• ALGAE
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• v.19 no.3
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• pp.175-190
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• 2004

The morphological and molecular characteristics of Pachydictyon coriaceum (Holmes) Okamura (1899) are described. Plants are collected from Korea all year round and have maximum height from August to September. The monthly variability of thallus growth is in the way with that of the seawater temperature. Two types of thallus structures, thick cortical layer tallus type and thin cortical cell layer type, are distinguished according to growing seasons. The habit of Korean plants is also classified into two thallus types, slender type and wide type, based on the length and the width of internodes, but this distinction between two types is not supported by either anatomical or molecular characteristics. P. coriaceum shares typical morphology in branching pattern and morphogenetic processes with the other species of Dictyota: 1) multi-cellular cortical and medullar layer in the partial of thallus, 2) same development of thallus from apical meristem cell, and 3) sub-lineage within Dictyota species lineage in rbcL, psaA and psbA gene sequences analyses. These characteristics lead to propose the new combination of Dictyota coriacea (Homes) I.K. Hwang, H.S. Kim et W.J. Lee, comb. nov.

• Proceedings of the Botanical Society of Korea Conference
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• 1985.08b
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• pp.35-48
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• 1985

Plastids, which are organelles unique to plant cells, bear their own genome that is organized into DNA-protein complexes (nucleoids). Regulation of gene expression in the plastid has been extensively investigated because this organelle plays an important role in photosynthesis. Few attempts, however, have been made to characterize the regulation of plastid gene expression at the chromosomal structure, using plastid nucleoids. In this report, we summarize the recent progress in the characterization of DNA-binding proteins in plastids, with special emphasis on CND41, a DNA binding protein, which we recently identified in the choloroplast nucleoids from photomixotrophically cultured tobacco cells. CND41 is a protein of 502 amino acids which consisted of a transit peptide of 120 amino acids and a mature protein of 382 amino acids. The N-terminal of the 'mature' protein has lysine-rich region which is essential for DNA-binding. CNA41 also showed significant identities to some aspartyl proteases. Protease activity of purified CND41 has been recently confirmed and characterized. On the other hand, characterization of accumulation of CND41 both in wild type and transgenic tobacco with reduced amount of CND41 suggests that CND41 is a negative regulator in chloroplast gene expression. Further investigation indicated that gene expression of CND41 is cell-specifically and developmentally regulated as well as sugar-induced expression. The reduction of CND41 expression in transgenic tobacco also brought the stunted plant growth due to the reduced cell length in stem. GA3 treatment on apical meristem reversed the dwarf phenotype in the transformants. Effects of CND41 expression on GA biosynthesis will be discussed

• Korean Journal of Soil Science and Fertilizer
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• v.36 no.6
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• pp.429-436
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• 2003

The relationship between seeding depth and apical hook opening was investigated in the hypocotyl hook of soybean (Glycine max Merr., cv. Hwanggeum). Seeds were sawn in different depths (2.5, 5.0, 7.5, and 10.0 cm). The hook opening was slowly progressed with seeding depth. Hook angle opening velocity was negatively correlated with hypocotyl growth at the significant level of P<0.01. It was also clearly observed that seeding depth was positively correlated with hypocotyl growth, suggesting the induction of hypocotyl growth by deep sawing. Futhermore, the contents of fructose and glucose in hypocotyls were about higher than in cotyledons. Both sugars in hypocotyls were highest at the emergence stage. After emergence, their levels were obviously reduced. Total soluble sugar contents continuously retained in cotyledons which were grown at 2.5 and 5.0 cm seeding depths whereas the contents in cotyledons of deep sawn soybean were extremely lowered. It seemed that sugars were actively used to cell construction during the hypocotyl elongation. The results demonstrated that apical hook opening is closely related with light signal after emergence. It implied that the delay of hook opening in deep sawn seeds was resulted from hypocotyl growth in darkness. We suggest that apical hook opening is progressed in sucrose catabolism by light.

• Applied Microscopy
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• v.26 no.3
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• pp.369-377
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• 1996

Ultrastructural changes of chloride cells in the gill from seawater-adapted killifish (Orizias latipes) were studied with a transmission electronmicroscope. Chloride cells contain many mitochondria and specifically developed tubular systems. Apical pits, formed by several neighboring chloride cells, were exposed to the environment. Degeneration and death of the chloride cells by apoptosis occurred more frequently than by necrosis. Apoptotic chloride cells shrank, became to apoptotic bodies, and eventually were phagocytosed and digested by the microphages around them. We conclude that apoptosis plays an important role in increased cellular turnover of chloride cells for the osmoregulation caused by changes in salinity of the environment.

• Korean Journal of Animal Reproduction
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• v.11 no.3
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• pp.206-217
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• 1987

Testes from the drake and the gander have been examined by the electron microscopy in thin sections in order to examine the spermiogenesis and the structure of spermatozoa. The spermiogenesis can be divided into three stages: early spermatid, nuclear elongation, and matured spermatid. In the early spermatid of the drake, there are thread-like material in the nucleus, a prominent nuclear envelope around the nucleus, and big lumens in the cytoplasm. The shape of the gander's mitochondria in the early spermatid is slender compared to that of the drake, and the inner membrane of the mitochondria is thicker than the outer membrane. The distal centriole of the drake and the gander in the early spermatid is a long hollow cylinder form. In the nuclear elongation stage, elongated nucleus forms two or three cross sections in one spermatid cell and it is surrounded by the amorphous sheath. The nucleus of the matured spermatid is compact and its apical end is covered with acrosome cap and acrosome spine. The axoneme is surrounded by the amorphous material.

• Journal of Dairy Science and Biotechnology
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• v.15 no.1
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• pp.27-32
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• 1997

Most lipids in milk are dispetsed as the form of fat globules. Apical portion of plasma membrane is coated with fat globules, which are synthesized from mammary epithelial cells and then secreted into the lumen. The unique phenomenon in separation of the plasma membrane from the cell is observed only in mammary system. It has been suggested that milk fat globule membrane(MFGM) is formed from endoplasmic reticulum, Golgi apparatus, secretory granule to plasma membrane. For this reason MFGM is important for nuderstanding the structure and function of biological membrane. Because MFGM also plays an important role in inhibition of lipase action, stimulation of nutrient digestion and absorption, emulsion or function as natural liposome, study of the major components in MFGM will provide the opportunity for more broad industrial uses of MFGM in the future.

• Journal of the Korean Society of Tobacco Science
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• v.21 no.2
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• pp.171-181
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• 1999

We examined the ultrastructure of eupyrene and apyrene spermatogenesis in the testis of Helicoverpa assulta (Lepidoptera: Noctuidae). The spermatogenesis was progressed near the fringe adjacent to the follicular layer of the testicular follicle, surrounding the apical cell concentrically. Eupyrene and apyrene were firstly distinguished at the telophase stage of the primary spermatocyte. Chromatin was evenly scattered in eupyrene nuclei, whereas it was lumped near the nuclear envelope in apyrene spermatogenesis. Then, the nucleus of eupyrene was transformed into two daughter nuclei by meiosis, while the nucleus of apyrene was divided into many micronuclei by irregular meiosis. After the meiosis was completed, a number of mitochondria in the cytoplasm of the early spermatids of the eupyrene and the apyrene were fused into one nebenkern. Also, as axial filament was formed due to the elongation of the spermatid, the nebenkern became splitted into mitochondrial derivatives. An acrosome precursor was present only in the eupyrene, attached to nuclear envelope.

• Journal of Biomedical Engineering Research
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• v.17 no.3
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• pp.355-364
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• 1996

Construction of the stable monolayer of endothelial cells onto physicochemically modified polymeric surFace is one of the appropriate method to develop the small caliber vascular graft with the long-term patency. In this study, we constructed the monolayer of endothelial cells on the fibronectin rind the extracellular matrix-coated polyurethane surface derived from human fibroblast cells. To elucidate the adhesion strength of endothelial cells on the extracellular matrix-coated polyurethane, a laminar flow chamber apparatus was developed to exposure the shear stress on the apical membrane of ondothelial cells. Endothelial cells show the strongest adhesion after two days of seeding onto the fibronectin-coated polyurethane surface, whereas endothelial cells on the extracellular matrix derived from the human flbroblast cells show the minimal doubling time of cellular growth.

• Proceedings of the Korean Biophysical Society Conference
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• 2001.06a
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• pp.27-27
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• 2001

In exocrine acinar cells, $Ca^{2＋}$ -activated Cl$^{[-10]}$ channels in the apical membrane are essential for fluid secretion, but it is unclear whether such channels are important for Cl$^{[-10]}$ uptake at the base. Whole cell current recording, combined with local uncaging of caged $Ca^{2＋}$, was used to reveal the Cl$^{[-10]}$ channel distribution in mouse pancreatic acinar cells, where ~90％ of the current activated by $Ca^{2＋}$ in response toacetylcholine was carried by Cl$^{[-10]}$ .(omitted)

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.234.3-235
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• 2003

The aim of this study is to evaluate the permeability of PEG-conjugated salmon calcitonin (sCT) across monolayers of Caco-2 cells that represent a model of the intestinal barrier. Caco-2 cells were grown to confluency on a permeable polycarbonate membrane to permit transport through it. Permeability experiments were performed with native-sCT and PEG-conjugated sCT (PEG M.W. 2000) at various concentrations (5uM, 10uM, 25uM, 50uM, 100uM) in the apical to basolateral direction. The barrier properties were assessed by detecting transport of markder molecules ($^3$H-mannitol) and by measuring transepithelial electrical resistance (TEER). (omitted)