Biomedical subjects

T Soji

Publications and source records attributed to T Soji.

At least 37 records · Page 2Linked to original sources

PubMed1997

Effects of ruthenium red on the cellular functions and ultrastructure in intact ferret ventricular muscles.

The effects of ruthenium red (RR) on the cellular functions (intracellular Ca2+ handling and contraction) and permeation of the dye through the cell membrane were investigated in intact ferret papillary muscles. The intracellular Ca2+ concentration ([Ca2+]i), measured using aequorin, was simultaneously recorded with tension. The permeation of the dye through the cell membrane was studied with electronmicroscopy. The preparation was continuously stimulated at 0.2 Hz and treated with 50 microM RR at 30 degrees C. [Ca2+]i was increased by electrical stimulation (0.07 and 2 Hz) and rapid cooling (from 30 to 4 degrees C) (RC). In electrical stimulation, RR time-dependently decreased the peak light of aequorin without a significant change in the time course at 30 degrees C. However, in RC, treatment with RR for about 100 min significantly prolonged the decay time of the light signal and increased the peak light. The peak tension in RC was decreased after treatment with RR for a longer time. The pCa-tension relation of skinned preparations was significantly shifted to the right by 50 microM RR. In the RR (50 microM)-treated specimens, mitochondrial outer membranes were darkly stained if OsO4 was used for fixation. Even though the specimen treated with 500 microM RR was fixed without OsO4 and electron staining, the matrices of mitochondria became electron dense. We concluded that RR could penetrate into intact mammalian cardiac myocytes, and that RR inhibits the release of Ca2+ from the sarcoplasmic reticulum in electrical stimulation, inhibits mitochondrial Ca2+ uptake, and decreases the Ca2+ sensitivity of the myofilaments.

Aequorin↗

PubMed1996

Participation of endodermal epithelial cells on the synthesis of plasma LDL and HDL in the chick yolk sac.

We ultrastructually examined the chick yolk sac endodermal epithelium and evaluated our findings in combination with the biochemical analysis of serum and yolk lipoproteins. Twenty-five to 30 nm-sized particles were demonstrated to be a principal element of the extracellular yolk mass and these were determined to be yolk very low density lipoprotein (VLDL). The particles were shown to be taken up by the epithelial cells via coated pits and engulfed by plasma membrane invaginations together with yolk subdroplets, another element of the yolk mass. Through apical vacuoles, the two yolk elements were incorporated into yolk drops, which were identified to be one of the lysosomal structures by a cytochemical procedure using acid phosphatase (AcP)ase activity. During the last week of incubation, which is the final third of the incubation period, the digestion seemed to progress rapidly in the yolk drops, which came to resemble lipolysosomes; lipoprotein production became active as expressed by an enlarged Golgi apparatus. The newly produced lipoprotein particles were electron-lucent and irregular in size (50-120 nm). They were sequestered in secretory vacuoles and secreted from the vascular surface of the epithelial cells. Finally, the particles were thought to be taken into the vitelline circulation as plasma lipoproteins. The major component of lipoprotein in serum was determined to be low density lipoprotein (LDL) and high density lipoprotein (HDL), while cholesterol content was found to increase during incubation. We concluded that endodermal epithelial cells participate the synthesis of plasma LDL and HDL. For this synthesis the cells probably apply lipids and apo-protein generated from yolk VLDL degradation.

Acid Phosphatase↗

PubMed1996

In vivo uptake of lecithin-coated polystyrene beads by rat hepatocytes and sinusoidal endothelial cells.

BACKGROUND: While phagocytosis by Kupffer cells (stellate perisinusoidal macrophages) is well known and that by endothelial cells also is thought to occur under certain conditions, the uptake of large particles by hepatocytes has not been well studied. We reported previously the selective phagocytic uptake of material by hepatocytes using egg lecithin-coated silicon particles. In the present work, we describe more precisely this process following the injection of lecithin-coated polystyrene beads. Additionally, we consider the possible significance of the transcytotic action by endothelial cells. METHODS: Polystyrene latex beads (240 nm in diameter) composed of two layers of polystyrene and methyl methacrylate with a central void cavity and diameter of 140 nm were injected into male Wister-Imamichi rats. The injections were administered through the hepatic portal vein in a volume of 3 ml (concentration of the lecithin-coated or uncoated beads was 2 mg/ml). Controls received the lecithin alone at a concentration of 2 mg/ml. Liver samples were taken 5, 10, or 15 min after injection, fixed, and processed for ultrastructural analysis. RESULTS: Both lecithin-coated and noncoated beads were mainly incorporated in the Kupffer cells as well as in the endothelial cells. Bristle-coated invaginations were observed in the uptake by both cell types; however, noncoated invaginations were also active in the endothelial cells, especially on the surface facing the perisinusoidal space of Disse. Only coated beads were observed within the space or in the hepatocytes. Once taken up by the hepatocytes, the lecithin-coated beads were found either within lysosomes or in a free state in the cytoplasm. CONCLUSIONS: Uptake of 240 nm lecithin-coated polystyrene beads was observed by Kupffer cells, endothelial cells and hepatocytes. These beads were considered to be transported across the endothelial cells by transcytosis. Pseudopodia and bristle-coated invaginations were not employed by the hepatocytes when incorporating the beads.

Animals↗

PubMed1994

Formation and accumulation of lipolysosomes in developing chick hepatocytes.

Formation and accumulation of lipolysosomes in developing chick hepatocytes were investigated by means of electron microscopy in combination with biochemical analyses of the lipid composition in liver homogenates. The lipolysosomes occurred with highest frequency from days 11 to 14 of incubation. They were usually small and electron-dense, but during development they gradually enlarged with an accompanying reduction in electron density. Coinciding with this enlargement was an accumulation of esterified cholesterol in the liver homogenates. After hatching, an immediate decrease in the size and number of lipolysosomes occurred along with a reduction in the concentration of esterified cholesterol, of which only a very small amount remained by 9 days of age. Instead of cholesterol, triglycerides subsequently increased in concentration and accounted for the major lipid content of the liver homogenates. In keeping with the ultrastructural changes, the total volume of cytoplasmic lipid droplets rapidly increased with increasing age. This transient accumulation of esterified cholesterol within lipolysosomes may be attributed to an excessive uptake and processing of plasma lipoprotein particles, probably derived from the egg yolk. This concept is supported by an abundance of coated pits, endosomes and multivesicular bodies in the embryonic hepatocytes.

Animals↗

PubMed1994

Septate-like junctions in the normal male rat pituitary gland.

Septate-like junctions were observed in the rat anterior pituitary gland of the adult male solely between adjacent folliculo-stellate cells. Considering their location, it is presumed that their function is cellular adhesion and mechanical support for the hypophyseal follicles.

Animals↗

PubMed1994

Immunohistochemical study of the post-natal development of the folliculo-stellate cells in the rat anterior pituitary gland.

We investigated the post-natal development of cell-to-cell communication within the rat anterior pituitary gland cells using immunohistochemistry of the S-100 protein. Tissues of animals from 10 to 60 days of age were analyzed. At 10 days of age, S-100 protein-containing cells were rarely observed. With age, the population of S-100 immunostained cells increased until day 40 when they were found to be quite numerous. No further changes were noted from day 40 through day 60. From our previous studies, we conclude that the cells which reacted with the S-100 antiserum were folliculo-stellate cells and their developmental pattern parallels that of the hypophyseal-gonadal axis.

Animals↗

PubMed1994

Egress route of emulsified 20 centistokes silicone oil from anterior chamber of rabbit.

Silicone oil is used in recent clinical practice, however, it may cause adverse reactions in the eyes. When the high viscosity silicone oil is contaminated with low molecular weight silicone oil, the contamination may cause ocular toxicity or elevation of the intraocular pressure. To obtain information on the distribution of this preparation, emulsified 20 centistokes silicone oil was injected into the anterior chamber of rabbit eyes. The silicone oil droplets were visualized by light and electron microscopy by using oil soluble phthalocyanine blue. This copper containing dye remains in the tissue after removal of the silicone oil by organic solvents. Two and 4 weeks after an injection, the silicone emulsion was observed as numerous small vacuoles with blue precipitate at the margin of vacuoles within elongated trabecular endothelial cells, fibroblasts along the route of uveoscleral outflow and cells of the iris. Three hours after the injection, only a few vacuoles were present in these cells. These results demonstrated that the emulsified silicone oil leaves the anterior chamber through the conventional and unconventional routes. Phagocytosis by the trabecular endothelial cells and fibroblasts along the uveoscleral route caused an accumulation of the emulsified silicone oil in these cells. With chronic exposure to emulsified silicone oil, changes in the trabecular meshwork may lead to a reduction in the outflow of aqueous humor and cause glaucoma.

Animals↗

PubMed1993

Intercellular communication within the rat anterior pituitary gland: V. Changes in cell-to-cell communications as a function of the timing of castration in male rats.

Cell-to-cell communication by gap junctions was investigated in the male rat anterior pituitary gland following several experimental regimens involving castration. The regimens included the following animals: (1) Group 1, castrated at 10-day intervals from day 10 to 50 and sacrificed at 60 days of age; (2) Group 2, castrated every 10 days from days 10 to 50 and sacrificed 50 days after castration; (3) Group 3, castrated at 5 days of age and sacrificed every 10 days from day 10 to 60; or (4) Group 4, remained intact and sacrificed every 10 days from days 10 to 60. In all of the castrated animals, numerous so-called castration cells were scattered throughout the pars distalis of the pituitary gland, with occasional "signet ring cells" being observed. In Groups 1 and 2, the pattern of gap junction development and their number was no different from the intact control (Group 4). In contrast, the number of gap junctions in the animals castrated on day 5 remained very small even into adulthood. These data demonstrate that gonadal steroids are important in the initial development of gap junctions within the pituitary gland but are not necessary to sustain their presence once an animal becomes an adult.

Animals↗

PubMed1993

Evidence that Müller cells can phagocytize egg-lecithin-coated silicone particles.

This study is designed to better understand the function of the Müller cells of the retina through the use of silicon particles that had been injected into the vitreous body of the eye and via an analysis of the number of gap junctions associated with these cells. Following intraocular injection of a silicone oil mixture into the rabbit retina, numerous small silicone particles less than 1 micron in diameter were found attached to the basement membrane of the inner limiting membrane, subjacent to the Müller cells. On the sites to which the silicone particles attached, the basement membrane was reduced in thickness or completely disappeared. The 'end-feet' of the cell membrane facing the silicone particles became concave appearing as if they were in the process of incorporating the particles into the cell. Similarly, the Müller cells occasionally extended cytoplasmic processes through the basement membrane and towards the silicone particles, as if to engulf them. Gap junctions were observed but only in association with the Müller cells. They were often found between the 'end-feet' of adjacent Müller cells or the 'end-feet' of one cell and very thin cytoplasmic process of a neighboring cell. On rare occasions, they were located between 'end-feet' of the same Müller cell. The percentage of 'end-feet' displaying gap junctions was 38 +/- 8% (mean +/- SE). These data suggest that the Müller cells are important in the maintenance of normal retinal function by their ability to phagocytize foreign substances and by their ability to transmit information to various parts of the retina through cell-to-cell connections established by gap junctions.

Animals↗

PubMed1992

Intercellular communication within the rat anterior pituitary gland: IV. Changes in cell-to-cell communications during pregnancy.

Cell-to-cell communication by gap junctions was investigated in the female rat anterior pituitary gland from 9 through 21 days of pregnancy and subsequently on days 2 and 20 of the lactational period. Compared with intact estrus females, the major morphological characteristics of the pituitary gland during pregnancy were remarkably developed prolactin cells and gonadotrophs. A close relationship of both cell types was clearly evident. Gap junctions were present at each of the time intervals studied; however, they were noted only between adjacent folliculo-stellate cells. No remarkable changes were noted in the number of gap junctions during the middle stage of pregnancy (day 9 through day 15), with the relative number resembling that found in intact, 90-day-old controls during estrus (0.47 +/- .01 junctions/follicle-control vs. 0.50 +/- 0.08--day 15 of pregnancy). In the later stages of pregnancy (day 17 through day 21), a demonstrable increase was observed (0.64 +/- 0.10--day 17, 0.79 +/- 0.11--day 19 and 0.72 +/- 0.12--day 21), whereas during the lactation, this pattern returned to that seen at midpregnancy. Since both prolactin and the gonadal steroid hormones dramatically fluctuate during pregnancy and lactation, it is postulated that they may have an active role in gap junction formation during these two phases of reproductive life.

Animals↗

PubMed1992

Evidence that hepatocytes can phagocytize exogenous substances.

Although the phagocytic action of Kupffer cells is well known, such a phenomenon has not been well documented for hepatocytes. Following the injection of a suspension of egg lecithin-coated silicon particles (0.5-1.5 microns in diameter) into the portal vein of rats, Kupffer cells showed minimal phagocytotic action, which was in contrast to the hepatocytes which displayed numerous phagocytized silicon particles. By comparison, when noncoated silicon particles of the same diameter as those that were coated were injected into the portal vein, the opposite observation was made. There was no uniformity in the ability of the hepatocytes to phagocytize either coated or noncoated particles from one lobule to another. Some showed active phagocytosis, while in others no evidence of such a process was observed. These data provide strong evidence for the selective phagocytic action of liver hepatocytes.

Animals↗

PubMed1991

Intercellular communication within the rat anterior pituitary gland. III. Postnatal development and periodic changes of cell-to-cell communications in female rats.

Cell-to-cell communication by gap junctions was investigated in the female rat anterior pituitary gland from 10 through 45 days of postnatal development and in 60-day-old animals. Gap junctions initially appeared between adjacent folliculo-stellate cells on day 25. Their appearance in female rats was 5 days later than that observed in males (Soji et al., 1990). Gap junction number increased until the animals became 40 days of age, when they reached a level that resembled that found in adults. In addition, a correlation was evident between the frequency of gap junctions and stages of the estrous cycle, where they were most numerous during either proestrus or estrus. These results along with those previously published suggest that gap junction formation within the female rat hypophysis is in part modulated by both gonadal steroid hormones as well as prolactin.

Animals↗

PubMed1991

Cytochemistry of Ca(++)-dependent adenosine triphosphatase (Ca-ATPase) in rat anterior pituitary cells.

In the present study, we demonstrate the localization of Ca(++)-ATPase in the anterior pituitary of the male rat. Ca(++)-ATPase was mainly distributed on the membrane system of the granular cells, which included the plasma membrane, the outer mitochondrial membrane, the enveloping membrane of secretory granules, the smooth endoplasmic reticulum and some components of the Golgi complex. No reaction product was detected on the membrane of the rough endoplasmic reticulum or that surrounding the lysosomes. A positive reaction was clearly observed on the membranes surrounding 'large' secretory granules, while that present on the membranes of the 'small' granules was comparatively weak. The cells which contained the 'large' granules were interpreted as growth hormone-secreting cells and those in which the 'small' granules were located as gonadotrophs. There were either no reaction or one that was barely detectable on the plasma membrane of the folliculo-stellate cells. These data along with our previous findings (Soji, 1982, 1984) suggest that the membranous enzymes are not uniformly distributed over all pituitary cells but rather are specific for a given cell population(s).

Animals↗

PubMed1991

Evidence that C4b-binding protein (proline-rich protein) is synthesized by hepatocytes.

C4b-binding protein (C4bp), a glycoprotein involved in regulating the classical pathway of the complement system, binds the activated form of C4b and accelerates the decay rate of the C4b, C2a complex. Recently, sequence analysis of the cDNA for proline-rich protein (PRP) demonstrated that PRP is identical with C4bp. We measured the concentration of C4bp in serum by single radial immunodiffusion in patients with various liver diseases. Concentration of C4bp was significantly lower in hepatic cirrhosis (P = 0.001) and higher in fatty liver (P = 0.0002) than the control values, after adjusting for age, sex, and concentration of total cholesterol, triglyceride, and C-reactive protein. Significant positive correlations were observed between the concentration of C4bp in serum and total protein, albumin, cholinesterase level, and lecithin-cholesterol acyltransferase activity. Immunohistochemical analysis of human liver with specific antiserum to human C4bp demonstrated reaction endproducts in the hepatocytes around the central veins. These observations provide evidence that C4bp is synthesized by hepatocytes.

Animals↗

PubMed1991

Experimental retinal tolerance to emulsified silicone oil.

Vitreous replacement by silicone oil has become increasingly popular in the treatment of severe and complicated retinal detachment. Several studies have suggested that silicone oil may be toxic to the retina or may stimulate periretinal proliferation. To better understand its effects, emulsified or nonemulsified silicone oil was injected into rabbit eyes that had undergone mechanical vitrectomy. Silicone oil was labeled with phthalocyanine blue to aid in histologic localization. Retinal changes were compared by light microscopy at 1, 4, and 12 weeks after intraocular injection. Emulsified silicone oil was found to penetrate the inner retina at 1 week and cause epiretinal membrane formation as early as 4 weeks after injection. Nonemulsified oil produced no histologic changes in the retina. No cytotoxic effects were observed in eyes treated with ether emulsified or nonemulsified silicone oil. It is concluded that emulsified silicone oil can both penetrate the retina and stimulate epiretinal membrane formation in the vitrectomized rabbit eye.

Animals↗

PubMed1990

Intercellular communication within the rat anterior pituitary gland. I. Postnatal development and changes after injection of luteinizing hormone-releasing hormone (LH-RH) or testosterone.

The postnatal development of gap junction formation and cell-to-cell communication were investigated in male rats from 10 through 40 days of age. These junctions initially appeared between adjacent folliculo-stellate cells on day 20. Their numbers increased until the animals reached the age of 40 days, when their frequency reached a level that resembled that found in adults. The ontogeny of these junctions was examined in rats treated with luteinizing hormone releasing hormone (LH-RH) or testosterone. The two hormones were injected for 1 week into rats aged 3, 13, 23, or 33 days. The appearance of gap junctions was accelerated in a similar fashion by LH-RH and testosterone, with their formation and numbers being advanced by 10 days over that observed in the untreated controls. The results suggest a role for the gonadal steroid hormones in the formation of gap junctions in the rat hypophysis.

Animals↗

PubMed1990

Intercellular communication within the rat anterior pituitary gland. II. Castration effects and changes after injection of luteinizing hormone-releasing hormone (LH-RH) or testosterone.

This study investigated the relationship between gap junction formation and sex steroids in the male rat anterior pituitary gland. Animals were castrated at 5 days of age and separated into the following three groups: 1) oil-treated controls, 2) those injected with LH-RH, and 3) those given testosterone. On days 10, 20, 30, and 40, five rats in each group were sacrificed and their hypophyses removed for ultrastructural examination. When compared with age-matched, intact animals, there was a marked suppression in follicular development and in the number of gap junctions present in the pituitary glands of both the castrated controls as well as the castrates given luteinizing hormone releasing hormone (LH-RH). In contrast, the morphology of these structures in the animals given testosterone was indistinguishable from that observed in the intact controls. These observations provide more definitive evidence that in the male rat pituitary gland maturation of the structural organization of the follicles, including gap junction formation, requires an intact hypophyseal-gonadal axis and is highly dependent on the hormone testosterone.

Animals↗

PubMed1989

Intercellular communication between rat anterior pituitary cells.

Cell-to-cell communication within the rat anterior pituitary was investigated in 60-day-old male rats with immunohistochemistry, scanning electron microscopy, freeze-fracture electron microscopy, and conventional transmission electron microscopy. A dense cytoreticular network of cytoplasmic processes from the folliculostellate cells was found to contain immunoreactive S-100 protein and was observed throughout the anterior pituitary. Nonimmunoreactive cells, which were granular, were situated in the center of each network. Almost all of the granulated cells were situated in close proximity to the folliculostellate cells. Scanning electron microscopy revealed that the gland consisted of microlobules enclosed by a basal lamina. On the surface of the microlobules were blood vessels whose branches invaded its internal structures. Cytoplasmic processes from folliculostellate cells projected outside the microlobule. Freeze-fracture electron microscopy demonstrated the presence of numerous intramembranous particles on the P-face of the plasma membrane. Scattered on the cell surface were groups of particles forming gap junctions. Meshworks of ridges which were representations of tight junctions were also observed near clusters of microvillous fragments. Clusters of particles forming small gap junctions were located between the meshworks of tight junctions. Small gap junctions were clearly observed by conventional electron microscopy between junctional complexes in a manner similar to that seen by freeze-fracture electron microscopy. Slender cytoplasmic processes of folliculostellate cells came in contact near the basal lamina and were adjoined by small gap junctions. The ratio of nongranular cells which contained gap junctions to those in which the junctions were absent was about 1:1. The size of the gap junctions ranged from 50 nm to 3 microns. No gap junctions were observed along the plasma membranes of the granular cells. The significance of an intercellular communication system within the anterior pituitary gland of the rat is to establish a mechanism for rapid transmission of information in an organ which lacks direct innervation.

Animals↗