• Clinical and Experimental Reproductive Medicine
• /
• v.46 no.4
• /
• pp.189-196
• /
• 2019

Objective: We aimed to evaluate the effects of different oxygen conditions (20% [high O₂], 5% [low O₂] and 5% decreased to 2% [dynamic O₂]) on mouse pre- and peri-implantation development using a novel double-channel gas supply (DCGS) incubator (CNC Biotech Inc.) to alter the oxygen concentration during in vitro culture. Methods: The high-O₂ and low-O₂ groups were cultured from the one-cell to the blastocyst stage under 20% and 5% oxygen concentrations, respectively. In the dynamic-O₂ group, mouse embryos were cultured from the one-cell to the morula stage under 5% O₂ for 3 days, followed by culture under 2% O₂ to the blastocyst stage. To evaluate peri-implantation development, the blastocysts from the three groups were individually transferred to a fibronectin-coated dish and cultured to the outgrowth stage in droplets. Results: The blastocyst formation rate was significantly higher in the low-O₂ and dynamic-O₂ groups than in the high-O₂ group. The total cell number was significantly higher in the dynamic-O₂ group than in the low-O₂ and high-O₂ groups. Additionally, the apoptotic index was significantly lower in the low-O₂ and dynamic-O₂ groups than in the high-O₂ group. The trophoblast outgrowth rate and spread area were significantly higher in the low-O₂ and dynamic-O₂ groups than in the high-O₂ group. Conclusion: Our results showed that a dynamic oxygen concentration (decreasing from 5% to 2%) had beneficial effects on mouse pre- and peri-implantation development. Optimized, dynamic changing of oxygen concentrations using the novel DCGS incubator could improve the developmental competence of in vitro cultured embryos in a human in vitro fertilization and embryo transfer program.

• The korean journal of orthodontics
• /
• v.48 no.1
• /
• pp.39-47
• /
• 2018

Objective: The aim of this study was to establish the normative data of dentofacial transverse dimensions according to the skeletal maturation stage in Korean adolescents with good occlusion, assess gender differences and determine correlations between transverse variables. Methods: A total of 577 Korean subjects between ages 7 to 19 years and exhibiting skeletal Class I occlusion were categorized by skeletal maturation index (SMI) of Fishman using hand-wrist radiographs. Dentofacial transverse dimensions were assessed using posteroanterior cephalograms. Independent two-sample t-tests were used to analyze differences between genders. Pearson correlation coefficient was used to determine the correlation between transverse measurements. Results: Dentofacial transverse norms relevant to skeletal maturation stages were established. The average maxillomandibular width difference and ratio at growth completion was 22.16 mm and 77.01% for males; 23.70 mm and 74.06% for females, respectively. Males had greater facial, maxillary and mandibular widths compared to females at every SMI stage. The maxillary and mandibular intermolar widths showed the strongest correlation for both sexes (r = 0.826 for males, r = 0.725 for females). Conclusions: Dentofacial transverse norms of Korean adolescents were established according to developmental stage. All dentofacial widths were greater in males at growth completion. Maxillary and mandibular intermolar widths were strongly correlated. This study may serve as a guideline for the assessment of dentofacial transverse growth according to skeletal maturation stage in Korean adolescents with good occlusion.

• Journal of Korean Elementary Science Education
• /
• v.21 no.2
• /
• pp.187-200
• /
• 2002

The purpose of this study is to examine how well students can acquire scientific knowledge from the process and activity presented in the textbook. This is achieved by analysing of comparison on the material area in the 6th and 7th national curriculums' 3rd and 4th grade science textbooks. The method of this study is to analyse the contents, teacher's instruction and illustrations of the textbooks in the material area in both 6th and 7th national curriculum's 3rd and 4th grade science textbooks. Following is the result of the study. First, compared to the 6th national curriculum's content. 7th national curriculum is composed by phenomenon and activity focused. This considers student's developmental stages and abilities of concentration so one topic in the textbook is divided into 16 small contents. Therefore the textbook content of the 7th curriculum seems to have desirable changes. Secondly, teacher's instruction in the textbook of the 7th curriculum has impartial distribution in part Ⅰ and part Ⅱ according to Homey's analysis. This shows that some problems of writing textbooks that were pointed in the 6th curriculum have been improved. Thirdly, the content of the textbook emphasizes inquiry process as the 6th curriculum did. The 7th curriculum, however, more deeply deals with expecting and inferring. Finally, the analysis of illustration shows that the proportion of motive induction is high. This is also desirable approach to give students more interests in studying science.

• Journal of Environmental Health Sciences
• /
• v.29 no.2
• /
• pp.7-15
• /
• 2003

Di-2-ethylhexyl phthalate (DEHP), is a widely used plasticizer known to be a suspected endocrine disrupter, but its exact effects on aquatic organisms are not yet known. When Japanese medaka (Oryzias latipes) were exposed from the time of hatching to 3 months of age to an aqueous DEHP solution at nominal concentrations of 1, 10, and 50 $\mu\textrm{g}$/l, DEHP treated female fish showed distinct reproductive effect. And the midge (Chironomus riparius.). an aquatic invertebrate, was exposed to DEHP to evaluate the effects on reproductive processes via sediment toxicity. The test endpoints included emergence, sex ratio, fecundity, and the viability of F1 offspring egg ropes. The result implied that the normal developmental and/or reproductive processes in C. riparius had been disrupted when exposed to DEHP, the effect also being displayed in the next generation. In summary, DEHP hinders the development of reproductive organs in the female Japanese medaka and C. riparius.

• Proceedings of the Korean Society of Crop Science Conference
• /
• 2017.06a
• /
• pp.230-230
• /
• 2017

About 200 rice varieties for irrigated and rainfed lowland ecosystems were released in the Philippines, which were bred for improving yield under favorable conditions. Root plasticity plays key roles in maintaining crop productivity under abiotic stressed conditions. We hypothesized that some of these varieties possess root plasticity traits in response to water stressed conditions. This study aimed to evaluate the root system development and dry matter production of 14 randomly selected rice varieties (6 irrigated lowland and 9 rainfed varieties) under progressive drought (PDR) and soil moisture fluctuations (SMF) stress conditions. Two experiments were done in rootbox and line source sprinkler systems (LSS). Each of the varieties was subjected to well-watered (WW), PDR and SMF conditions during vegetative stage in rootbox system while the same genotypes were subjected to different intensities of drought stress under LSS. Under rootbox system, PDR and SMF significantly reduced shoot dry matter production in all varieties relative to their WW controls. Among varieties, NSIC Rc238 (irrigated lowland) showed the least reduction in shoot dry weight (SDW) in both PDR (by 11.8%) and SMF (by 26.9%) conditions. Less reductions in SDW of NSICRc238 were partially attributed to the promotion of L-type lateral roots, thus increasing total lateral root length by 24.2% and 30.7% under PDR and SMF, respectively. In LSS, SDW of NSIC Rc238 under mild drought stress (16-21% soil moisture content (SMC) had 31.8% reduction relative to its WW control (${\geq}22%SMC$) and had lower sensitivity drought index. Compared with the IR64 susceptible check and NSIC Rc9 tolerant check, NSIC Rc238 had higher SDW by 90.8% and 38.6%, respectively. Furthermore, no rainfed lowland varieties included in the experiment performed well under different water stress treatments. The results implied that some other irrigated lowland rice varieties may also possess drought dehydration avoidance root plasticity traits under water-stressed growing environments.

• The Journal of the Korea Contents Association
• /
• v.16 no.1
• /
• pp.438-444
• /
• 2016

Previous findings on Social Loafing indicated that Social Loafing explained the organizational commitment, that the lower level of Social Loafing they had, the higher performance they would have, and that it is a useful index for effectiveness of the organization. This study explored the Police Organizational culture & Organizational Commitment on Social Loafing. The Police officers' Police Officer's Organizational culture & Organizational Commitment and Social Loafing has been measured, and then how Organizational culture & Organizational Commitment affects Police Officer's Social Loafing has been examined. The study results may be used as a theoretical basis to assert the need of Organizational culture & Organizational Commitment to decrease the Police Officer's Social Loafing. Independent variable is Police Officer's Social Loafing and Dependent variable is comprises 2 categories; Police Organizational culture(The group culture, The hierarchical culture, The developmental culture, The rational culture), & the Organizational Commitment(Affective Commitment, Continuance Commitment, Normative Commitment). The result of analysis showed that The group culture & Normative Commitment influenced in Social Loafing(positive), and The Rational culture, Affective Commitment, & Continuance Commitment in Social Loafing(negative).

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.33 no.3
• /
• pp.184-191
• /
• 2000

Gametogenesis and the reproductive cycle of the marsh clam, Corbicula leana(Prime} were investigated monthly Hyongsan estuary, Korea from January to December 1998 by histological observation. C. leana had separate sexes, and oviparous. The gonads were located between the sub-region of mid-intestinal gland in visceral cavity and reticular cennective tissue. The ovary and testis were composed of a number of ovarian and testicular tubules, respectively, Mature oocytes were characterized by germinal vesicles with nucleoli and their sizes ranged $70\;to\;80{\mu}m$ in diameter. A number of mesenchymal tissues and pigment granular cells were distributed in the growing oocytes and spermatocytes during early developmental stages. With the further development of gonad, these tissuse and cells gradually disappeared. The monthly changes in the fatness index were closely related to reproductive cycle. Minimun size for sexual maturity was reached over 10.0 mm in shell length. The reproductive cycle could be classified into 6 stages : multiplicative (March to April): early growing and growing (May to June), mature (July to August), spent (September), degenerative (October) and recovery (November to February).

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.33 no.3
• /
• pp.219-224
• /
• 2000

Reproductive biology of the naked-headed goby, Faronigobius gymnauchen was investigated by means of histological methods. The ovary was consisted of several ovarian lamellae and the oogonia originated from the inner surface of the ovarian lamella. The testis was seminiferous tubule One in internal structure. Seminiferous tubule was consisted of many testicular cysts which contained numerous germ cells in a same developmental stage. The size of group maturity was 4.5 cm intotal length. Gonadosomatic index(GSI) of the female and male was the highest in June and July, respectively. Reproductive cycle could be classified into the growing ($January{\~}March$), maturation ($April{\~}May$), ripe and spent (June{\~}July$), and recovery and resting ($August{\~}December$). Oocyte development was group-synchronous, and yolk nucleus was observed in the early growing oocyte.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.29 no.1
• /
• pp.26-34
• /
• 1996

Copulation process, fertilization and gestation of the viviparous teleost surfperch, Ditrema temmincki were investigated by using photomicroscopy. Samples were collected from the vicinity of Suyoung Bay, Pusan, Korea from May 1992 to August 1993. During the copulation period, the copulatory organs were protruded at the base part of right and left soft ray of the anal fin in mature male. Secondary sexual characteristics index (SSCI) of male participated in copulation was above 3.5. Mature oocytes appeared only in the female containing sperms in the ovarian cavity. Transport of the spermatozoa into the ovarian cavity during copulation belonged to a spermatophore type. After copulation, spermatozoa remained in the ovarian cavity for about one month untill fertilization. Fertilization occured within the follicular cavity. Fertilized eggs were released into the ovarian cavity where they developed during gestation period. Developmental sequence of the female was as following: fertilization-ovulation-hatching-parturition. Right before parturition, the total length (TL) of the embryo was about 63.0 mm. When TL of maternal body was 20.0 cm, the mean numbers of the embryo were 18. The numbers of the embryo were positively related to the maternal body size.

• Development and Reproduction
• /
• v.20 no.4
• /
• pp.305-314
• /
• 2016

The marine medaka, Oryzias dancena is a suitable sample as a laboratory animal because it has a small size and clearly distinguishes between female and male. Data on the growth and maturity of the diploid and triploid sea cucurbit species suitable for laboratory animals are very useful for studying other species. Triploidy was induced in the marine medaka by cold shock treatment ($0^{\circ}C$) of fertilized eggs for 45 min, applied two minutes after fertilization. The diploid and triploid male fish were larger than their female counterparts (P<0.05), and the concentrations of thyroid stimulating hormone (TSH) and thyroxine (T4) were higher in the induced triploids over 1 year (P<0.05). In both the diploid and tri-ploid groups the concentrations of TSH and T4 were higher in the male fish than in the females (P<0.05), while the testo-sterone and estradiol-$17{\beta}$ concentrations in the induced triploids were lower than in the diploids (P<0.05). The gonadosomatic index (GSI) of the triploid fish was lower than that for the diploids, and the GSI for females in each ploidy group were higher than that for the males. For both groups the GSI was highest at 4 months of age, and decreased thereafter to 12 months. Analysis of the gonads of one-year-old triploid fish suggested that the induction of triploidy probably causes sterility in this species; this effect was more apparent in females than in males.