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Biomedical subjects

I Hori

Publications and source records attributed to I Hori.

At least 19 recordsLinked to original sources
PubMed2003

Quantitative changes in nuclear pores and chromatoid bodies induced by neuropeptides during cell differentiation in the planarian Dugesia japonica.

Neuropeptides were used in experiments to assess their effects on planarian cells. Intact and decapitated planarians exposed to 10(-6) M neuropeptides for two days were examined electron microscopically and quantitative changes in the nuclear pores and chromatoid bodies in various types of cells were ascertained. The data clearly indicated the diversity of effects produced in planarian cells by neuropeptide treatments. The number of nuclear pores increased considerably in each cell type treated with neuropeptides. In particular, the effects of neuropeptides were strongest in differentiating cells which were forming the regeneration blastema. Neuropeptide-treated cells also experienced a dramatic increase in the number of chromatoid bodies. The results obtained in this study suggest that synthesis of RNAs leading to increases in the numbers of nuclear pores and chromatoid bodies is facilitated in neuropeptide-treated cells which are undergoing cell differentiation. The different mechanisms of the effects induced in undifferentiated cells by neuropeptides are discussed.

Animals↗
PubMed2001

Metamorphosis of coeloblastula performed by multipotential larval flagellated cells in the calcareous sponge Leucosolenia laxa.

The calcareous sponge Leucosolenia laxa releases free-swimming hollow larvae called coeloblastulae that are the characteristic larvae of the subclass Calcinea. Although the coeloblastula is a major type of sponge larva, our knowledge about its development is scanty. Detailed electron microscopic studies on the metamorphosis of the coeloblastula revealed that the larva consists of four types of cells: flagellated cells, bottle cells, vesicular cells, and free cells in a central cavity. The flagellated cells, the principal cell type of the larva, are arranged in a pseudostratified layer around a large central cavity. The larval flagellated cells characteristically have glutinous granules that are used as internal markers during metamorphosis. After a free-swimming period the larva settles on the substratum, and settlement apparently triggers the initiation of metamorphosis. The larval flagellated cells soon lose their flagellum and begin the process of dedifferentiation. Then the larva becomes a mass of dedifferentiated cells in which many autophagosomes are found. Within 18 h after settlement, the cells at the surface of the cell mass differentiate to pinacocytes. The cells beneath the pinacoderm differentiate to scleroblasts that form triradiate spicules. Finally, the cells of the inner cell mass differentiate to choanocytes and are arranged in a choanoderm that surrounds a newly formed large gastral cavity. We found glutinous granules in these three principal cell types of juvenile sponges, thus indicating the multipotency of the flagellated cells of the coeloblastula.

Animals↗
PubMed1997

Cytological approach to morphogenesis in the planarian blastema. II. The effect of neuropeptides.

The regeneration blastema consists of three cell types, undifferentiated cells, regenerative cells, and differentiated cells all of which can be identified by their ultrastructural characteristics. Quantitative changes in the numbers of these cells within the blastema offer important clues about the detailed process of regeneration. When decapitated worms were allowed to regenerate in neuropeptide-containing tap water, the undifferentiated cells accumulated rapidly and initiated blastema formation. These cells were then replaced with regenerative cells, and subsequently with differentiated cells. In the non-treated regenerating worms, the proportion of undifferentiated cells was much lower than in the neuropeptide-treated ones. The results of this study indicate that neuropeptides have a remarkable effect on the early stage of regeneration in planarians. Immunoelectron microscopy using a gold-conjugated anti-neuropeptide antiserum revealed the presence of neuropeptides in some kinds of parenchymal cells in the post-blastemal area.

Animals↗
PubMed1996

Expression, purification and characterization of recombinant C. Elegans UNC-18.

The Caenorhabditis elegans unc-18-encoded protein (UNC-18) is implicated in the processes of vesicle targeting, docking, and/or fusion. To further characterize the properties of this important neural protein, we expressed it at a high level in Spodoptera frugiperda Sf21 cells using a baculovirus expressing system. A cDNA containing the coding sequence for UNC-18 was inserted into the transfer vector pBlueBac to yield the recombinant virus pAcNPV/unc-18. At maximal expression, the recombinant virus produces a protein of 67 kDa, which constitutes about one-third of total cell protein. The UNC-18 protein was highly purified and its biochemical and functional properties were assessed. The protein is globular with an isoelectric point of 6.95. Circular dichroism spectroscopy indicated that the alpha-helix and beta-sheet account for 10.0 and 59.0%, respectively. Immunolabeling the Sf21 cells expressing UNC-18 showed that the expressed UNC-18 is predominantly localized in the cytoplasm as a soluble monomer. The protein is phosphorylated by protein kinase C and binds to the recombinant C. elegans syntaxin in vitro. These findings suggest that in vesicle traffic UNC-18 is a regulator factor associated with the plasma membrane through syntaxin, although intrinsically cytoplasmic.

Animals↗
PubMed1994

Mutations in the unc-41 gene cause elevation of acetylcholine levels.

Mutations in the Caenorhabditis elegans unc-41 gene result in an allele-dependent elevation of acetylcholine content. Eight recessive alleles (cn252, e268, e399, e650, e1175, e1199, e1294, and e870) lead to phenotypes including uncoordinated locomotion, slow growth, a small mature body, and resistance to the acetylcholinesterase inhibitors as well as the elevation of acetylcholine content. The remaining two alleles, e554 and e1162, exhibit normal acetylcholine levels but display the short-body phenotype in a semidominant way. To determine the localization of the elevated acetylcholine content, a method for the isolation of synaptic vesicles from C. elegans was established. The elevation of acetylcholine content in the unc-41 mutants is accompanied by the accumulation of synaptic vesicles. We propose that at least one function of the unc-41 gene relates to the release of neurotransmitters.

Acetylcholine↗
PubMed1993

The C. elegans unc-18 gene encodes a protein expressed in motor neurons.

The C. elegans unc-18 gene is required to maintain normal acetylcholine levels. We determined the complete structure of an unc-18 cDNA that encodes a protein of 591 highly charged and hydrophilic amino acids. The protein shows sequence similarity with elements of the secretory pathway in the yeast S. cerevisiae. Antibodies raised against a portion of the unc-18-encoded protein (UNC-18) detected a 68 kd soluble antigen on immunoblots and intensely stained all vertical cord motor neurons in situ. These findings suggest that UNC-18 participates in the axonal transport system and influences the acetylcholine flow in motor neurons.

Amino Acid Sequence↗
PubMed1993

Evaluation of the pharyngeal airway in patients with sleep apnea: value of ultrafast MR imaging.

OBJECTIVE: Sleep apnea is often caused by obstruction of the pharyngeal airway. The goal of this study was to use ultrafast MR imaging to examine the pharyngeal airway in patients with sleep apnea and to evaluate the usefulness of this technique for localizing the site of obstruction. SUBJECTS AND METHODS: Fifteen patients with sleep apnea and five healthy volunteers underwent ultrafast MR imaging while awake and during sleep induced with hydroxyzine hydrochloride. Sequential midline sagittal images of the pharynx were obtained and displayed in the cine mode. RESULTS: Patients with sleep apnea were found to have sites of pharyngeal abnormality that were not present in healthy volunteers. Nine sites of narrowing in seven patients (47%) were detected with the patient awake; 21 sites of obstruction in 13 patients (87%) were diagnosed with the patient asleep. Six patients showed only one obstruction, and seven had several obstructions: five had obstructions at the velum palatinum and at the oropharynx; one had obstructions at the velum palatinum, oropharynx, and hypopharynx; one had obstructions at the velum palatinum and the hypopharynx. The sites of narrowing during wakefulness and the sites of obstruction during sleep were the same in only four (31%) of the patients with pharyngeal airway obstruction. CONCLUSION: Ultrafast MR imaging is useful for localizing the sites of pharyngeal airway obstruction in patients with sleep apnea.

Adolescent↗
PubMed1991

[Clinical trial of color-hybrid images for assessment of Gd-DTPA contrast enhancement].

Gd-DTPA (Gd) has been shown to provide effective contrast enhancement in MR imaging. However, it is sometimes impossible to evaluate Gd contrast enhancement (C.E.) in high intensity tissues like fat and bone marrow. To solve this problem, color-hybrid images (hybrid images) were generated by the use of an RGB mixing method. A total of 54 lesions, including 30 bone and soft tissue lesions and 24 gynecological lesions, were studied. In most cases, the hybrid images were superior to the original ones in terms of both morphologic and temporal evaluation of Gd C.E. The hybrid images helped to define the localization and extent C.E., by providing better visualization through the use of color display.

Adult↗
PubMed1991

Further cytological observation on 'activation' by superimposed antigen of inflammation-mediated macrophages.

Compact cell aggregates were induced by an injection of a superimposed antigen, sheep erythrocytes (SRBC) into PSK (a protein-bound polysaccharide)-'prepared' mouse footpad. Major cell types in the cell aggregate were macrophages which rapidly digested superimposed SRBC but not PSK substances which were retained over seven days within their phagosomes. Macrophages without PSK like substances-containing phagosomes occurred invariably outside the cell aggregate. The macrophages in the cell aggregate were interlocked via their cytoplasmic projections. Ruthenium red, a specific dye for extracellular proteoglycans, clearly revealed their surface coats and also closely contacted zones of adjoining macrophages. The surface coats were not uniform in distribution and became sporadically thickened deposits at invaginations of the plasma membrane. Ladder-like structures among adjacent cytoplasmic projections also showed a strong affinity to the dye. It is suggested that a primary function of these structures is the maintenance of close contact of aggregating macrophages. Another observation was that binucleate macrophages occurred in the cell aggregates. Careful inspection on sections of well-preserved tissues concludes that such cells were not formed by a cell fusion between mononucleate macrophages in the cell aggregates. Formation of such a binucleate cell from the macrophage in the aggregates is also discussed.

Animals↗
PubMed1991

Role of fixed parenchyma cells in blastema formation of the planarian Dugesia japonica.

Observations of fixed parenchyma cells using electron microscopy were carried out in an attempt to understand the morphogenetic process of blastema formation in regenerating planarians. Fixed parenchyma cells could be found throughout one-day blastemata. In the mid-blastema region where migrating regenerative cells build up a compact cell aggregate, long and slender cytoplasmic processes of the fixed parenchyma cells were seen occupying spaces among regenerative cells. A characteristic feature of such processes was orderly arranged microtubules. Ruthenium red staining revealed thickened portions of cell coats on these processes and occasional formation of gap junctions between the cytoplasmic process of the fixed parenchyma cell and the regenerative cell undergoing migration. Colchicine treatment (M/1,000) caused detachment of the cytoplasmic processes from the regenerative cells. Microtubules within such processes became depolymerized. As a result, directional migration of regenerative cells was inhibited by colchicine treatment. To determine the extracellular site of fibronectin, immunoelectron microscopy was performed in one-day blastema. Immunogold labeling was detected at the surface area of fixed parenchyma cells and regenerative cells. In particular the reactivity was conspicuous at the cytoplasmic process of the fixed parenchyma cells. These observations suggest that the cytoplasmic processes of fixed parenchyma cell are related to directional movement of regenerative cells by providing a contact guidance system. The biological implications of this system are discussed in relation to the extracellular matrix components.

Animals↗
PubMed1990

[Fundamental experiment of expansile force of expandable metallic stent].

So far expansile force of expandable metallic stent has been estimated by only wall-distending pressure P. We estimated expansile force of stent by not only P but also a force per one unit length of wire F. F corresponds to the degree of digging into the vessel wall. P and F were thought to be useful in selecting the best stent.

Elasticity↗
PubMed1990

Cell surface changes of in situ macrophages induced by superimposed antigen.

Mice received an injection of sheep erythrocytes (SRBC) into the footpad " prepared" or "not prepared" with a 7-day-prior injection of a protein-bound polysaccharide from Coriolus versicolor (PSK; Krestin), and the ultrastructure of in situ macrophages was studied at various intervals after the injection. A single SRBC injection into the footpad induced linear cell arrangements of several macrophages. The macrophages showed no prominent morphological alterations after SRBC digestion. When PSK-stimulated subcutaneous macrophages were challenged by SRBC, they rapidly sent out numerous long cytoplasmic projections which radiated in all directions. Such projections of neighboring macrophages tended to contact one another. At the following stage, a pronounced sequential alteration was noted, characterized by the interlocking of elongated projections. This provided massive aggregations of "activated" macrophages. These observations suggest the possibility that intercellular communication among "activated" macrophages was elicited, particularly in the subcutaneous region, and maintained through an intensive interaction of cytoplasmic projections. Further, the present results histologically support our previous report which shows that the "PSK-prepared" footpad site but not the "prepared" one supports development of a splenic humoral immune response following injection of superimposed SRBC.

Animals↗
PubMed1990

Effects of varying the injection routes of PSK or OK-432 on development of immune responses against a superimposed antigen.

The present study examined functional and morphological modifications of development of immune responses to an unrelated antigenic stimulus by an ongoing response to a biological response modifier such as PSK or OK-432. Development of the immune responses was found to be strictly dependent upon the site where the ongoing response was occurring. In some cases, injection into the intraperitoneal site slightly augmented the development of a humoral immune response against a superimposed antigen, sheep erythrocytes, when the antigen had been injected into the site within 3 h after an injection of PSK. Thereafter, however, inhibition of the response was observed. Subcutaneous injection into the foot pad, but not into the upper chest, augmented the response. This augmentation occurred only when a superimposed antigen was injected into the site "prepared" with a previous injection of PSK, and showed a bell-shaped dependence on the dose of PSK. The foot pad site was also associated with an augmented development of a delayed type hypersensitivity against sheep erythrocytes when the antigen was injected into the "prepared" site. Morphological examination shows accumulation of inflammatory cells at the sites 2 to 7 days after an injection of PSK. The macrophages in the foot pad retained their "activated" state for at least 7 days after the injection whereas those in the peritoneal cavity were not sufficiently "activated" even after 2 days.

Animals↗
PubMed1989

Observations on planarian epithelization after wounding.

Wound closure of planarian regenerates was studied by light and electron microscopy. Quick response of epidermal cells after amputation depended on muscular contraction near the open wound. Early epithelization involved both active and passive cell migration phenomena. First, the old cells from the dorsal and ventral epidermis facing the wound simultaneously spread to close the wound surface, joining first near the wound center. This was facilitated by the contraction. Cell stratification at the wound margin was the result of active cell migration at the time of amputation. Secondly, these cells were passively stretched from the wound margin so that the stratification disappeared. Partial relaxation of the wound was a causative factor for extreme elongation of the wound epidermal cells. Disappearance of hemidesmosomal attachments was initiated by the collapse of the basal lamina. This was obviously linked to cell locomotion. Further development of the wound epidermis was accomplished by the successive supplementation of precursor cells from the newly formed regeneration blastema (mainly rhabdite-forming cells).

Animals↗
PubMed1980

Localization of newly synthesized precursors of basal lamina in the regenerating planarian as revealed by autoradiography.

Autoradiography has been carried out to investigate the site of synthesis of the basal lamina in the regenerating planarian, Dugesia japonica. Since the basic collagenous structures of the basal lamina rose from RR-positive amorphous precursor, [3H]proline, [3H]glucose and [35S]sodium sulphate were used as radioactive precursors of collagen, unsulphated and sulphated GAG respectively. Cytoplasm of the most regenerating epidermal cells was heavily labeled with [3H]proline during epithelization. A quantitative uptake analysis of [3H]proline indicates a progressive decline in the amount of labeled precursor in the epidermis with a corresponding increase in deposition of the labeled collagen at the presumptive basal lamina. Several myoblasts at the subepidermal region were highly labeled with both [3H]glucose and [35S]sodium sulphate. Silver grains of these labeled precursors were also present in the presumptive portion of basal lamina. These observations suggest that the regenerating epidermal cell is the only site of synthesis of the basal lamina collagen while the myoblast exclusively secretes extracellular GAG. Some of the GAG may be closely associated with the amorphous zone.

Animals↗
PubMed1979

Structure and regeneration of the planarian basal lamina: an ultrastructural study.

The structure and regeneration of the planarian subepidermal basement membrane or basal lamina have been electron microscopically examined, particularly in relation to the changes of extracellular products at the wounded area. The intact basal lamina consists of three structural elements; namely, an electron-lucent zone, a limiting layer and a microfibrillar layer. Ultrastructural changes during wound healing have suggested that the amorphous material secreted in the interspace between the epidermal cells and blastema contains precursors of the basal lamina. Within the amorphous zone two distinct phases of the basal lamina regeneration are observed: one is a reconstitution of the limiting layer and the other is a polymerization of the microfibrils. The limiting layer arises from areas subjacent to newly developed hemidesmosomes of epidermal cells. The unit microfibrils are formed from an accumulation of the precursors through transitional smaller microfibrils. At the late stage, individual mature microfibrils are regularly lined with the limiting layer and cell membranes of the newly differentiated muscle fibres. On the basis of these observations we suggest that the planarian basal lamina is regenerated by the interaction between epidermal cells and myoblasts.

Animals↗