Ultrastructure of the osphradium of Aplysia californica

Summary The osphradium of Aplysia californica, a sensory organ, is a small yellow-brown epithelial patch located in the mantle cavity immediately anterior to the rostral attachment of the gill. Scanning electron microscopy reveals a round ellipsoid structure of 0.6–1 mm in diameter with a central, occasionally folded, sensory epithelium. The central area is covered with microvilli and surrounded by a densely ciliated epithelium. Transmission electron micrographs show that the columnar supporting cells in the sensory epithelium contain an abundance of apical pigment granules and microvilli. Between the epithelial-supporting cells, the putative sensory elements consist of thin neurites (0.4–1.5 m in diameter) that reach the sea-water side of the osphradium. The neurites contain many neurotubules, mitochondria, vesicles and cilia in their apices. The nerve endings originate from cell bodies up to 40 m below the epithelium or in the osphradial ganglion itself, as revealed by electron microscopy and retrograde labeling with Lucifer yellow. There appear to be two populations of putative sensory cells, a large population of heavily stained cell bodies 4–10 m in diameter and a few scattered cells of large diameter (25–60 m). Following lanthanum impregnation, septate junctions can be seen between all types of cells in the epithelium, 3–5 m below the sea-water surface. This study provides new information for further investigation of osmo- and mechanosensation in Aplysia californica.     

Structure and synaptic organization of the osphradium of the lamellibranch mollusk Unio pectorum

The osphradial organ has been studied in Lamellibranchia--Unio pectorum--by means of scanning and transmissive electron microscopy. On the surface of the distal part of this hemosensory organ there is a distinct division into zones. The central part of the osphradial torus is occupied by the receptory zone, formed predominantly by supporting cells with microvilli and by peripheral processes of the subepithelial receptory cells. The lateral surfaces are occupied with ciliar areas of the ciliar supporting cells. In the receptory zone two types of the peripheral processes of the receptory cells are identified; they differ by the number of kinocilia and by ultrastructural organization of the apical part. Axon-like processes of the receptory cells interact with axons and dendrites of the ganglionic cells, forming axo-axonal, axodendritic and axosomatic synapses. The facts revealed demonstrate a high level of specialization of the osphradial receptory surface, connected with polymodality of this organ.     

Ultrastructure of the osphradium of Siphonaria grisea (Mollusca, Pulmonata)

By means of scanning and transmissive electron microscopic methods osphradium of Siphonaria grisea has been studied. The osphradium of the animal is presented as a small torulus formed by supporting ciliated cells. Among them bodies of receptory cells are situated; they are of smaller size and decorated with a bundle of microvilli. Central processes of the receptory cells, penetrating through a thick layer of the connective tissue, reach the subepithelial neural trunk. Concentration of the neural cells in the periphery of the trunk is small, and in the central area no chemical synapses are revealed. The data presented demonstrate a primitive structure of the osphradial chemoreceptory organ in Siphonaria.     

Ultrastructure of Mycobacterium marinum granuloma in striped bass Morone saxatilis

An emerging epizootic of mycobacteriosis currently threatens striped bass Morone saxatilis populations in Chesapeake Bay, USA. Several species of mycobacteria, including Mycobacterium marinum, species resembling M. avium, M. gordonae, M. peregrinum, M. scrofulaceum and M. terrae, and the new species M. shottsii have been isolated from diseased and healthy bass. In this study, we describe the ultrastructure of developing M. marinum granulomas in experimentally infected bass over a period of 45 wk. The primary host response to injected mycobacteria was formation of large macrophage aggregations containing phagocytosed bacilli. M. marinum were always contained within phagosomes. Close association of lysosomes with mycobacterial phagosomes, as well as the presence of electron-opaque material within phagosomes, suggested phagolysosomal fusion. Development of granulomas involved epithelioid transformation of macrophages, followed by appearance of central necrosis. Desmosomes were present between mature epithelioid cells. The necrotic core region of M. marinum granulomas was separated from overlying epithelioid cells by several layers of flattened, electron-opaque spindle-shaped cells. These cells appeared to be formed by compression of epithelioid cells and, aside from a flattened nucleus, did not possess recognizable organelles. Following the development of well-defined, paucibacillary granulomas, secondary disease was observed. Recrudescence was marked by bacterial replication followed by disruption of granuloma architecture, including loss of epithelioid and spindle cell layers. In advanced recrudescent lesions, normal tissue was replaced by macrophages, fibroblasts, and other inflammatory leukocytes. Large numbers of mycobacteria were observed, both intracellular and suspended in cellular debris.     

On the structure of the pulmonate osphradium

Summary The cellular organisation of the osphradium of Planorbarius as revealed by the previously described light microscope studies is confirmed in the present study. A third epithelial cell type, the basal cell, is described. Perception is carried out by dendritic processes from osphradial sensory neurones, forming free nerve-endings in the sensory region of the osphradial epithelium. Ciliated cells and secretory cells of the osphradial epithelium are concerned with the transport of material in the osphradial canal. Many of the ultrastructural features of molluscan central ganglia are present in the osphradial ganglion, including inter-axonal chemical synapses. Neuromuscular junctions are present in the sheath surrounding the organ and these may be involved in a behavioural response of the organ. The need for further electrophysiological studies is emphasised.     

On the structure of the pulmonate osphradium

Summary The osphradium of Planorbarius consists of a blindly-ending ciliated canal, formed by an infolding of the mantle epithelium, and a basal ganglion of nerve cells which is comparable in complexity with ganglia of the central nervous system. The distribution of cell types in the osphradial epithelium is specialised so that three regions can be recognised; the ciliated, the secretory and the sensory regions. The basal sensory region of the canal epithelium consists of ciliated cells and is innervated by sensory neurones of the osphradial ganglion. The middle secretory region contains mainly of mucus-secreting cells and the epithelium adjacent to the osphradial aperture of ciliated cells and secretory cells of a second type. The sensory neurones of the osphradial ganglion are bipolar or of a modified monopolar type. Other monopolar neurones, similar to those common in the central nervous system are of non-sensory function. The osphradium of Paludina, although of typical prosobranch form, possesses ciliated pits similar to the single canal of Planorbarius, which may indicate a shared modality of receptor function. A definite function cannot be ascribed to the pulmonate osphradium based on morphological evidence alone.     

Ultrastructure of the centrosome in L cells

Three types of microtubule-organizing centers are present in the interphase L-cells: centriolar matrix, pericentriolar satellites, and electron-dense bodies that are not attached to the centrioles. Different types of microtubule-organizing centers may be present simultaneously in the same centrosome. In most of the cells some microtubules have their proximal ends free, rather than attached to the microtubule-organizing center. A network of intermediate filaments is condensed around the centrosome. The intermediate filaments run from the centrosome parallel to the microtubules. Although the filaments are often in close proximity to the centrioles and microtubules, direct contacts between them are rare. The intermediate filaments have convergence foci of their own in the centrosome.     

Ultrastructure of the L forms of meningococcus]

The authors carried out an electron microscope study of the ultrastructure of the L-form of meningococcus. Several types of cells differing by shape, size, and electron density were revealed. Sharply angular cells closely adjacent to one another prevailed in the culture. Structureless material, possibly representing material of cellular wall was not infrequently revealed around the cells. Elemental bodies and membranous structures of the lamellar type were revealed within the cells.     

Acetylcholinesterase in the brain of the marine gastropod Murex trunculus L. (Prosobranchia). Isolation and properties

• 1.1. Cholinesterase (ChE) of two types—acetylcholinesterase (AChE, acetylcholine hydrolase, EC 3.1.1.7) and propionylcholinesterase (PrChE, acylcholine hydrolase, EC 3.1.1.8)—was found in the brain of the marine gastropod Murex trunculus L. (Prosobranchia).
• 2.2. PrChE is a soluble enzyme which can be easily extracted by salt solution after freezing-thawing of the untreated brain.
• 3.3. AChE is membrane-bound. It was solubilized by a 0.2% solution of Triton X-100.
• 4.4. Some part of AChE (up to 36%) can spontaneously pass into solution.
• 5.5. The specific activity of AChE in Triton X-100 extracts is 100 ± 10 nmol acetylcholine/mg protein/min.
• 6.6. Enzyme hydrolysis of acetylcholine (ACh), acetylthiocholine (ATCh) and propionylthiocholine (PrTCh) is suppressed by excess of substrate. Michaelis constants (K_m) for their hydrolysis by AChE are 0.33, 0.017 and 0.018 mM, respectively.
• 7.7. Bimolecular rate constants with organophosphorus inhibitors of different structure points to a similarity of the gastropod brain AChE to the typical enzyme of vertebrates in the structure of the active surface.

     

The mouth apparatus of the Cambrian gilled lobopodian Pambdelurion whittingtoni

Omnidens is a large feeding apparatus composed of circlets of teeth, first documented from the early Cambrian of China. Originally interpreted as the oral cone of a radiodontan, it was later reinterpreted as the introvert of a priapulan. In both cases the Omnidens mouthparts underpinned estimates of gigantic (c. 2 m) body size. Recent evidence has been used to suggest that pharyngeal teeth and radially‐arranged oral plates in the stem‐group onychophoran Hallucigenia and the lower stem‐group euarthropod Jianshanopodia are homologous to structures of the introvert in priapulans and other scalidophorans, and are thus primitive characters for moulting animals (Ecdysozoa) as a whole. Here we show that the early Cambrian gilled lobopodian Pambdelurion whittingtoni from Sirius Passet, Greenland, possesses a mouth apparatus identical to Omnidens, being composed of the same three zones with detailed similarities of sclerites in each zone. An oral cone with rings of pharyngeal teeth, radial plates and outer scalid‐like plates are ecdysozoan characters retained in the euarthropod stem group. Omnidens from China probably belongs to an unrecognized Pambdelurion‐like animal rather than being part of a giant priapulan.     

Ultrastructure of the surface of multiple scars inSaccharomycodes ludwigii

The use of induced primuline fluorescence led to the discovery of a new type of yeast scars (multiple scars) in the generaKloeckera, Saccharomycodes, Nadsonia andHanseniaspora. The structure and ultrastructure of their surface was studied by electron microscopy, using carbon replicas and isolated cell walls.     

Ultrastructure of the L forms of Streptococcus group B

The submicroscopic organization of the L-forms of beta-hemolytic streptococci of group B has been studied in the course of their cultivation. The L-forms of group B streptococci differ from those of group A streptococci by a higher growth rate. On the submicroscopic level, the activity of ATP-ase has been revealed on the internal side of the cytoplasmic membrane. Regularities in the localization of intramembranous particles sized 6-18 nm in the hydrophobic area of the membrane have been established by means of freezing-etching. With the adequate methods of fixation, the continuous three-layer structure of the cytoplasmic membrane can be determined in all elements of the L-form population.     

Anthraquinone profile and chemical fingerprint of Rhamnus saxatilis L. from Italy

Several species belonging to the genus Rhamnus (Rhamnaceae), comprising ones among which are found the most typical plants of the Italian flora, are known to contain biologically active anthraquinone secondary metabolites. Although several Rhamnus species were so far investigated, no information is available concerning the content and relative abundances of anthraquinones in R. saxatilis. In this study we used a simple, reliable, and accurate analytical method to determine the anthraquinones in bark of R. saxatilis. This allowed us also to trace a comparative study on the efficacy of different extraction solvents in ultrasonication time dependent assays. Separation and quantification of anthraquinones were accomplished using a C18 column with the mobile phase of H₂O:methanol (40:60, v/v, 1% formic acid) at a flow rate of 0.7 mL/min and a detection wavelength of 254 nm, while the qualitative analyses were also achieved at a wavelength of 435 nm.Finally, the described HPLC method, was used to obtain a specific chemical fingerprint for this species in comparison with other species from the same family.     

Taxonomic status of the Trematoda larvae of the Himasthla genus (Trematoda: Echinostomatidae) from the Littorina saxatilis mollusk in the Kandalaksha bay of the White sea

In the Kandalaksha Bay (White Sea), the experiments have been carried out to study the life cycle of the larval trematodes of the genus Himasthla (Dietz, 1909) from the intertidal whelk Littorina saxatilis. It has been established that the blue mussel, Mytilus edulis, is the second intermediate host for this species. The seagull Larus canus is the final host. The species has been identified as Himasthla elongata.