Mugio Kato

Strong expression of glutathione S-transferase placental form in early preneoplastic lesions and decrease with progression in hamster buccal pouch carcinogenesis

The objective of this work was to investigate the expression of glutathione S-transferase placental form (GST-P) in 9,10-dimethyl-1,2-benzanthracene (DMBA)-induced hamster buccal pouch carcinogenesis. Lesions were classified histopathologically into four categories, simple hyperplasia, papillary and nodular (PN) hyperplasia, papilloma and squamous cell carcinoma (SCC). Respective mean percentage GST-P positive areas were 81.6 +/- 7.3%, 76.1 +/- 7.3%, 25.8 +/- 4.9% and 1.9 +/- 1.2%, with significant (P < 0.001) differences confirmed between each of the lesions. These results indicate that GST-P is a useful positive marker for neoplastic lesions and that a decreased expression occurs with progression so that it may be predictive of future development of malignancy.

Promotional effects of CO2 laser on DMBA-induced hamster buccal pouch carcinogenesis as shown by immunohistochemistry of the placental form of glutathione S-transferase

The purpose of the present study was to investigate the kinetics of the expression of the placental form of glutathione S‐transferase (GST‐P), a useful marker of premalignant lesions, and cell proliferation after CO2 laser surgery on the carcinogen‐initiated epithelium.

Effects of Carbon Dioxide Laser Vaporisation on Oral Precancerous Lesions: Promotional Effects for Malignant Transformation

Abstract Objective: To investigate the effects of carbon dioxide laser vaporisation on oral precancerous lesions. Materials and Methods: Oral precancerous lesions were induced in rat tongues by 4-nitroquinoline 1-oxide. Four types of surgical intervention were applied to the precancerous lesions: steel scalpel excision (group 2), electric scalpel excision (group 3), 1-time carbon dioxide laser vaporisation (group 4), and 3-time carbon dioxide laser vaporisation (group 5). The epithelium was incised and vaporised on suitable precancerous lesions in a crosswise pattern. The process of wound healing was evaluated histopathologically 16 weeks after wound initiation, and the results compared with a group receiving no treatment (group 1). Results: The incidence of cancer was lower in all surgical treatment groups than in the group receiving no treatment. However, both laser vaporisation groups tended to show a wider area of invasive cancer than the group receiving no treatment and the electric scalpel groups, and deeper invasion than the group receiving no treatment. Cancer invasion was significantly deeper in group 5 (p Conclusion: There is a risk of cancer promotion from the surviving epithelia if the oral pre cancerous lesions were not completely removed by laser therapy. Laser vaporisation involves a high risk for cancer promotion. Key words: Lasers, Precancerous conditions, Wound healing

Fundamental Studies on Tissue Reaction after Low Power Laser Irradiation

It is generally recognized that the lower power Nd: YAG laser provides some therapeutic effects on tissue without irreversible changes. On the other hand, high power laser causes irreversible changes. The criterion about low and high power laser is, however, not established. The aim of this study is to verify the effect of lower and high power laser on wound healing of rat skin by measuring blood flow and histomorphologic findings with HE and SEM. Each laser were irradiated to the center of 6mm round full-thickness skin defect at the back of the rat at either (1) 300mW×3min, (2) 500mW×3min, (3) 700mW×3min, (4) 300mW×20min, (5) 500mw×20min, (6) 700mW×20min.The results obtained are as follows;1) The histological findings showed that irradiation time caused more tissue damage in the deeper layer, whereas irradiation power caused more damage to the surrounding tissue.2) Small craters were starred on the bottom of the damaged tissue by laser irradiation at 700 mW x 20min. The formation of these craters was related to the absorption of laser irradiation.3) On the irradiated area, blood volume decreased significantly as irradiation power increased. However, both blood flow and tissue damage increased as irradiation time increased. As for the surrounding tissue, the findings showed an increase in the blood flow and tissue damage as irra diation power increased.4) High power laser at 700mW caused tissue damage regardless of irradiation time. On the other hand, 500mW irradiation power caused minimum damage to the tissue. Therefore, the range between 300 to 500mW and the irraditation time over 3min to less than 20min are classified as a lower power laser.

The Effect of Low-Power Laser Irradiation

We postulated that low-power laser irradiation could produce analgesia, nerv ous activation, and enhancement of wound healing in association with changes in the microcirculation. In order to confirm this hypothesis, we monitored blood flow in rats be fore and after laser treatment. A Ga-Al-As semiconductor laser (wave length: 810nm) was used. Rats were treated at either (1) 300mW×3min, (2) 500mW×3min, (3) 700mW×3min, (4) 300mW×20min, (5) 500mW×20min, or (6) 700mW×20min. Blood flow was monitored in the dorsal skin before and after irradiation using a Laser-Doppler flowmeter. The peripheral circu lation was improved by 20min of irradiation with a 300mW or 500mW semiconductor laser without any irreversible tissue damage, and it was inferred that tissue restoration would result from this change. Different responses were produced depending on the irradiation condi tions, and this suggested that there is a safe range between transition from non effective to effective and from effective to irreversible damage. This range was considered to be the saf est and most effective for low-power laser treatment.