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Biomedical subjects

N W Johnson

Publications and source records attributed to N W Johnson.

At least 145 records · Page 8Linked to original sources
PubMed1983

A quantitative histochemical study of glucose-6-phosphate dehydrogenase activity in premalignant and malignant lesions of human oral mucosa.

The levels of glucose-6-phosphate dehydrogenase activity have been assayed by quantitative histochemistry in normal, benign, potentially malignant and carcinomatous lesions of human oral mucosa. Dysplastic epithelium showed a higher activity of this enzyme than did morphologically normal, benign hyperplastic and neoplastic lesions and this may be an aid to early diagnosis. The increases in glucose-6-phosphate dehydrogenase activity in dysplastic human oral epithelium are sufficient to warrant a longitudinal study to evaluate further the significance of these changes in the process of malignant transformation.

Epithelium↗
PubMed1983

Experimental iron deficiency in Syrian hamsters (Mesocricetus auratus).

An animal model was developed in which the effect of iron deficiency on the oral mucosa could be studied. Iron deficiency was induced by feeding hamsters a low-iron powdered diet together with withdrawal of 0.5 ml of blood weekly, for a period of 9 weeks. At the end of this period the mean haematological values for control animals were, Hb 15.9 g/dl, plasma iron 40.3 mumol/l, TIBC 90.5 mumol/l and transferrin saturation 44.5%, compared with 7.4, 7.2, 111.4 and 6.5 respectively for experimental animals. These results were reproducible in successive groups of animals and indicate that this is a useful model for the study of iron deficiency anaemia.

Anemia, Hypochromic↗
PubMed1983

Kinetics of osteoclast formation: the significance of blood monocytes as osteoclast precursors during 1 alpha-hydroxycholecalciferol-stimulated bone resorption in the mouse.

The significance of blood monocytes as a source of osteoclast precursors was investigated during 1 alpha-hydroxycholecalciferol-stimulated bone resorption in mice. Animals were given three injections of tritiated thymidine at 8 hourly intervals in order to label blood monocytes. The proportion of labelled monocytes was then compared with the proportion of labelled nuclei in osteoclasts, the formation of which was provoked by daily injections of 1 alpha-hydroxycholecalciferol, beginning 48 hours after the first injection of isotope. Although more than 60% of blood monocytes were labelled during the period of peak osteoclast formation, labelling of osteoclast nuclei in the metaphyseal endosteum of the femur never exceeded 8%. These results suggest strongly that the majority of osteoclast nuclei were derived from a source of unlabelled precursors, and that very few osteoclasts were derived directly from blood monocytes. Although few labelled osteoclasts were found, the proportion of labelled spindle shaped cells in the metaphyseal endosteum rose gradually to 16%. It is likely, therefore, that labelled mononuclear cells, possibly blood monocytes, were attracted to the endosteum where they formed a population of tissue macrophages. At this site they may participate in bone resorption, either individually or by providing a local pool of osteoclast precursors.

Animals↗
PubMed1983

Regional differences in the distribution of dividing cells in hamster cheek pouch epithelium.

Examination of vinblastine-arrested metaphase figures in sections from the medial wall of 15 hamster cheek pouches showed that: (1) the distribution of dividing cells was non-random and (2) mitotic activity declined in an anteroposterior direction. Although there was some variation between different pouches these features were statistically significant (P less than 0.05) in individual pouches from half the animals and highly significant (P less than 0.005) when the data from all pouches were pooled. The average sample size required to determine a mitotic index representative of the whole length of the pouch was equivalent to approximately 32 mm of surface length of epithelium or 4562 basal cells. This estimate exceeds the sample size generally examined and it is suggested that inadequate sampling could account for some of the inconsistencies in the literature on hamster cheek pouch cell kinetic data.

Animals↗
PubMed1982

Prognostic significance of STNMP and velocity of tumor growth in oral cancer.

Regression analysis using actuarial life tables has been applied to the STNMP system for the grading and staging of oral cancer. Based on 170 patients, the five-year survival figures were 78% for Stage 1, 67% for Stage 2, 36% for Stage 3, and 20% for Stage 4. This represents a considerable improvement in prognostic differentiation over existing TNM system applied to the same cohort of patients. A further variable, velocity of tumor growth, was also assessed and shown to be of value in predicting the ultimate survival of the patients.

Age Factors↗
PubMed1982

Bacterial invasion of the periodontium in a case of juvenile periodontitis.

A case of juvenile periodontitis is described where biopsy material taken from a lower right incisor during periodontal surgery revealed plaque-derived bacteria present within the periodontal connective tissue. The gingival connective tissue contained an inflammatory infiltrate which exhibited a profound loss of collagen and was dominated by plasma cells, many of which had a bizarre cytoplasmic morphology, The invading bacteria were morphologically heterogeneous but mainly gram-negative. Some were found in a patchy distribution in the apical margins of the inflammatory infiltrate and more numerous groups of organisms were in the collagenous connective tissue apical to the infiltrated area. Polymorphonuclear neutrophils (PMN) were seen in association with the bacteria and some PMN showed phagocytosis of bacteria without significant degranulation. This is the first description of bacterial penetration of the periodontium in juvenile periodontitis; it is not known how frequently this occurs but it is an interesting finding in a condition where there is known impairment of one branch of the host's defence mechanisms, namely pMN phagocytosis and degranulation.

Adult↗
PubMed1982

Epithelial cells kinetics. A review of methods of study and their application to oral mucosa in health and disease. Part B. Comparison of cell kinetics in normal and abnormal epithelia.

In Part A, the techniques most commonly used to study epithelial cell kinetics and their suitability for use in man are reviewed. In Part B, the application of such methods to comparative studies of normal and abnormal oral epithelial of both man and experimental animals is examined. Claims regarding the possible prognostic value of LI's or MI's of biopsies of potentially or overtly malignant human oral lesions are also considered. Normal and abnormal kinetic data for other lining epithelia, e.g., skin, uterine cervix and gastrointestinal mucosa are assessed where they provide a better illustration of some of the problems arising in such comparative investigations. Finally, the present and likely future areas in which cell kinetic studies may provide a guide to expected tumour prognosis and optimum treatment are summarized.

Animals↗
PubMed1981

The in vivo effects of lymphokines on mitotic activity and keratinization in guinea pig epidermis.

Lymphokines may alter epidermal growth and differentiation contributing to changes such as acanthosis and hyperkeratosis. The main in vivo effects of lymphokines on epidermal mitotic activity were therefore investigated. Guinea pigs were injected intradermally with antigen-stimulated lymphocyte culture supernatants and a partially purified lymphokine preparation in phosphate buffered saline (PBS) 18, 24, 36 and 48 hr prior to biopsy. Control sites were injected with unstimulated supernatants and PBS respectively and the mitotic activity determined by use of a stathmokinetic agent. Both lymphokine injected areas and controls showed significantly increased mitotic indices compared to untreated skin which was apparent only at 24 hr. However mitotic activity in lymphokine lesions was significantly higher than in control lesions. There was no difference in the effect on mitotic activity between PBS and unstimulated culture supernatants. Lymphokine lesions at 24 hr also exhibited marked epidermal edema and acanthosis compared to minimal changes in controls. A variable patchy parakeratosis developed between 18 and 24 hr in areas injected with partially purified lymphokine but not in control sites or after injection with unpurified supernatants. The lymphokine-induced inflammatory infiltrate was mild and consisted mainly of neutrophils not differing significantly from that of the control lesions. This strongly suggests that lymphokines induce an alteration in epidermal kinetics and keratinization by a direct effect on keratinocytes and not indirectly via the dermal inflammatory infiltrate.

Animals↗
PubMed1981

Osteoclast formation in response to intraperitoneal injection of 1 alpha-hydroxycholecalciferol in mice.

In order to assess osteoclast formation in response to 1 alpha-hydroxycholecalciferol, osteoclast counts per cm of bone surface were performed on paraffin sections of femurs of male CBA mice killed at daily intervals up to 5 days. All animals received daily intraperitoneal injections of 1 alpha-hydroxycholecalciferol up to the time of death. Peak osteoclast formation occurred during the third day, by the end of which maximum numbers of osteoclasts were achieved (11.9 +/- 0.9 osteoclast cm-1) compared to controls (3.5 +/- 0.6 osteoclast cm-1), this increase being highly significant (p less than 0.01). Although the osteoclast population was most dense at the metaphyseal plate in both experimental and control groups, osteoclast counts in this region only doubled whereas overall osteoclast counts more than tripled. The number of nuclei per osteoclast did not significantly alter following four daily injections of 1 alpha-hydroxycholecalciferol.

Animals↗
PubMed1981

Formation of osteoclasts from blood monocytes during 1 alpha-OH Vit D-stimulated bone resorption in mice.

In order to investigate a monocyte origin for osteoclasts, tritiated thymidine labelled blood monocytes, harvested from the blood of donor mice, were injected intravenously into syngeneic recipient animals in which osteoclast formation was being stimulated by concomitant intraperitoneal injections of 1 alpha-hydroxycholecalciferol. Labelled osteoclasts were found in autoradiographs prepared from the femurs of recipient mice, demonstrating for the first time that, during hormonally stimulated osteoclast formation, blood monocytes form one source of osteoclasts.

Animals↗
PubMed1980

A quantitative cytochemical study of three oxidative enzymes during experimental oral carcinogenesis in the hamster.

The activities of three oxidative enzymes have been assayed by quantitative cytochemical methods during chemically induced carcinogenesis in the hamster cheek pouch. Changes in the levels of succinate and glucose-6-phosphate dehydrogenases were apparent in the early stages of carcinogenesis prior to the development of lesions recognisable histologically as squamous cell carcinomas. In contrast the activity of lactate dehydrogenase remained constant until malignant lesions were well established. These changes were not observed in benign hyperplastic lesions, suggesting that such enzyme assays may be of value in the diagnosis of premalignant lesions of the oral mucosa.

Animals↗
PubMed1980

A comparison of in vivo and in vitro stathmokinetic methods for the study of cell proliferation in hamster oral epithelia.

Mitotic indices (MI) expressed as numbers of metaphase fingers per 100 basal cells in the cheek pouch and palatal epithelium of the Syrian hamster following metaphase arrest with vinblastine sulphate (VLB) were compared using in vivo and in vitro techniques. The MI in vivo 4 1/2 hr after intraperitoneal injection of 4 mg VLB/kg body weight 2.69 +/- 0.37 for check pouch and 12.08 +/- 1.09 for palate. MI in vitro was measured using small tissue explants cultured for 4 hr in medium supplemented with VLB at concentrations ranging from 6-600 micrograms/ml. The maximum MI for cheek pouch epithelium in vitro (2.7) did not differ signficantly from that observed in vivo (P > 0.50) and was obtained in the presence of 12-30 micrograms VLB/ml, a concentration comparable with that used in vivo. In contrast, the maximum MI for palate epithelium in culture (5.6) was significantly lower than that in vivo (P < 0.001) and was only achieved in the presence of extremely high concentrations of VLB. Possible reasons are discussed for the discrepancy between the MI for palatal epithelium in vivo and in vitro.

Animals↗