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Plants have a high regeneration capacity and some plant species can regenerate clone plants, called plantlets, from detached vegetative organs. We previously outlined the molecular mechanisms underlying plantlet regeneration from Rorippa aquatica (Brassicaceae) leaf explants. However, the fundamental difference between the plant species that can and cannot regenerate plantlets from vegetative organs remains unclear. Here, we hypothesized that the viability of leaf explants is a key factor affecting the regeneration capacity of R. aquatica. To test this hypothesis, the viability of R. aquatica and Arabidopsis thaliana leaf explants were compared, with respect to the maintenance of photosynthetic activity, senescence, and immune response. Time-course analyses of photosynthetic activity revealed that R. aquatica leaf explants can survive longer than those of A. thaliana. Endogenous abscisic acid (ABA) and jasmonic acid (JA) were found at low levels in leaf explant of R. aquatica. Time-course transcriptome analysis of R. aquatica and A. thaliana leaf explants suggested that senescence was suppressed at the transcriptional level in R. aquatica. Application of exogenous ABA reduced the efficiency of plantlet regeneration. Overall, our results propose that in nature, plant species that can regenerate in nature can survive for a long time.

Some plant species have a striking capacity for regeneration in nature, including regeneration of the entire individual from explants. However, due to the lack of suitable experimental models, the regulatory mechanisms of spontaneous whole plant regeneration are mostly unknown. In this study, we established a novel model system to study these mechanisms using an amphibious plant within Brassicaceae, Rorippa aquatica, which naturally undergoes vegetative propagation via regeneration from leaf fragments. Morphological and anatomical observation showed that both de novo root and shoot organogenesis occurred from the proximal side of the cut edge transversely with leaf vascular tissue. Time-series RNA-seq analysis revealed that auxin and cytokinin responses were activated after leaf amputation and that regeneration-related genes were upregulated mainly on the proximal side of the leaf explants. Accordingly, we found that both auxin and cytokinin accumulated on the proximal side. Application of a polar auxin transport inhibitor retarded root and shoot regeneration, suggesting that the enhancement of auxin responses caused by polar auxin transport enhanced de novo organogenesis at the proximal wound site. Exogenous phytohormone and inhibitor applications further demonstrated that, in R. aquatica, both auxin and gibberellin are required for root regeneration, whereas cytokinin is important for shoot regeneration. Our results provide a molecular basis for vegetative propagation via de novo organogenesis.

In order to maintain organs and structures at their appropriate sizes, multicellular organisms orchestrate cell proliferation and post-mitotic cell expansion during morphogenesis. Recent studies using Arabidopsis leaves have shown that compensation, which is defined as post-mitotic cell expansion induced by a decrease in the number of cells during lateral organ development, is one example of such orchestration. Some of the basic molecular mechanisms underlying compensation have been revealed by genetic and chimeric analyses. However, to date, compensation had been observed only in mutants, transgenics, and γ-ray-treated plants, and it was unclear whether it occurs in plants under natural conditions. Here, we illustrate that a shift in ambient temperature could induce compensation in Rorippa aquatica (Brassicaceae), a semi-aquatic plant found in North America. The results suggest that compensation is a universal phenomenon among angiosperms and that the mechanism underlying compensation is shared, in part, between Arabidopsis and R. aquatica.

We performed a 5-year clinical and electrophysiologic follow-up study on two sibling cases with myoclonus epilepsy with ragged-red fibers. Both had myoclonus, intention tremor, slight muscle weakness, slight mental disturbance, hearing impairment, and optic atrophy. Neither had epileptic attacks or truncal or gait ataxia. Biochemical activity of cytochrome c oxidase was at the lower limit of the normal range of values, and an adenine to guanine transition mutation at nucleotide 8344 in the transfer RNA specific for lysine of mitochondrial DNA was detected in both cases. The electroencephalograms showed slowing of basic patterns, diffuse spike-and-wave complexes, occipital dominant wave-and-spike phantoms, 6-and 14-Hz positive spikes, and photosensitivity. No definite deterioration of basic patterns was seen, and diffuse spike-and-wave complexes and photosensitivity gradually disappeared during the slowly progressive clinical course. P2 latencies of pattern-reversal visual evoked potentials throughout the clinical course and III through V interpeak latencies of auditory brainstem responses at follow-up were prolonged without giant sensory evoked potentials in both cases. (J Child Neurol 1993;8:366-372).

To assess the clinical applicability of dipole tracing in childhood epilepsy, the location and stability of electric source generator of focal spikes seen in EEG of epileptic children were investigated using this method. The patients were divided into 3 groups; benign childhood epilepsy with centrotemporal spikes (BCECS, Group A, n = 14), other types of epilepsy with centrotemporal spikes (Group B, n = 15) and epilepsy with focal spikes in other areas (Group C, n = 13). The spike dipole in each group was analyzed using dipole tracing method. The following results were obtained. (1) The spikes of BCECS were characterized by constantly stable dipoles, compared to those of the other types of childhood epilepsy. The spikes of epileptic children with mental retardation mostly lacked the stability of dipoles. These seemed to suggest that the stability of dipoles was closely related to the prognosis and pathophysiology of epilepsy. (2) The dipoles of BCECS were localized strictly in the Rolandic area. Dipole tracing from EEG spikes was considered to contribute to the elucidation of the pathophysiology of childhood epilepsy.

Forty-six children with refractory epilepsy (12 with symptomatic generalized epilepsy, 14 with symptomatic partial epilepsy, and 20 with undetermined epilepsy) were treated by high-dose (serum level above 100 micrograms/ml) valproate (VPA) therapy. Monotherapy was used with 34 patients and two drugs with 12. Serum VPA concentrations ranged from 105.1 to 198.4 micrograms/ml. Assessment of initial response to treatment, after the serum level had reached the appropriate level, showed seizures to be completely controlled in 15 (32.6%) of 46 patients and improved in 12 (26.1%) (50% or more). Follow-up of more than 6 months after the time of initial response showed control of seizures in 14 (30.4%) and improvement in 11 (23.9%). The initial effect on EEG was the disappearance of epileptic discharges in 3 (6.5%) of 46 patients and marked improvement in 15 (32.6%). Follow-up revealed the disappearance of epileptic discharges in 7 (15.2%) and marked improvement in 9 patients (19.6%). High-dose VPA therapy was especially effective for West syndrome and for epilepsy with continuous spike-waves during slow-wave sleep. Control of atypical absences and myoclonic seizures was relatively good. Hypofibrinogenemia and thrombocytopenia were sometimes encountered but these side effects were reversible with reduction of dosage.

A long-term follow-up study of 89 patients of Lennox-Gastaut syndrome (LGS) disclosed the persistent occurrence of seizures in 68 patients (76.4%) and severe mental defect in 48 (53.9%). An analysis of the correlation between the mental and seizure prognoses confirmed that the persistence of minor seizures could result in mental deterioration. An examination of the evolutional changes in EEG demonstrated that diffuse slow spike-waves characteristic of LGS gradually disappeared, while focal epileptic discharges, especially multifocal spikes, appeared in spite of the persistence of minor seizures. The diagnostic criteria were satisfied in only 31 (47.0%) of 66 patients with the persistence of minor seizures. Patients with multiple independent spike foci and minor seizures were considered to belong to a specific type of epilepsy, namely the severe epilepsy with multiple independent spike foci (the severe epilepsy with MISF). The seizure and mental prognoses were poorer in patients who evolved into the severe epilepsy with MISF than others.

A pair of monozygotic twins manifested widespread ichthyosis on the trunk and extremities, mainly on the extensor surface of the lower legs. Both patients had severe developmental retardation, microcephalus, spastic quadriplegia, myoclonus, and hearing impairment. Cranial computed tomography and magnetic resonance imaging revealed diffuse cortical atrophy. Electroencephalography documented diffuse slow wave dysrhythmia and marked epileptic discharges, namely bilateral occipital dominant, and low-voltage multifocal spikes which appeared asynchronously as a burst, mainly during sleep. Skin biopsy revealed hyperkeratosis with parakeratosis. Granular cell layer was not thickened and diminished. Papillomatosis was absent. Electron microscopy did not reveal any distinctive abnormalities. Sjogren-Larsson syndrome and other known ichthyosis syndromes were excluded because of the difference in localization of skin lesions, skin manifestations, lack of papillomatosis, the nature and severity of neurologic symptoms and marked electroencephalographic abnormalities.

West症候群 (W) からLennox-Gastaut症候群 (LGS) への変容を示した30例を対象に変容過程の詳細について臨床的脳波学的に検討した。1) シリーズ形成性tonic spasmsの消退および単発性tonic spasmsの出現は生後6ヵ月から1歳に最も多く認められた。2) Hypsarythmiaの消退は生後6カ月から1歳に, diffuse slow spike-and-waveはやや遅れて1歳から2歳に最も多く出現した。3) WからLGSへの変容の時期は1歳から3歳に集中しており, その変容過程は数ヵ月のうちに漸進的に進行した。4) Wから変容したLGSでは臨床発作および脳波像がそれ以外のLGSに比較し特徴があり, 予後は特に不良であった。以上の事実よりWからLGSへの変容を阻止することが臨床上重要であることが示唆された。

小児の難治てんかんの実態を解明するために, 初診時年齢が15歳未満で初診後3年以上追跡された小児てんかん561例のうち, 追跡時点で初診時に比して発作頻度が不変または増悪している難治群について調査した。あわせて追跡時点で3年以上発作が抑制されている経過良好な対照群と比較検討した。難治群は41例 (7.3%), 対照群は375例 (66.8%) であった。難治群の比率をてんかん分類別にみると, Lennox-Gastaut症候群で28.2%と最高率で, 次いでWest症候群10.5%, severe myoclonic epilepsy in infancyは症例数が少ないが, 全例難治であった。初発年齢別では生後6カ月未満の症例で難治率が高率であった。一方, 対照群の比率は特発性全般てんかんでは85.6%で高率であった。対照群との比較では有意差を示したのは難治群で初発年齢が生後6カ月未満のものが高率なこと, 基礎疾患を有するものが多く, 成因では家族歴が低率で出生前要因が高率なこと, 精神遅滞, 運動障害の重複, てんかん重積状態, 新生児痙攣の既往も高率であった。難治群の治療の評価ではみせかけの難治例が比較的多いことが注目された。

A multifaceted study on childhood refractory epilepsy disclosed an insufficient classification of epilepsies and epileptic seizures, and inappropriate polypharmacy as the most important factors preventing appropriate therapy. By means of an adjustment of AEDs based on the accurate classification of epilepsies and epileptic seizures, the number of AEDs could be reduced in 37.5% and monotherapy was successful in 13.8% of refractory cases. Most of the latter were those of partial epilepsy and generalized epilepsy with the monoseizure type. The exacerbation of seizures due to AEDs was also mentioned as one of the important side effects of AEDs.