The effect of electrical field strength on activation and development of cloned caprine embryos.

The activation procedure used in nuclear transfer (NT) is one of the critical factors affecting the efficiency of animal cloning. The purpose of this study was to compare the effect of two electrical field strengths (EFS) for activation on the developmental competence of caprine NT embryos reconstructed from ear skin fibroblasts of adult Alpine does. The NT embryos were obtained by transfer of the quiescent fibroblasts at the fourth passage into the enucleated metaphase II (M II) oocytes. Four to five hours after electrical fusion, the NT-embryos were activated by EFS either at 1.67 or at 2.33 kV/cm and immediately incubated in 6-DMAP (2 mM) for 4 h. The cleavage rate of the NT-embryos activated with 2.33 kV/cm was greater than that activated with 1.67 kV/cm after in vitro culture for 18 h (65.6% versus 19.6%, p < 0.001). No pregnancy was found in 14 recipient does after transferring 51 NT embryos at 1-2 cell stages activated with 1.67 kV/cm. In contrast, two of the seven recipients were pregnant and gave birth to three kids after transferring 61 NT embryos at 1-2 cell stages activated by 2.33 kV/cm. The birth weights of three cloned kids were within the normal range of Alpine goats. However, one kid died 1h after birth while the remaining two are still healthy. DNA analysis by polymerase chain reaction (single-strand conformation polymorphism, SSCP) confirmed that the three kids were genetically identical to the nuclear donor.

Evoked responses of the anterior cingulate cortex to stimulation of the medial thalamus.

In the present study we characterized the field potentials in the anterior cingulate cortex (ACC) evoked by electrical stimulation of the medial thalamus (MT), and elucidated the synaptic organization of the ACC. Male Sprague Dawley rats were maintained in general anesthesia by alpha-chloralose (50 mg/kg, i.v.). Tungsten micro-electrodes were used for electric stimulation and recordings. The field potentials and multiple unit activities in the ACC were evoked by electric stimulation of the MT where the nociceptive responses were identified. A MT-evoked positive-negative potential was recorded on the medial frontal surface. The polarity of the surface negative potential was reversed between 0.5 to 1.0 mm in the deep layer of the ACC. Maximum evoked negative potential appeared at about 4 mm anterior to the bregma and 1 mm lateral to the midline. The maximum evoked positive potential occurred at about 3 mm anterior to the bregma and 1 mm lateral to the midline. The evoked multiple unit activities coincided with the deep negative field potential at a latency between 16 ms and 24 ms at a depth between 0.5 mm and 1.5 mm in the ACC. These electrophysiological findings confirmed that nociceptive information in the MT is transmitted to the ACC and trans-synaptically activates deeper and more superficial layers of cortical neurons.