Tomohiko Murase

Calcium-bindings of wild type and mutant troponin Cs of Caenorhabditis elegans

Apparent Ca(2+)-binding constant (K(app)) of Caenorhabditis elegans troponin C (CeTnC) was determined by a fluorescence titration method. The K(app) of the N-domain Ca(2+)-binding site of CeTnC was 7.9+/-1.6 x 10(5) M(-1) and that of the C-domain site was 1.2+/-0.6 x 10(6) M(-1), respectively. Mg(2+)-dependence of the K(app) showed that both Ca(2+)-binding sites did not bind competitively Mg(2+). The Ca(2+) dissociation rate constant (k(off)) of CeTnC was determined by the fluorescence stopped-flow method. The k(off) of the N-domain Ca(2+)-binding site of CeTnC was 703+/-208 s(-1) and that of the C-domain site was 286+/-33 s(-1), respectively. From these values we could calculate the Ca(2+)-binding rate constant (k(on)) as to be 5.6+/-2.8 x 10(8) M(-1) s(-1) for the N-domain site and 3.4+/-2.1 x 10(8) M(-1) s(-1) for the C-domain site, respectively. These results mean that all Ca(2+)-binding sites of CeTnC are low affinity, fast dissociating and Ca(2+)-specific sites. Evolutional function of TnC between vertebrate and invertebrate and biological functions of wild type and mutant CeTnCs are discussed.

Kinetic analysis on nitric oxide binding of recombinant Prolixin-S, a nitric oxide transport protein from the bloodsucking bug, Rhodnius prolixus

Kinetics of the NO binding and removal reaction of recombinant Prolixin-S (rProlixin-S) were analyzed using stopped-flow spectrophotometry. The reaction was observed as a biphasic process. The rate constant of the fast phase increased linearly as NO concentration increased. The rate constant at the slow phase increased as NO concentrations increased at low NO concentration, then reached a plateau at high NO concentration. These NO dependencies of the reaction are characteristic of a bimolecular two-step consecutive reaction. The reaction consisted of the fast NO binding reaction of rProlixin-S and the following slow structural change of NO-protein complex. Kinetic studies revealed that the NO binding rate constant was independent of pH, but the rate constant of the NO removal reaction increased as pH increased. The apparent NO dissociation constant (Kd) of rProlixin-S was also calculated from the values of the kinetic parameters obtained in this work. The Kd value increased as pH and temperature increased. The Kd value of rProlixin-S and NO was 10-300 nM in regular physiological condition, which is 103 higher and 103 lower than those of the other ferric and ferrous hemoproteins and NO, respectively. These results indicate that Prolixin-S is one of NO transport proteins regulating blood pressure.

Follicle dynamics: visualization and analysis of follicle growth and maturation using murine ovarian tissue culture

PurposeTo visualize and analyze follicle development in ovarian tissue culture using physiological concentrations of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in order to establish an ovarian tissue culture system that enables efficient in vitro growth of follicles.MethodsOvarian tissues from 4-week-old female ICR mice were sliced and cultured. Images of ovarian tissues in culture were obtained at 24-h or 30-min intervals by using a microscope. The area of each follicle observed in the ovarian tissue slices was tracked and analyzed in association with oocyte maturation.ResultsWe were able to track the development of each follicle using this culture system. Follicle growth was associated with oocyte maturation. Meiotically matured oocytes (MII) were obtained from 33% of all follicles investigated. Approximately, a quarter of follicles (24%) did not grow and resulted in atresia.ConclusionFollicle dynamics were successfully visualized and analyzed in murine ovarian tissue culture. We were able to obtain mature oocytes from the fully grown follicles in vitro. This culture system would be helpful for efficient in vitro culturing of ovarian tissues.

Protective effects of mangafodipir against chemotherapy-induced ovarian damage in mice

BackgroundGiven the seriousness of chemotherapy-induced ovarian injury in female cancer patients, the preservation of fertility, including through the use of cryopreservation technology and pharmaceuticals, requires investigation. Previous studies have shown that damage to the ovaries is related to oxidative stress caused by anticancer drugs. Therefore, superoxide dismutase (SOD) may represent a key factor in the pharmacological protection of the ovaries. The aim of our study was to identify the effects of mangafodipir, a manganese chelate and SOD-mimetic, on suppression of apoptosis in granulosa cells and primordial follicle activation induced by anticancer drugs.MethodsCell viability assays using methyltrichlorosilane solutions and immunoblotting for cleaved caspase-3 were performed in in vitro experiments with the simultaneous addition of mangafodipir to human non-luteinized granulosa cell line (HGrC) cultures treated with hydrogen peroxide (H2O2), cisplatin, or paclitaxel. Count and morphological analyses of follicles at each developing stage in the ovaries and immunohistochemistry for cleaved caspase-3, Ki67 and 4-hydroxynonenal, a marker for oxidative stress, were also performed using mangafodipir-injected 6-week-old female ICR mice treated with cisplatin or paclitaxel. Further, mangafodipir was injected into 6-week-old female BALB/c mice inoculated with ES-2 to analyze whether mangafodipir inhibits the anti-tumor effects of cisplatin or paclitaxel treatment.ResultsMangafodipir attenuated apoptosis induced by H2O2 and anticancer drugs in vitro. Mangafodipir also decreased the expression of 4-hydroxynonenal and reduced cisplatin- and paclitaxel-induced apoptosis in granulosa cells in vivo. In addition, mangafodipir inhibited the loss of primordial follicles. Tumor xenograft studies in mice showed that mangafodipir did not affect anticancer drug antitumor effects.ConclusionsOxidative stress might be one of the mechanisms of cisplatin- and paclitaxel-induced the loss of primordial follicles. Mangafodipir can reduce cisplatin- and paclitaxel-induced apoptosis in granulosa cells and primordial follicle activation partially via its SOD activity. At the same time, mangafodipir might have other potential mechanisms to inhibit the activation of primordial follicles. Further, mangafodipir attenuated the ovarian damage caused by cisplatin and paclitaxel without affecting their antitumor activities. Mangafodipir, therefore, though its efficacy might be limited, may be a new option for the preservation of fertility during anticancer treatment.

Ovarian Tissue Culture to Visualize Phenomena in Mouse Ovary

Mammalian females periodically ovulate an almost constant number of oocytes during each estrus cycle. To sustain such regularity and periodicity, regulation occurs at the hypothalamic-pituitary-gonadal axis level and on developing follicles in the ovary. Despite active studies, follicle development mechanisms are not clear because of the several steps involved from the dormant primordial follicle activation to ovulation, and because of the regulation complexity that differs at each follicular stage. To investigate the mechanisms of follicle development, and the dynamics of follicles throughout the estrus cycle, we developed a mouse ovarian tissue culture model that can be used to observe follicle development using a microscope. Systematic follicle development, periodical ovulation, and follicle atresia can all be reproduced in the cultured ovary model, and the culture conditions can be experimentally modulated. Here, we demonstrate the usefulness of this method in the study of the regulatory mechanisms of follicle development and other ovarian phenomena.

Clinical application of serum anti‐Müllerian hormone as an ovarian reserve marker: A review of recent studies

It has been more than 15 years since the measurement of serum anti‐Müllerian hormone (AMH) first allowed the quantitative assessment of ovarian reserve. Meanwhile, the clinical implication of serum AMH has been expanding. The measurement of serum AMH has been applied in various clinical fields, including assisted reproduction, menopause, reproductive disorders and assessment of ovarian damage/toxicity. Well‐known findings about the usefulness of serum AMH revealed by numerous studies executed in the early era include decline with aging, a good correlation with oocyte yield in assisted reproduction, upregulation in polycystic ovarian syndrome and a decrease on ovarian surgery and toxic treatment. More intensive research, including a meta‐analysis, cutting‐edge clinical trial and advances in AMH assays, has yielded newer findings and firmer clinical interpretations in serum AMH in the past few years. Variations in the AMH decline trajectory in the general population do not support the accurate prediction of menopause. The ability to predict pregnancy in infertility treatment and natural conception is poor, while a nomogram integrating serum AMH as a stimulation protocol is useful for avoiding poor and/or hyper‐responses. On the other hand, improvements in measuring very low concentrations of serum AMH may be capable of distinguishing women with poor ovarian function. Age‐independent standardization of AMH values may be helpful for comparing ovarian reserves among women at different ages.

The Regulation of Ovarian Follicular Growth by Anti-Müllerian Hormone

Abstract: Anti-Müllerian hormone (AMH) was originally discovered as the factor responsible for the regression of the Müllerian duct during male sexual differentiation. Through studies of AMH knockout mice, AMH has also been found to regulate primordial follicle recruitment and FSH-dependent cyclic recruitment. However, the details of how AMH influences follicular growth have not been elucidated. Since the early 2000s, when serum AMH concentration was found to be a reliable biochemical marker of ovarian reserve, AMH has been in the spotlight in reproductive medicine. Several studies of AMH have led to new insights on the mechanism of AMH-regulated follicular growth. Here, we review from the earliest studies to the latest findings, AMH regulation of follicle growth with reference to the potential clinical uses of AMH and AMH inhibitors.

Thyroid Autoantibodies do not Impair the Ovarian Reserve in Euthyroid Infertile Women: A Cross-Sectional Study

Patients with primary ovarian insufficiency (POI) have a high prevalence of thyroid autoimmune disorders. However, the extent of the contribution of thyroid autoantibodies or elevated thyroid-stimulating hormone (TSH) levels to decreased ovarian reserve is unclear. Therefore, we evaluated the serum levels of anti-Müllerian hormone (AMH) and thyroid autoantibodies [antithyroperoxidase antibody (TPOAb), and antithyroglobulin antibody (TgAb)] in euthyroid infertile women. One hundred and fifty-three women with normal menstrual cycles were recruited for this retrospective study. Serum levels of AMH were compared between patients with positive and negative thyroid autoantibodies. The correlation between serum levels of AMH and each thyroid autoantibody was also evaluated. Participants were observed to be either TPOAb or TgAb positive (n=27), only TPOAb positive (n=8), only TgAb positive (n=7), TPOAb and TgAb positive (double positive; n=12), and TPOAb and TgAb negative (double negative; n=126). No significant differences were found in serum AMH levels between the TPOAb- or TgAb-positive women and the antibody-double negative women. Serum AMH levels did not show a significant correlation with the concentration of TgAb or TPOAb. On the other hand, serum AMH levels negatively correlated with TSH levels in patients who were either positive for TPOAb or TgAb. Thyroid autoantibodies are not likely to influence ovarian reserve in euthyroid women whose TSH levels fall within the normal range although elevated TSH levels may be involved in the decline of serum AMH levels.