic effect produced by AMB, at least in murine ependymoblastoma.

Amphotericin B↗
PubMed1978

Effect of a nitrogen analog of tetrahydrocannabinol on cancer pain.

Two consecutive, randomized, double-blind trials were performed to test the analgesic properties of a synthetic nitrogen analog of tetrahydrocannabinol (NIB). In the first trial, the test preparation was superior to placebo and approximately equivalent to 50 mg of codeine phosphate. In the second study, the tetrahydrocannabinol analog was superior to placebo and to 50 mg secobarbital. NIB is not useful clinically because of the frequency of side effects.

Analgesics↗
PubMedDate not supplied

Incomplete quality of life data in randomized trials: missing items.

Missing data has been a problem in many quality of life studies. This paper focuses upon the issues involved in handling forms which contain one or more missing items, and reviews the alternative procedures. One of the most widely practised approaches is imputation using the mean of all observed items in the same subscale. This, together with the related estimation of the subscale score, is based upon traditional psychometric approaches to scale design and analysis. We show that it may be an inappropriate method for many of the items in quality of life questionnaires, and would result in biased or misleading estimates. We provide examples of items and subscales which violate the psychometric foundations that underpin simple mean imputation. A checklist is proposed for examining the adequacy of simple imputation, and some alternative procedures are indicated.

Female↗
PubMedDate not supplied

Incomplete quality of life data in randomized trials: missing forms.

Analysing quality of life (QOL) data may be complicated for several reasons, such as: repeated measures are obtained; data may be collected on ordered categorical responses; the instrument may have multidimensional scales, and complete data may not be available for all patients. In addition, it may be necessary to integrate QOL with length of life. The major undesirable effects of missing data, in QOL research, are the introduction of biases due to inadequate modes of analysis and the loss of efficiency due to reduced sample sizes. Currently, there is no standard method for handling missing data in QOL studies. In fact, there are very few references to methods of handling missing data in this context. The aim of this paper is to provide an overview of methods for analysing incomplete longitudinal QOL data which have either been presented in the QOL literature or in the missing data literature. These methods of analysis include complete case, available case, summary measures, imputation and likelihood-based approaches. We also discuss the issue of bias and the need for sensitivity analyses.

Bias↗
PubMedDate not supplied

Suggestions for the presentation of quality of life data from clinical trials.

Quality of life (QOL) data is complex since it is both multidimensional and longitudinal. This complexity is compounded with its unbalanced nature through missing observations as a consequence of patient non-compliance with assessment schedules, and, for example, in cancer clinical trials data absence due to patient attrition often through death. QOL data poses difficulties for presentation and analysis and hence interpretation. This paper illustrates, using data from a randomized trial of the United Kingdom Medical Research Council Lung Cancer Working Party, a step-by-step approach to presentation of QOL data. This begins with a description of compliance and its relationship with patient attrition caused by death, to a final summary profile to indicate change over time. We recognize that no single summary statistic is likely to be able to encapsulate all the subtleties of QOL data. We stress the importance of examining data graphically before performing detailed analysis and also to facilitate interpretation in the final clinical report. Although a description of analytical methods is not the purpose of this paper, we draw attention to the need for imputing missing values and to the (multi-level) modelling approach to summarizing the data, both essential adjuncts to the less formal methods described here.

Authorship↗