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Biomedical subjects

N W Johnson

Publications and source records attributed to N W Johnson.

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

Epithelial cell kinetics--A review of methods of study and their application to oral mucosa in health and disease. Part A. Methods for studying cell proliferation and some sources of variation.

Despite extensive investigation of cell kinetic parameters in wide range of normal and abnormal tissues and their potential value in understanding the pathogenesis of many disease states, as well as in prognosis and treatment planning, their application to oral epithelia remains limited. In part A the methods most commonly applied to the study of epithelial cell kinetics, i.e., isotope labelling, mitotic arrest and flow cytophotorimetry are reviewed with special emphasis on their technical limitations, sources of variation and inapplicability to humans in vivo. The ability of in vitro methods to reliably reproduce in vivo cell kinetic parameters is also considered. The application of cell kinetic studies to normal and abnormal oral tissues will be discussed in part B.

Cell Cycle↗
PubMed1979

The role of diffusible ionic species in the bonding of polycarboxylate cements to dentine: an in vitro study.

Treatment of freshly-cut dentine with fluoride ions or high concentrations of metal ions produced changes ranging from mineralization of tubule contents to precipitation of adherent surface layers. Combinations of these treatments with application of fluoridated and non-fluoridated polycarboxylate cements and glass ionomer cements produced both increases and reductions in bond strength which are explained by ionic diffusion at the interface prior to setting.

Acrylic Resins↗
PubMed1978

Early colonisation of a local inflammatory lesion and its relationship to changes in systemic leucocyte availability: a study of turpentine-induced lesions in the rat.

The changes in both peripheral blood leucocyte counts and lesion inflammatory cells have been measured at intervals up to 24 hr following the subcutaneous injection of turpentine in rats. The lesion PMNL changes were characterised by a sharp rise between 0 and 6 hr and a less-rapid fall between 6 and 24 hr. The half-life of lesion PMNL's, as determined by tritiated thymidine labelling between 12 and 24 hr after turpentine injections, was 13 hr and there was a significant correlation between blood and lesion PMNL counts throughout the experimental period. A dependence of the lesion PMNL population on the availability of these cells is thus suggested. Mononuclear cells, which were predominantly monocyte-derived, showed a sharp rise between 6 and 12 hr, plateauing thereafter. These changes were not associated with significant alterations in blood monocyte counts. Although significant changes in blood lymphocyte counts were observed, these were not reflected in the local inflammatory lesion.

Animals↗
PubMed1978

The effect of ultra-violet radiation and restricted diet on rat labial mucosa.

The combined effect of ultra-violet radiation and a restricted diet on oral mucosa was investigated using the labial mucosa of pigmented rats. Twenty-four rats were divided so that 12 experimental animals received 50% of the average daily diet of the remaining 12 normal controls. After 1 month, the epithelium of the restricted group had thinned to 2/3 of that of the controls. Nine rats from each group were then subjected to daily ultra-violet irradiation of the labial mucosa, three animals in each group remaining as unirradiated controls. After 1, 4 and 8 weeks irradiation, three experimental and one unirradiated control from each group were sacrificed. Microscopic examination showed that the thickness of the epithelium and the mitotic index increased in both normal and restricted animals at 4 weeks. The increase in thickness was maintained at 8 weeks, but the mitotic index declined in the deficient animals at this time. Evidence of epithelial dysplasia was seen in the normal animals at 4 weeks, and this increased at 8 weeks; such changes were rarely seen in the restricted animals. It thus appears that the extent of ultra-violet induced dysplasia may be related to the mitotic index, a lower mitotic index implying less dysplasia.

Animals↗
PubMed1978

The inflammatory response to paraffin in the peritoneal cavity of the rat.

The inflammatory response to intraperitoneal paraffin in hte rat has been defined in terms of the fluid influx and the pattern of cell accumulation. The volume of fluid exudate in the peritoneal cavity was small and did not change dramatically with time, but there was a moderate cellular influx which was biphasic with peaks at 24 and 72 h. Mononuclear phagocytes and eosinophils were the major cell types found in the exudate, neutrophils, lymphocytes, and mast cells being much less numerous. The neutrophil influx was apparent by 4 h. It was early, short-lived and of low magnitude. In contrast, the eosinophil response was later and more prolonged, cell numbers reaching a peak at 72 h when they were the predominant cell type. The response of the mononuclear phagocytes was multiphasic, with peaks in cell numbers occurring at 24 and 96 h, and 3 weeks after stimulation, by which time they exhibited the morphological features of large activated macrophages which were highly phagocytic for paraffin. The method is useful for the production of mixed inflammatory cell populations from which the fluid phase can readily be separated, and may be a valuable model for the study of esoinophil kinetics.

Animals↗
PubMed1977

Oral cancer: the behaviour and response to treatment of 194 cases.

During the 16 year period 1960-1975, 350 cases of Oral Cancer were seen in the Department of Oral and Maxillo-Facial Surgery at the London Hospital. Detailed records were available for 250 patients. After excluding tumours of the salivary glands, sarcomata and tumours of the reticulo-endothelial system 194 cases remained and these were subjected to a computer analysis. The overall 5 year survival figure, not corrected for age and sex was, 32.8%. The local recurrence rate for all sites was 44%, 90% of these recurred within 2 years of diagnosis. The overall uncorrected 5 year survival figure for females was 42.1% and that for males was 22.9%. Analysis of the material has not provided a satisfactory explanation for this; lesions do not present at an earlier stage in females neither do they occur in younger patients. The distribution of the lesions by site and histology was the same for both sexes. Survival rates analysed by clinical staging at presentation confirm that the prognosis for early stage lesions is very much better than for late stage lesions, the 5 year survival for Stage I being 50% whereas that for Stage IV is only 20%.

Adolescent↗
PubMed1977

Methyl green-pyronin with hematoxylin and orange G for the identification of inflammatory cells in tissue sections.

Methyl green-pyronin is a notoriously difficult stain to reproduce. Although very useful in detecting cells containing substantial amounts of RNA, it is of limited use in broader problems of cell identification. By careful standardization of the proportions of methyl green to pyronin and combination of these stains with hematoxylin to enhance nuclear contrast and with orange G to improve connective tissue staining, it was possible to produce a consistently reliable staining preparation in which it is possible to identify all the component cells of a mixed inflammatory infiltrate in routine paraffin sections.

Animals↗
PubMed1977

Histological and histochemical studies of oral cancer.

Increasing attempts are now being made to measure and to assess the relative importance of histologic features in oral premalignant and malignant conditions in order to improve the accuracy of diagnosis and prognosis. Though certain individual features, such as DNA content of cell nuclei, or stereological parameters like nuclear : cytoplasmic ration or desmosome density can be very accurately quantified, no single feature can completely characterize the neoplastic process. Multifactorial studies are thus of great importance, even though it is not practicable to measure all the parameters included with the sam accuracy; in such studies retrospective computation of the relative importance of individual parameters is of greater value than arbitarily assigned weights. So far as early prediction of malignant transformation in oral premalignant lesions is concerned, great interest is now being shown in the reactivity of glucose-6-phosphate dehydrogenase in epithelial cells. For predicting the prognosis of patients with established squamous cell carcinoma of the mouth, it is now realized that thenature and intensity of the host immune inflammatory response seen in the connective tissue within the surrounding the tumour and in affected regional lymph nodes, is at least as important as are the features of the tumour cells themselves.

Cell Division↗
PubMed1976

Alterations in peripheral blood leucocyte distribution in response to local inflammatory stimuli in the rat.

Changes in peripheral blood leucocyte distribution were monitored following subcutaneous injections of turpentine and subcutaneous and intrapleural injections of dextran. The responses in all three groups were similar; marked increases in total counts occurred at 6 hr, due largely to significant increases in neutrophil counts. Increases in lymphocyte counts also occurred and were more marked in the dextran-treated animals. By 12 hr, total counts fell, due to drops in both neutrophil and lymphocyte counts. In both dextran groups, neutrophil counts rose again between 24 and 72 hr, but in the turpentine group the fall persisted until 96 hr before counts reached a second peak at 14 days. In all groups lymphocytes showed an increase again at 18-72 hr. The rise in neutrophil counts observed 6 hr after the injection of turpentine was shown to be due principally to premature release of neutrophils from the bone marrow maturation compartment. Depletion of this compartment resulted in a drop in numbers of circulating neutrophils between 6 and 12 hr, in spite of the continued release of progressively less mature cells. The recovery in neutrophil counts between 72 and 96 hr was thought to be the expression of an increase in the rate of stem cell division. The continued rise to a second peak at 7 days probably resulted from increased marrow cellularity. It is suggested that the fluctuations in peripheral blood leucocyte counts may influence the initial colonisation of the local inflammatory lesion. The increase in neutrophil counts at 6 hr corresponds with the time of maximum neutrophil emigration reported by other workers and the fall in counts at 12 hr corresponds with the time of decreased neutrophil emigration.

Adult↗