Narrow Results

A method of quantitative elemental analysis of mosquitoes which convey serious infectious diseases, such as Japanese encephalitis and Dengue fever, has been developed in order to clarify their mode of life and sphere of action. The method was developed on the basis of a standard-free method for biological samples. The method enables us to perform quantitative analysis of untreated mosquito. Moreover, the method was successfully applied to quantitative analysis of each part of mosquito's body such as head and chest, abdomen, leg and wing. It was found that there are clear differences among parts in the body of mosquito, and also among different species such as Culex tritaeniorhynchus and Aedes albopictus. The method was successfully applied to quantitative analysis of small fly belonging to Sciaridae (Bradysia.praecox) whose size is smaller than that of mosquito. It was also confirmed that the method is applicable to other kind of bio-samples of small quantities such as a grain of egg of Alaska pollock whose dry weight is less than 100 μg.

In this paper, methods of quantitative elemental analysis of very small quantity of cultured cells were developed. First of all, an internal-standard method for the solution containing cells whose density is more than 1 × 10⁶ cells/mL was established and then a standard-free method for cultured cells was developed. It was confirmed that the method allows us to quantitatively analyze more than 25 elements in the samples containing only 20,000 cells. Also, the methods for removing cultured cells from a flask were examined in order to improve accuracy and sensitivity of analysis since the use of trypsin and PBS sometimes brings a large amount of sodium, phosphorus and potassium, which have direct effect upon accuracy of analysis based on the standard-free method. It was found that the method of removing cells with a scraper without using trypsin and PBS is the best manner. Also, the effects of using thinner backing materials were examined in order to improve sensitivity of analyses. It is expected that accurate analysis of samples containing nearly two thousand cells is possible on the basis of the standard-free method when using a thinner backing material.

We developed a standard-free method for untreated hairs and the method has been applied to quantitative analysis of more than 30,000 hairs taken from the people concerned in order to evaluate exposure to some toxic elements and intakes of essential elements. Besides these analyses, we have measured nearly 2000 hairs collected from healthy people in Japan over the past 20 years. It was found that concentrations of some elements, such as vanadium, chromium, manganese, copper and mercury, keep increasing up to the present. Such tendencies were particularly notable for female, while not clearly observed for male. Concentrations of some essential elements, such as calcium, magnesium and zinc, show no obvious long-term variations. On the other hand, iron and selenium show slightly decreasing tendencies. With regard to toxic elements, it was found that arsenic, chromium and mercury are tending to increase year by year.

A standard-free method for untreated hairs has been applied to quantitative analysis of the hairs taken from 1256 healthy people living in the Iwate prefecture, Japan. It was found that there are clear sex-specific differences in the concentration of some elements. Concentrations of many essential elements, such as calcium, magnesium, iron, copper, zinc and bromine, are clearly higher for female. In particular, calcium concentration is 2.6 times higher for female in comparison with that for male. Contrarily, concentrations of some toxic elements such as chromium, arsenic and mercury are higher for male. On the other hand, concentrations of many elements vary with age. Those of calcium, magnesium and zinc start to increase in the middle of teens and reach maximum in the middle of twenties for female. Mercury concentration increases as the ages advance, while those of chromium, arsenic and lead show no clear changes with age.

More than 4000 beard samples were collected from a single person every morning over a 12-year period and analyzed using a standard-free method. We detected significant annual variations in the concentrations of magnesium and calcium in the study period, although significant monthly and seasonal variations were not noted. Calcium tends not to be obtained from season-specific foods or drinks, so its variations may be affected by changes in the metabolism of the body. In contrast, however, potassium showed marked long-term variations with significant seasonal differences. As our previous studies confirmed that green vegetables contain large quantities of potassium and that their supply and consumption increase from May to July, the seasonal variations in potassium concentration were attributed to the ingestion of green vegetables. Although magnesium is also contained in green vegetables in large quantities, its principle supply sources are diverse and its concentration did not show any clear seasonal changes.