Biomedical subjects

A Shimozawa

Publications and source records attributed to A Shimozawa.

At least 19 recordsLinked to original sources

PubMed1995

Incilaria mucus agglutinated human erythrocytes.

The body surface mucus from the land slug, Incilaria fruhstorferi, not only opsonized sheep red blood cells (SRBC) and agglutinated human types A and B erythrocytes (HRBC) but also caused hemolysis of B type HRBC 12 h after agglutination. The mucus-induced hemagglutination was specifically inhibited by a low concentration of N-acetyl D-galactosamine (GalNAc), and all of this activity was completely inactivated by heating at 56 degrees C for 30 min. SDS-polyacrylamide gel electrophoresis of water soluble fraction of the mucus showed that this fraction contained several proteins, the molecular mass of the main band being 35 KD.

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PubMed1994

Inductive action of epithelium on differentiation of intestinal connective tissue of Xenopus laevis tadpoles during metamorphosis in vitro.

The action of the epithelium on differentiation of connective tissue cells of Xenopus small intestine during metamorphosis was investigated by using culture and morphological techniques. Connective tissue fragments isolated from the small intestine at stage 57 were cultivated in the presence or absence of homologous epithelium. In the presence of the epithelium, metamorphic changes in the connective tissue were fully induced by hormones including thyroid hormone (T3), as during spontaneous metamorphosis, whereas they were partially induced in the absence of the epithelium. Macrophage-like cells showing non-specific esterase activity in the connective tissue were much fewer in the absence of the epithelium than in the presence of it, and aggregates of fibroblasts possessing well-developed rough endoplasmic reticulum developed only in the presence of the epithelium. Just before the aggregation of the fibroblasts, the connective tissue close to the epithelium became intensely stained with concanavalin A (ConA) and wheat germ agglutinin (WGA). The present results indicate that the epithelium plays important roles in the differentiation of intestinal connective tissue cells, which in turn affect the epithelial transformation from larval to adult form during anuran metamorphosis. Thus, the tissue interaction between the epithelium and the connective tissue in the anuran small intestine is truly bidirectional.

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PubMed1994

Anatomical observations on the musculi suprahyoidei and apparatus hyoideus with special reference to the musculus jugulohyoideus and os stylohyoideum of the mouse, hamster and rat.

The musculi suprahyoidei and apparatus hyoideus were investigated using a combination of gross dissection and histological techniques in the mouse, hamster and rat. The new findings with regard to these are as follows: (1) the musculus jugulohyoideus, which runs from the processus jugularis to the os stylohyoideum, exists in the mouse and hamster, but is absent in the rat; (2) the m. jugulohyoideus is innervated with the ramus jugulohyoideus from the nervus facialis; (3) the os stylohyoideum and the os tympanohyoideum exist on the lateral surface of the bulla tympanica in the mouse, hamster and rat, and (4) four kinds of muscle (m. stylohyoideus, m. styloglossus, m. stylopharyngeus, m. jugulohyoideus) attach to the os stylohyoideum in the mouse and hamster; however, no muscles attach to the os stylohyoideum in the rat.

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PubMed1994

Phagocytotic cells in the fish heart.

Comparatively little is known about host-defense activities in the fish heart. Investigations showed that intraperitoneally injected carbon particles are actively taken up by the cardiac endothelial cells of the medaka Oryzias latipes, but less so by those of the goldfish Carassius auratus and lemon tetra Hyphessobrycon pulchripinnis. (In vitro experiments confirmed these species differences in endocytic activities by these cells.) Electron microscopy revealed that endothelial cells of the medaka atrium have large cytoplasm with many organelles, and ingested carbon particles were observed within phagosomes of cardiac endothelial cells even at 4 degrees C. Phagocytic cells, which apparently reside in the heart, were found in all the species examined. These cells were located on the endothelial cells and developed cytoplasmic processes extending toward the heart lumen and/or the intercellular spaces of the endothelial cells. The heart with its resident phagocytes is proposed to function as a host defense organ--at least in certain fish species.

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PubMed1994

Motor unit size of M. stylohyoideus and M. stapedius in the mouse.

To elucidate the relation between the caliber of myelinated nerve fibers (MNFs) and motor unit size (i.e., number of muscle fibers per motor unit), motor unit size was measured for the mouse m. stylohyoideus, innervated predominantly by extra large MNFs, and compared with that of the mouse m. stapedius, innervated predominantly by large MNFs. All muscle fibers and MNFs were counted morphologically, and mean motor unit size was calculated for each muscle. The results showed that the average of 12 mean motor unit sizes for the m. stylohyoideus (35.8 +/- 8.2), innervated predominantly by extra large MNFs, was greater than that for the m. stapedius (6.5 +/- 1.3), innervated predominantly by large MNFs.

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PubMed1994

Blood cell-producing site in the land slug, Incilaria fruhstorferi.

Blood cell-producing site in a yeast-particle-injected slug, Incilaria fruhstorferi, was studied by light and electron microscopy, in vivo and in vitro. Cells lining the vascular system and hemocoel wall were discontinuous, scattered, and morphologically resembled fibroblasts. One hour after injection of yeast-particles as foreign material, the lining cells projected into the lumen and 3 h later, the cells were gradually released from the wall. They were morphologically similar to macrophage-like cells that phagocytose foreign material. In tissue culture of the hemocoel wall from yeast-injected slugs, cells that migrated from the explants consisted mainly of fibroblast- and macrophage-like cells. These two kinds of cells were weakly positive to non-specific esterase reaction, whereas circulating hemolymph cells were strongly positive. After administration of bromodeoxy-uridine (BrdU), labeled cells were most commonly found in the ventral side of the body and around the hemal space of the center of the dorsal wall. These results agree with our hypothesis that fibroblasts in the connective tissue of the hemocoel wall of the land slug can transform into macrophages of hemolymph.

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PubMed1993

Melano-macrophage centre-like structure in the heart of the medaka, Oryzias latipes.

Endocardial lining cells in the heart of certain teleosts are phagocytic against foreign materials. In the medaka Oryzias latipes, in addition to the endocardial lining cells, cells in the subendocardial spaces are also phagocytic. Most subendocardial cells contain yellowish-brown pigments and are often aggregated to form nodules resembling splenic and kidney melano-macrophage centres. Subendocardial cells are positive to PAS and Schmorl's reaction. Macrophages containing large heterogeneous inclusions together with lymphocytes, were observed with the TEM. The definitive characteristics of reticular cells, including the cell sheaths, were not observed. Because of these two characteristics they were regarded as more primitive aggregates of macrophages than the ordinary melano-macrophage centres. The possible analogy between these structures and MMCs is discussed.

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PubMed1993

Electron microscopic nerve fiber caliber analysis in the nerve branches to the M. mylohyoideus in mouse.

Nerve fiber counts and caliber analysis of the nerve branches to m. mylohyoideus were performed with an electron microscope on 5 sides from 3 mice. The nerve branches contained an average of 93.6 (54.7%) myelinated fibers, 76.2 (44.6%) unmyelinated fibers and 1.7 (0.7%) undetermined fibers. 60.3% of the myelin sheaths of the myelinated fibers in the nerve branches were 3.5-6.0 microns in major diameter and 67.8% were 2.5-5.0 microns in minor diameter. 81.7% of the axons of the myelinated fibers were 1.5-4.5 microns in major diameter and 83.1% were 1.0-3.5 microns in minor diameter. The diameter frequency distributions of the myelin sheaths and axons of myelinated fibers in the nerve branches were similar in pattern to that of the facial trunk distal to the stylomastoid foramen. On the other hand, these frequency distributions of the nerve branches showed that the diameters of the myelinated fibers of the nerve branches were approximately 1-2 microns smaller than those of the r. digastricus, r. stylohyoideus and the nerve branch to venter rostralis of m. digastricus. Average ratios of the cross-sectional areas of myelin sheaths to those of axons of the myelinated fibers in the various axon area classes were 0.59-1.18, and those ratios tended to decrease in the larger axon classes.

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PubMed1992

Programmed cell death and heterolysis of larval epithelial cells by macrophage-like cells in the anuran small intestine in vivo and in vitro.

The degenerative processes in the larval small intestine of Xenopus laevis tadpoles during spontaneous metamorphosis and during thyroid hormone-induced metamorphosis in vitro were examined by electron microscopy. Around the beginning of spontaneous metamorphic climax (stages 59-61), both apoptotic bodies derived from larval epithelial cells and intraepithelial macrophage-like cells suddenly increase in number. The macrophage-like cells become rounded and enlarged because of numerous vacuoles containing the apoptotic bodies. Mitotic profiles of the macrophage-like cells, however, are localized in the connective tissue where different developmental stages of macrophage-like cells are present. After stage 62, the intraepithelial macrophage-like cells decrease in number, while large macrophage-like cells which include the apoptotic bodies and retain intact cell membranes and nuclei appear in the lumen. Degenerative changes similar to those during spontaneous metamorphosis described above could be reproduced in vitro. In tissue fragments isolated from the small intestine of stage 57 tadpoles and cultured in the presence of thyroid hormone, the number of intraepithelial macrophage-like cells reaches its maximum around the 3rd day of cultivation when the larval epithelial cells most rapidly decrease in number. These results suggest that the rapid degeneration of larval epithelial cells occurs not only because of apoptosis of the epithelial cells themselves but also from heterolysis by macrophages. The macrophages probably originate in the connective tissue, actively proliferate, migrate into the larval epithelium around the beginning of metamorphic climax, and are finally extruded into the lumen.

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PubMed1991

Induction of metamorphosis by thyroid hormone in anuran small intestine cultured organotypically in vitro.

We have developed an organ culture system of the anuran small intestine to reproduce in vitro the transition from larval to adult epithelial form which occurs during spontaneous metamorphosis. Tubular fragments isolated from the small intestine of Xenopus laevis tadpoles were slit open and placed on membrane filters in culture dishes. In 60% Leibovitz 15 medium supplemented with 10% charcoal-treated serum, the explants were maintained in good condition for at least 10 days without any morphologic changes. Addition of triiodothyronine (T3) at a concentration higher than 10(-9) M to the medium could induce cell death of larval epithelial cells, but T3 alone was not sufficient for proliferation and differentiation of adult epithelial cells. When insulin (5 micrograms/ml) and cortisol (0.5 microgram/ml) besides T3 were added, the adult cells proliferated and differentiated just as during spontaneous metamorphosis. On Day 5 of cultivation, the adult cells rapidly proliferated to form typical islets, whereas the larval ones rapidly degenerated. At the same time, the connective tissue beneath the epithelium suddenly increased in cell density. These changes correspond to those occurring at the onset of metamorphic climax. By Day 10, the adult cells differentiated into a simple columnar epithelium which possessed the brush border and showed the adult-type lectin-binding pattern. Therefore, the larval epithelium of the small intestine responded to the hormones and transformed into the adult one. This organ culture system may be useful for clarifying the mechanism of the epithelial transition from larval to adult type during metamorphosis.

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PubMed1990

Changes in lectin-binding pattern in the digestive tract of Xenopus laevis during metamorphosis. I. Gastric region.

The distribution of structural and secretory glycoconjugates in the gastric region of metamorphosing Xenopus laevis was studied by the avidin-biotin-peroxidase (ABC) histochemical staining method using seven lectins (concanavalin A, Con A; Dolichos biflorus agglutinin, DBA; peanut agglutinin, PNA; Ricinus communis agglutinin I, RCA-I; soybean agglutinin, SBA; Ulex europeus agglutinin I, UEA-I; and wheat germ agglutinin, WGA). Throughout the larval period to stage 60, the epithelium consisting of surface cells and gland cells was stained in various patterns with all lectins examined, whereas the thin layer of connective tissue was positive only for RCA-I. At the beginning of metamorphic climax, the connective tissue became stained with Con A, SBA, and WGA, and its staining pattern varied with different lectins. The region just beneath the surface cells was strongly stained only with RCA-I. With the progression of development, both the epithelium and the connective tissue gradually changed their staining patterns. The surface cells, the gland cells, and the connective tissue conspicuously changed their staining patterns, respectively, for Con A and WGA; for Con A, PNA, RCA-I, SBA, and WGA; and for Con A, RCA-I, and WGA. At the completion of metamorphosis (stage 66), mucous neck cells became clearly identifiable in the epithelium, and their cytoplasm was strongly stained with DBA, PNA, RCA-I, and SBA. These results indicate that lectin histochemistry can provide good criteria for distinguishing among three epithelial cell types, namely, surface cells, gland cells, and mucous neck cells, and between adult and larval cells of each type.

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PubMed1990

Changes in lectin-binding pattern in the digestive tract of Xenopus laevis during metamorphosis. II. Small intestine.

The binding of seven lectins (concanavalin A, Con A; Dolichos biflorus agglutinin, DBA; peanut agglutinin, PNA; Ricinus communis agglutinin I, RCA-I; soybean agglutinin, SBA; Ulex europeus agglutinin, UEA-I; and wheat germ agglutinin, WGA) to the small intestine in metamorphosing Xenopus laevis was studied by the avidin-biotin-peroxidase (ABC) method. The staining pattern of the epithelium with all lectins except for UEA-I and Con A changed gradually during metamorphic climax; the main component of the epithelium, absorptive cells, gradually became positive for DBA, PNA, and SBA and the scattered goblet cells for RCA-I and WGA. On the other hand, the change of the staining pattern in the connective tissue occurred only for Con A, RCA-I, and WGA, and this change took place rapidly at the beginning of climax (stage 60). Increased staining for Con A and WGA at stage 60 was observed only in a group of connective tissue cells close to the epithelium and in the basement membrane. As metamorphosis progressed, this localization of the staining intensity became less clear. At the completion of metamorphosis (stage 66), the absorptive cells were stained with all lectins except for UEA-I, whereas the goblet cells stained only with RCA-I and WGA. These results indicate that lectin histochemistry can distinguish between larval and adult cells of both two epithelial types (absorptive and goblet cells). The technique may also identify a group of connective tissue cells, close to the epithelium, that possibly induce the metamorphic epithelial changes.

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PubMed1990

Electron microscopic nerve fiber caliber analysis in the nerve branch to the venter rostralis of the M. digastricus in mice.

Nerve fiber counts and caliber analysis were performed with an electron microscope on 5 nerve branches to the venter rostralis of m. digastricus (VRD) from 3 mice. Branches contained an average of 42.4 (79.4%) myelinated fibers and 11.0 (20.6%) unmyelinated fibers. 68.4% of the sheaths of the myelinated fibers in the nerve branches were 6.5-8.5 microns (peak 7.0-7.5 microns) in major diameter and 76.4% were 5.0-7.5 microns (peak 6.0-6.5 microns) in minor diameter, 68.8% of the axons of the myelinated fibers were 4.5-6.5 microns (peak 5.5-6.5 microns) in major diameter and 76% were 3.5-5.5 microns (peak 4.0-5.0 microns) in minor diameter. The frequency distribution of the diameters showed that the nerve branch to VRD consisted of extra large myelinated fibers as in the r. digastricus to the venter caudalis of m. digastricus (VCD). Average ratios of the areas of the myelin sheaths to those of axons of the myelinated fiber transverse sections in the various axon area classes of the nerve branches were 0.7-2.9, and those ratios tended to decrease in the larger axon classes.

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PubMed1990

Hemolymph cells and the platelet-like structures of the land slug, Incilaria bilineata (Gastropoda: Pulmonata).

3 morphologically distinct hemolymph cell-types, Types I, II and III, were found by light and electron microscopy of hemolymph from the land slug, Incilaria bilineata. In addition, vast numbers of the platelet-like structures were present in the collected hemolymph. Type I cells were macrophage-like, Type II cells were lymphocyte-like and Type III cells were fibroblast-like. Among these hemolymph cells, only Type I cells could recognize foreign materials and phagocytose them. Type I cells, whether from circulating hemolymph or from the heart-kidney region (regarded as a hemopoietic organ), could be maintained for only 4 d in cultivation because the cells gradually divided within 3 or 4 d. Thus, the platelet-like structures appear to be derived from Type I cells, which readily fragmentize and function by clamping onto foreign materials.

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PubMed1987

Ultrastructural changes in the intestinal connective tissue of Xenopus laevis during metamorphosis.

Ultrastructural changes in the intestinal connective tissue of Xenopus laevis during metamorphosis have been studied. Throughout the larval period to stage 60, the connective tissue consists of a few immature fibroblasts surrounded by a sparse extracellular matrix: few collagen fibrils are visible except close to the thin basal lamina. At the beginning of the transition from larval to adult epithelial form around stage 60, extensive changes are observed in connective tissue. The cells become more numerous and different types appear as the collagen fibrils increase in number and density. Through gaps in the thickened and extensively folded basal lamina, frequent contacts between epithelial and connective tissue cells are established. Thereafter, with the progression of fold formation, the connective tissue cells become oriented according to their position relative to the fold structure. The basal lamina beneath the adult epithelium becomes thin after stage 62, while that beneath the larval epithelium remains thick. Upon the completion of metamorphosis, the connective tissue consists mainly of typical fibroblasts with definite orientation and numerous collagen fibrils. These observations indicate that developmental changes in the connective tissue, especially in the region close to the epithelium, are closely related spatiotemporarily to the transition from the larval to the adult epithelial form. This suggests that tissue interactions between the connective tissue and the epithelium play important roles in controlling the epithelial degeneration, proliferation, and differentiation during metamorphic climax.

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PubMed1987

Muscle fiber type analysis in the mouse m. digastricus, m. stylohyoideus, m. zygomaticus and m. buccinator.

It is generally accepted in vertebrates that large motor nerve fibers innervate the white (fast) muscle fibers and small motor nerve fibers innervate the red (slow) muscle fibers. In the previous study (SHIMOZAWA, NAKAMURA 1985), we showed that nerve branches to the venter caudalis m. digastrici and m. stylohyoideus of the mouse consist of considerably larger myelinated nerve fibers compared with the truncus facialis distal to the foramen stylomastoideum innervating the other skeletal muscles in the face. To examine the relationship between the size of nerve fibers and the type of muscle fibers, we performed, in this investigation, quantitative analysis of muscle fiber types (white, intermediate and red) in the venter rostralis (RD) et venter caudalis (CD) m. digastrici, m. stylohyoideus (St), m. zygomaticus (Zy) and m. buccinator (Bu) of the mouse with the Sudan Black B stain preparations. Ratios of the number of muscle fibers of 3 types were RD (28.1%), CD (24.6%), St (27.5%), Bu (28.5%) less than Zy (40.8%) for the white muscle fibers, the RD (58.5%), CD (62.9%), St (53.9%), Bu (60.3%) greater than Zy (47.3%) for the red muscle fibers, while differences between the ratios for these muscles were not significant for the intermediate muscle fibers. Mean major and minor diameters and average transverse areas of the muscle fibers of 3 types were white greater than intermediate greater than red muscle fiber in all muscles examined in this study. When compared between these muscles, they were RD, CD, St greater than Zy, Bu for any type of muscle fibers.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1987

Phagocytosis by hemolymph cells of the land slug, Incilaria fruhstorferi Collinge (Gastropoda: Pulmonata).

Phagocytosis by hemolymph cells of the land slug, Incilaria fruhstorferi Collinge, were studied with the scanning electron microscopy (SEM) and the transmission electron microscopy (TEM). The fate of foreign materials, i.e., sheep red blood cells (SRBC) and latex beads, introduced into the hemocoel of the slug were followed. Certain hemocytes named as Type I cell were involved in spontaneous cyto-adherence while both Type II and III cells were not observed to adhere to foreign materials. SRBC and latex beads (luminal diameter 0.79 micron) were phagocytosed and latex beads (luminal diameter 15.8 micron) were engulfed by Type I cells. In vitro phagocytosis experiments showed that SRBC formed the rosette structure surrounding a Type I cell and both SRBC and latex beads (luminal diameter 0.79 micron) were swallowed by Type I cells in vivo. The plate-like structures with long fine fibers attached the latex beads. The latex beads were often seen deep in the aggregates of plate-like structures.

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PubMed1987

Development of the connective tissue in the digestive tract of the larval and metamorphosing Xenopus laevis.

Developmental changes, until the completion of metamorphosis, of the connective tissue of the digestive tract in the South African clawed frog Xenopus laevis were examined by light and scanning electron microscopy. During the pre- and prometamorphosis (stages 50 through 59) the layer of connective tissue was prominent in the typhlosole, while that in the rest of the intestine and stomach remained very thin. Most of the connective tissue cells were fibroblasts and were concentrated mainly in the typhlosole, the boundaries of which were distinct. In the anterior part of the typhlosole just behind the stomach, the layers of connective tissue and muscle were the thickest and the boundary between these 2 layers was obscure. Although the mitotic cells of the connective tissue were rare, if any, and no migrating cells were observed on the surface of the connective tissue, the connective tissue of the intestine gradually increased in cell number during the pre- and prometamorphosis. In the stomach, on the other hand, there was no such increase. At the beginning of the metamorphic climax (stages 60 and/or 61), the layer of connective tissue suddenly became thick in both the stomach and the intestine. The boundaries of the typhlosole became less distinct. Mitotic index of the connective tissue became high, and its cells dramatically increased in number and contained many undifferentiated mesenchyme-like cells. In the stomach, these connective tissue cells invaded the glands of the larval epithelium into just below the surface epithelium and mitotic index of the entire stomach epithelium increased. In the intestine, in contrast, mitotic epithelial cells were localized in the islets which invaginated into the connective tissue and later formed the adult epithelium. With the growth of islets, the intestinal folds were formed as straight rows and, after stage 63, were modified into a zigzag pattern and had mitotic cells localized in the troughs of folds. The present results indicate that dramatic changes of the connective tissue of both the stomach and the intestine occur at the beginning of the metamorphic climax, concomitantly with those of the epithelium. Moreover, the results also show that, before the climax, even when there were no indications of metamorphic changes in the epithelium, cells of the connective tissue gradually increased in number in the intestine (but not in the stomach). It is also suggested that the muscle cells of the typhlosole just behind the stomach may participate in this gradual increase of connective tissue cells.

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