Autoradiographic study on some proliferative properties of human buccal mucosa

Indicators of Genotoxicity in Farmers and Laborers of Ecological and Conventional Banana Plantations in Ecuador

Banana farming represents an important segment of agricultural production in Ecuador. The health of farmworkers might be compromised by the extensive use of pesticides in plantations applied under poorly regulated conditions. Due to an increased awareness of pesticide-related problems for nature, as well as for worker and consumer health, ecological farming has been established in some plantations of Ecuador. We set out to investigate the occupational health of workers in both conventional and ecological farming. Nuclear anomalies in buccal epithelial cells were used as short-term indicators for genotoxicity and a potentially increased cancer risk in the two groups of farmworkers. By application of the Buccal Micronucleus Cytome Assay (BMCA), we found the frequency of micronuclei in conventional pesticide using farmworkers significantly increased by 2.6-fold, and other nuclear anomalies significantly increased by 24% to 80% (except pyknosis with a non-significant increase of 11%) compared to the farmworkers on ecological plantations. These results demonstrate that ecological farming may provide an alternative to extensive pesticide use with significantly reduced indicators of cancer risk. In conventional farming, improvements in education and instruction regarding the safe handling of pesticides and protective equipment, as well as regulatory measures, are urgently needed.

Principles of geriatric dentistry and their application to the older adult with a physical disability

The older adult living with a physical disability faces many daily challenges. Limited hand function or impaired cognition often has profound effects on activities of daily life including oral hygiene. This article explores age-related changed in dentition and common causes of pathology of the oral cavity with special emphasis in populations with impaired hand function or cognition. This article will also assist the treating physician as it relates to oral diagnosis and patient management.

In vitro labelling studies and the measurement of epithelial cell proliferative activity in the human oral cavity

Samples (110) of human mandibular gingiva and buccal mucosa, harvested from patients undergoing third-molar surgery, were subjected to in vitro labelling with tritiated thymidine, bromodeoxyuridine, or a sequential double-labelling technique comprising tritiated thymidine followed by bromodeoxyuridine, in order to determine the efficacy of a new incubation labelling technique, and to characterize S-phase labelling indices in human oral mucosa. Whilst, there were no demonstrable differences in labelling indices obtained by single thymidine, single bromodeoxyuridine or double labelling, there was a significant difference between anatomical sites, with higher S phase labelling observed in buccal mucosa (mean LI 11.7) than mandibular gingiva (mean LI 8.5; P<0.01). There was, however, no significant correlation between individual labelling indices and patient age, sex or the time of day when tissue was harvested. The in vitro labelling technique provides a reliable and quantifiable method of characterizing proliferative labelling indices in the human oral cavity. Further investigation is being carried out to profile wider age and anatomical ranges and to utilize the double-labelling technique to calculate S-phase durations and cell-cycle times. These profiles may have a future role in the assessment of oral mucous membrane disease.

Markers of proliferation in normal and leukoplakic oral epithelia

We have reviewed the recent literature on immunohistochemical markers of cell proliferation in normal oral epithelia and leukoplakias. Most findings, including our own, point to an increased proliferation in oral leukoplakias that correlates with the degree of dysplasia. Although the basal layer of normal oral epithelia showed a very low proliferative activity, oral leukoplakias, even those containing low-grade dysplasia, exhibited a very significant increase in proliferation. High-grade dysplasia could be clearly differentiated from both low-grade dysplasia and normal oral epithelia by the presence of proliferating cells in the superficial cell strata, i.e. above or superficial to the parabasal layer. These changes were detected with several markers including PCNA, Ki-67 (Mib-1), cyclin D1 and CENP-F as well as with procedures using pulse labeling with BrDU, IrDU and tritiated thymidine. Comparison of all methods showed more similarities than discrepancies. Nevertheless, because of its relative simplicity of use and universal acceptance in many other sites, Ki-67 (Mib-1) seems to be the most reliable immunohistochemical marker for future use in cancer prevention and therapeutic clinical trials.

Mapping dynamic epithelial cell proliferative activity within the oral cavity of man: a new insight into carcinogenesis?

Our aim was to characterize epithelial cell proliferative activity within the oral cavity and to find out if there were differences between sites with high and low incidence of cancer. A total of 105 samples of clinically normal mucosa were harvested from various intra-oral sites. Excised specimens were incubated in vitro with tritiated thymidine and bromodeoxyuridine to 'double label' cells undergoing DNA synthesis, and enable calculation of the duration of S phase and estimation of variables of cell flux to and from S. Mean labelling indices (percentage of cells within the S phase of the cell cycle) were highest in the floor of mouth (12.3%) and ventral tongue (10.1%), while activity was lowest in the dorsum of tongue (4.3%) and the palate (7.2%), P<0.001. In general, both cell influx and the duration of S increased proportionally to the labelling index. Sites with a high incidence of cancer were characterized by high labelling indices, increased cell influx and a prolonged S phase.

A quantitative histometric murine in vivo model of radiation-induced oral mucositis

Gastrointestinal toxicity is a limiting factor in the effectiveness of cancer therapy. This toxicity is most visible in the mouth. There is considerable interest in developing strategies involving growth-factor manipulation of the epithelial stem cells to afford protection to these cells during treatment and/or to speed up the regenerative process following treatment. In order for this to be achieved, studies have to be undertaken in animal systems to demonstrate the proof of principle and determine optimal protocols. Here, a murine model for oral mucositis based on measurements of tissue cellularity at various times after exposure to radiation was used to investigate cytotoxicity. Several sites in the mouth were analysed and the pronounced circadian rhythm in these various epithelial sites determined. The circadian rhythm is important in that it would determine the timing of administration of growth factors. A microscope with an interactive computer was used to define areas of epithelium and lengths of basal layer, within which, and along which, the total number of cell nuclei was determined over a range of times following exposure to 10, 20 and 30 Gy of X-rays. For various practical reasons, the ventral surface of the tongue was identified as the most appropriate tissue to analyse. Here, measurements of cellularity reached minimum values between 6 and 8 days following 20 Gy. Labelling of S-phase cells demonstrated foci of regeneration and a burst of proliferative regeneration that commenced at about 5 days and reached peak values at 8 days after irradiation. This burst of regenerative proliferation was coincident with the minimum in tissue cellularity on about day 8. The lower dose of radiation (10 Gy) had minimal effects on cellularity: after the higher dose (30 Gy), there was clearly a more severe level of cellular depletion. This quantitative model of oral mucositis could be used to study the effects of other cytotoxics, including combinations of agents, and the potential role of growth factors to reduce the severity of the cellular depletion and to speed up the kinetics of regeneration.

Epithelial cell kinetics in oral leukoplakia

Cell proliferation in oral leukoplakia has been studied by estimating the number of cells in the S phase using in vitro 3H thymidine labelling. The labelling index was found to be increased 1.77 fold in leukoplakias compared to the clinically normal control sites (P < 0.005). This rise in labelling index was found to be related to an increase in the proportion of the cells in the basal cell layer engaged in cell production. Both leukoplakia and the control specimens showed epithelial atypia, although in the latter samples this was mild yet suggestive of a possible field change in the oral epithelium of a small group of tobacco users. A significant positive correlation was found between the epithelial atypia score and the labelling index. This raises the possibility of using the labelling index as an objective prognostic marker in assessing potential malignancy in oral leukoplakia lesions.

Diurnal variation in labelling index in human buccal epithelium

Diurnal variations in the number of DNA-synthesizing cells (labelling index) in human buccal epithelium were studied by in vitro pulse labelling with tritiated deoxythymidine. Eleven male volunteers provided 33 biopsy specimens at six time periods. The results showed a 24-h periodicity in the labelling index in this tissue. The mean peak labelling index obtained at 22:00 h (3.20 +/- 0.18) was significantly different from the means obtained at the rest of the times. The 24-h mean labelling index (labelled cells/100 cells) was 2.48 +/- 0.47 for three subjects who volunteered samples at all six time periods. The labelling index obtained around the middle part of the day for all subjects (2.44-2.59) appears to be representative of a 24-h basal or reference value.

Oral mucosal appearance is unchanged in healthy, different-aged persons

Oral mucosal status in 182 different-aged, healthy, community-dwelling persons was evaluated. Ninety-four men and 88 women, ranging in age between 20 and 95 years, participated in this study. Oral mucosal status was assessed according to both subjective complaints and a semiquantitative clinical rating scale. No changes in either criterion were detected with increasing age. Oral mucosal status of the older subjects of this study was comparable to that found in a previous study with a randomly enrolled, noninstitutionalized older population in Iowa. The results of this study suggest that aging per se does not lead to changes in the appearance of oral mucosa.

The oral mucosal punch biopsy: indications and technique

The indications for advantages and disadvantages of the punch biopsy technique in the diagnosis of oral mucosal disease are discussed. The punch biopsy is recommended for use by the general practitioner as a simple, fast, inexpensive, and safe procedure for the diagnosis of oral mucosal lesions.

Rates of epithelial cell proliferation in the oral mucosa and skin of the tamarin monkey (Saguinus fuscicollis)

Epithelial cell proliferation was determined in skin and various regions of the oral cavity of the tamarin monkey and was expressed by means of two mitotic indices: the number of metaphases per mm of epithelial surface, and the number of metaphases per mm basement membrane. A significant correlation was obtained between the rank ordering of the different regions according to each index. Generally, the non-keratinized tissues of the oral cavity had mitotic rates higher than those of the keratinized oral regions, with the epidermis having the lowest value. The mitotic index also correlated significantly with epithelial thickness, with the thicker regions showing a higher rate of proliferation. These results represent the first comprehensive set of values for a primate and are in general agreement with data obtained from non-primate species; the values support the concept that the oral lining tissue turns over more rapidly than does the masticatory mucosa (Bhaskar, 1980).