The surface fine structure of the bovine subcommissural organ

The bovine subcommissural organ was studied by using scanning electron microscopy. The most prominent findings was the existence of protruded and dilated endings of the ependymal cells. The majority of these cells were ciliated with two or more cilia; only a few unciliated cells were seen. Some pore-like structures were also seen on the surface. From the functional point of view, the most interesting finding was an amorphous heterogeneous material on the subcommissural ependyma. Especially in the caudal part of the organ this material accumulated in abundance. No real filamentous structures such as Reissner's fibre could be seen, however, it was assumed that the heterogeneous material corresponds to this formation. No supraependymal neurones were demonstrated.     

The fine structure of the light organ of the glowworm Lampyris noctiluca

Summary The four main parts of the glowworm light organ are the cuticle, the hypodermis, the photocyte layer and the reflector cell layer. The hypodermis is one cell thick and it contains hypodermic glands. These glandular cells have a lumen that opens to the outside of the cuticle. Projecting into the lumen are numerous microvilli. Between the hypodermis and photocytes are typical insect tunicated nerve fibres. They pass down between the photocyte and reflector layer cells. They do not appear to innervate the photocytes and they are thought to innervate adjacent muscle fibres or to be sensory. Tracheoles are commonly present between the photocytes but no tracheolar end organs are found. The photocytes contain amorphous granules, mitochondria, photocyte granules and a vesiculated reticulum. All, except the mitochondria, are absent from the reflector layer and so probably have some connection with light production. The reflector layer contains glycogen granules, clear spaces thought to be the sites of urate crystals, and membranous granules. The latter granules are sometimes found in photocytes adjacent to the reflector layer whilst amorphous granules are sometimes absent from these adjacent cells. So a cell layer with some features of the photocyte and reflector layer cells is present. These morphological findings are discussed with regard to the unknown function of the reflector layer and the control of light emission. Acknowledgments. We would like to thank Professor J. Z. Young and Dr. E. G. Gray for their advice and encouragement, Mrs. Jane, Astafiev for drawing fig. 1, Mr. S. Waterman for photographic assistance, Miss Cheryl Martin for secretarial assistance, and many colleagues for help in collecting specimens of glowworms.     

Modelling the subgenual organ of the honeybee, Apis mellifera

In a recent study on the honeybee (Apis mellifera), the subgenual organ was observed moving inside the leg during sinusoidal vibrations of the leg (Kilpinen and Storm 1997). The subgenual organ of the honeybee is suspended in a haemolymph channel in the tibia of each leg. When the leg accelerates, the inertia causes the haemolymph and the subgenual organ to lag behind the movement of the rest of the leg. To elucidate the biophysics of the subgenual organ system of the honeybee, two mathematical models to simulate the experimentally observed mechanical response are considered. The models are a classical mass-spring model and a newly developed tube model consisting of an open-ended, fluid-filled tube occluded by an elastic structure midway. Both models suggest that the subgenual organ included in the haemolymph channel resembles that of an overdamped system. In resembling the biophysics of the subgenual organ system in the honeybee, we consider the tube model to be the better of the two because it simulates a mechanical response which complies best with the experimental data, and the physical parameters in the model can be related to the␣constituent parts of the subgenual organ included in the haemolymph channel. Received: 25 July 1997 / Accepted in revised form: 8 December 1997     

Functional morphology of the subgenual organ of the carpenter ant

Using light microscopy, confocal microscopy, electron microscopy and histochemistry, the subgenual organ (SGO) of an ant, Camponutas ligniperda, is investigated. Sensory units and attachment cells together enclose a large extracellular cavity, which is filled by acid mucopolysaccharides, as revealed by staining with ruthenium red. Due to this cavity, the whole SGO has the shape of a deformed sphere and the scolopidia exhibit a distribution of angles between 0 degrees and 60 degrees with the tibial long axis (as is shown by phalloidin-rhodamin staining of the actin filaments of the scolopale, viewed in situ by laser scanning confocal microscopy). The subgenual organ is innervated by a branch of the tibial nerve, which splits within or shortly distal to the femur-tibia joint. The other features of the SGO of Camponotus ligniperda are similar as in other insects: the SGO of Camponotus ligniperda contains about 35 scolopidial sensilla; it is fixed to the subgenual nerve on its proximal end, by its attachment cells to the opposite part of the cuticle; the fixation by the attachment cells is accomplished by a vast quantity of cytoplasmic microtubules; the construction of the sensory units is the same as in other mononematic scolopidial organs. The role of the extracellular lumen inside the organ and the special shape of the SGO of Camponotus ligniperda in mechanical transmission is discussed.     

Biophysics of the subgenual organ of the honeybee, Apis mellifera

The subgenual organ of the honeybee (Apis mellifera) is suspended in a haemolymph channel in the tibia of each leg. When the leg is accelerated, inertia causes the haemolymph (and the subgenual organ) to lag behind the movement of the rest of the leg. The magnitude of this phase lag determines the displacement of the subgenual organ relative to the leg and to the proximal end of the organ, which is connected to the cuticle. Oscillations of the subgenual organ are visualised during vibration stimulation of the leg, by means of stroboscopic light. Video analysis provides fairly accurate values of the amplitude and phase of the oscillations, which are compared with the predictions of a model.   The model comparison shows that the haemolymph channel can be described as an oscillating fluid-filled tube occluded by an elastic structure (probably the subgenual organ). The mechanical properties of the subgenual organ and haemolymph channel resemble those of an overdamped mass-spring system. A comparison of the threshold curve of the subgenual organ determined using electrophysiology with that predicted by the oscillating tube model suggests that the sensory cells respond to displacements of the organ relative to the leg. Accepted: 10 May 1997     

The cockroach heart as a bioassay organ

Detailed procedures are presented for denervation of the American cockroach heart, Periplaneta americana L., by removal of the lateral cardiac nerve cords. Results of bioassay with the innervated heart are also presented and compared to responses obtained from identical assay conditions with the denervated heart.The response of the innervated heart to 10^-3M sodium azide, slight changes in the concentration of sodium ion, reduced glutathione, saline dilutions, and low amounts of ethanol and acetone was characterized by the immediate appearance of irregularities in the heartbeat. In contrast, the responses of the denervated heart to the first three of these compounds were always characterized by a smooth even heartbeat changing gradually in amplitude and/or rate and/or contractile state of the alary muscles. All assay conditions examined caused qualitatively less response in the beat of the denervated heart.Irregularities in the beat of the innervated heart which were induced in bioassay were found to be due to extreme sensitivity of the spontaneously active cardiac neurons.

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Zusammenfassung Das isolierte abdominale Herz von Periplaneta americana L. reagiert auf Durchspülung mit 10^-3 Mol Natriumazid in physiologischer Kochsalzlösung mit einem unmittelbaren Anstieg des Tonus bis zu fast systolischer Hemmung. Danach verringert das Herz den Tonus allmählich, schlägt unregelmäßig und tritt in eine kurze Periode diastolischer Pause ein, bevor es in Diastole stehen bleibt. Die Herzschlagaktivität wurde wieder aufgenommen, wenn das Natriumazid durch Spülung mit physiologischer Kochsalzlösung ersetzt wird.Nach Entfernung beider Paare der Herzseitennerven gab das Herz von P. americana auf Bespülung mit 10^-3 Mol Natriumazid in physiologischer Kochsalzlösung keine Initialreaktion. Statt dessen stieg der Herzschlag nach 2 min allmählich leicht an und die Herzschlagamplitude nahm im Verlaufe von 6 min sehr allmählich ab. Nach 6 min blieb das Herz in Diastole stehen.Die Herzreaktionen der amerikanischen Küchenschabe waren bei Auftropf-Tests mit anormaler Natriumchloridkonzentration, herabgesetztem Glutathion und Lösungsmitteln ähnlich den für Natriumazid beschriebenen. Die Reaktion des denervierten Herzens ist durch das Fehlen von Unregelmäßigkeiten im Herzschlagmuster gekennzeichnet.Sowohl das denervierte wie das innervierte Herz reagieren auf Testtropfen von nur etwas anormalen Calciumchloridkonzentrationen.

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Supported by USPHS Training grant PHS GM 1076.     

The histology and fine structure of the olfactory organ of the squid Lolliguncula brevis Blainville.

The olfactory organ of the squid has a thick, pseudostratified epithelium containing five morphological types of ciliated receptors. In the simplest receptors the cilia originate separately in the distal pole of the cell. All other receptors have some type of cilia filled cavity, varying from a simple pocket of cilia at the surface to a completely closed vesicle filled with cilia in cells deep in the epithelium. The receptors are compared to cells in the rhinophore of Nautilus and the olfactory organs of coleoid cephalopods. Possible functions of the olfactory organ, based on its morphology, are discussed.     

Specialized ependyma in the posterior mesencephalon of the chicken: The fine structure of the subtrochlear organ

Summary A formation of specialized ependymal cells in the posterior mesencephalon of the domestic fowl, designated as the subtrochlear organ, was examined with light-,scanning-and transmission electron microscopy. This organ possessing the form of the letter V is located in the ventricular wall of the posterior mesencephalon. Its apex marks the median sulcus, while the arms of the V are directed rostrolaterally. Ependymal cells lining the subtrochlear organ usually project an extremely elongated process into the subependymal region and are classified into three types according to their surface features: (1) cells with a bulbshaped protrusion that projects into the ventricle, (2) single cilium-bearing cells, and (3) cells with a tuft of cilia. The first type of cell is restricted to the median portion of the subtrochlear organ; its bulb-shaped protrusion contains numerous ribosomes. The second type of cell predominates in the arm (rostrolateral) area; in its apical cytoplasm such ciliary structures as basal body are rarely seen. The third type of cell is usually assembled into several small islands on the arm area; it has many basal bodies and other ciliary structures in the apical cytoplasm.     

东亚飞蝗Locusta migratoria manilensis（Mey．）膝下器中感觉细胞的超微结构

东亚飞蝗滕下器由具橛感器组成,每一具橛感器主要由三类细胞组成,即：感觉细胞、感橛细胞和冠细胞。感觉细胞位于最近端．细胞核圆且大,细胞质内含有丰富的线粒体、高尔基体、多泡小体等细胞器。感觉细胞向近端发出轴突进入中枢神经系统,向远端发出树突。树突内古有大量的线粒体、纵行微管,树突内最复杂的结构当属纤毛根,从近端到远端依次由远端基体、近端基体、主纤毛根和纤毛小报组成。树突顶端,由远端基体发出一条感觉纤毛,纤毛具有典型的“9 0”结构。主纤毛根和纤毛小根具有明暗相间横纹结构,两横纹间的间隔距离约为65nm。感觉纤毛穿过由感橛细胞形成的感橛空隙,末端进入一高电于密度的顶端细胞外结构——帽。感橛细胞内最明显的特征为具有感橛,感橛细胞围绕着远端树突和感觉纤毛部分,冠细胞紧密地包围着感橛细胞和帽。东亚飞蝗膝下器中同时古有一或两个感觉细胞的具橛感器,这在以往研究报道中是较为少见的。本研究的主要目的在于为以后对此器官的生理功能研究提供形态学的基础材料。     

The fine structure of the axial organ of the feather star Nemaster rubiginosa (echinodermata: crinoidea)

The fine structure of all the constituent cell type of the crinoid axial organ is described (coelomic epithelial cells, muscles, free cells, gland cells and neurons) ; also described is the fine structure of the extracellular haemal fluid. The gland cells of the glandular tubules of the axial organ have the characteristic fine structure of protein exporting cells and may produce granular and filamentous components of the haemal fluid. The neurons (perikarya and axons) of the axial organ may possibly be neurosecretory, since they are filled with electron-dense granules. Homologies between the axial organs of different echinoderm classes are discussed.     

The tarso-pretarsal chordotonal organ as an element in cockroach walking

Many types of sense organs have been demonstrated to show repetitive discharges during walking that could provide informational cues about leg movements and other parameters of locomotion. We have recorded activities of receptors of the distal (tarsal) segments of the cockroach hindleg in restrained and freely moving animals while they were videotaped. These recordings show peaks of activities at the onset and termination of the stance phase. We have morphologically and physiologically identified a joint angle receptor, the tarso-pretarsal chordotonal organ, that contributes to the discharges seen late in stance, prior to the onset of leg flexion in swing. This sense organ encodes the angle and rate of change of the most distal leg joint and specifically discharges when the claws are disengaged from the substrate. Applied displacements of the claws in restrained preparations elicit reflex activation of the tibial flexor muscle and a crossed extensor reflex in the opposite hindleg. These reflexes could function to insure that leg flexion in swing does not occur until the claws are disengaged and to enhance support by the opposite hindleg. Thus, the regular discharges of the chordotonal organ could assure efficient and coordinated muscle contractions and movements during normal, unperturbed walking. Accepted: 2 January 1997     

The fine structure of amylopectin

A critical examination of an enzymic method for determining the ratio of A and B chains in amylopectin leads to a value of ～ 1:1, and not 2:1 as suggested other workers. Partial debranching with pullulanase gave results consistent with earlier suggestions that A chains are predominantly and selectively removed. The ratio of A and B chains in a partially branched amylopectin has been determined, and the results are discussed in relation to possible structures for amylopectin.     

The fine structure of the perineural endothelium

Summary Fine strands of motor nerves were examined with the electron microscope using thin section as well as freeze-etching techniques. The specimens were taken from frog cutaneous pectoris nerve, rat sciatic nerve, mouse and shrew phrenic nerves and from human skin nerves. The perineural sheath (Henle, Ranvier, Key and Retzius) consists of one to several concentric laminae of endothelial cells; it encases nerve fascicles and eventually individual nerve fibers and terminals. The endothelial cells are extremely thin and fitted together smoothly by overlap and dove-tailing of their border zones. The cell contacts are formed by continuous zonulae occludentes, often reinforced by maculae adhaerentes, and in depth they comprise 3–15 strands with an average of 5–6 strands per junction. The membranes of endothelial cells are studded with attachment sites and stomata of plasmalemmal vesicles suggesting a high level of pinocytotic activity. This phenomenon is by no means restricted to the external laminae of the endothelial sheath. Each endothelial lamina is vested with basement membranes on both (epineural and endoneural) sides, and the spaces between laminae contain a few collagen fibers and fibroblasts. Occasionally, punctate tight junctions are seen between laminae. Cytological evidence supports the hypothesis that the perineural endothelium provides a relatively tight and highly selective barrier separating the peripheral nerves from surrounding tissue and its extracellular fluid spaces. This effect is achieved on the one hand by the sealing of pericellular spaces and on the other hand by a membrane controlled transcellular transport mechanism (pinocytosis), both of which are enhanced by their serial arrangement.Dedicated to Professor Wolfgang Bargmann, Kiel, on the occasion of his 70th birthday.The technical assistance of Dr. F. Dreyer, Mr. D. Savini, Miss H. Claassen and Miss R. Emch is gratefully acknowledged.Financial support was received by the following institutions: Swiss National Foundation for Scientific Research, grants Nrs. 3.368.0.74, 3.774.72, 3.259.74, 3.045.73. Deutsche Forschungsgemeinschaft (Sonderforschungsbereich 38, Projekt N). The Dr. Eric Slack-Gyr Stiftung in Zürich and the Hartmann-Müller Stiftung for Medical Research in Zürich.