• Korean Chemical Engineering Research
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• v.52 no.1
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• pp.75-80
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• 2014

The convective flow structures in the vapor phase on earth are shown to be single unicellular, indicating the solutally dominant convection is important. These findings reflect that the total molar fluxes show asymmetrical patterns in a viewpoint of interfacial distributions. With decreasing the gravitational level form $1g_0$ down to $1.0{\times}10^{-4}g_0$, the total molar fluxes decay first order exponentially. It is also found that the total molar fluxes decay first order exponentially with increasing the partial pressure of component B, PB (Torr) form 5 Torr up to 400 Torr. Under microgravity environments less than $1g_0$, a diffusive-convection mode is dominant and, results in much uniformity in front of the crystal regions in comparisons with a normal gravity acceleration of $1g_0$.

• Journal of Dairy Science and Biotechnology
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• v.36 no.1
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• pp.14-25
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• 2018

Melatonin, an indolic tryptophan-derived compound, is secreted rhythmically from the pineal gland, mainly under the regulation of the circadian clock located in the suprachiasmatic nuclei (SCN) of the hypothalamus. Melatonin is widely present in nature, with biological activities in unicellular organisms, plants, and animals. A major function of melatonin is to transmit information to organisms about certain physiological functions in response to daily and seasonal variations in their environment. In this paper, we review a variety of melatonin's functional properties, its occurrence in plants, and its synthesis by yeasts. Fermented milk supplemented with melatonin-rich plants and yeasts can be used for the effective treatment of sleep disorders.

• Animal cells and systems
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• v.4 no.3
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• pp.201-214
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• 2000

Two quite different types of plant cells are analysed with regard to transduction of the gravity stimulus: (i) Unicellular rhizoids and protonemata of characean green algae; these are tube-like, tip-growing cells which respond to the direction of gravity. (ii) Columella cells located in the center of the root cap of higher plants; these cells (statocytes) perceive gravity. The two cell types contain heavy particles or organelles (sataoliths) which sediment in the field of gravity, thereby inducing the graviresponse. Both cell types were studied under microgravity conditions ($10^{-4}$/ g) in sounding rockets or spacelabs. From video microscopy of living Chara cells and different experiments with both cell types it was concluded that the position of statoliths depends on the balance of two forces, i.e. the gravitational force and the counteracting force mediated by actin microfilaments. The actomyosin system may be the missing link between the gravity-dependent movement of statoliths and the gravity receptor(s); it may also function as an amplifier.

• Journal of Microbiology and Biotechnology
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• v.29 no.7
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• pp.1014-1021
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• 2019

In the bacterial community, unicellular organisms act together as a multicellular being. Bacteria interact within the community and programmed cell death (PCD) in prokaryotes is a sort of altruistic action that enables the whole population to thrive. Genetically, encoded cell death pathways are triggered by DNA damage or nutrient starvation. Given the environmental and bacterial diversity, different PCD mechanisms are operated. Still, their biochemical and physiological aspects remain unrevealed. There are three main pathways; thymineless death, apoptosis-like death, and toxin-antitoxin systems. The discovery of PCD in bacteria has revealed the possibility of developing new antibiotics. In this review, the molecular and physiological characteristics of the three types of PCD and their development potential as antibacterial agents are addressed.

• Journal of Microbiology and Biotechnology
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• v.31 no.2
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• pp.171-180
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• 2021

Caffeine, a methylxanthine analog of purine bases, is a compound that is largely consumed in beverages and medications for psychoactive and diuretic effects and plays many beneficial roles in neuronal stimulation and enhancement of anti-tumor immune responses by blocking adenosine receptors in higher organisms. In single-cell eukaryotes, however, caffeine somehow impairs cellular fitness by compromising cell wall integrity, inhibiting target of rapamycin (TOR) signaling and growth, and overriding cell cycle arrest caused by DNA damage. Among its multiple inhibitory targets, caffeine specifically interacts with phosphatidylinositol 3-kinase (PI3K)-related kinases causing radiosensitization and cytotoxicity via specialized intermediate molecules. Caffeine potentiates the lethality of cells in conjunction with several other stressors such as oxidants, irradiation, and various toxic compounds through largely unknown mechanisms. In this review, recent findings on caffeine effects and cellular detoxification schemes are highlighted and discussed with an emphasis on the inhibitory interactions between caffeine and its multiple targets in eukaryotic microorganisms such as budding and fission yeasts.

• Journal of Plant Biology
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• v.33 no.3
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• pp.169-172
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• 1990

The epidermal structure and development of stomata in four taxa of Zingiberaceae viz: Aframomum melegueta K. Schum, Aframomum sceptrum K. Schum, Curcuma longa L. and Zingiber officinale Rosc. have been investigated. Unicellular, eglandular trichomes are observed on the epidermis of A. sceptrum and Z. officienal. Anomocytic stomata with agenous ontogeny, paracitic stomata with eumesogenous ontogeny and tetracytic stomata with mesoperigenous ontogency are recorded in Z. officinale, Aframomum species and C. longa respectively. Stomata of Z. officinale are the smallest in size (20.6$\times$14.3$\times$10.5${\mu}{\textrm}{m}$) while those of C. longa are the largest (42.5$\times$31.5$\times$20.2${\mu}{\textrm}{m}$). These two taxa also recorded the highest (43.7/mm2) and lowest (28.6/mm2) stomatal frequency respectively which suggests a linear regression of frequency on size.

• Journal of Species Research
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• v.12 no.1
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• pp.48-54
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• 2023

Foraminifera are unicellular eukaryotes widely distributed in marine and transitional marine environments. They play important roles in marine food webs and geochemical cycles and have physiological properties like the formation of calcareous tests and nitrogen respiration. Research on species diversity, distribution and endemism are essential in biogeography and biodiversity conservation. Here, we report three unrecorded species of foraminifera (Hemirotalia foraminulosa, Planispirillina denticulogranulata and Oolina brevisolenia) collected from Jeju Island and the South Sea (Korea). Planispirillina denticulogranulata is the second Planispirillina species recorded in Korea, which can be distinguished from congeners by its tubercles on the ventral side and grooves on the spiral suture. Hemirotalia foraminulosa is differentiated from the only congener H. calvifacta by multiple-scattered pits on the umbilicus, and it is the first report of Hemirotalia from Korean water. Oolina brevisolenia has specific bifurcating costae that characterize it from other congeners. This study contributes to documentation of the foraminiferal biodiversity in Korea, moreover, provides an essential basis for the expanded studies on modern foraminifera.

• Journal of Species Research
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• v.12 no.1
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• pp.95-108
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• 2023

Ciliates are unicellular eukaryotes and one of the most abundant and speciose protistan groups. However, their diversity is underestimated, and many new species are waiting for our discovery. During several field surveys conducted from 2018 to 2021 to document indigenous Korean ciliates, 10 unrecorded ciliate species were collected and investigated from freshwater, marine, and semiterrestrial habitats. The morphology of these species was studied based on observation of living and protargol-stained specimens. These species belong to five classes as follows: 1) class Heterotrichea - Peritromus faurei; 2) class Spirotrichea - Heterotachysoma dragescoi, Pseudokeronopsis parasongi, and Certesia quadrinucleata; 3) class Nassophorea - Chilodontopsis depressa; 4) class Prostomatea - Plagiocampa rouxi and Urotricha furcata; and 5) class Oligohymenophorea - Metanophrys similis, Uronema gallicum, and Protocyclidium citrullus. Also, we provide a brief diagnosis, photomicrographs, and information of the locality for each species. Further, we compare each species with the most recent description and with similar congeners.

• Korean Journal of Environmental Biology
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• v.40 no.2
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• pp.157-163
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• 2022

We analyzed the hair microstructure of Korean small terrestrial mammals, such as Rodentia and Lagomorpha, to classify the characteristics of hair morphology. Micromys minutus showed a unicellular irregular type of medulla structures; on the other hand, the other mammals showed multicellular structures. Regarding the cuticular scale structures, the Rodentia species exhibited a narrow and broad diamond petal type, while the Lagomorpha species exhibited an elongated petal type. Interestingly, the hair cross-sections showed quite unique characteristics. We constructed hair identification keys to distinguish species with a single hair. The dichotomous key of Rodentia and Lagomorpha can be used for their behavioral ecology and dietary analysis of upper predators to serve as the basis for ecological research.

• Journal of Species Research
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• v.12 no.4
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• pp.313-320
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• 2023

Diatoms are unicellular eukaryotic microalgae, and they are highly diversified in aquatic environments. We describe an unrecorded diatom species Fragilaria saxoplanctonica Lange-Bertalot & Ulrich (Bacillariophyceae) collected from Paldang Reservoir, Korea, on 4 April 2022. The valve was needle shaped and narrowly rectangular, its ends were rounded, and no spines were found on the outline of their valves. The valve was 67.2-70.2㎛ in length and 1.4-2.9㎛ in width. The ratio of width-to-length was 1 : 23.2-50.1. The pattern of striation was alternate or opposite, and the number of striae in 10㎛ was 24-26. Molecular comparisons of the 18S rDNA and rbcL sequences showed that it belonged to the genus Fragilaria. These morphological and phylogenetic results confirmed that our species was F. saxoplanctonica, and it was the first record in Korea.