Biomedical subjects

Hironori Okada

Publications and source records attributed to Hironori Okada.

6 recordsLinked to original sources

PubMed2006

[Effects of sevoflurane and propofol on evoked potentials during neurosurgical anesthesia].

BACKGROUND: The effect of anesthetics on somatosensory evoked potential (SEP) and auditory brain stem response (ABR) has been a subject of intense reseach over the last two decades. In fact, volatile anesthetics have been repeatedly shown to decrease cortical amplitude in a dose-dependent fashion but the information regarding the effect of propofol is incomplete. The purpose of this study was to compare the effects of sevoflurane and propofol on evoked potentials during comparable depth of anesthesia guided by bispectral index (BIS). METHODS: Forty four patients scheduled for neurosurgery were studied. Anesthesia was maintained with intravenous propofol using target controlled infusion (TCI). We measured the change of amplitude and latency of SEP(N20-P25), ABR (V wave) and visual evoked potential (VEP: P100) at three sets of sevoflurane (0%, 1%, 2%) or propofol concentrations (effect site concentration of 1.5, 2.0, 3.0 microug x ml(-1)). BIS monitor was used to measure relative depth of hypnosis. RESULTS: With increasing concentrations of sevoflurane (0, 1% and 2%), SEP showed dose-related reduction in its amplitude, ABR produced less marked changes and VEP showed a significant reduction at 1%. VEP at the propofol concentration of 3.0 microg x ml(-1) was decreased significantly compared with the amplitude at 1.5 microg x ml(-1) concentration. No significant change was observed with SEP and ABR during the change of propofol dosages. BIS values were almost the same with each anesthetics. CONCLUSIONS: VEP was most strongly affected with anesthetics, and ABR showed less marked influence of sevoflurane and propofol. Propofol based TIVA technique would induce less change in evoked potentials than sevoflurane.

Aged↗

PubMed2005

Differential development of rabbit embryos following microinsemination with sperm and spermatids.

Microinsemination is the technique of delivering male germ cells directly into oocytes. The efficiency of fertilization after microinsemination and subsequent embryo development may vary with the animal species and male germ cells used. The present study was undertaken to observe the in vitro and in vivo developmental ability of rabbit embryos following microinsemination with male germ cells at different stages. First, we assessed their oocyte-activating capacity by injecting them into mouse and rabbit oocytes. The majority of mouse oocytes were activated irrespective of the type of rabbit male germ cell injected (61-77%), whereas rabbit oocytes were activated differently according to the type of male germ cells (89%, 75%, and 29% were activated by spermatozoa, elongated spermatids, and round spermatids, respectively; P < 0.05). After 120 hr in culture, 66%, 45%, and 13%, respectively, of these activated rabbit oocytes (pronuclear eggs) developed into blastocysts (P < 0.05). Additional electric pulse stimulation of round spermatid-injected oocytes increased the blastocyst rate to 43%. After 24 hr in culture, some four to eight cell embryos were transferred into the oviducts of pseudopregnant females. Normal pups were born from spermatozoa and elongated spermatids, but not from round spermatids. Karyotypic analysis at the morula/blastocyst stage revealed that the majority of round spermatid-derived embryos had abnormal ploidy (8 out of 12 embryos). Our study indicates that rabbit male germ cells acquire the ability to activate oocytes and to support subsequent embryo development as they undergo spermiogenesis. As these differential developmental patterns are similar to those reported for humans in vitro and in vivo, rabbits may provide an alternative small animal model for studying the biological nature and molecular basis of human microinsemination techniques, especially those using immature male germ cells.

Analysis of Variance↗

PubMed2005

Buffalo rat liver cells produce factors that support preimplantation development of mouse embryos cultured in vitro.

To examine the effects of buffalo rat liver (BRL) cells on the preimplantation development of mouse embryos in vitro, we first cultured two-cell mouse embryos alone in serum-free Dulbecco modified Eagle medium. As expected, the embryos did not develop to subsequent stages. However, when cocultured with BRL cells, the embryos developed to the blastocyst stage efficiently. Direct contact of embryos with BRL cells was not necessary for development: the medium conditioned by BRL cells contained soluble factors that supported the preimplantation development of mouse embryos. Embryos cultured with BRL-conditioned medium that was replaced at various intervals had a further increased rate of development to the blastocyst stage. This finding indicated that the activities of the factors were maintained only briefly. Seven proteins between 35 and 44 kDa that were detected in the medium were highly beneficial to the development of the embryos. Follistatin-related protein and pigment epithelium-derived factor are believed to be the factors supporting embryo development. The other five proteins also may improve the environment for the development of mouse embryos cultured in vitro.

Amino Acid Sequence↗

PubMed2004

Zona-float method for separating mouse eggs from other cells.

We have developed a new method for separating mouse eggs from other cells, such as cumulus cells, using centrifugation with Percoll. Solutions of 45, 22.5, 11.3, and 5.6% Percoll were tested. With the 22.5% solution, 99% of whole eggs obtained by in vitro fertilization were collected from the upper part of the Percoll solution, and 98% of 2-cell embryos collected from these eggs developed to the blastocyst stage. Offspring were obtained after transfer of collected embryos to female mice. The greatest advantage of this method is that undamaged eggs are separated from other cells in one simple operation, regardless of the number of eggs.

Animals↗

PubMed2003

Pregnancy by the tubal transfer of embryos developed after injection of round spermatids into oocyte cytoplasm of the cynomolgus monkey (Macaca fascicularis).

BACKGROUND: Round spermatids have been used as substitute gametes in basic reproductive research and in infertility clinics. In humans, however, the efficiency of fertilization and pregnancy is generally much lower after round spermatid injection (ROSI) than after injection with mature sperm. We examined the ability of round spermatids to support embryonic development using a non-human primate as a model. We chose cynomolgus monkeys because, as in humans, their round spermatids have the oocyte-activating capacity of mature sperm. METHODS: We examined fertilization and subsequent development of embryos after ROSI and then transferred the embryos into the oviducts of female monkeys. RESULTS: Seventy-seven per cent of survived oocytes were activated and had formed pronuclei or the second polar body; 79% of the oocytes cultured developed to the 2-cell stage, and 23% developed to the blastocyst stage. Ultrasonography showed a normal-sized fetus in the uterus of a recipient, but the fetus spontaneously aborted at day 103. CONCLUSIONS: The round spermatids of cynomolgus monkeys can be used as substitute gametes to support embryonic development at least to mid-gestation. This non-human primate is a suitable animal model for round spermatid conception in mammals, especially humans, and for biological and genetic characterization of events following ROSI.

Animals↗

PubMed2003

Aspiration method to collect epithelial cells from mouse, rat, and monkey oviducts.

When oviduct epithelial cells are collected by using enzymatic methods that involve protease such as trypsin, other cells unintentionally are collected as well, especially from small laboratory animals such as mice and rats, thus contaminating the collected sample. We therefore developed a simple nonenzymatic method that involves using a glass micropipette to aspirate the oviduct epithelial cells from the oviduct. This aspiration method easily removed oviduct epithelial cells from mice, rats, and cynomolgus monkeys. Culture of the collected oviduct epithelial cells confirmed that the cells could adhere and grow on a petri dish. Although this aspiration technique was developed for use in small animals, our results show that it can be applied to cynomolgus monkeys. The advantages of this technique are its simplicity and its success in collecting oviduct epithelial cells from oviducts.

Animals↗