Hisayo Kubota

Dietary exposure to low doses of bisphenol A: effects on reproduction and development in two generations of C57BL/6J mice.

The present study was conducted to examine the effects of low‐dose exposure to bisphenol A on reproduction and development in two generations of mice. Pregnant female C57BL/6J mice (F0) were fed a diet containing low doses of bisphenol A (0, 0.33, 3.3, or 33 ppm) from gestational day 6 through postnatal day 22, and the weanlings (F1 and F2) from each F0 and F1 dam group, respectively, were also fed these same concentrations of bisphenol A ad libitum until sacrifice. There were no treatment‐related changes in body weight, body weight gain, food consumption, gestation length, or the number of live births on postnatal day 1 in F0 dams between the control group and bisphenol A groups. Sex ratio and viability were similar in all F1 pups. No treatment‐related changes were observed in body weight, food consumption, developmental parameters, anogenital distance, or weight of any of the organs (liver, kidney, heart, spleen, thymus, testis, ovary, or uterus) in F1 and F2 adults in either sex. The epididymis weight was slightly higher with 0.33 and 3.3 ppm in F1 males, but this slight increase was neither dose dependent nor seen across generations. There were no treatment‐related effects of bisphenol A on cauda epididymal sperm count or sperm motility in F1 or F2 males. These findings indicate that dietary exposure to bisphenol A between 0.33 and 33 ppm does not adversely affect reproduction or development as assessed in two generations of mice.

Intratracheal Instillation Methods and the Distribution of Administered Material in the Lung of the Rat

Intratracheal instillation is widely used for respiratory toxicity tests in experimental animals. However, there are wide variations in the techniques used for instillation, and it is thus difficult to compare the results obtained using different techniques. To examine the effect of instillation methods, we compared the distribution of a test substance in the lungs of rats after intratracheal instillations under various conditions. Rats received an intratracheal instillation of 0.3 mL of india ink suspension under different conditions as follows: 3 different angles of body restraint, 0° (supine horizontal), 45° (supine head up) and 90° (vertical head up); 2 instillation speeds, high (40 mL/min) and low (4 mL/min); and 2 different devices, a standard bulb-tipped gavage needle and an aerosolizing microsprayer designed for intratracheal instillation. One hour after treatment under these various conditions, rats were sacrificed, and the local distribution of the suspension in the lungs was observed. No animal restrained in the supine head-up or vertical head-up position died from the treatment; however, fatalities were observed when rats were restrained in the supine horizontal position except under high-speed dosing conditions with a microsprayer. Better distribution of the suspension in the lungs was observed in the rats restrained in the supine head-up position after instillation at high speed when compared with other conditions. These results indicated that high-speed instillation to the subject restrained in the supine head-up position is an appropriate condition for performing intratracheal instillation.

Approach to the Exposure Assessment of MWCNT by Considering Size Distribution and Oxidation Temperature of Elemental Carbon

Multi-walled carbon nanotubes (MWCNTs) have many beneficial characteristics, but it is concerned that exposure to MWCNTs may pose health risks. As an approach to the quantitative exposure assessment of MWCNTs, we have characterized and determined MWCNTs by elemental carbon (EC) using an aerosol carbon monitor. The EC fractions oxidized at different temperatures correspond sample characteristic such as diameter of MWCNT or origins of particles. As MWCNTs aggregate/agglomerate easily, they are usually observed as micron-size particles. Whereas, EC contained in ambient particulate matter (APM) is mainly observed in fine particles. Therefore, the size of airborne particles is a good parameter to distinguish MWCNT from other carbonaceous particles, especially APM. The size and oxidized temperature of EC suggested the origin of the carbonaceous aerosol samples. Exposure assessment of MWCNT was conducted by utilizing the size distribution of EC in the environment where particulate MWCNT or MWCNT-containing composite was handled. A procedure for exposure assessment of MWCNT-related workplace is proposed.

Expression of cytokines and proteases in mast cells in the lesion of subcapsular cell hyperplasia in mouse adrenal glands.

To examine the possible roles of mast cells in the pathogenesis of subcapsular cell hyperplasia (SCH) in the adrenal glands of mice, we investigated the expression of certain cytokines, including stem cell factor (SCF), tumor necrosis factor-alpha (TNF-α), nerve growth factor (NGF), and basic fibroblast growth factor (bFGF), and mast cell-specific proteases, such as mouse mast cell protease (mMCP)-2 and mMCP-7. The mRNAs of c-kit (SCF receptor), bFGF, TNF-α, mMCP-2, and mMCP-7 were expressed in both the adrenal glands and the mouse bone marrow-derived mast cells (mBMMCs). Immunoreactivities for cytokines (SCF, NGF, TNF-α) and proteases (mMCP-2, mMCP-7) were exclusively located in the mast cells in SCH lesions. The immature mBMMCs did not express the mRNAs of SCF and NGF, whereas the mast cells in the SCH lesions showed the expression of SCF and NGF. These findings suggest that SCH may provide a favorable microenvironment for functional maturation of mast cells to produce SCF and NGF, and the mast cells in SCH lesions synthesize SCF and NGF and may, in part, use them in autocrine fashion for their survival and differentiation. Therefore, mast cells may contribute to SCH pathogenesis by producing a range of multifunctional cytokines and proteases.

Identification of a quantitative trait locus regulating B cell-dominant infiltration into autoimmune sialitis lesions of the IQI mouse model of primary Sjögren's syndrome.

Sjögren’s syndrome (SS) is caused by an autoimmune sialodacryoadenitis, and up to 5% of patients with SS develop malignant B cell growth. The IQI mouse is a spontaneous model of primary SS in which B cells are the dominant cellular subpopulation among mononuclear infiltrates in sialitis lesions. Understanding the genetic control of aberrant B cell growth in IQI mice may help elucidate the genetic mechanisms involved in B-lineage hyperplasia leading to malignant transformation in human SS. B cell-dominant infiltration in the submandibular glands of 6-month-old IQI and C57BL/6 (B6) mice and their F1 and F2 progenies was quantified as B-lymphocytic sialitis score, and a genome-wide scan of 179 (IQI x B6) F2 females was performed to identify a quantitative trait locus (QTL) controlling this phenotype. A QTL significantly associated with variance in B-lymphocytic sialitis score was mapped to the D6Mit138 marker (position of 0.68cM) on proximal chromosome 6, with a logarithm of odds score of 4.3 (p = 0.00005). This QTL, named autoimmune sialitis in IQI mice, associated locus 1 (Asq1), colocalized with Islet cell autoantigen 1 (Ica1), which encodes a target protein of the immune processes that define the pathogenesis of primary SS in humans and in the nonobese diabetic mouse model.