Involution of the caudal musculature during metamorphosis in the ascidian,Botryllus schlosseri

Summary The caudal musculature of the free-swimming tadpole of the ascidian, B. schlosseri consists of cylindrical mononucleated cells connected in longitudinal rows flanking the axial notochord. During resorption of the larval tail, which is apparently induced by the contraction of the epidermis, muscle cells are dissociated and pushed into the body cavity where most of them are rapidly engulfed by phagocytes. In the initial stages of tail withdrawal muscle cells display surface alterations due to the disruption of intercellular junctions and disarrangement of myofibrils. Extensive degenerative changes, with shrinkage of mitochondria and disintegration of the contractile material are subsequently observed. Lysosomes and autophagic vacuoles are rarely seen and appear to play a secondary role in the degradation of the muscle cells, which occurs predominantly within the phagocytes. Myofilaments and myofibrils have never been observed within autophagic vacuoles. Clumps of muscle fragments and degenerated phagocytes undergo eventual dissolution in the blood lacunae, concomitantly with the differentiation of the young oozooid.This investigation was supported in part by a grant from the Muscular Dystrophy Associations of America and by CNR contract No. 7100396/04115542 from the Istituto di Biologia del Mare, Venice. We gratefully acknowledge the skillful assistance of Mr. G. Gallian, Mr. M. Fabbri and Mr. G. Tognon. We also thank the staff of the Stazione Idrobiologica at Chioggia for collecting the colonies.     

Die Feinstruktur des paraganglionären Gewebes im Plexus suprarenalis des Meerschweinchens

Zusammenfassung Die Feinstruktur der chromaffinen paraganglionären Zellinseln im Endoneuralraum des Plexus suprarenalis wird beschrieben.Das paraganglionäre Gewebe liegt neben Kapillaren mit teilweise fenestrierten Endothelien und spärlich verstreuten Bindegewebszellen. Es wird von zwei Zellarten aufgebaut:Typ I-Zellen (chromaffine Zellen) mit großen, locker strukturierten Kernen enthalten im Zytoplasma elektronendichte Granula (1000–1600 Å Durchmesser) mit eng anliegender Membranbegrenzung und Vesikel von 2000–4000 Å Durchmesser, deren dichter Inhalt meist exzentrisch gelegen und durch einen weiten Spalt von der Membran getrennt ist. Weiters beobachtet man ausgedehnte Golgiregionen und in ihrer Nähe uncharakteristische (Entwicklungs-) Formen der beschriebenen Granula, Mitochondrien, Ergastoplasma und freie Ribosomen. Mikrotubuli und Plasmafilamente sind regelmäßig, multivesiculated bodies gelegentlich zu finden.Typ II-Zellen (Hüllzellen) bilden eine Basalmembran aus und umgeben die chromaffinen Zellen mit dünnen Fortsätzen. Die Zellorganellen sind in der Nähe des Kernes gelegen, die Fortsätze weisen eine dichte, z. T. geordnete, fibrilläre Strukturierung auf. An der Zelloberfläche beobachtet man regionäre Zytoplasmaverdichtungen. Die Hüllzellen enthalten keine Bläschen mit elektronendichtem Inhalt.Markfreie Nerven, in Schwannsche Zellen und Hüllzellen gelagert, ziehen an die Typ I-Zellen heran und bilden an deren Oberfläche synaptische Verbindungen aus. Dabei erscheinen die chromaffinen Zellen stets als postsynaptischer Teil der Formation.Die Typ I-Zellen werden als endokrin tätige Zellen aufgefaßt, die durch Abgabe von Katecholaminen hemmend auf die Impulstransmission wirken. Die Typ II-Zellen entsprechen den Schwannschen Zellen.

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Fine structure of paraganglionic tissue in the suprarenal plexus of the guinea pig

Summary The fine structure of chromaffin paraganglionic tissue situated in the endoneural space of the plexus surparenalis is described.The paraganglionic tissue is found near capillaries with partially fenestrated endothelial cells and rarely scattered connective tissue cells. Two cell types are observed:Type I-cells (chromaffin cells) with great, fine structured nucleus show in their cytoplasm electron dense granules (1,000–1,600 Å in diameter) with clinching membranes and vesicles of 2,000 to 4,000 Å in diameter. In the latter the normally excentric situated dense core is separated from the membrane by a wide cleft. Further large Golgi areas and near them uncharacteristic (developing) kinds of the granules, as described above, mitochondria, ergastoplasm and ribosomes occur. Microtubules and filaments are regularely, multivesiculated bodies occasionally found.Type II-cells (surrounding cells) produce a basement membrane and envelope the chromaffin cells with fine processes. The cell organells are near the nucleus. The processes show a compact, partially fibrillar structure. On the cell surface condensations of the cytoplasm are observed in some regions. The surrounding cells do not contain vesicles with an electron dense core.Myelinated nerves, wrapped by Schwann cells and surrounding cells approach to type I-cells and build synaptic junctions to their surface. In such cases constantly the chromaffin cells are seen as the postsynaptic part of the formation.The type I-cells are thought to be of endocrine function, having an inhibitory effect on impulse transmission by secreting catecholamines. The type II-cells correspond to the cells of Schwann.

     

Die Feinstruktur der peribronchialen Mikroparaganglien beim Meerschweinchen

Zusammenfassung Das Parenchym der peribronchialen Mikroparaganglien wird von zwei Zellarten aufgebaut: Chromaffine Zellen (Typ I-Zellen) und Hüllzellen (Typ II-Zellen).Die chromaffinen Zellen sind durch ihren reichen Gehalt an Vesikeln mit elektronendichtem Inhalt gekennzeichnet, deren Durchmesser 700–1300 Å beträgt. Markfreie Nerven ziehen an die Typ I-Zellen heran und bilden synaptische Kontakte aus. Die chromaffinen Zellen sind dabei der postsynaptische Teil der Verbindung. Die Hüllzellen entsprechen strukturell und funktionell den Schwannschen Zellen.Ein Mikroparaganglion wird von 10 bis 15 chromaffinen Zellen und deren Hüllzellen aufgebaut. Sie liegen dicht um fenestrierte Kapillaren, die von den Aa. bronchiales aus versorgt werden. Die Paraganglien sind von den Nervenzellen des peribronchialen Plexus durch dessen Perineurium getrennt. Selten findet man solitäre chromaffine Zellen innerhalb der Nervengeflechte. Es wird angenommen, daß die Paraganglien endokrine Funktionen erfüllen.

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The fine structure of the guinea pig peribronchial micro-paraganglia

Summary The parenchyma of peribronchial microparaganglia consists of two different cell types: chromaffin cells (type I-cells) and surrounding cells (type II-cells).The chromaffin cells contain numerous vesicles with electron dense content, their diameter ranging from 700 to 1,300 Å. Unmyelinated nerves form synapses with type I-cells. The surrounding cells structurally and functionally correspond to Schwann cells.A micro-paraganglion consists of ten to fifteen chromaffin cells and their satellite cells. They are situated close to fenestrated capillaries, which are supplied from the Aa. bronchiales. A perineurial sheath separates the paraganglia from the nerve cells of the peribronchial plexus. Single chromaffin cells are found seldom within the nervous plexus.The paraganglia are thought to have an endocrine function.

     

Characterization of human mammary cell types in primary culture: Immunofluorescent and immunocytochemical indicators of cellular heterogeneity

Summary Parenchymal organoidal structures that were obtained from collagenase digestion of reduction mammoplasty specimens of apparently normal human breasts have been grown in short-term primary cultures, either on plastic or on floating gels of polymerized rat-tail collagen. Three morphologically distinct major cell types are readily observed in both systems: cuboidal cells, which occupy apical positions on collagen gels; larger, epithelioid, or basal cells on gels; and elongated cells which penetrate into the gel. In addition, a fourth cell type, that of a large, flat cell, is observed less readily by phase contrast microscopy on the surface of cultures grown on plastic. Immunofluorescent and immunocytochemical staining of cultures on plastic or histologic sections of cultures on gels have been undertaken with antisera and other histochemical reagents that stain the different parenchymal cell types in vivo. Thus antisera to epithelial membrane antigen(s), monoclonal antibodies (MABs) to the defatted mammary milk fat globule membrane, peanut lectin, and keratin MAB LE61, which preferentially stain the epithelial cells of ducts in vivo, also stain the cuboidal/apical cells in vitro. The large, flat cells are stained intensely by the first three reagents but not by the last one. Antisera to collagen IV, laminin, fibronectin, actin, keratin MAB LP34, MABs to the common acute lymphoblastic leukemia antigen, and MAB LICR-LON-23.10, which showed enhanced staining for the ductal myoepithelial cells in vivo, also stain the epithelioid/elongated cells in vitro. However, the effect of the last four reagents is reduced considerably in most elongated cells, and MAB LP34 stains the large, flat cells intensely. Heterogeneous cells of intermediate morphologies and staining patterns between the cuboidal/flat cells and large epithelioid cells have also been identified. The results suggest that the cuboidal cells and large, flat cells are related to mammary epithelial cells, whereas the large epithelioid/elongated cells have some characteristics of myoepithelial cells, and that intermediate forms may exist in culture between the two parenchymal cell types. This work was supported in part by the Ludwig Institute for Cancer Research and the Cancer and Polio Research Fund. Dr. M. J. Warburton is supported by the Cancer Research Campaign.     

Improved maintenance of adult rat hepatocytes in a new serum-free medium in the presence or absence of barbiturates

Summary For serum-free primary culture of adult rat hepatocytes, a synthetic medium DM-160 and rat-tail collagen were selected for the basal medium and for the culture substratum, respectively. Barbiturates, such as phenobarbital and 1-ethyl-5-isobutylbarbiturate, efficiently supported survival of hepatocytes and maintained their morphologic features at lower concentrations under the serum-free conditions than under the serum-supplemented conditions. However, the hepatocyte survival rates under the serum-free conditions were lower than those under the serum-supplemented conditions in the presence or absence of barbiturates. Supplementation of the basal medium with a combination of five groups of factors (5Fs), such as eight amino acids (Ala, Arg, Gly, Ile, Met, Phe, Pro, and Trp), two unsaturated fatty acids (linoleate and oleate), a protease inhibitor (aprotinin), three vitamins (A, C, and E), and five trace elements (Mn, Fe, Cu, Zn, and Se), improved the hepatocyte survival under the serum-free conditions in the presence or absence of barbiturates. In other words, the serum could be completely substituted by the 5Fs. Hepatocyte cultures maintained in the 5Fs-suppelemented basal medium showed excellent induction of tyrosine aminotransferase activity in response to dexamethasone in the presence or absence of barbiturates. The efficiency of the 5Fs-supplemented basal medium for maintaining hepatocytes was not inferior to those of other media in common use with hepatocytes, such as Williams' medium E and Waymouth's medium MB-752/1. In conclusion, maintenance of functional hepatocytes in serum-free primary culture could be improved by use of the new medium preparation (the 5Fs-supplemented DM-160) in the presence of barbiturates. This work was supported by a grant no. 61771923 from the Ministry of Education, Science and Culture of Japan.     

Regulation of insulin synthesis in an insulin-producing cell line (RINm5F): Long-term experiments

Summary The insulin-producing cell line RINm5F, has been used in short-term experiments to evaluate insulin secretion. We sought to maintain the responsiveness of these cells to stimuli for up to 2 days. We examined the course of new insulin synthesis over this period by measuring at intervals immunoreactive insulin (IRI) in two parts: IRI in the medium (M) and IRI extracted from the cells (C). Control cells were incubated in RPMI 1640/2.8 mM glucose/10% fetal bovine serum/200 μg/ml bacitracin (to prevent insulin degradation). The addition of dibutyryl cAMP 10 mM to the experimental dishes significantly increased total (M+C) IRI at 48 hr to 37% above the insulin content of the control dishes (p<0.01). Theophylline 10 mM increased total (M+C) IRI by 24% over control (p<0.05) after 24 hrs. Glucose, glyceraldehyde, leucine, arginine, glucagon and tolbutamide, other stimulants of insulin production, had no effect. Under the experimental conditions reported here, including the use of bacitracin, IRI synthesis can be studied for up to 48 hr. Portions of this study have been published in abstract form for the 47th Annual Meeting of the American Diabetes Association, Indianapolis, Indiana, 1987. Supported in part by the American Diabetic Association, Maryland Affiliate.     

Tissue culture of Ecklonia radiata (Phaeophyceae,Laminariales): effects on growth of light,organic carbon source and vitamins

The effects of light quality and irradiance, and supply of organic carbon and vitamins on the growth of two forms of Ecklonia radiata in tissue culture were examined. A callus of unpigmented cells developed over the cut surface of newly excised explants of stipe. This growth was best in the dark but stopped after 10 weeks. Pigmented, mainly filamentous clumps of cells developed from explants after several weeks in culture. These required light for growth, with growth being enhanced by increasing photon flux density up to 30 μmol photon m^-2 s^-1, with the active spectral component being red light (> 600 nm). The addition to the medium of a range of organic carbon sources or vitamins did not stimulate growth of either culture type in the dark. author for correspondence