PubMed Health⌕ Search

Biomedical subjects

K Bae

Publications and source records attributed to K Bae.

24 records · Page 2Linked to original sources
PubMed1998

Antimicrobial activity of magnolol and honokiol against periodontopathic microorganisms.

Magnolol (1) and honokiol (2), main compounds from the stem bark of Magnolia obovata Thunb., were evaluated for an antimicrobial activity against periodontopathic microorganisms, Porphyromonas gingivalis, Prevotella gingivalis, Actinobacillus actinomycetemcomitans, Capnocytophaga gingivalis, and Veillonella disper, and a cytotoxicity against human gingival fibroblasts and epithelial cells. Our results indicate that magnolol and honokiol, although less potent than chlorhexidine, show a significant antimicrobial activity against these microorganisms, and a relatively low cytotoxic effect on human gingival cells. Thus, it is suggested that magnolol and honokiol may have a potential therapeutic use as a safe oral antiseptic for the prevention and the treatment of periodontal disease.

Aggregatibacter actinomycetemcomitans↗
PubMed1998

Circadian regulation of a Drosophila homolog of the mammalian Clock gene: PER and TIM function as positive regulators.

The Clock gene plays an essential role in the manifestation of circadian rhythms (approximately 24 h) in mice and is a member of the basic helix-loop-helix (bHLH) PER-ARNT-SIM (PAS) superfamily of transcription factors. Here we report the characterization of a novel Drosophila bHLH-PAS protein that is highly homologous to mammalian CLOCK. (Similar findings were recently described by Allada et al. Cell 93:791-804, 1998, and Darlington et al., Science 280:1599-1603, 1998.) Transcripts from this putative Clock ortholog (designated dClock) undergo daily rhythms in abundance that are antiphase to the cycling observed for the RNA products from the Drosophila melanogaster circadian clock genes period (per) and timeless (tim). Furthermore, dClock RNA cycling is abolished and the levels are at trough values in the absence of either PER or TIM, suggesting that these two proteins can function as transcriptional activators, a possibility which is in stark contrast to their previously characterized role in transcriptional autoinhibition. Finally, the temporal regulation of dClock expression is quickly perturbed by shifts in light-dark cycles, indicating that this molecular rhythm is closely connected to the photic entrainment pathway. The isolation of a Drosophila homolog of Clock together with the recent discovery of mammalian homologs of per indicate that there is high structural conservation in the integral components underlying circadian oscillators in Drosophila and mammals. Nevertheless, because mammalian Clock mRNA is constitutively expressed, our findings are a further example of striking differences in the regulation of putative circadian clock orthologs in different species.

Amino Acid Sequence↗
PubMed1996

Resetting the Drosophila clock by photic regulation of PER and a PER-TIM complex.

Circadian clocks can be reset by light stimulation. To investigate the mechanism of this phase shifting, the effects of light pulses on the protein and messenger RNA products of the Drosophila clock gene period (per) were measured. Photic stimuli perturbed the timing of the PER protein and messenger RNA cycles in a manner consistent with the direction and magnitude of the phase shift. In addition, the recently identified clock protein TIM (for timeless) interacted with PER in vivo, and this association was rapidly decreased by light. This disruption of the PER-TIM complex in the cytoplasm was accompanied by a delay in PER phosphorylation and nuclear entry and disruption in the nucleus by an advance in PER phosphorylation and disappearance. These results suggest a mechanism for how a unidirectional environmental signal elicits a bidirectional clock response.

Animals↗
PubMed1990

Comparison of lodging safety factor of untreated and succinic Acid 2,2-dimethylhydrazide-treated shoots of mulberry tree.

This study examined the lodging resistance of mulberry tree (Morus bombycis Koidz. cv Kenmochi) shoots treated or not treated with succinic acid 2,2-dimethylhydrazide (SADH). The lodging safety factor, an indicator of lodging resistance, was defined as the ratio of critical lodging load to the leaf fresh weight observed, provided that the distribution of the critical lodging load along the stem was similar to that of the leaf fresh weight observed. The critical lodging load was experimentally estimated by loading weights onto the stems. In the untreated trees, the lodging safety factor was maintained at about 3.2. In the SADH-treated trees, the stem elongation was inhibited to about 80% of that in the untreated trees, and the percentage of shoot dry matter partitioned into the leaves was always larger than that of the untreated trees. This dwarfing of the stem caused by SADH increased the critical lodging load supported by the unit stem dry weight, while this large investment of materials in leaves increased the leaf fresh weight supported by the unit stem dry weight. Since the increments canceled each other, the lodging safety factor of the SADH-treated shoots was similar to that of the untreated ones. These results suggest that the shoot formation of the mulberry tree is controlled to maintain the lodging safety factor at a constant level.

Journal Article↗
PubMedDate not supplied

A new diterpenoid alkaloid from Aconitum jaluense.

A new diterpenoid alkaloid, jaluenine (1), has been isolated from the roots of Aconitum jaluense. The structure of jaluenine was determined by spectroscopic methods including two dimensional NMR (1H-1H COSY, HMQC, HMBC, NOESY).

Aconitum↗