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Biomedical subjects

D Pollet

Publications and source records attributed to D Pollet.

11 recordsLinked to original sources
PubMed1999

Coenzyme Q10, a cutaneous antioxidant and energizer.

The processes of aging and photoaging are associated with an increase in cellular oxidation. This may be in part due to a decline in the levels of the endogenous cellular antioxidant coenzyme Q10 (ubiquinone, CoQ10). Therefore, we have investigated whether topical application of CoQ10 has the beneficial effect of preventing photoaging. We were able to demonstrate that CoQ10 penetrated into the viable layers of the epidermis and reduce the level of oxidation measured by weak photon emission. Furthermore, a reduction in wrinkle depth following CoQ10 application was also shown. CoQ10 was determined to be effective against UVA mediated oxidative stress in human keratinocytes in terms of thiol depletion, activation of specific phosphotyrosine kinases and prevention of oxidative DNA damage. CoQ10 was also able to significantly suppress the expression of collagenase in human dermal fibroblasts following UVA irradiation. These results indicate that CoQ10 has the efficacy to prevent many of the detrimental effects of photoaging.

Antioxidants↗
PubMed1998

Kinetics of DNA strand breaks and protection by antioxidants in UVA- or UVB-irradiated HaCaT keratinocytes using the single cell gel electrophoresis assay.

The aim of this study was to characterize the genotoxic action of UVA and UVB in human keratinocytes by application of the single cell gel electrophoresis assay (SCGE assay). Dose dependence of DNA damage, the time course of its repair, and the influence of cellular antioxidant status were assessed. Irradiation with UVA or UVB both resulted in a dose-dependent increase in the level of DNA damage. A time course study to evaluate the repair kinetics in keratinocytes irradiated with 5 J/cm2 UVA revealed an immediate occurrence of DNA effects which subsequently disappeared within about 1 h, indicating removal of DNA lesions. This rapid repair of DNA damage is consistent with the observation that 5 J/cm2 UVA did not impair cellular viability. In contrast, exposure to 15 mJ/cm2 UVB resulted in a prolonged repair of DNA damage which lasted about 25 h. Thus, the repair kinetics of UVA- and UVB-induced DNA damage clearly differed from each other, implicating the induction of different types of DNA lesions by UVA and UVB. Neither a pretreatment with Mg-ascorbyl phosphate or D,L-alpha-tocopherol, nor depletion of endogenous glutathione altered cellular sensitivity to UVB. In contrast, the DNA damaging effects of UVA could be counteracted by a pretreatment with these antioxidants. These observations confirm that the UVA-induced effects on DNA are related to radical mediated strand breaks and DNA lesions forming alkali-labile sites. The UVB-induced effects mainly occur as a consequence of excision repair-related strand breaks. The observed repair kinetics of DNA lesions and the influence of cellular antioxidant status may help to elucidate protective mechanisms against the carcinogenic effects of UV radiation present in sunlight.

Antioxidants↗
PubMed1995

[Seroprevalence of hepatitis C virus among persons visiting the Burundi health services].

The epidemiology of hepatitis C (HCV), especially on the African continent, is not well known. In this study, we investigated the presence of antibodies to HCV in 685 out-patients, seen in several health care centers or hospitals in different regions in Burundi from January to February 1991. Serological tests of the second generation were used. The global prevalence varied from 3.2% to 14.1% according to the center. Urban seroprevalence tended to be higher than rural prevalence. Also, with increasing age, a higher prevalence was observed. Anti-HCV antibodies were absent in patients younger than 21, while specific antibodies were detected in 23.1% of patients older than 50. Although the prevalence in men (10.4%) was higher than in women (7.4%), this difference was not statistically significant. Taking into account the selection of subjects participating in this evaluation, the results can not be extrapolated to the general population. No association between HCV and human immunodeficiency virus (HIV) was seen in this study. In contrast to previously described results from studies using reagents of the first generation, no cross-reactions were observed with anti-malarial antibodies.

Adolescent↗
PubMed1992

[Development and concept of a new operatory chair].

We present a novel type of operatory chair which directs an operation microscope by remote control using infrared beams: XV, zoom, focal and accessories. The advantage of this system is the absence of transmission cables, and consequently represents an important improvement in terms of flexibility. It is a vast improvement as well for maintaining sterile conditions in the operation room. The ergonomics of this chair was especially designed for microsurgery. The adjustment and stability of the forearm has been considerably improved.

Equipment Design↗
PubMed1985

Screening of sera and tumor extracts of cancer patients using a monoclonal antibody directed against human placental alkaline phosphatase.

A sensitive endogenous enzyme immunoassay involving an anti-human placental alkaline phosphatase (PLAP) monoclonal antibody was used in the screening of sera and tumor extracts of patients with various types of cancer. In sera of breast cancer patients an incidence of 5.2% was recorded. This value rose to 43% when tumor extracts were analyzed. For lung and bronchial cancers we found 11.2% seropositive patients. On several occasions a good correlation was observed between the PLAP determinations and the histopathological staging of tumor tissue.

Adult↗
PubMedDate not supplied

Analysis of UV-B-induced DNA damage and its repair in heat-shocked skin cells.

The heat-shock response is a cellular defence mechanism against environmental stresses that is evolutionarily conserved from bacteria to man. Numerous reports demonstrate the beneficial effects of heat-shock protein induction on cell survival under toxic or oxidative stress, e.g., in cardiac and cerebral ischemia or prior to organ transplantation. However, there is little data on the effects of heat treatment on damage caused by UV irradiation. Applying three independent techniques, we have tested the influence of thermal pretreatment of skin cells (1 h, 43 degrees C) on the initial extent of UV-B-induced DNA damage and its subsequent repair. For cultured human epidermal keratinocytes and dermal fibroblasts we can show reduced levels of nucleotide-excision-repair-associated DNA strand incision in the comet assay. Moreover, immunostaining and flow cytometric quantitation of thymidine dimers immediately and one day after irradiation, respectively, reveal that the initial DNA damage is not (keratinocytes) or only moderately (fibroblasts) lower in heat-shocked cells as compared to untreated controls. However, excision repair of dimers is significantly attenuated during the first 24 h in both cell types. Furthermore, using a modified host-cell reactivation assay, we are able to demonstrate that repair of UV-B-damaged plasmid DNA is lower if the transfected cells are previously heat shocked. In summary, heat treatment (1 h, 43 degrees C) inducing heat-shock proteins reduces nucleotide excision repair of UV-B-mediated DNA lesions in fibroblasts and keratinocytes during the following 24 h. This is not necessarily caused by elevated heat-shock protein levels themselves. Possibly the direct thermal damage of repair enzymes is more severe than the potential protective effects of heat-shock proteins.

Adult↗