Somatic embryogenesis and plant regeneration from immature zygotic embryos of Cryptomeria japonica D. Don.

This report describes the successful plant regeneration via somatic embryogenesis from immature zygotic embryos of Cryptomeria japonica D. Don. For the induction of embryogenic tissue, we determined that the optimal medium contained N6-benzyladenine and 2,4-dichlorophenoxyacetic acid. Immature zygotic embryos that were collected at the end of June yielded embryogenic tissue at the highest frequency. Embryogenic tissues that had proliferated in liquid medium included small and loosely packed cells and elongating or elongated cells. We used ten cell lines to determine the optimal medium for the development of somatic embryos. Induced somatic embryos germinated with synchronous sprouting of cotyledons, hypocotyls and roots. Gibberellin A3 in the germination medium had a positive effect on both the elongation of hypocotyls and the survival of seedlings. The frequencies of induction and germination of somatic embryos differed among the cell lines examined. Most of the seedlings grew normally. This system of somatic embryogenesis required 4-5 months for the regeneration of C. japonica plantlets from immature zygotic embryos.

Inhibition of the light-independent synthesis of chlorophyll in pine cotyledons at low temperature.

Cotyledons of Japanese black pine (Pinus thunbergii) were yellow when they developed in darkness at 8 degrees C since the light-independent synthesis of chlorophyll was almost completely inhibited in these cotyledons. The level of chlorophyll in dark-grown cotyledons was less than one-twentieth of that in light-grown cotyledons at the same temperature. In the yellow cotyledons, levels of transcripts of cab, rbcS, rbcL and psbA genes were quite high. The large and small subunits of ribulose-1,5-bisphosphate carboxylase/oxygenase were also detected at relatively high levels in yellow cotyledons. However, the accumulation of the two apoproteins of the light-harvesting chlorophyll a/b-binding protein of PSII was limited because of the limited supply of chlorophyll.

[New protocol for memory-related potential].

A new P300 testing protocol for evaluating memory function is proposed. Four stimuli (S1, S2, S3 and S4) are presented to the subject at 1.5 sec intervals and the subject is instructed to judge whether S4 was the same (80%) or not (20%) as S1, as well as whether S3 was the same (80%) or not (20%) as S2. The S2-S3 comparison acts as an attention shifting mechanism, and by inserting this comparison between S1 and S4, the subject must memorized S1 at the memory site in the brain until S4 is presented. This protocol was performed using both auditory and visual stimulations with 24 college students (age range: 19-28 years old) and a patient (23 years old) with bilateral medial temporal lobe lesions caused by limbic encephalitis. The P300 brain potentials after S3 and S4 were compared. The Wechsler memory scale-revised (WMS-R) test was also assessed in all subjects. The latency of P300 after S4 had a significantly (p < 0.01) longer than that after S3. The latency of P300 after S4 in the patient, who showed the severe auditory as well as the mild visual memory impairment, was longer than the mean + 2 SD in the normal subjects for auditory stimuli, but not for visual stimuli, whereas the latency of P300 after S3 in the patient was longer than the mean + 2 SD in the normal subjects only for visual stimuli. The brain potential after S4 might be more reflective of a degree of memory disorder as compared with that after S3. Furthermore, the latency of P300 after S4 showed a more significant correlation with some WMS-R scores (verbal memory, general memory and verbal delay) than the latency of P300 after S3. These results suggest that measuring the P300 latency after attention shifting in the new protocol is useful for the evaluation of memory functions.

Agrobacterium tumefaciens-mediated transformation of Robinia pseudoacacia.

ROBINIA PSEUDOACACIA: (black locust) plants were regenerated after co-cultivation of stem and leaf segments with Agrobacterium tumefaciens strain GV3101 (pMP90) that harbored a binary vector that included genes for ß-glucuronidase (GUS) and hygromycin phosphotransferase. Successful transformation was confirmed by the ability of stem and leaf segments to produce calli in the presence of hygromycin, by histochemical and fluorometric assays of GUS activity in plant tissues, and by Southern blotting analysis. In this transformation system, about 2 months were required for regeneration of transgenic plants from stem and leaf segments. The frequency of transformation from stem segments was approximately 24%, and the morphology of regenerated plants resembled that of the original parental strain.

Gustatory evoked magnetic fields in humans.

Magnetic fields evoked by taste stimuli of the human tongue were measured over the whole head using a helmet-shaped 64 channel magnetoencephalography system in five normal subjects. The stimuli were 10% glucose and 0.3 M NaCl solutions and distilled water. The most prominent peak (N175m) appearing over the bilateral hemispheres had a latency of 150-210 ms. The N175m sources were located using a two-dipole model in a spherical conducting medium based on the individual head dimensions and superimposed on magnetic resonance images. The N175m dipoles due to 10% glucose and 0.3 M NaCl stimuli were located at the operculum and circum-insular areas in both hemispheres, but those due to distilled water could not be located accurately.