• Journal of Plant Biology
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• 제36권3호
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• pp.285-292
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• 1993

Cellular compatibility in the self-parasitism of Cuscuta australis R. Brown was studied at the ultrastructural level. The front cells of the haustorium penetrated the host stems independently grew within the host tissues and transformed into elongate, filamentous hyphae. Each hyphal cells contained a large nucleus and dense cytoplasm with abundant cell organelles. Multilamellar structures were contained in the cytoplasm and cell walls of the penetrating hyphal cells. When the hyphal cells did not yet invade the host cells, the middle lamella and the fused cellulosic cell walls of the two partners at the host-parasite interface were preserved well. As the invasion of the parasitic hyphal cells progressed, however, the middle lamella was not found at the interface and the host cell walls and plasma membranes were partially broken down. A hyphal cell penetrated deeply into the host cell had a more darkly stained cytoplasm with numerous of cell organelles. In the host cells attacked by the hyphal cells the limiting membranes of plastids were broken down and several vesicles were arrayed near the cell walls. No plasmodesmatal connections between the host and parasite cell walls were found; however, half-plasmodesmata were observed frequently on the side of the hyphal cell walls. These results suggested that the compatibility response in the self-parasitism of Cuscuta was expressed by cell walls, not by plasmodesmata, between the host and the parasite cells.

• ALGAE
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• 제20권3호
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• pp.225-232
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• 2005

Optical microscopy of recently living and cleared material of the fucoid, Ascophyllum nodosum (L.) Le Jolis, revealed novel aspects of its interaction with the ascomycete Mycophycias ascophylli (Cotton) Kohlmeyer and Kohlmeyer (previously Mycosphaerella ascophylli Cotton). Most host cells are associated with hyphae by lateral attachment of cell walls. Hyphae form extensive networks throughout the host thallus and show considerable differentiation in the various host tissues. In the base of epidermal cells, hyphae form multicellular rings around each host cell to produce a continuous network. In medullary regions, long, relatively unbranched and longitudinally aligned hyphae occur, with radial branches extending into cortical regions. Scattered in the inner cortex of host tissue are numerous multicellular nodes of smaller, polygonal to irregular shaped cells with five or more radiating arms of hyphae. Individual hyphal cells show a variety of specializations including swellings and appressoria-like attachments to some host cells. These observations provide the morphological basis for the mutualistic symbiosis supported by recent experimental work. We conclude that this association is best described by the term “symbiotum.”

• IMMUNE NETWORK
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• 제21권1호
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• pp.3.1-3.16
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• 2021

Coronavirus disease 2019 caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been spreading worldwide since its outbreak in December 2019, and World Health Organization declared it as a pandemic on March 11, 2020. SARS-CoV-2 is highly contagious and is transmitted through airway epithelial cells as the first gateway. SARS-CoV-2 is detected by nasopharyngeal or oropharyngeal swab samples, and the viral load is significantly high in the upper respiratory tract. The host cellular receptors in airway epithelial cells, including angiotensin-converting enzyme 2 and transmembrane serine protease 2, have been identified by single-cell RNA sequencing or immunostaining. The expression levels of these molecules vary by type, function, and location of airway epithelial cells, such as ciliated cells, secretory cells, olfactory epithelial cells, and alveolar epithelial cells, as well as differ from host to host depending on age, sex, or comorbid diseases. Infected airway epithelial cells by SARS-CoV-2 in ex vivo experiments produce chemokines and cytokines to recruit inflammatory cells to target organs. Same as other viral infections, IFN signaling is a critical pathway for host defense. Various studies are underway to confirm the pathophysiological mechanisms of SARS-CoV-2 infection. Herein, we review cellular entry, host-viral interactions, immune responses to SARS-CoV-2 in airway epithelial cells. We also discuss therapeutic options related to epithelial immune reactions to SARS-CoV-2.

• Animal cells and systems
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• 제1권3호
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• pp.491-496
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• 1997

When olfactory placodes are transplanted at stages 23/24 from Xenopus laevis to Xenopus borealis hosts of the same age, it is possible to distinguish the cell populations of the host and donor due to the peculiar nuclear Q bands specific to X. borealis. I have replaced the eye anlage in each of a number of X. borealis with the transplanted olfactory placode of an individual X. laevis, or vice versa. In most instances, the placode of the donor fuses with that of the host. When fusion occurs, but not when the host and donor orqans grow separately, the cells of the donor were replaced gradually and according to a characteristic pattern by cells of the host. The basal cells of the donor were the first to be replaced, followed by the more matured cells of the sensory epithelium. This cellular substitution, proceeding in an orderly fashion from bottom to upper layers of the epithelium, depends on the fusion of the two organs. This observation suggests intercellular contacts in the mitotic zone of the two organs favor the host's cells over those of the donor.

• Applied Microscopy
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• 제15권2호
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• pp.1-9
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• 1985

The portion of Cuscuta japonica haustorium which lies internal to the host tissues, the endophyte, was examined at the ultrastructural level. The endophyte consisted of mainly small parenchymatous cells and large, slightly elongate cells at the tip. The tip cells were characterized by the presence of large and lobed nucleus, several small vacuoles, dense cytoplasm, abundant rough endoplasmic reticulum, dictyosomes, and mitochondria, and thus suggested to have a high metabolic activity. The shape, arrangement, and cytological characteristics of the parenchymatous and tip cells consisting the endophyte were very similar to those of the dividing cells and idioblasts, respectively, which appeared in the endophyte primordium of the upper haustorium. The tip cells with the thickened-apical wall were observed to grow intrusively through the host cell walls and to engulf the remnants of the degenerated host cells. In the former case intrusive growing cell was regarded to develop into the filamentous cell, the hypha. Plasmodesmata through the cell wall were not observed between host and parasite cells. Some host cells that in contact with the penetrating tip cells of the endophyte, showed the degenerating features such as a loss of cytoplasm, a beaded fashion of small vesicles, and deformation of chloroplasts.

• The Korean Journal of Physiology and Pharmacology
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• 제16권5호
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• pp.349-353
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• 2012

Activated T cells express inhibitory receptors such as CTLA-4 that can downregulate immune responses. Blockade of or genetic deficiency in CTLA-4 can result in autoimmunity. Therefore, strategies to increase the inhibitory function of CTLA-4 may be attractive in settings of undesirable T cell responses such as autoimmunity or transplant rejection. We have tested the hypothesis that transgenic constitutive expression of CTLA-4 can further attenuate immune responses when compared with normal inducible expression. Our results indicate that transgenic expression of CTLA-4 in mouse T cells (CTLA-4-Tg T cells) results in reduced cell cycle progression and increased apoptosis of TCR-stimulated T cells. CTLA-4-Tg T cells display reduced T cell proliferation in an in vivo model of graft versus host disease (GVHD). These results further our understanding of how CTLA-4 can be manipulated to inhibit immune responses and may help development of new therapeutic strategies for clinical settings of autoimmunity and transplantation.

• 대한약학회:학술대회논문집
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• 대한약학회 2002년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2
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• pp.151-152
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• 2002

Bacterial infection is a very complex process in which both pathogenic microorganisms and host cells play crucial roles, and it is the outcome of interactions between the two participants. To elucidate the bacterial pathogenesis mechanisms, therefore, it is essential to understand the cellular and systemic responses of the host as well as the virulence factors of the pathogen. Infection of a host by pathogenic bacteria causes drastic changes in the physiology of host cells, leading to activation of a program of various gene expression. (omitted)

• Parasites, Hosts and Diseases
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• 제38권4호
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• pp.257-261
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• 2000

This study was focused on the effects of microfilament inhibitor, Cytochalasin D (CD) on the invasiveness of sporozoites of Cryptosporidiun spp. into the host cells. MDCK and AGS cell lines were used as host cells for C. parvum and C. muris, respectively. When MDCK cells were pretreated with CD for 1 hr before inoculation of the sporozoites, C. parvum infection was significantly inhibited when compared to the control cells. These inhibitory effects of CD on the rate of infection were dose-dependent. In addition, C. muris infection was hampered when AGS cell lines were pretreated with CD. However, the capability of invasiveness of the sporozoites into the host cells was not greatly influenced by the pretreatment of sporozoites with CD before infection. These results suggest that microfilaments of host cells, rather than parasites, play an important role for the invasion of Cryptosporidium spp.

• Parasites, Hosts and Diseases
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• 제54권2호
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• pp.147-154
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• 2016

Toxoplasma gondii infection induces alteration of the host cell cycle and cell proliferation. These changes are not only seen in directly invaded host cells but also in neighboring cells. We tried to identify whether this alteration can be mediated by exosomes secreted by T. gondii-infected host cells. L6 cells, a rat myoblast cell line, and RH strain of T. gondii were selected for this study. L6 cells were infected with or without T. gondii to isolate exosomes. The cellular growth patterns were identified by cell counting with trypan blue under confocal microscopy, and cell cycle changes were investigated by flow cytometry. L6 cells infected with T. gondii showed decreased proliferation compared to uninfected L6 cells and revealed a tendency to stay at S or G2/M cell phase. The treatment of exosomes isolated from T. gondii-infected cells showed attenuation of cell proliferation and slight enhancement of S phase in L6 cells. The cell cycle alteration was not as obvious as reduction of the cell proliferation by the exosome treatment. These changes were transient and disappeared at 48 hr after the exosome treatment. Microarray analysis and web-based tools indicated that various exosomal miRNAs were crucial for the regulation of target genes related to cell proliferation. Collectively, our study demonstrated that the exosomes originating from T. gondii could change the host cell proliferation and alter the host cell cycle.

• Journal of Plant Biology
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• 제28권4호
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• pp.261-270
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• 1985

The portion of Cuscuta japonica haustorium which lies external to the host tissues, the upper haustorium, was investigated at the light- and electron-microscopic levels. The haustorium lightly contacted with the host was formed by the expansion of the epidermis and cortex of the stem at the contact side, and to have a group of meristematic cells within the haustorial cortex. When such a haustorium was closely contacted with the host, the meristematic region transformed into a primordial structure of the endophyte (endophyte primordium, EP) which may penetrate into the host tissues. EP consisted of the three kinds of cell group: dividing cells at the adaxial or proximal side; large, elongate cells (idioblasts) at the middle portion,; compressed cells at the abaxial or basal side. the idioblasts were characterized by the presence of large nucleus, dense cytoplasm, several small vacuoles, and abundant cell organelles including the multilamellar structures and cytosegresomes, and thus suggested to have a high metabolic activity. The features of the EP were discussed in relation to the possibility of the penetrating into host tissues.