Biology subjects

Suh, D.

Publications and source records attributed to Suh, D..

3 recordsLinked to original sources

bioRxiv2024

A new tuna specimen (Genus Auxis) from the Duho Formation (middle Miocene) of South Korea

A partially preserved caudal vertebrae imprint of a tuna was discovered from the Duho Formation (Miocene) of South Korea. This specimen was assigned to the genus Auxis and represents the second record of fossil Auxis found in South Korea and in the world. We compared the vertebral morphology of the studied specimen to that of currently known species of Auxis, including extinct taxa. However, the specimen could not be assigned to any extant or new species of Auxis due to anatomical differences and a lack of comparability. The discovery of a new specimen of Auxis aligns with theories of high marine biodiversity in the East Sea (Sea of Japan) and its opening in the Early to Middle Miocene. A widely opened East Sea and upwelling activities might have increased the abundance and diversity of large oceanic fishes such as tunas during the deposition of the Duho Formation. The specimen supports paleoenvironmental interpretations of the Duho Formation as pelagic and subtropical. A taphonomic scenario of the specimen was inferred based on the lack of anal pterygiophores and the leaf imprint on the matrix. The specimen would have been exposed for at least a month in a low-energy sedimentary environment at the deep-sea bottom and would have undergone disintegration before being buried.

paleontology↗

bioRxiv2024

Continuous exposure to 60 Hz extremely low frequency electromagnetic field at 10 to 16 mT promotes various human cell proliferation by activating extracellular-signal-regulated kinase

We previously showed that continuous exposure to 60 Hz extremely low-frequency electromagnetic fields (ELF-EMF) at 6 mT promotes cell proliferation. Here, we investigated the cellular effect of 60 Hz ELF-EMF at over 10 mT. We revised the ELF-EMF-generating device to increase the magnetic flux density of the ELF-EMF stably without thermal effect. We investigated the cellular effect of 10-16 mT ELF-EMF on various mammalian cells including human cervical carcinoma HeLa, rat neuroblastoma B103, liver cancer stem cells Huh7 and Hep3B, immortalized normal hepatic cell MIHA, and normal fibroblast IMR-90. Cell proliferation was promoted around 20% or more in all cells through continuous ELF-EMF exposure at 10 and 14 mT for 72 h, compared with the sham exposure group. In the cells whose proliferation was activated by 14 mT ELF-EMF, the MEK-ERK pathway and NF-{kappa}B were activated but not Akt. These cells showed a slight increase in the S phase population in BrdU incorporation and Ki-67 expression. In these cells, intracellular and mitochondrial ROS levels were not changed, and the proliferation-activating cellular effects of ELF-EMF were maintained even when oxidative phosphorylation was interrupted by CCCP. Additionally, no changes in intracellular calcium levels were observed in ELF-EMF-exposed cells and the proliferation-activating cellular effects of ELF-EMF were maintained in the presence of a calcium chelator, BAPTA-AM. These observations suggested that ROS and intracellular calcium do not mediate ELF-EMFs proliferation-activating physiological effect. Altogether, we demonstrated that 60 Hz ELF-EMF at 10 to 14 mT promotes cell proliferation by activating ERK1/2 and does not affect intracellular ROS and calcium levels.

cell biology↗

bioRxiv2023

1.7 GHz long-term evolution radiofrequency electromagnetic field with efficient thermal control has no effect on the proliferation of different human cell types

Long-term evolution (LTE) radiofrequency electromagnetic field (RF-EMF) is widely used in communication technologies. As a result, the influence of RF-EMF on biological systems is a major public concern, and its physiological effects remain controversial. In our previous study, we showed that continuous exposure of various human cell types to 1.7 GHz LTE RF-EMF at specific absorption rate (SAR) of 2 W/Kg for 72 h can induce cellular senescence. To understand the precise cellular effects of LTE RF-EMF, we elaborated the 1.7 GHz RF-EMF cell exposure system used in the previous study by replacing the RF signal generator and developing a software-based feedback system to improve the exposure power stability. This refinement of the 1.7 GHz LTE RF-EMF generator facilitated the automatic regulation of RF-EMF exposure, maintaining target power levels within a 3% range and a constant temperature even during the 72-h exposure period. With the improved experimental setup, we examined the effect of continuous exposure to 1.7 GHz LTE RF-EMF at up to SAR of 8 W/Kg of adipose tissue-derived stem cells and Huh7, HeLa, and B103 cells. Surprisingly, the proliferation of all cell types, which displayed different growth rates, did not change significantly compared with that of the unexposed controls. However, when the thermal control system was turned off and the subsequent temperature increase induced by the RF-EMF was not controlled during continuous exposure to SAR of 8 W/Kg LTE RF-EMF, cellular proliferation increased by 35.2% at the maximum. These observations strongly suggest that the cellular effects attributed to 1.7 GHz LTE RF-EMF exposure were primarily due to the induced thermal changes, rather than the RF-EMF exposure itself.

cell biology↗