• Proceedings of the Microbiological Society of Korea Conference
• /
• 2008.05a
• /
• pp.39-41
• /
• 2008

The yeast Saccharomyces cerevisiae has been shown to contain three isoforms of citrate synthase (CS). The mitochondrial CS, Cit1, catalyzes the first reaction of the TCA cycle, i.e., condensation of acetyl-CoA and oxaloacetate to form citrate [1]. The peroxisomal CS, Cit2, participates in the glyoxylate cycle [2]. The third CS is a minor mitochondrial isofunctional enzyme, Cit3, and related to glycerol metabolism. However, the level of its intracellular activity is low and insufficient for metabolic needs of cells [3]. It has been reported that ${\Delta}cit1$ strain is not able to grow with acetate as a sole carbon source on either rich or minimal medium and that it shows a lag in attaining parental growth rates on nonfermentable carbon sources [2, 4, 5]. Cells of ${\Delta}cit2$, on the other hand, have similar growth phenotype as wild-type on various carbon sources. Thus, the biochemical basis of carbon metabolism in the yeast cells with deletion of CIT1 or CIT2 gene has not been clearly addressed yet. In the present study, we focused our efforts on understanding the function of Cit2 in utilizing $C_2$ carbon sources and then found that ${\Delta}cit1$ cells can grow on minimal medium containing $C_2$ carbon sources, such as acetate. We also analyzed that the characteristics of mutant strains defective in each of the genes encoding the enzymes involved in TCA and glyoxylate cycles and membrane carriers for metabolite transport. Our results suggest that citrate produced by peroxisomal CS can be utilized via glyoxylate cycle, and moreover that the glyoxylate cycle by itself functions as a fully competent metabolic pathway for acetate utilization in S. cerevisiae. We also studied the relationship between Cit1 and apoptosis in S. cerevisiae [6]. In multicellular organisms, apoptosis is a highly regulated process of cell death that allows a cell to self-degrade in order for the body to eliminate potentially threatening or undesired cells, and thus is a crucial event for common defense mechanisms and in development [7]. The process of cellular suicide is also present in unicellular organisms such as yeast Saccharomyces cerevisiae [8]. When unicellular organisms are exposed to harsh conditions, apoptosis may serve as a defense mechanism for the preservation of cell populations through the sacrifice of some members of a population to promote the survival of others [9]. Apoptosis in S. cerevisiae shows some typical features of mammalian apoptosis such as flipping of phosphatidylserine, membrane blebbing, chromatin condensation and margination, and DNA cleavage [10]. Yeast cells with ${\Delta}cit1$ deletion showed a temperature-sensitive growth phenotype, and displayed a rapid loss in viability associated with typical apoptotic hallmarks, i.e., ROS accumulation, nuclear fragmentation, DNA breakage, and phosphatidylserine translocation, when exposed to heat stress. Upon long-term cultivation, ${\Delta}cit1$ cells showed increased potentials for both aging-induced apoptosis and adaptive regrowth. Activation of the metacaspase Yca1 was detected during heat- or aging-induced apoptosis in ${\Delta}cit1$ cells, and accordingly, deletion of YCA1 suppressed the apoptotic phenotype caused by ${\Delta}cit1$ mutation. Cells with ${\Delta}cit1$ deletion showed higher tendency toward glutathione (GSH) depletion and subsequent ROS accumulation than the wild-type, which was rescued by exogenous GSH, glutamate, or glutathione disulfide (GSSG). Beside Cit1, other enzymes of TCA cycle and glutamate dehydrogenases (GDHs) were found to be involved in stress-induced apoptosis. Deletion of the genes encoding the TCA cycle enzymes and one of the three GDHs, Gdh3, caused increased sensitivity to heat stress. These results lead us to conclude that GSH deficiency in ${\Delta}cit1$ cells is caused by an insufficient supply of glutamate necessary for biosynthesis of GSH rather than the depletion of reducing power required for reduction of GSSG to GSH.

• The Korean Journal of Mycology
• /
• v.20 no.4
• /
• pp.337-346
• /
• 1992

Trichoderma spp. are an effective control agent for damping-off or other plant diseases. The interaction between. T. hamatum and Rhizoctonia solani on the rhizosphere or surface soil were examined to assess the possible roles of antibiosis or competition in the mechanisms of biological control agents as a basic research. In a proportional comparison, total bacteria, fungi, actinomycetes and Trichoderma spp were 65%, 8.8%, 25.9% and 0.28% respectively in their distribution in the soil. Among Trichoderma spp isolated, the 5 species of Trichoderma spp were indentified as T. koninggii, T. pseudokoninggii, T. aureoviridi, T. hamatum and T. viride respectively. In a mycoparasitic test, one isolate of T. hamatum strain Tr-5 showed an enzymatic ability to break fungal hyphae into piecies and infected on the R. solani hyphae showing a parasitism. Spore germination of the all isolates of Trichoderma spp showed a 1.7-7.3% of germination in natural soil conditions, but the percentage was high in sterile soil indicating all the natural soil were fungistatic on conidia of Trichoderma spp. In rhizosphere competent assay in pea plant, the antagonistic T. hamatum, T. viride, T. koninggii, T. pseudokoninggii showed a colonizing upper soil depth in rhizosphere around 1-3 cm in root zone, but the colonizing ability was much reduced along the deeper the soil depth. Propagule density was decreased in deeper the soil layer. Disease development rate treated alone with plant pathogens, Fusarium solani, Rhizoctonia solani, Cylindrocarpon destructans increased, but disease incidence rate reduced in treatment with combinations with antagonistic T. hamatum strain Tr-5.

• Journal of Applied Biological Chemistry
• /
• v.62 no.4
• /
• pp.327-332
• /
• 2019

Alzheimer's disease (AD) is a common neurodegenerative disease. Oxidative stress by amyloid beta peptide (Aβ) of neuronal cell is the most cause of AD. In the present study, protective effects of several flavonoids such as kaempferol (K), kaempferol-3-O-glucoside (KG), quercetin (Q) and quercetin-3-β-ᴅ-glucoside (QG) from Aβ_25-35 were investigated using C6 glial cell. Treatment of Aβ_25-35 to C6 glial cell showed decrease of cell viability, while treatment of flavonoids such as Q and QG increased cell viability. In addition, treatment of flavonoids declined reactive oxygen species (ROS) production compared with Aβ_25-35-induced control. The ROS production was increased by treatment of Aβ_25-35 to 133.39%, while KG and QG at concentration of 1 μM decreased ROS production to 107.44 and 113.10%, respectively. To study mechanisms of protective effect of these flavonoids against Aβ_25-35, the protein expression related to inflammation under Aβ_25-35-induced C6 glial cell was investigated. The results showed that C6 glial cell under Aβ_25-35-induced oxidative stress up-regulated inflammation-related protein expressions. However, treatment of flavonoids led to reduction of protein expression such as inducible nitric oxide synthase, cyclooxygenase-2 and interleukin-1β. Especially, treatment of KG and QG decreased more effectively inflammation-related protein expression than its aglycones, K and Q. Therefore, the present results indicated that K, Q and its glycosides attenuated Aβ_25-35-induced neuronal oxidative stress and inflammation.

• Applied Biological Chemistry
• /
• v.41 no.2
• /
• pp.130-136
• /
• 1998

Microsomes of tomato roots were prepared and the activities of microsomal ATPases were measured in order to understand the molecular mechanisms of various ion transports. The activities of plasma membrane $H^+-ATPase$ and vacuolar $H^+-ATPase$ were evaluated to ${\sim}30%$ and ${\sim}38%$ of total microsomal ATPase activity by using their specific inhibitor, vanadate and nitrate $(NO^-_3)$, respectively. The inhibitory effects of vanadate and $NO^-_3$ were additive and the simultaneous additions of these two inhibitors decreased the total activity up to $50{\sim}70%$. The microsomal ATPase activity was regulated key pH and the maximal activity was obtained at pH 7.4. The activity of microsomal ATPase was increased by $K^+$ up to ${\sim}30%$ at the concentration of $K^+$ above 10 mM. However, the $K^+-induced$ increase in the activity was completely inhibited by the simultaneous addition of $Na^+$. To identify the ATPase activity regulated by $K^+$, the effects of specific inhibitors were measured. Vanadate and $NO^-_3$ inhibited total ATPase activity by 27% and 32% in the absence, of $K^+$ and by 27% and 40% in the presence of 120 mM $K^+$, respectively. These results suggest that $K^+$ increases the activity of $NO^-_3-sensitive$ vacuolar $H^+-ATPase$ but not that of vanadate-sensitive plasma membrane $H^+-ATPase$ since vanadate has no effect on $K^+-induced$ increase in ATPase activity. The microsomal ATPase activity was also decreased by increasing $Ca^{2+}$ concentration. Interestingly, $NO^-_3$ blocked the $Ca^{2+}-induced$ inhibition of microsomal ATPase activity; however, vanadate had no effect. These results imply that vacuolar $H^+-ATPase$ is activated by $K^+$ and inhibited by $Ca^{2+}$.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.36 no.5
• /
• pp.394-406
• /
• 1991

It was proved that cold tolerance of rice plants at the young microspore stage was affected by water temperature and nitrogen application from the spikelet differentiation stage to the young microspore stage, and this mechanism could be explained in the point of view of pollen developmental physiology. The cold tolerance of rice plants at the young microspore stage was severely affected by water temperature (Previous water temperature) and nitrogen application(Previous nitrogen application) from the spikelet differentiation stage to the spikelet differentiation stage. Although the duration is only 10 days or so from the spikelet differentiation stage to the young microspore stage, these days are very important period to confirm the cold tolerance of rice plants at the young microspore stage. The higher previous water temperature up to $25^{\circ}C$ and the deeper previous water depth up to 10cm caused the more cold tolerance of rice plants. Water irrigation of 10cm before the cretical stage showed lower cool injury than that of water irrigation of 20cm during the critical stage. The preventive effect of cool injury by combined treatment of the deep water irrigation before and during the critical stage was not additive but synergistic. The cold tolerance of rice plants grown in previous heavy nitrogen level was rapidly decreased when nitrogen content of leaf blade at the young microspore stage was excessive over the critical nitrogen level. Nitrogen content of leaf blade at the changing point of cold tolerance was estimated as about 3.5% for Japonica cultivars and about 2.5% for Indica x Japonica cultuvars. It is considered that these critical nitrogen contents of leaf blade can be used as a index of the safe critical nitrogen level for the preventive practices to cool injury. It was summarized that increase of engorged pollens per anther by high previous water temperature resulted from the increase of number of differentiated microspores per anther, otherwise, the increase of engorged pollens by the decrease of previous nitrogen level was caused by the decrease of the number of aborted microspores per anther.

• Economic and Environmental Geology
• /
• v.24 no.2
• /
• pp.131-150
• /
• 1991

The Weolseong diatreme was temporally and spatially related to the intrusion of the Gadaeri granite, and was -mineralized by meteoric aqueous fluids. In the Nokdong As-Zn deposit, pyrite, aresenopyrite and sphalerite are the most abundant sulfide minerals. They are associated with minor amount of magnetite, pyrrhotite, chalcopyrite and cassiterite, and trace amounts of Pb-Sb-Bi-Ag sulphosalts. The AsZn ore probably occurred at about $350^{\circ}C$ according to fluid inclusion and compositional data estimated from the arsenic content of arsenopyrite and iron content of sphalerite intergrown with pyrrhotite + chalcopyrite + cubanite. Heating studies of fluid inclusions in quartz indicate a temperature range between 180 and $360^{\circ}C$, and freezing data indicate a salinity range from 0.8 to 4.1 eq.wt % NaCl. The coexisting assemblage pyrite + pyrrhotite + arsenopyrite suggests that $H_2S$ was the dominate reduced sulfur species, and defines fluid parameter thus: $10^{-34.5}$ < ${\alpha}_{S_2}$ < $10^{-33}$, $10^{-11}$ < $f_{S_2}$ < $10^{-8}$, -2.4 < ${\alpha}_{S_2}$ < -1.6 atm and pH= 5.2 (sericte stable) at $300^{\circ}C$. The sulfur isotope values ranged from 1.8 to 5.5% and indicate that the sulfur in the sulfides is of magmatic in origin. The carbon isotope values range from -7.8 to -11.6%, and the oxygen isotope values from the carbonates in mineralized wall rock range from 2 to 11.4%. The oxygen isotope compositions of water coexisting with calcite require an input of meteoric water. The geochemical data indicate that the ore-forming fluid probably was generated by a variety of mechanisms, including deep circulation of meteoric water driven by magmatic heat, with possible input of magniatic water and ore component.

• Economic and Environmental Geology
• /
• v.43 no.4
• /
• pp.305-314
• /
• 2010

The stabilization process using limestone ($CaCO_3$) and steel making slag as the immobilization amendments was investigated for As contaminated farmland soils around Chonam abandoned mine, Korea. Batch and continuous column experiments were performed to quantify As-immobilization efficiency in soil and the analyses using XRD and SEM/EDS for secondary minerals precipitated in soil were also conducted to understand the mechanism of Asimmobilization by the amendments. For the batch experiment, with 3% of limestone and steel making slag, leaching concentration of As from the contaminated soil decreased by 62% and 52% respectively, compared to that without the amendment. When the mixed amendment (2% of limestone and 1% of steel making slag) was used, As concentration in the effluent solution decreased by 72%, showing that the mixed of limestone and steel making slag has a great capability to immobilize As in the soil. For the continuous column experiments without the amendment, As concentration from the effluent of the column ranged from 50 to $80\;{\mu}g/L$. However, with 2% limestone and 1% steel making slag, more than 80% diminution of As leaching concentration occurred within 1 year and maintained mostly below $10\;{\mu}g/L$. Results from XRD and SEM/EDS analysis for the secondary minerals created from the reaction of the amendments with $As^{+3}$ (arsenite) investigated that portlandite ($Ca(OH)_2$), calcium-arsenite (Ca-As-O) and calcite ($CaCO_3$) were main secondary minerals and the distinct As peaks in the EDS spectra of the secondary minerals can be observed. These findings suggest that the co-precipitation might be the major mechanisms to immobilize As in the soil medium with limestone and steel making slag.

• Development and Reproduction
• /
• v.6 no.1
• /
• pp.55-66
• /
• 2002

Embryonic stem cells(ES cells) are derived from the inner cell mass(ICM) of blastocysts, which have the potentials to remain undifferentiated, to proliferate indefinitely in vitro, to differentiate into the derivates of three embryonic germ layers. ES cells are an attractive model system for studying the initial developmental decisions and their molecular mechanisms during embryogenesis. Additionally, ES cells of significant interest to those characterizing the various gene functions utilizing transgenic and gene targeting techniques. We investigated the effects of reproductive hormones, gonadotropins(GTH) and steroids on the induction of differentiation and expressions of their receptor genes using the newly established mouse ES cells. We collected the matured blastocysts of inbred mice C57BL/6J after superovulation and co-cultured with mitotically inactivated STO feeder cells. After 5 passages, we confirmed the expression alkaline phosphatase(Alk P) activity and SSEA-1, 3, 4 expressions. The protocol devised for inducing ES differentiation consisted of an aggregation steps, after 5 days as EBs in hormone treatments(FSH, LH, E$_2$, P$_4$, T) that allows complex signaling to occur between the cells and a dissociation step, induced differentiation through attachment culture during 7 days in hormone treatments. Hormone receptors were not increased in dose-dependent manner. All hormone receptors in ES cells treated reproductive hormones were expressed lower than those of undifferentiated ES cell except for LHR expression in E$_2$-treated ES cells group. After hormone induced differentiation, at least some of the cells are not terminally differentiated, as is evident from the expression of Oct-4, a marker of undifferentiated. To assess their differentiation by gene expression, we analyzed the expression of 7 tissue-specific markers from all three germ layers. Most of hormone-treated group increased in the expression of gata-4 and $\alpha$ -fetoprotein, suggesting reproductive hormone allowed or induced differentiation of endoderm.

• Korean Journal of Animal Reproduction
• /
• v.9 no.1
• /
• pp.9-30
• /
• 1985

The study was carried out to find out the changes of the sex hormone levels in the milk of Holstein cows during the reproductive stages such as the estrous cycle, pregnancy and periparturient period. The FSH, LH, estradiol-17$\beta$ and progesterone from the milk samples were assayed by radioimmunoassay methods. The results of this study were summarized as follows: 1. The levels of progesterone and estradiol-17$\beta$ were similar among inter-quarters, but they were higher in after milking than before milking times, with no statistical significance. 2. The milk progesterone levels during the estrous cycles reached a peak mean level of 3.55$\pm$0.26ng/$m\ell$ at 15 days after estrus and they did not show any differences among the length of estrous cycles. The estradiol-17$\beta$ levels during the estrous cycles showed a peak level of 36.40$\pm$2.38pg/$m\ell$ at estrus, and decreased(17.20$\pm$0.46 pg/$m\ell$ to 18.65$\pm$1.26pg/$m\ell$) at luteal phase. 3. The FSH levels during the estrous cycles ranged from 2.25$\pm$0.23mIU/$m\ell$ to 4.35$\pm$0.24mIU/$m\ell$ showing significant changes. The LH levels during the estrous cycles gradually increased and remained a peak level of 10.90$\pm$0.36mIU/$m\ell$ from 20 to 25 days after estrus. 4. The progesterone levels during the pregnancy were decreased from 30 to 60 days after artificial insemination, and therafter continuously increased until 240 days. The estradiol-17$\beta$ levels during the pregnancy were 24.56$\pm$1.19pg/$m\ell$ at day 30 after artificial inseminaton, and increased rapidly until 180 days. The levles were agagin decreased by 26.17$\pm$3.03pg/$m\ell$ until 210 days and markedly increased by 68.00$\pm$8.70pg/$m\ell$ until 240 days. 5. The prolactin levels during the pregnancy were 31.27$\pm$2.31ng/$m\ell$ and 42.60$\pm$2.37ng/$m\ell$ at day 150 and 240 after artificial insemination respectively. The LH levels during the pregnancy reached a peak of 27.47$\pm$7.90mIU/$m\ell$ at day 30 after artificial insemination, and thereafter gradually decreased. 6. The progesterone levels during the periparturient period reached a peak of 4.61$\pm$0.34ng/$m\ell$ at day 3 prepartum, and thereafter gradually decreased, and showed 2.05$\pm$0.60ng/$m\ell$ at day 7 postpartum. The estradiol-17$\beta$ levels during the periparturient period showed high level from 207.23$\pm$6.04pg/$m\ell$ at day 1 prepartum to 239.90$\pm$13.90pg/$m\ell$ at day 2 prepartum, and thereafter began to decline and reached 51.87$\pm$1.72pg/$m\ell$ at by 7 postpartum. 7. The prolactin levels during the periparturient period showed relatively higher level at the time of parturition. The LH levels during the periparturient period rnage from 6.32$\pm$0.32mIU/$m\ell$ to 13.90$\pm$1.37mIU/$m\ell$ showing significant changes. 8. The progesterone levels(4.6$\pm$0.8ng/$m\ell$) of the pregnant cows were significantly higher than those (1.84$\pm$1.4ng/$m\ell$) of nonpregnant cows. The cows of artificial insemination from 61 to 90 days after parturition showed higher progesterone levels. 9. During 20 to 25 days after artificial insemination, the accuracy of pregnancy diagnosis from milk progesterone levels were 94.4% for nonpregnant cows(<2.3ng/$m\ell$), and 75.0% for pregnant cows( 3.2ng/$m\ell$). The average overall accuracy of pregnancy prediction for nonpregnant and pregnant cows 83.3% 10. The results obtained this study suggest that the understanding of the endocrinological mechanisms by means of milk hormone analysis during the estrous cycle, pregnancy and parturition would give the basic information needed for increasing efficiency of reproduction. This study would not only provide an accurate method of the early pregnancy diagnosis by milk progesterone levels but also contribute to the research of providing the method of detecting of FSH levels in milk, which was difficult in blood serum.

• Korean Journal of Environmental Agriculture
• /
• v.16 no.3
• /
• pp.249-254
• /
• 1997

The constructed wetland system which is applicable to rural wastewater treatment was examined by pilot plant experiment. Removal rates of nutrients including nitrogen and phosphorus and total coliform were evaluated. The $NH_4\;^+$ concentration of the influent was in the range of 91.57 to 275.88mg/l and the effluent concentration was about 40% lower than the influent. The decreasing of the $NH_4\;^+$ concentration might be due to volatilization, plant uptake, adsorption onto soil particles, and mainly nitrification. However, generally concentrations of $NO_2\;^-$ and $NO_3\;^-$ were increased in the effluents compared to the influent concentrations, which implies that nitrogen components in the system were nitrified. Overall, the average removal rate of the nitrogen was about 5% which seems inadequate as a wastewater treatment system, and this system needs improvement on nitrogen removal mechamism. The removal rate of the phosphorus was quite high and effluent concentration was very low. Reason for high removal rate of the phosphorus might be mainly strong adsorption characteristic onto soil particles. The average removal rate of the total coliforms was about 83%, and main removal mechanisms are thought to be adsorption onto soil and inability to compete against the established soil microflora. From the results of the study, the constructed wetland system needs to be improved in nitrogen removal mechanism for field application.