The fine structure of cephalopod blood vessels

Summary The fine structure of blood vessels of the retina and arms of Octopus and the lip of Sepia is described.There are two main types of vessels. The first type (type 1) has a complete basement membrane, an incomplete lining of endothelial cells formed into finger—like processes, and a complete investment of pericytes surrounding the vessel. These latter cells contain myofilaments. The second type (type 2) is smaller and contains few if any myofilaments, and has a less complexly folded endothelium. This type is subdivided into three forms depending on the number of pericytes and the form of the endothelial lining.Amoebocytes are described and these form a distinct group of cells.The fine structure of hemocyanin is observed in normally fixed material and is correlated with its previously described structure.These observations are related to their possible functional importance.

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Zusammenfassung Die Ultrastruktur von Blutgefäßen der Retina und der Arme von Octopus und der Lippe von Sepia wird beschrieben.Es bestehen vorwiegend zwei Gefäßtypen. Der erste Typ (Typ 1) zeigt eine geschlossene Basalmembran, eine unvollständige Begrenzung durch Endothelzellen, die fingerförmige Fortsätze bilden und eine vollständige Pericytenhülle um das Gefäß. Die letztere enthält Myofilamente. Der zweite Typ (Typ 2) ist kleiner und enthält wenig oder keine Myofilamente. Er besitzt ein weniger komplex gefaltetes Endothel. Dieser Typ wird gemäß der Zahl der Pericyten und der Form der endothelialen Begrenzung in drei Gruppen unterteilt.Deutlich verschiedene Amoebozyten werden beschrieben.Die Ultrastruktur von Haemocyanin ist an normal fixiertem Material zu beobachten. Sie wird zu ihrer in früheren Arbeiten beschriebenen Struktur in Beziehung gebracht.Die Beobachtungen werden in Hinblick auf ihre mögliche funktionelle Bedeutung diskutiert.

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Acknowledgements. We would like to acknowledge the encouragement and advice of Professor J. Z. Young and Dr. E. G. Gray. Mrs. J. I. Astafiev did the drawings and Mr. A. Aldrich and Mr. S. Waterman helped with the photography.     

The fine structure of cephalopod blood vessels II. The vessels of the nervous system

Summary Blood vessels of the perioesophageal nerve ganglia (brain) of Octopus vulgaris and the stellate ganglia of Sepia officinalis are described. The vessels have an incomplete endothelium, a complete basement membrane and a complete investment of pericytes. The pericytes are joined by specialised membrane junctions but these are not tight junctions. The main type of neuron/vessel arrangement is one where there is a collagen-filled space between the pericytes and the surrounding glial cells. Axons or neurons are sometimes applied directly to the vessel pericytes and in the neuropil, pericytes contact glial cells that ensheath bundles of axons. Blood spaces between neurons are also present.We would like thank Professor J. Z. Young and Dr. E. G. Gray for encouragement and advice, Mrs. Jane Astafiev for drawing Fig. 11, Mr. S. Waterman for photographic assistance and Miss Cheryl Martin for secretarial and other assistance.     

The fine structure of intracerebral vessels

Summary Intracerebral vessels of the parietal lobe of the rhesus monkey have been examined by electron microscopy with special reference to the relationship between the leptomeninges and the cerebral cortex. A perivascular reticular sheath, in apparent communication with the subarachnoid space surrounds intracerebral arterioles. Myo-endothelial junctions occur in intracerebral arterioles, but no nerve fibres are found in association with such vessels. This indicates that the tone of these vessels may be regulated by chemical mechanisms, possibly mediated through the myo-endothelial junctions.     

Studies on the fine structure of invertebrate blood vessels

Summary The position, structure and function of the valves within the lateral sinus of the medical leech, Hirudo medicinalis, are described on the basis of vital, light- and electron microscopy. In this species the valvular apparatus consists of multiple elongated fir cone-shaped fibrous villi surrounding the orifices of the latero-lateral and latero-dorsal vessel like a tentacular crest. Each villus is covered by a thin sheet of a continuous endothelium. The valves prevent the backflow of hemolymph during systolic contraction of the lateral sinus.The endothelium contains many small mitochondria and polyribosomes in the perinuclear cytoplasm and it develops deep projections into the underlying connective tissue. Each of these consists of a multilayered system of closely interwoven thin endothelial membranes. The endothelium is anchored to its basement membrane by means of a great number of poorly defined hemidesmosomes. The fibrous tissue of the villi consists mainly of a homogeneous vitreous matrix in which few cellular components and very fine filaments are dispersed. Close to the endothelium this matrix appears to be condensed to form a multilayered framework made out of a basement membrane-like material.Though the valves themselves are devoid of muscle cells, those situated at their base and thus belonging to the vascular wall proper, display some specific morphological features: in particular the nuclei of these cells show a distinct fibrous lamina. Moreover, these muscle cells seem to be innervated only by one type of axon, containing both small, lucent synaptic vesicles as well as some of the dense-core variety.These findings are compared with data from earlier works and are discussed in relation to the hemodynamic functions of this valvular apparatus.     

Adrenergic innervation of human mesenteric blood vessels.

A fluorescent histochemical technique has been applied to study the adrenergic innervation of human superior mesenteric arteries obtained at autopsy. Specific catecholamine fluorescence was demonstrated in the smaller branches of this artery taken from three infants and one child. No specific fluorescence was seen in arteries from three adult subjects.     

The fine structure of the sense organs of the cephalopod mollusc Nautilus

Summary The structure of the rhinophore, digital tentacles, post-ocular tentacles and the eye of Nautilus macromphalus are described. The rhinophore is composed of mucous cells, ciliated cells, and flask-shaped ciliated cells. The latter are probably olfactory receptors. The digital tentacles are composed of mucous cells and pigmented cells. Motor-end-plates found in the muscle layer below the epithelium of the digital tentacles are similar to those described in other cephalopods. The post-ocular tentacle contains receptor cells that bear macrocilia. These may be mechanoreceptors. The retina is composed of retinula cells and supporting cells. A complex rhabdom is formed at the distal ends of the retinula cells. The supporting cells send processes up between these rhabdoms. Both types of cells contain pigment granules but the retinula cell has a complex membranous structure in its perikaryon. No synapses were found at the bases of the retinula cells. At the side of the retina are mucous cells that are presumed to produce the jelly-like substance that fills the inside of the eye in life. The likely function of the eye is discussed and it is suggested that it is capable of simple discriminations. It is suggested that the sense organs are probably comparatively unchanged from those of fossil nautiloids. Acknowledgements. This paper is dedicated to the late Dr. Yves Merlet who collected the nautiluses used in this study.We would like to thank Prof. J. Z. Young for all his support and encouragement. The Royal Society, The Percy Sladen Memorial Fund, and University College, London, provided the financial support that enabled one of us (V.C.B.) to collect nautiluses. The Science Research Council, U.K., provided the electron microscope used in the major part of the study and a grant to one of us (V.C.B.). We would also like to thank Prof. J. B. Gilpin-Brown who provided Fig. 1, Dr. R. Catala, for aquarium facilities, Mr. M. P. Legand and the Institut Français d'Oceanie, Noumea, New Caledonia, for laboratory facilities, Dr. J.-M. Bassot and Dr. Anna Bidder for advice on catching and preserving nautiluses, Mrs. Judy Parkes and Mr. M. Barker for photographic assistance, and Miss J. Date for secretarial assistance.     

The fine structure of the branchial heart appendage of the cephalopod Octopus dofleini martini

Summary The branchial heart appendage of Octopus dofleini martini has been investigated electron microscopically. This organ is dominated by peripherally lobed blood sinuses. It contains free hemocyanin (often aligned in rows), amoebocytes, endothelial cells, and muscle cells which occur mainly in connection with neurons. The neurons are often exposed to the blood. The blood sinuses are enclosed by a basement membrane which contains collagen equivalents and fine fibrillar elements. The sinuses are covered by two different epithelia: 1) the epithelium in the caoity of the appendage consisting of irregularly shaped cells with processes, the so called ( 30 high) podocytes, and 2) the epithelium ( 40 in height) on the surface of the organ, which is composed of two parts: a) a lacuna-forming portion directly adjacent to the basement membrane, which is topped by b) a continuous tissue portion with occasional lacuna-canals. The intercellular spaces of the inner and outer epithelium are connected. The structures of these epithelial cells are discussed in relation to the formation of the pericardial fluid.Our thanks are given to Professor Dr. Georg Kümmel, Freie Universität Berlin, for suggesting the theme and his scientific guidance; to Dr. Kenneth M. Towe, Smithsonian Institution, Washington D.C., for generously allowing the use of his instruments and for his technical assistance; to Mr. Frank Denys, Medical Dental School of Georgetown University, Washington D.C., for sharing with me his technical skills and for making possible the occasional use of a dark room; and finally to Dr. Fred E. Witmer, Office of Saline Water, U.S. Dept. of Interior, Washington D.C., for his help with the translation, and for taking all the side effects of this study as patiently as he did.Supported in part by Grant number GB 17539 of the National Science Foundation. Used as part of a thesis submitted to the Freie Universität Berlin.     

The fine structure of a multiterminal innervation of an insect muscle

The detailed structure of nerve branches, neuromuscular junctions, and muscle fibers of a multiterminal innervation of cockroach abdominal muscle has been studied with the electron microscope. The muscle fiber is of the banded myofibril type; with paired mitochondria and abundant endoplasmic reticulum. The peripheral nerve branches are multiaxonal with large central axon and several small peripheral tunicated axons. Tracheoblasts closely accompany the nerve branches. The multiple neuromuscular junctions show typical axonal vesicles, muscle aposynaptic granules, and close plasma membrane apposition with no interposition of basement membrane material.     

Aminergic innervation of the blood vessels of Octopus vulgaris

Evidence is presented from fluorescence histochemistry studies that blood vessels in the viscera of octopus vulgaris are innervated by nerve fibres containing catecholamines. This, with other evidence, suggests that cephalopods, like vertebrates, may be capable of regulating their peripheral vasculature by central neural control.     

The fine structure of the cysticercoid of Hymenolepis diminuta. III. The scolex.

Transmission electron microscopy of the scolex of the 8-day-old Hymenolepis diminuta cysticercoid demonstrates its resemblance to the scolex of the adult. A syncytial tegument composed of external and internal layers is connected by cytoplasmic extensions. Fully developed microtriches are present. Furthermore, a basement membrane, muscle layers, and medullary region containing flame cells, nerve tissue, and other cell bodies are observed. Of particular interest is the presence of discrete sensory endings whose function is discussed.     

The fine structure of cockroach blood cells

Electron-mictoscopic observations of the blood cells (Haemocytes) in the legs of the cockroach Blaberus discoidalis reveal three 'types' of cells distinguishable on the basis of fine structure. One type of cell contains numerous membrane-limited opaque bodies which may be lysosomes. A second type contains abundant digestive vacuoles and appears phagocytic. A third type, frequently encountered in rewlymoulted untanned animals but less often observed in mature adults, contains membrane-limited tubule-containing bodies (TCB) filled with rows of 340 A tubules which are quite different from cytoplasmic microtubules. It is suggested that haemocytes containing TCB may be equivalent to the coagulocytes (cystocytes) of light microscopy which actively participate-in-the process of haemolymph coagulation in Orthoptera. No attempt whatsoever is made at classification. Since considerable overlap in fine structure exists between cell types, it seems probable that the electron-images of fixed cells observed in this study represent several morphological expressions of which an individual cell may be capable during its lifetime.     

The structure of some cephalopod statoliths

Summary The statoliths of Sepia officinalis, Octopus vulgaris, Alloteuthis subulata and Taonius megalops have a smooth outline, but an irregular shape. They have projections and indentations. The statoliths from a pair of statocysts are usually quite similar in size and shape, and the general pattern is probably maintained throughout the size range of the species. Statoliths from large animals are marginally larger than those from smaller ones. The statolith usually occupies only a small part of the cavity of the statocyst, and it is situated in the anterior part of the statocyst. They are joined to the macula by hairs extending from it. These hairs are very delicate and easily broken during preparation of the specimens. The hairs are much longer and narrower than the receptor cilia of the macula. The receptor cilia are enclosed within holes in the tangled hairlike anchoring fibrils.The statolith is made up of crystalline subunits, the statoconia. The crystals vary in size, they are usually elongated, hexagonal with pointed ends. The statolith consists of a closely packed mass of these crystals, sometimes they are irregularly arranged, where in others they are stacked with their long axes parallel. In Sepia officinalis and Taonius megalops, the crystals are arranged in regular shaped packets and these packets of crystals are stacked together. These larger subunits are not always arranged in a regular way, and their major axes can be organised in several different ways. The size and outline of these large subunits do vary in different parts of the statolith.The external surface of the statolith is macroscopically smooth. Over some parts there is a surface layer covering the rod-like crystals that make up the major bulk of the stone. In other regions, the surface is rough at a microscopic level, the roughness is produced by the exposed ends of the filamentous crystals. The crystals are composed of calcium carbonate in the form of aragonite.I wish to thank Professor J.Z. Young, FRS, for considerable help, advice and encouragement throughout this study. Dr. A. Boyde generously allowed me to use his scanning electron microscope and gave freely of his expertise and time. Dr. J. Fitch kindly gave me some fossil statoliths and Dr. J. Elliott examined them with his x-ray diffraction apparatus. Dr. Marion Nixon helped me to collect and prepare the specimens. Mrs. E. Bailey, Miss P. Stephens and Mr. R. Moss provided the expert technical assistance     

The innervation and fine structure of paraneuronic cells in an amphibian pulmonary artery

Summary The pulmonary artery of Bufo marinus contains large numbers of bipolar cells situated in the tunica adventitia and in the outer layers of the media. These cells show a bright green-yellow fluorescence (emission spectra 485 nm) after formaldehyde pre-treatment suggesting that they contain a primary monoamine. The most characteristic fine-structural feature of these cells is the presence of numerous dense-cored vesicles (80—300 nm diameter) in their cytoplasm. The cells are in close contact (20 nm gap) with both agranular and granular nerve fibres. Both EM-cytochemical and formaldehyde-induced fluorescence tests indicate that the granule-containing nerve fibres are adrenergic. The agranular nerve fibres form discrete synaptic contacts with pre-and post-synaptic membrane thickenings on the cells. This was never observed with respect to the adrenergic fibres. Each process of the cells is about 45 m long. The processes do not bear any special relationship to either vessels of the arterial vasa vasorum or medial smooth muscle cells. Their location in the wall of the artery suggests that they are functionally significant with respect to activity of the arterial media.