Biomedical subjects

Katsuhiko Takahashi

Publications and source records attributed to Katsuhiko Takahashi.

8 recordsLinked to original sources

PubMed2006

Adiponectin plays an important role in efficient energy usage under energy shortage.

Adiponectin is an adipose tissue-specific secretory protein known to be an insulin-sensitizing protein. In this study, we generated adiponectin sense and antisense transgenic (Tg) mice to investigate whether adiponectin plays a role in the regulation of energy homeostasis during the growth stage. Spontaneous motor activity of antisense Tg mice were markedly reduced during fasting, particularly in young female mice, compared with wild type (Wt) and sense Tg mice. Furthermore, both body weight and adipose tissue mass of the antisense female Tg mice drastically reduced during fasting. To examine the relationship between the collapse of abdominal white adipose tissue (WAT) and serum adiponectin level, we measured the expression of genes related to energy expenditure, such as uncoupling protein (UCP). Notably, the mRNA of UCP1 in the WAT of antisense Tg female mice was markedly less than that of Wt mice and the UCP1 mRNA was strongly increased during fasting. These findings suggest that the serum adiponectin is important to maintaining energy homeostasis under energy shortage conditions, such as over female pubertal development.

Adiponectin↗

PubMed2005

Perinatal outcome of blastocyst transfer with vitrification using cryoloop: a 4-year follow-up study.

OBJECTIVE: To evaluate perinatal outcome of ultrarapid vitrified blastocyst transfer. DESIGN: Retrospective study. SETTING: Private IVF clinics. PATIENT(S): One hundred eight women, who delivered 147 babies. INTERVENTION(S): Supernumerary blastocysts were vitrified using cryoloop method and transferred after warming. MAIN OUTCOME MEASURE(S): Survival rate of blastocyst after vitrification, implantation and pregnancy rates, neonatal outcome and congenital birth defects. RESULT(S): A total of 1,129 vitrified blastocysts from 435 cycles were warmed and 967 survived (85.7%). In 413 cycles of transfer, the pregnancy, implantation, and abortion rates were 44.1%, 29.0%, and 22.0%, respectively. Of 108 deliveries, 34 (32.9%) were multiple pregnancies and 20 were preterm (18.5%). Out of 147 children born, 50.3% were male and congenital birth defects were observed in 1.4%. These results were similar with those of fresh blastocyst transfer program. CONCLUSION(S): The vitrification of blastocyst using cryoloop is a simple, easy, and quick method. This technique yields the same high pregnancy and implantation rates as fresh blastocyst transfer. Congenital defect rate in this study was similar to fresh blastocyst transfer, proving the method to be safe.

Adult↗

PubMed2004

GnRH antagonist improved blastocyst quality and pregnancy outcome after multiple failures of IVF/ICSI-ET with a GnRH agonist protocol.

BACKGROUND: To determine the efficacy of a gonadotrophin-releasing hormone (GnRH) antagonist, cetrorelix, in improving the quality of embryos and pregnancy outcome, we performed a study in patients with a history of multiple failures of in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) cycles with a GnRH agonist (GnRHa) long protocol. METHODS: Forty women with no live births after conventional IVF or ICSI embryo transfer (ET) and subsequent blastocyst transfer (BT) with a GnRHa long protocol entered this study. The treatment protocol consisted of a daily dose of clomiphene citrate 100 mg for 5 days and gonadotrophin injections daily from cycle day 4 onward. Cetrorelix, 0.25 mg/day, was started when the leading follicle reached 14 mm. Induction of ovulation was triggered with human chorionic gonadotrophin (HCG) (N = 36) or GnRHa (N = 4). It was possible to perform BT in 38 patients. RESULTS: Comparison of the results with the results for BT with the previous GnRHa protocol showed no significant differences in number of oocytes retrieved or the zygote- and blastocyst-development rate. With the cetrorelix protocol, however, number of patients whose embryos had developed to at least one expanded blastocyst on day 5 was significantly higher than with the GnRHa protocol (25 vs. 9) (p < 0.001), and 16 of the women became pregnant (42.1%), with 7 delivering 9 infants, 4 ending in abortion (25%), and 5 in progressing. CONCLUSIONS: The use of a GnRH antagonist in controlled ovarian hyperstimulation improves the outcome of pregnancy of patients with a history of multiple failure of IVF/ICSI-ET in a GnRHa protocol, most likely due to improvement of the quality of the blastocysts generated.

Adult↗

PubMed2003

p57KIP2 modulates stress-activated signaling by inhibiting c-Jun NH2-terminal kinase/stress-activated protein Kinase.

p57KIP2, a member of the Cip/Kip family of enzymes that inhibit several cyclin-dependent kinases, plays a role in many biological events including cell proliferation, differentiation, apoptosis, tumorigenesis and developmental changes. The human p57KIP2 gene is located in chromosome 11p15.5, a region implicated in sporadic cancers and Beckwith-Wiedemann syndrome. We here report that p57KIP2 physically interacts with and inhibits c-Jun NH2-terminal kinase/stress-activated protein kinase (JNK/SAPK). The carboxyl-terminal QT domain of p57KIP2 is crucial for the inhibition of JNK/SAPK. Overexpressed p57KIP2 also suppressed UV- and MEKK1-induced apoptotic cell death. p57KIP2 expression during C2C12 myoblast differentiation resulted in repression of the JNK activity stimulated by UV light. Furthermore, UV-stimulated JNK1 activity was higher in mouse embryonic fibroblasts derived from p57-/- mice than in the cells from wild-type mice. Taken together, these findings suggest that p57KIP2 modulates stress-activated signaling by functioning as an endogenous inhibitor of JNK/SAPK.

Animals↗

PubMed2003

Cellular localization of prolactin-releasing peptide receptors in the human pituitary.

The recently identified prolactin (PRL)-releasing peptide (PrRP) is the first hypothalamic peptide hormone found to operate as a ligand of an orphan receptor that specifically stimulates PRL production from the pituitary gland. However, its other biological functions remain unknown. Using immunohistochemistry, we examined the distribution of the PrRP receptor in various human tissues, as well as the precise localization of the PrRP receptor in the human normal pituitary. Among various tissues examined, PrRP receptor-immunopositive cells were detected only in the pituitary gland. A double immunohistochemical procedure was used to examine PrRP receptor-positive cells from ten normal human pituitary glands, and it was determined that numerous PrRP receptor-positive cells are also positive for adrenocorticotropic hormone (ACTH) but negative for PRL. Growth hormone-, beta-thyroid-stimulating hormone-, beta-follicle-stimulating hormone-, beta-luteinizing hormone- or alpha-subunit-positive cells did not test positive for the presence of PrRP receptors. Thus, we suggest that PrRP receptor and probably PrRP may play a regulatory role in ACTH secretion, rather than in the release of PRL from the human anterior pituitary. This is the first report to demonstrate colocalization of the PrRP receptor and ACTH by immunohistochemistry.

Animals↗

PubMed2003

Blastocyst cryopreservation: ultrarapid vitrification using cryoloop technique.

Human embryos have been cryopreserved mainly by slow freezing, but vitrification has also proven effective for embryos at early cleavage stages. However, clinical results on blastocyst cryopreservation have not been consistent. A feasible option appears to be ultrarapid vitrification, in which embryos are vitrified with a reduced amount of solution to achieve extremely high rates of cooling and warming. The cryoloop is a tiny nylon loop connected to the lid by a small metal tube; a metal insert on the lid enables the use of a stainless steel handling rod with a small magnet, and the loop can be stored in the cryovial. In the HART Clinic group, of 444 supernumerary human blastocysts that were vitrified by cryoloops 79% survived after warming, and of 126 recipients 36% became pregnant. The outline of ultrarapid vitrification using cryoloops is described.

Blastocyst↗

PubMed2002

Increased expression of vascular endothelial growth factor in placentas of p57(Kip2) null embryos.

Placentas of mice lacking p57(Kip2) expression have trophoblastic hyperplasia. To elucidate the mechanism underlying this phenomenon, we studied expression of two angiogenic factors, vascular endothelial growth factor (VEGF) and placenta growth factor (PlGF). Immunohistochemical analysis with anti-VEGF antibodies indicated that VEGF expression was stronger and more clearly detectable in placentas of p57(Kip2) null embryos compared to wild-type placentas. PlGF showed no significant differences between placentas of p57(Kip2) null and wild-type embryos. In quantitative analysis, placentas of p57(Kip2) null embryos showed higher VEGF messenger (m)RNA and protein levels than did wild-type placentas. PlGF mRNA and protein levels were not significantly different. These findings suggest that VEGF is involved in the hyperplasia that occurs in placentas of p57(Kip2) null embryos.

Animals↗

PubMed2002

Deficiency in p57Kip2 expression induces preeclampsia-like symptoms in mice.

p57Kip2, a potent inhibitor of several cyclin/cyclin dependent kinase complexes (CDK ), is a paternally imprinted gene in both humans and mice, and here we show that pregnant mice which are heterozygous for p57Kip2 deficiency display symptoms similar to preeclampsia. p57-/+ (heterozygotes for p57Kip2 ) female mice that were mated with p57-/+ males showed hypertension, proteinuria, thrombocytopenia, decreased anti-thrombin III activity, and increased endothelin levels during late pregnancy. In their kidneys, endotheliosis of glomeruli were recognized along with fibrinoid or hyalinoid deposits. These characteristics were also observed in pregnant p57-/+ females that were mated with wild type males, but not in pregnant wild type females mated with p57-/+ males or wild type males. The pregnant p57-/+ mice had conceptuses both with and without p57Kip2 expression. The conceptuses without p57Kip2 expression showed trophoblastic hyperplasia, which mimics the hallmark proliferation of intermediate trophoblasts in clinical preeclampsia. It is suggested that the preeclampsia-like symptoms of the pregnant p57-/+ mice might have been induced by the conceptus(es) without p57Kip2 expression. In addition, pregnant p57-/+ mice might serve as a new animal model for preeclampsia characterized by trophoblastic hyperplasia.

Animals↗