Emiko Matsumoto

Structure of retinular cells in a Drosophila melanogaster visual mutant, rdgA, at early stages of degeneration

SummaryA Drosophila visual mutant rdgA has photoreceptive cells which degenerate gradually after eclosion. Fine structure of the retinular cells of rdgAKS60and rdgAK014 was studied during early stages of degeneration to determine the initial morphological defects. The retinular cells of these two alleles showed the following structural abnormality within 1 day after eclosion: (1) rhabdomeres were small and irregular in shape; (2) cisternae of the rough endoplasmic reticulum were more numerous than those in normal retinular cells; (3) submicrovillar cisternae were absent; and (4) lysosomes were fewer than normal. Three-dimensional reconstruction of serial sections of the ommatidia showed that the degeneration of mutant rhabdomeres proceeds more rapidly in regions remote from the nuclei. These results suggest that the process of turnover of rhabdomeric microvilli is abnormal in rdgA. We also confirmed an increase of lysosomes and destruction of cellular organelles, as reported by previous investigators at more advanced stages of degeneration.

Bioremediation of the organochlorine pesticides, dieldrin and endrin, and their occurrence in the environment.

Dieldrin and endrin are persistent organic pollutants that cause serious environmental problems. Although these compounds have been prohibited over the past decades in most countries around the world, they are still routinely found in the environment, especially in the soil in agricultural fields. Bioremediation, including phytoremediation and rhizoremediation, is expected to be a useful cleanup method for this soil contamination. This review provides an overview of the environmental contamination by dieldrin and endrin, along with a summary of our current understanding and recent advances in bioremediation and phytoremediation of these pollutants. In particular, this review focuses on the types and abilities of plants and microorganisms available for accumulating and degrading dieldrin and endrin.

Estimation of the contribution of ultrafine particles to lung deposition of particle-bound mutagens in the atmosphere

The present study was performed to estimate the contributions of fine and ultrafine particles to the lung deposition of particle-bound mutagens in the atmosphere. This is the first estimation of the respiratory deposition of atmospheric particle-bound mutagens. Direct and S9-mediated mutagenicity of size-fractionated particulate matter (PM) collected at roadside and suburban sites was determined by the Ames test using Salmonella typhimurium strain TA98. Regional deposition efficiencies in the human respiratory tract of direct and S9-mediated mutagens in each size fraction were calculated using the LUDEP computer-based model. The model calculations showed that about 95% of the lung deposition of inhaled mutagens is caused by fine particles for both roadside and suburban atmospheres. Importantly, ultrafine particles were shown to contribute to the deposition of mutagens in the alveolar region of the lung by as much as 29% (+S9) and 26% (-S9) for the roadside atmosphere and 11% (+S9) and 13% (-S9) for the suburban atmosphere, although ultrafine particles contribute very little to the PM mass concentration. These results indicated that ultrafine particles play an important role as carriers of mutagens into the lung.

Development of the vitamin A-storing cell in mouse liver during late fetal and neonatal periods

SummaryVitanim A-storing cells in perinatal mouse liver were studied by chemical and autoradiographic analyses of exogenous vitanim A. The amount of retinyl palmitate in the fetal liver increased significantly following oral administration of retinyl acetate to the mother, suggesting the existence of storage sites of the vitanim in fetal liver. Light microscope semi-serial autoradiography of the fetal liver on the 15th day of gestation showed that 3H-vitamin A administered to the mother was incorporated into cells distributed exclusively along the hepatic blood vessels and the blood islands. Mitotic figures of the labeled cells were frequently observed. Electron microscope autoradiography revealed that the vitamin was incorporated into lipid droplets, rough endoplasmic reticulum and Golgi apparatus of the fibroblast-like cells in close apposition to the endothelial cells. The labeled cells differed in their ultrastructure from the vitamin A-storing cells (Ito cells) of the adult liver. In the later gestational period, silver grains tended to be more concentrated in lipid droplets, and the cytological features of the labeled cells became similar to those of the vitamin A-storing cells. Both retinyl palmitate content and the labeling of lipid droplets increased rapidly in the liver of neonates after commencement of suckling. The labeled cells had the same appearance as the vitamin A-storing cells (Ito cells). It is concluded that vitamin A transported across the placenta is taken up in the fetal liver by the cells distributed along the blood vessels, and that these cells proliferate in accordance with vascular development and gradually take on the characteristics of vitamin A-storing cells during the perinatal period. A defensive role of the vitamin A-storing cell against the toxic effects of vitamin A is also suggested.

Morphological and functional development of plasma membranes of mouse hepatocytes: An autoradiographic study of asialoglycoprotein uptake during the postnatal period

The morphological development of the postnatal mouse liver was studied with reference to the specialization of sinusoidal plasma membranes of hepatocytes. Numerous hemopoietic islands were distributed at random among hepatocytes at neonatal stages. The hemopoietic fronts of hepatocytes were flat and showed few structures indicating endocytotic and exocytotic activities. They gradually acquired structural characteristics of the sinusoidal region as the processes of the endothelial cells extended in the space between hemopoietic cells and hepatocytes. The degree of attenuation and fenestration of the sinusoidal endothelial cells increased as the postnatal day advanced. In the course of these changes, microvilli, pinocytotic pits, and vesicles of sinusoidal regions of hepatocytes increased as well. The functional development of sinusoidal regions of hepatocytes was investigated by the quantitative analysis of autoradiograms of [3H]asialoorosomucoid (ASOR). Silver grains were distributed only in the regions where the structural specializations of the sinusoidal region were observed. They increased as the maturation of sinusoidal structure advanced. These results suggest that the sinusoidal regions of hepatocytes specialize structurally and functionally, as regards ASOR-uptake capability, in correlation with the structural establishment of sinusoids.