Search PubMed⌕ Search

Biomedical subjects

P B Silcocks

Publications and source records attributed to P B Silcocks.

At least 37 records · Page 2Linked to original sources
PubMed1993

Quantitation of the renal arterial tree by fractal analysis.

To determine whether the renal arterial system has a fractal structure, the fractal dimension of renal angiograms from 52 necropsy cases was measured using an implementation of the box-counting method on an image analysis system. The method was validated using objects with known fractal dimensions. The method was accurate with errors of less than 1.5 per cent and reproducible with initial values within 1.2 per cent of the mean of ten sets of measurements (reliability coefficient 0.968, 95 per cent confidence limits 0.911-0.984). In the 36 satisfactory angiograms the mean fractal dimension was 1.61 (SD 0.06), which was significantly greater than the topological dimension of 1 (P < 0.0001), indicating that the renal arterial tree has a fractal structure. There was no significant relationship between age (P = 0.494), sex (P = 0.136), or systolic (P = 0.069) or diastolic (P = 0.990) blood pressure, but two congenitally abnormal kidneys (hypoplastic dysplasia and renal artery stenosis) had fractal dimensions at the lower end of the normal range (third percentile). Since the renal arterial tree has a fractal structure, Euclidean geometric measurements, such as area and boundary length, are invalid outside precisely defined conditions of magnification and resolution.

Adult↗
PubMed1993

p53 and c-myc expression in stage A1 prostatic adenocarcinoma: useful prognostic determinants?

Forty-five stage A1 prostatic adenocarcinomas from patients with a mean age of 65 years were examined for p53 and c-myc expression to determine whether the presence or absence of these proteins could predict tumor behavior. Thirteen (6 of 45) and seventy-three percent (33 of 45) of cases were respectively p53 and c-myc positive. p53 expression was confirmed to the tumor cells, whereas c-myc immunoreactivity was present in both malignant and surrounding hyperplastic prostate. Statistical analysis showed that although p53 and c-myc expression were positively correlated, expression of neither nuclear protein was associated with a significantly worse survival (p53: p = 0.0791 exact two-tailed; c-myc: p = 0.738 exact two-tailed). These results suggest that while both p53 and c-myc may play a role in prostatic carcinogenesis, neither appears to identify patients who may benefit from treatment in stage A disease.

Adenocarcinoma↗
PubMed1993

'Anti-metastatic' nm23 gene product expression in keratoacanthoma and squamous cell carcinoma.

An inverse correlation has been demonstrated between nm23 gene expression and metastasis. The gene is located on chromosome 17q (q1.1-q2.1), a region distinct from tumour suppressor gene p53. We have previously reported expression of mutant products of p53 gene to be significantly associated with worsening degrees of differentiation in squamous cell carcinoma. nm23 gene product, which shows complete identity to human erythrocyte nucleoside diphosphate kinase, was used to raise an affinity-purified polyclonal antibody Ab-11 which is applicable to formalin-fixed and paraffin-embedded tissues. Keratoacanthomas and squamous cell carcinomas of the epidermis form a fascinating human tumour model in which to test the hypothesis that the nm23 gene confers 'anti-metastatic' properties, since the former never metastasise while the latter have this potential. Two observers rated immunohistochemistry for the nm23 gene product as the proportion of tumour positive from grades 1-4 (corresponding to 25, 50, 75 and 100% of tumour cells stained). Nineteen typical keratoacanthomas, 20 well, 21 moderately and 8 poorly differentiated epidermal squamous cell carcinomas were studied. The Jonckheere-Terpstra test statistic of association between staining grade and lesion type was 762.5, p = 0.189 (2 tails), p = 0.0945 (1 tail). There was no statistically significant trend in tumour staining from keratoacanthoma through decreasing grades of differentiation of squamous cell carcinoma. nm23 product expression does not appear to correlate with differentiation, itself an indicator of metastatic potential, in this system of human squamous cell neoplasms.(ABSTRACT TRUNCATED AT 250 WORDS)

Carcinoma, Squamous Cell↗
PubMed1992

Delay in fixation does not affect the immunoreactivity of proliferating cell nuclear antigen (PCNA).

The effect of delayed fixation on the immunoreactivity of proliferating cell nuclear antigen (PCNA) was investigated using eight breast carcinomas. Topologically shuffled samples of each tumour were immersed in fixative at times of 0.5, 1, 2, 4, 6, 18, and 24 h after surgical removal. In addition to a PCNA index (percentage of positive cells per 1200 tumour cells), a semi-quantitative PCNA grading system was used, based on estimates of more than or less than 50 per cent of positive tumour cells at each time interval. The PCNA index of six tumours increased by a mean of 10 per cent with a fixation delay of 24 h. The PCNA grade of all eight tumours showed no change with delayed fixation.

Antigens, Neoplasm↗
PubMed1992

Mutant p53 oncogene expression in keratoacanthoma and squamous cell carcinoma.

The tumour suppressor gene p53, located on the short arm of chromosome 17, encodes for a nuclear protein which regulates cell proliferation by inhibiting cells entering S-phase. p53 mutations are alleged to be the commonest genetic abnormality in human cancer. We studied mutant p53 oncoprotein expression, using PAb1801 monoclonal antibody immunohistochemistry, in 25 'ideal' keratoacanthomas and 26 well-, 19 moderately and 18 poorly differentiated squamous cell carcinomas of the skin. While there was a highly significant trend in the proportion of p53 oncoprotein-positive lesions from keratoacanthomas to poorly differentiated squamous cell carcinomas (chi 2 = 17.13, df = 1, exact P = 0.00003), p53 expression was inadequate for distinguishing keratoacanthoma from well-differentiated squamous cell carcinoma (chi 2 = 2.55, df = 1, exact P = 0.18; corresponding to a sensitivity of 0.84 and a specificity of only 0.36).

Carcinoma, Squamous Cell↗
PubMed1992

General practitioners, skin lesions and the new contract.

We reviewed all skin lesions received in our laboratory from general practitioners (GPs) during a three-month period before the introduction of the new contract for GPs and during the same period a year later. For comparison we also reviewed skin lesions received from the general and plastic surgeons. Particular attention was paid to the completeness of excision. There was a significant increase in the number of skin lesions removed in general practice after the introduction of the new contract. Both benign and malignant lesions were more likely to be incompletely excised by GPs compared with surgeons. The GPs first noted to carry out minor surgery after the new contract came into force were less likely to have completely excised lesions than their more experienced colleagues. We suggest the future monitoring of lesions removed in general practice, possibly by the formation of a joint audit group.

Biopsy↗
PubMed1991

A case-control study of dietary carotene in men with lung cancer and in men with other epithelial cancers.

Dietary carotene intake during the year before diagnosis was estimated for 96 men with lung cancer, 75 men with other epithelial cancers, and 97 hospital controls. Relative to those of men in the lowest third of carotene intake (less than 1,683 micrograms/day), the smoking-adjusted odds ratios for men in the middle (1,683-2,698 micrograms/day) and upper (greater than 2,698 micrograms/day) thirds of carotene intake were 0.67 and 0.45, respectively, for lung cancer (one-sided test for trend, p = 0.048) and 0.63 and 0.65, respectively, for other epithelial cancers (one-sided test for trend p = 0.074). The protective effect of estimated dietary carotene intake was considerably stronger than was the effect of total intake of carotene-rich vegetables and fruits (grams per day), providing some evidence that the protective factor is carotene itself rather than another component of vegetables and fruits.

Aged↗
PubMed1989

Making cancer statistics more informative: measures of the quality of recorded diagnosis in a population-based registry.

The quality of the recorded diagnosis is a major limit to the usefulness of Cancer Registry statistics that is easily overlooked by users of the data. With data from a large population-based cancer registry as an example, we demonstrate how Registry statistics could be improved by wider use of three simple indices, namely (1) the proportion histologically verified (adjusted for age), (2) the proportion of verified cases with an uninformative diagnosis, and (3) the proportion of cases that are staged. We believe that greater awareness of the deficiencies of Cancer Registry statistics will lead to a more critical interpretation of them, and help stimulate efforts to rectify matters.

Aged↗
PubMed1989

Can we achieve 100% ascertainment in cancer registration?

Completeness of ascertainment is a central issue for any disease register. We outline the process of cancer registration as carried out in a large population-based Registry and argue that none of the various methods proposed to estimate the completeness of ascertainment are satisfactory. We suggest an alternative way of looking at the issue and describe various constraints that hamper attempts to achieve complete registration.

Death Certificates↗
PubMed1988

Rapidly progressive cervical cancer: is it a real problem?

The appearance, in younger women, of a rapidly progressive form of cervical carcinoma has been suggested. This, together with evident deficiencies in the provision and technique of screening services, has been taken to indicate a need for more frequent screening. We show that a substantial increase in the observed number of such rapidly progressive cancers would be expected simply on the basis of changes in population structure, a general increase in cervical cancer rates and increases in the proportion of women screened.

Adolescent↗
PubMed1987

Squamous and adenocarcinoma of the uterine cervix: a comparison using routine data.

We studied the clinical, demographic and survival characteristics of more than 5,000 women registered with either squamous or adenocarcinoma of the uterine cervix in South Thames Cancer Registry over the period 1968-81. There were similarities with respect to social class, smoking habit, oestrogen/oral contraceptive use and time trends in incidence but differences between the two cancers were found with respect to age distribution, parity, method of detection and survival. Some of the data are of limited value, having been obtained only from case notes, so the results need some caution in their interpretation. However the results are broadly consistent with those of studies performed in other countries on smaller samples. A methodological issue is also raised, viz. the appropriateness of a disease with well-known characteristics as a comparison group. From our results the likely size of various associations can be judged and used in the design of future studies to clarify the epidemiology of cervical adenocarcinoma.

Adenocarcinoma↗
PubMed1987

Relative risk estimation from vital statistical data: validation, a pitfall and an alternative method.

A previously described method of obtaining an estimate of relative risk from routinely available data was applied to data on cigarette consumption and lung cancer mortality to test its validity. Some shortcomings of the method were noted and an alternative approach using weighted logistic regression gave results closer to those predicted on the basis of other studies, without the disadvantages of the original technique.

Female↗
PubMed1986

Evaluation of PAS-diastase and carcinoembryonic antigen staining in the differential diagnosis of malignant mesothelioma and papillary serous carcinoma of the ovary.

A series of malignant mesotheliomas and papillary serous carcinomas of the ovary were stained using the periodic acid Schiff reaction with diastase digestion (PAS-D) and an immunoperoxidase technique for carcinoembryonic antigen (CEA). The methods were evaluated in terms of repeatability and validity. Staining reactions were classed as positive or negative by three 'blinded' observers. Within-observer repeatability was greater for PAS-D than for CEA but there was no statistically significant difference for between-observer repeatability. The validity of the methods clearly differed, however, since the sensitivity and specificity of CEA were consistently less than that of PAS-D. Our most consistent estimates of sensitivity and specificity were compared with those of other studies and the reasons for this difference were analysed. Positive PAS-D and CEA staining were uncorrelated but a combination of the two did not appear significantly superior to PAS-D alone. We believe that PAS-D remains the method of choice for differentiating peritoneal mesotheliomas and disseminated papillary serous carcinoma of the ovary in the absence of reliable evidence of an ovarian primary because the significance of CEA positivity in occasional mesothelial tumours remains to be determined.

Amylases↗
PubMed1983

Measuring repeatability and validity of histological diagnosis--a brief review with some practical examples.

Evaluation of histological diagnosis requires an index of agreement (to measure repeatability and validity) together with a method of assessing bias. Cohen's kappa statistic appears to be the most suitable tool for measuring levels of agreement, which if unsatisfactory may be caused by bias. Further study of bias is possible by examining levels of agreement for each diagnostic category or by searching for categories of disagreement in which more observations occur than would be expected by chance alone. This article gives reasons for choosing the kappa statistic, with examples illustrating its calculation and the investigation of bias.

Adenocarcinoma, Bronchiolo-Alveolar↗
PubMed1981

Histology of experimental stress ulcer: the effect of cimetidine on adrenaline-induced gastric lesions in the rabbit.

The gastric mucosal injury produced by i.p. instillation of adrenaline in the rabbit was examined and assessed histologically. Mucosal lesions were classified by microscopy into two types bearing distinct histological features. In Type A oedema only was seen and in Type B erosion and/or haemorrhage were added. Statistical analysis revealed that mucosal lesions were related to adrenaline dose. Cimetidine was ineffective in protecting against the stress-related gastric lesion in the present rabbit model. Biochemical studies demonstrated that severe lesions were associated with depleted mucosal histamine.

Animals↗
PubMed1980

Catecholamines and experimental stress ulcer: morphological and biochemical changes in the gastric mucosa.

A model for the production of gastric mucosal haemorrhages and ulcers, similar in morphology and distribution to those seen in stress states in man, has been produced by the intraperitoneal injection of adrenaline in single, double or treble doses of 0.6 mg/kg. Lesions were produced in 2 or 3 h, without ligation of the pylorus. Severe mucosal changes were associated with a fall in gastric mucosal histamine concentration. Mucosal serotonin did not change. Rises in mucosal adrenaline were accompanied by a fall noradrenaline, total catecholamine levels being unchanged.

Animals↗