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Biomedical subjects

Yukio Takizawa

Publications and source records attributed to Yukio Takizawa.

5 recordsLinked to original sources
PubMed2003

Health effects from stratospheric ozone depletion and interactions with climate change.

The potential health effects of elevated levels of ambient UV-B radiation are diverse, and it is difficult to quantify the risks, especially as they are likely to be considerably modified by human behaviour. Nevertheless epidemiological and experimental studies have confirmed that UV radiation is a definite risk factor for certain types of cataract, with peak efficacy in the UV-B waveband. The causal link between squamous cell carcinoma and cumulative solar UV exposure has been well established. New findings regarding the genetic basis of skin cancer, including studies on genetically modified mice, have confirmed the epidemiological evidence that UV radiation contributes to the formation of basal cell carcinomas and cutaneous melanomas, For the latter, animal models have demonstrated that UV exposure at a very young age is more detrimental than exposure in adulthood. Although suppression of certain immune responses has been recognised following UV exposure, the impact of this suppression on the control of infectious and autoimmune diseases is largely unknown. However, studies on several microbial infections have indicated significant consequences in terms of symptoms or reactivation of disease. The possibility that the immune response to vaccination could be depressed by UV-B exposure is of considerable concern. Newly emerging possibilities regarding interactions between ozone depletion and global climate change further complicate the risk assessments for human health but might result in an increased incidence of cataracts and skin cancer, plus alterations in the patterns of certain categories of infectious and other diseases.

Cataract↗
PubMed2003

Free water 3H concentrations in serum samples collected during 1969-1992 in Akita, Japan.

The measurements for human and environmental samples from the 1960's and 1970's are important to understand the long-term transfer of 3H from the environment to the human body. The authors have previously reported 3H concentrations in diet samples collected in Akita Prefecture during 1969-1988. Serum samples from persons living in Akita Prefecture during 1969-1992 were recently obtained. The samples were originally gathered for medical examinations and stored in freezers at -20 degrees C. Composite samples from 100 persons on average were made for analysis. The free water 3H (FWT) concentrations in those samples were determined and compared with 3H concentrations in diet samples and precipitation. The long-term variation pattern of the FWT concentrations in the serum samples was similar to patterns in the diet samples and precipitation, but the FWT concentrations in the serum samples were slightly higher than those in the latter two. A single compartment model calculation showed that the apparent mean residence time of serum FWT was 1.4 y using precipitation as an input to the compartment.

Adolescent↗
PubMed2003

Validation of ICRP metabolic models for the transuranics in a Japanese population.

Distributions of (239,240)Pu and 241Am in the tissues of Japanese were determined and then compared to those estimated using recent ICRP metabolic models. Intakes by inhalation and ingestion were calculated and used as input to the ICRP-30 model or a combination of the ICRP-66 lung model and the ICRP-67 metabolic model. The (239,240)Pu distribution in the lung, liver, skeleton, kidney, and muscle using the combination ICRP-66 and 67 models agreed well with the measured data. However, the measured plutonium concentration in the spleen was higher than predicted and than found in the kidney or muscle and indicates that the spleen should be treated as a separate organ in the ICRP model. The fractional uptake via ingestion of (239,240)Pu was estimated to be 11% with 5 x 10(-4) as the f1 value. The combination of ICRP-66 and 67 models were adequate descriptors of the organ burdens of 241Am measured in Akita and Niigata district populations. The 241Am ingrowth from 241Pu taken into in the human body contributes 90% of the measured burden.

Administration, Inhalation↗