In vitro production of viable eggs from isolated mouse primary follicles by successive culture

To produce viable eggs from single primary follicles in vitro, primary follicles containing oocytes (average 39.0 ± 0.2 µm in diameter) were isolated from the ovaries of 1-week-old mice, and cultured in combination with culture membranes for the first 8 days up to the secondary follicle stage, followed by the next 12 days to the later stages. After culture with a combination of first and second culture membranes using high and low adhesion characteristics, the average oocyte diameters of the surviving follicles increased by almost two-fold in all four groups. Further, the oocyte maturation rate was the highest (74.1%) in the culture group with low adhesion with collagenase and high adhesion. In this culture group, when the O₂ concentration was changed from 20% in the first culture to 5% in the second culture, the cleavage rate increased to 47.5%, which was comparable to the level of the in vivo control (34.6%). Finally, 39 embryos at the 2- to 8-cell stages were transferred into the oviducts of three pseudopregnant females, and eight live pups (20.5%) were obtained. Of the eight pups, six survived for at least six months and were fertile. The present study shows successive in vitro cultures of single isolated primary follicles for the production of viable eggs. We believe that this culture system, with a combination of culture membranes under controlled O₂ conditions, is applicable to other mammalian species, including humans.

Regulation of a novel human phospholipase C, PLCepsilon, through membrane targeting by Ras

Phosphoinositide-specific phospholipase C (PI-PLC) plays a pivotal role in regulation of intracellular signal transduction from various receptor molecules. More than 10 members of human PI-PLC isoforms have been identified and classified into three classes beta, gamma, and delta, which are regulated by distinct mechanisms. Here we report identification of a novel class of human PI-PLC, named PLCepsilon, which is characterized by the presence of a Ras-associating domain at its C terminus and a CDC25-like domain at its N terminus. The Ras-associating domain of PLCepsilon specifically binds to the GTP-bound forms of Ha-Ras and Rap1A. The dissociation constant for Ha-Ras is estimated to be approximately 40 nm, comparable with those of other Ras effectors. Co-expression of an activated Ha-Ras mutant with PLCepsilon induces its translocation from the cytosol to the plasma membrane. Upon stimulation with epidermal growth factor, similar translocation of ectopically expressed PLCepsilon is observed, which is inhibited by co-expression of dominant-negative Ha-Ras. Furthermore, using a liposome-based reconstitution assay, it is shown that the phosphatidylinositol 4,5-bisphosphate-hydrolyzing activity of PLCepsilon is stimulated in vitro by Ha-Ras in a GTP-dependent manner. These results indicate that Ras directly regulates phosphoinositide breakdown through membrane targeting of PLCepsilon.

Origin of frontal N15 component of somatosensory evoked potential in man

Origin of the frontal somatosensory evoked potential (SEP) by median nerve stimulation was investigated in normal volunteers and in patients with localized cerebrovascular diseases, and the following results were obtained. (1) In normal subjects, SEPs recorded at F3 (or F4) contralateral to the stimulating median nerve were composed of P12, N15, P18.5 and N26. Similar components were recognized in SEP recorded at Fz. (2) In patients in whom putaminal or thalamic hemorrhages had destroyed the posterior limbs of the internal capsules, frontal N15 and parietal N18 (N20) disappeared. These components were also absent in patients with cortical (parietal) infarctions. Among these patients, the thalamus was not affected in cases with putaminal hemorrhages and cortical infarctions. These facts indicate that the generator of the frontal N15 does not exist in the thalamus but that it originates from the neural structure central to the internal capsule, which suggests a similarity to the generator of the parietal N18. Because N15 was recorded in the midline of the frontal region with shorter latency than parietal N18, the frontal N15 might represent a response to the sensory input of the frontal lobe via the non-specific sensory system.