• Parasites, Hosts and Diseases
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• v.28 no.1
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• pp.31-38
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• 1990

Cryptosporidium, a coccidian parasite first described by Tyzzer (1907) from a laboratory mouse, has become an important human enteric pathogen causing overwhelming diarrhea especially in immunocompromised patients such as AIDS. This parasite has been reported from over 20 countries and is recognized as a cosmopolitan species. In Korea, however, thEre has been no report on human as well as animal cryptosporidiosis. This study was performed so as to verify the presence of Cryptosporidium in Korea by activating the parasite from laboratory mice by immunosuppression. Total 65 conventionally.bred ICR mice including a control (5 mice) and 3 experimental groups (20 each) were used for this study. Group I was immunosuppressed with Prednisolone injection (1 mg IM, every other day) for 7 weeks. Group II (prednisolone injection and tetracycline administration) and Group III. (prednisolone injection and trimethoprim-sulfamethoxazole administration) were prepared to observe the effect of antibacterial agents on the activation of cryptosporidiosis. In fecal examinations of mice Cryptosporidium oocysts($4-6{\mu\textrm{m}}$ in size) were detected from 1 week after the start of immunosuppression and the mice began to die. In H-E stained tissue sections of the lower jejunum, numerous very small ($2~4{\;}{\mu\textrm{m}}$), dense, ovoid or spherical, slightly basophilic bodies were seen attached on the free border of mucosal epithelial cells. In scanning and transmission electron microscopic observations, these organisms were identified as various developmental stages of Cryptosperidium. The species is considered to be C. parvum. Cryptosporidiosis was activated not only in Group I but also in Group II and III, indicating no protective effects of the antibacterial agents used, although the mice in Group II and III lived longer than those in Group I. The present study confirmed that Cryptosporidium exists in laboratory mice bred in Korea, and predicts possible occurrence of human cryptosporidiosis in Korea.

• Journal of the Korean Wood Science and Technology
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• v.34 no.6
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• pp.1-11
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• 2006

Grafted tissues were investigated using various microscopic techniques. Pinus thunbergii was used as stock and scion and autografted by cleft graft method. Histochemically, grafting processes can be proceeded by four stages: 1) formation of necrotic layer, 2) proliferation of callus, 3) development of neo-cambium from callus, and 4) restoration of new vascular xylem. Necrotic la yer composed of pectin and lignin was gradually degraded during grafting process and disappeared when new union was formed between stock and scion. A large number of starch and lipid bodies in the cytoplasm were also gradually degraded during grafting process and disappeared at the grafting interface. Nucleus and plasmodesmata were not changed. Bubble-like callus was generated from all living parenchyma cells and from the callus. The tracheary elements differentiated from the callus had either reticulate or pit-like thickenings in the secondary walls with bordered pits. Secondary cell wall thickening occurred toward filing to the void parts between reticulated secondary wall. Tracheids formed in the secondary xylem were short with irregular wall thickness. New secondary xylem cells with swirled shapes, which developed in graft union were oriented horizontally and obliquely to axis of the stem.

• The Korean Journal of Malacology
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• v.32 no.2
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• pp.133-139
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• 2016

The incubation time required for hatching of O. ocellatus were investigated through the processes of egg and embryonic developments by the dissecting microscopic and visual observations. And differences in ecological characteristics of the plankton mode of life or the benthic mode of life according to total numbers of the suckers on each short arm of the hatched juvenile larvae of O. ocellatus were studied by comparisons with other octopodidae species. Compared with the recent a few results reported by other researchers associated with the incubation time required for hatching by female adult mother of O. minor (73-90 days after spawning at $20.9-21.5^{\circ}C$ ranges), in this study, the incubation time required for hatching by female adult mother of O. ocellatus was 56-57 days after spawning at $11.0-20.4^{\circ}C$. Therefore, the incubation time required for hatching by female adult mother varied with Octopodidae species. In this studies, each ovarian egg laid by a female was connected to an egg string attaching to the surface of the wall or bottom of vacunt shell of Rapana venosa. Egg and embryonic developments of this species were studied in the indoor aquaria, in the specific gravity ranging 1.024-1.025. the hatched juvenile of O. ocellatus is 10.3 mm in the mean total length and 4.5 mm in mantle length, and each of its short arms has 18-20 suckers. The just hatched juvenile larvae of O. ocellatus enter the benthic mode of life (benthic larval stage) after hatching. In particular, regarding differences in ecological characteristics of the mode of life according to total numbers of the suckers, O. vulgaris may not need to have many suckers because they enter the planktonic mode of life after hatching, however O. ocellatus may need to have many suckers, because they should adapt to the benthic mode of life. And also the just hatched juvenile larvae of O. minor (bearing many suckers more than O. ocellatus) enter the benthic mode of life (benthic larval stage) after hatching. Therefore, the total number of the suckers on each short arm of the hatched juvenile larvae can be used for determining whether an octopus species has planktonic larval stages or benthic larval stage (benthic mode of life). In particular, The intracohort cannibalism phenomena appeared at the hatched juvenile larval stage because the larval stage of O. ocellatus and O. minor enter into the benthic larval stage in the early stage, unlike entering into the plaktonic larval stage in other Octopus species such as O. vulgaris: at this time, the early hatched larvae fed the late hatched larvae (they are the same species and almost same ages). Therefore, the intracohort cannibalism pheneomena occur in the just hatched juvenile stage of only O. ocellatus and O. minor.

• Applied Microscopy
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• v.35 no.4
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• pp.91-97
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• 2005

The acinar cells and secretory granules of the parotid salivary gland were examined in the lesser white toothed shrew, Crocidura suaveolens and the big white-toothed shrew, C. lasiura. The parotid gland of both species were a serous gland having only one kind of serous acinar cells, and had conventional arrangement of acini and intercalated, granular and striated ducts. In case of C. suaveolens, serous acinar cells had well developed rER, prominent Golgi complex, several large mitochondria and abundant moderate dense secretory granules with various stages of the maturing or fusing process. Immature acinar secretory granules were only or mainly filled with fine strong dense specks and had an indistinct limiting membrane, and mature granules were filled with homogeneous pale large round center and had fine strong dense specks at the periphery of the homogeneous pale center and a distinct limiting membrane. In case of C. lasiula, serous acinar cells had well developed rER, prominent Golgi complex, several large mitochondria and abundant dense secretory granules with maturing or fusing process. Immature acinar secretory granules were only filled with pale rough specks and had an indistinct limiting membrane, and mature granules were only filled with rough dense specks and had a distinct limiting membrane. Eventually The acinar secretory granules of C. suaveolens were seen moderate at the light and ultrastuctural level, those of C. lasiura were strong dense at the light microscopic level and dense at the ultrastructural level.

• Parasites, Hosts and Diseases
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• v.36 no.4
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• pp.217-225
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• 1998

A scanning electron microscopic study was performed to observe surface ultrastructures of excysted metacercariae and adults of Metagonimus miyatai. Metacercariae were collected from the scale of the pale chub (Zacco platypus). and adult flukes were harvested 1-4 weeks after infection to rats. In excysted metacercariae, the oral sucker was devoid of tegumental spines and had type I and type II sensory papillae. Anteriorly to the ventral sucker, spines were dense and digitated into 5-7 points, whereas near the posterior end of the body spines were sparse and digitated into 2-3 points. In one-week adults, 7 type II sensory papillae were arranged around the lip of the oral sucker. and at inner side of the lip one pair of small and two pairs of large type I sensory papillae were seen on each side. The distribution of tegumental spines was similar to that of metacercariae, but they were more differentiated with 9-11 pointed tips. In two- to four- week old adults, the surface ultrastructure was nearly the same as in one-week old adults, however, sperms were frequently seen entering into the Laurer＇s canal. Conclusively, the surface ultrastructure of M. miyatai was generally similar to that of M. yokogawai, however, differentiation of tegumental spines and distribution of sensory papillae around the oral sucker were different between the two species. which may be of taxonomic significance.

• Journal of Life Science
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• v.14 no.2
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• pp.331-338
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• 2004

Growth and sexual differentiation of the seaweed Porphyra pseudolinearis Ueda have been investigated monthly in the intertidal zone of the East Sea, Korea. Young blades of P. pseudolinearis appeared at the beginning of October. Carp os pores were released at the end of November immediately after carposporangia formation. Then the thalli of P. pseudolinearis were extinguished at the end of March. Young thalli were budded through the stages of conchocelis and conchospore. Thalli showed lanceolate type in shape, cordate type in holdfast, absence of microscopic spinulate process and sexual generation. Ratios of length to width in female thalli ranged from 5.6 to 7.4 at the maturation in December and slightly decreased 3.3 to 4.8 in January and 4.9 to 7.3 in December while the ratios of male thalli ranged from 4.2 to 4.8 in January. On October 12, average five individuals were obsered in a quadrate (30 cm ${\times}$ 30 cm), 238$\pm$18 individuals for the maturation stage in December and then it was reduced to 150 individuals in February and 15 individuals in March. Average sex ratios for female, male and vegetative thalli were 31.3% 46.9% and 21.9% respectively in early December, the beginning time of sex maturation. The sex ratio of female and male thalli in December 17, changed to 69.4%, 30.6% respectively.

• The Korean Journal of Zoology
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• v.20 no.2
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• pp.77-92
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• 1977

A study has been made to correlate morphological and biochemical differentiation in the oocytes of a tubiculous polychaete, Schizobranchia insignis. The pressent paper is concerned with an examination of the cytological changes during oogenesis and annual size distribution of oocytes, The oocytes are released from the ovary into the coelomic sac at the end of the oogonial division and grow to a maximum size (180 $\\mu$ diameter). Oogensis takes place continuously throughout a year, although the breeding season is the period between January and March. When the oocytes reach the largest size class, they remain constant in size thereafter and accumulate in the coelomic sac. The nucleolus, which first appears in the oocytes 5-10$\\mu$ diameter, grows in the early stages of oogenesis, becomes maximum in the oocytes 100-120$\\mu$ diameter, and is constant throughout the rest of the pertiod. The nuclelus initially has a single comartment but becomes bipartite prior to vitello genesis. Three types of yolk including lipid droplets, proteid granules and oval granules oof unknown composition form at different times of oogenesis. The lipid droplets and oval granules appear in the early stage, but mainly in the oocytes larger than 80 $\\mu$ diameter. Proteid yolk and cortical granules appear only in the oocytes larger than 80 $\\mu$ diameter Microvilli are abundant in the oocyte 80 $\\mu$ diameter and embedded in the vitelline membranc. In the oocytes 180 $\\mu$ diameter they have retracted from the vitelline membrane.

• Journal of Veterinary Clinics
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• v.22 no.2
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• pp.157-159
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• 2005

Two-month old male Shih Tzu weighing 2.1 kg was presented with alopecia in black-haired areas of the skin. The hair loss had been present since five weeks of age. There was no history of pruritus on any part of the body. No other symptoms had been recognized. Physical examination found no abnormalities other than hair loss. Skin examination showed marked alopecia of black-haired area of the body. The white areas appeared to have hair growth of normal density and texture. Affected pigmented areas showed no evidence of skin lesions. Skin scraping and fungal culture were negative. Microscopic examination of plucked black hairs showed marked pigment clumping in the remnants of the follicles and were mainly in telogen phase. But white hairs were normal in various stages of hair growth. The diagnosis of black hair follicular dysplasia was made based on the history, alopecia of the pigmented areas, the confinement of abnormalities to dark areas, and the normal unpigmented areas.

• The korean journal of orthodontics
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• v.24 no.2
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• pp.331-348
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• 1994

The purpose of this study was to investigate changes in the shape and ultrastructure of the articular disc of the rat mandibular joint with aging. Mechanical stress applied to the articular disc changes during neonatal, suckling, juvenile, adult and senile stages. Mandibular joints of 6 groups of rats(1-, 7-, 17-, 27-, 55-day and over-1-year groups) were removed en bloc and processed for light and electro microscopic study. The changes in the shape of articular disc were examined by light microscope in each group. Structural and ultrastructural changes in the articular disc were examined by light and electron microscope in each group. The results were as follows : In the 1-day and 7-day groups, the articular disc was long and slender in shape and the articular disc was not fitted with the shape of the mandibular fossa and condyle. However' after that time, the anterior and posterior portions of the articular disc were more bulged and the middle portion was shorter and biconcave. Thus the articular disc was well fitted with the shape of the mandibular fossa and condyle. The cell density decreased with aging. In the l -day and 7-day groups, the Golgi apparatus, rough endoplasmic reticulum and free ribosome, which are involved in the synthesis of intracellular and extracellular matrix, were developed. In the 17-day, 27-day and 55-day groups, not only the cell organelles involved in the synthesis of the intracellular and extracellular matrix but also the cell organelles involved in the remodeling of the extracellular matrix(i.e., finger-like cell process, lysosome and mitochondria)were well developed. With advancing age, intracytoplasmic microfilaments were more accumulated and condroid cells increased. In the over-1-year group, the majority of cells of the articular disc were chondroid cells. The majority of cytoplasmic compartment were filled with intracytoplasmic microfilaments and cell organelles were not developed. Therefore, metabolic activities of the cell was markedly reduced and cells contained structures enduring mechanical stress, and cells which were in the process of degeneration were observed occasionally.

• Journal of the Korean Chemical Society
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• v.64 no.5
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• pp.304-317
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• 2020

This study was conducted on four 11^th grade students at a high school in a small town to determine the effectiveness of responsive teaching. The three phases of the responsive teaching method proposed in the previous study were subdivided into six stages; Step 1 is elicitation of students' thoughts related to macroscopic world, Step 2 is drawing of students' early thoughts related to microscopic world, Step 3 is disciplinary connections with ideas of the particle, Step 4 is to clarify the learner's thoughts on the particle by the teacher's involvement, Step 5 is deepening students' thoughts, and Step 6 is expanding ideas. In Step 4, students came to the recognition that the cause of mass was atoms and that the cause of volume was molecules. In Step 5, students led to a shift in thinking that could ignore the volume of the molecules themselves through the properties of protons and neutrons that affect mass from a particle perspective. In the Step 6 of expanding ideas, students explained molecular motion by the concept of material point which ignores the volume of particles. This steps gave students perspectives on the relationship between the mass and volume of particles required by Avogadro's law. The students recognized that some systems could be studied only indirectly because they were too small, too large, too fast, or too slow to observe directly.