Discoid Bodies Research Articles

First record of trace fossils in the Ediacaran–Cambrian transition on the northern Gondwana platform (Anti-Atlas, Morocco)

The Anti-Atlas Mountains of Morocco preserve one of the most complete latest Neoproterozoic to Cambrian stratigraphic successions worldwide, with high-resolution chemostratigraphic δ13Ccarb coverage. However, the exact stratigraphic position of the Ediacaran–Cambrian boundary remains unresolved. Until now, no trace fossils or body fossils have been recorded from the terminal Ediacaran strata in the Anti-Atlas Mountains. The only exception is a discoidal body fossil-like structure from the shallow-marine sandstones of the Ediacaran Tabia Member, Adoudou Formation, in the Taroudant Group in the Igherm inlier. For the first time, we document the occurrence of abundant trace fossils from the base of the Adoudou Formation, including Treptichnids, Monomorphichnus isp., Helminthoidichnites isp., Gordia isp., Palaeophycus isp., Planolites isp., and Conichnus isp. The integration of both trace fossils and carbon isotope δ13Ccarb records suggests that the Ediacaran–Cambrian transition in the Sous Basin can be placed at the contact between the Tifnout and Tabia Members, which chemostratigraphically coincides with the large negative δ13Ccarb excursion that had been previously suggested for the Ediacaran–Cambrian boundary (BACE) in the western Anti-Atlas Mountains.

Mantle-hosted ophiolitic chromitites from Colombia: implications for petrogenesis and geodynamic evolution

ABSTRACT Chromitite bodies can be found within ophiolitic mantle sections in three locations in Colombia: Medellín, Planeta Rica, and La Guajira. These chromitites are typically massive pods that are often surrounded by lateritic soil in Medellín and Planeta Rica, or small discoidal bodies in La Guajira. Inclusions in chromite are preserved to varying degrees in the three localities: olivine and pargasite are partially preserved in Medellín and Planeta Rica, whereas inclusions in La Guajira chromitites are completely altered to chlorite. Compositionally, chromite from the chromitites is high-Al in Medellín (Cr#[Cr/(Cr+Al) atomic ratio] = 0.41–0.51) and Planeta Rica (Cr# = 0.49–0.57), and high-Cr in La Guajira (Cr# = 0.75–0.76), whereas TiO2 contents are low in the three localities (0.12–0.43 wt%). Regarding trace elements composition, the chromitites are similar to others formed in supra-subduction zone settings; the chromite from the high-Al chromitites is similar to that in MORB/BABB, whereas chromite from the high-Cr chromitites has a strong boninitic affinity. Chromitites from Planeta Rica are richer in Ti, possibly due to the presence of nearby gabbroic bodies and impregnated peridotites. The alteration in chromite rims and silicate matrix is related to metamorphic processes. Bulk-rock platinum-group element (PGE) contents range from 30 to 487 ppb, and chondrite-normalized PGE patterns show the typical enrichment in IPGE relative to PPGE observed in most ophiolitic chromitites. The estimated melts in equilibrium with the different chromitites correspond to MORB-like melts for the Medellín and Planeta Rica chromitites and to boninites for La Guajira chromitites. However, the estimated TiO2 content in the melt is too low for a typical MORB, indicating back-arc basin basalts and a back-arc setting for the formation of the Medellín and Planeta Rica chromitites during the Late Triassic and the Late Jurassic, respectively. La Guajira chromitites are interpreted to have formed in a fore-arc basin related to subduction-initiation during Cretaceous times.

Esophageal discoid foreign body detection and classification using artificial intelligence.

Early and accurate radiographic diagnosis is required for the management of children with radio-opaque esophageal foreign bodies. Button batteries are some of the most dangerous esophageal foreign bodies and coins are among the most common. We hypothesized that artificial intelligence could be used to triage radiographs with esophageal button batteries and coins. Our primary objective was to train an object detector to detect esophageal foreign bodies, whether button battery or coin. Our secondary objective was to train an image classifier to classify the detected foreign body as either a button battery or a coin. We trained an object detector to detect button batteries and coins. The training data set for the object detector was 57 radiographs, consisting of 3 groups of 19 images each with either an esophageal button battery, esophageal coin or no foreign body. The foreign bodies were endoscopically confirmed, and the groups were age and gender matched. We then trained an image classifier to classify the detected foreign body as either a button battery or a coin. The training data set for the image classifier consisted of 19 radiographs of button batteries and 19 of coins, cropped from the object detector training data set. The object detector and image classifier were then tested on 103 radiographs with an esophageal foreign body, and 103 radiographs without a foreign body. The object detector was 100% sensitive and specific for detecting an esophageal foreign body. The image classifier accurately classified all 6/6 (100%) button batteries in the testing data set and 93/95 (97.9%) of the coins. The remaining two coins were incorrectly classified as button batteries. In addition to these images with a single button battery or coin, there were two unique cases in the testing data set: a stacked button battery and coin, and two stacked coins, both of which were classified as coins. Artificial intelligence models show promise in detecting and classifying esophageal discoid foreign bodies and could potentially be used to triage radiographs for radiologist interpretation.

Hiemalora stellaris from Ediacaran Sonia Sandstone of Jodhpur Group of Marwar Supergroup, Western Rajasthan, India

Abstract The present study reports and discusses discoidal Ediacaran body fossils identified as Hiemalora stellaris from the Sonia Sandstone of Jodhpur Group, Marwar Supergroup, Western Rajasthan, India. These are preserved as positive relief on the yellowish-brown to pinkish-brown medium to fine-grained sandstone bedding surfaces in Sursagar area. Morphologically, these are circular to sub-circular, mostly flat-discoidal forms or discs surrounded by numerous radiating arms or appendages resembling tentacles. Hiemalora is reinterpreted and reconstructed as discoidal hold fast of benthic organism but not found the attached fronds or stem-like structures of the hold fasts in the present materials. The systematic palaeontology, palaeobiology, palaeoenvironment and age of the Hiemalora bearing Ediacaran Sonia Sandstone have been also discussed.

Morphology of gemmae, an overlooked taxonomic trait in the genus Marchantia L. (Marchantiaceae)

Most taxa of the genus Marchantia L. (Marchantiaceae) produce multicellular gemmae within gemma cups. They are discoid bodies with two notches and a trace of stalk. Although gemmae of Marchantia have been of interest to physiological and developmental studies, they have been rarely used as a taxonomic character. To improve understanding of the taxonomic significance of gemma morphology, we investigated gemmae of six Japanese Marchantia (including four subspecies) and provide comparative morphological descriptions and a key. Several characters of the gemmae, including size, shape, morphology of marginal cells, and the presence or absence of mucilage hairs were useful in species identification. Morphological similarity of gemmae between M. polymoprpha and M. paleacea, as well as between M. emarginata and M. pinnata, was consistent with the results of molecular phylogenetic analyses. We recommend that morphology of gemmae should be used as a new taxonomic character in the genus Marchantia.

Influence of Low Dietary Inclusion of the Microalga Nannochloropsis gaditana (Lubián 1982) on Performance, Fish Morphology, and Muscle Growth in Juvenile Gilthead Seabream (Sparus aurata).

Simple SummaryCurrently plant products are used to partially replace fish meals and oils in fish diets. However, the excessive use of these products can cause nutritional imbalances and environmental problems in their production. For this reason, microalgae appear as an alternative, since they have a high nutritional value and improve the immune status of fish. In the present work Nannochloropsis gaditana was included at 2.5% and 5% in substitution of plant products to observe its influence on the growth and morphology of gilthead seabream at low inclusion levels. Furthermore, cellulases were used to degrade cell walls and to increase the bioavailability of the intracellular bioactive compounds. The results showed that the inclusion of N. gaditana at low levels in the raw state was sufficient to obtain optimum growth, so it can be used as a partial substitute of vegetables in gilthead seabream diets, without substantially increasing the cost of the feed.A 90-d feeding trial was conducted in which five groups of gilthead seabream (11.96 g initial body weight) were fed with a microalgae-free diet (control group, C) or four diets containing the microalgae Nannochloropsis gaditana at two inclusion levels (2.5% or 5%), either raw (R2.5 and R5 batches) or cellulose-hydrolyzed (H2.5 and H5 batches), to study their effect on the body and muscle growth. At 40 days, the highest values of body length and weight were reached in R5 group, but at 64 and 90 days, these were reached in R2.5. However, feed conversion rate, specific growth, daily intake, and survival (100%) were similar in all the groups. The acquisition of a discoid body shape was accelerated depending on the inclusion level of N. gaditana in the diets. Moreover, H5 diet affected the fish geometric morphology compared to R5 diet. The white muscle transverse area was similar in all groups at 40 days, with the exception of H2.5 group, which showed the lowest area. At day 90, C and R2.5 displayed the highest muscle growth, attributable to increased hyperplasia in C, and higher hypertrophy in R2.5. However, the highest proportion of small and medium fibers was observed in R5 and H5.

Equilibrium shapes of tubular lipid membranes.

Tubular vesicles represent abundant structural motifs which are observed both in experiments and in nature. We analyse them within the theory of bending elasticity and determine the equilibrium solutions at fixed volume, surface area, and segment length without imposing any specific symmetry or periodicity. We identify four different non-periodic equilibrium shapes. Depending on the precise value of the constraints or the corresponding Lagrange multipliers, these four shapes include: (i) snake-like and (ii) helical structures, (iii) tubes with a spherical body, and (iv) tubes with a discoidal body. However different in the details, all of the shapes have the same general cylindrical morphology which is either globally modulated or is a superposition of an additional structural motif and the cylinder. These results point to a great significance of the circular cylindrical shape and offer a comprehensive and general analysis of the shape of tubular vesicles.

Morphological description of two new ciliates (Ciliophora, Karyorelictea, Cryptopharyngidae): Apocryptopharynx discoidalis spec. nov. and Cryptopharynx minutus spec. nov.

The karyorelictids, a highly specialized group of ciliates, mostly inhabit marine biotopes, and there is very little information about their diversity, taxonomy, and systematics. The present paper investigates two new cryptopharyngid ciliates, Apocryptopharynx discoidalis spec. nov. and Cryptopharynx minutus spec. nov., which were isolated from the intertidal zone of Diaosuyuan Beach in Qingdao, China. Apocryptopharynx discoidalis spec. nov. can be distinguished from related species by its oval discoid body shape and highly structured epipellicular scales covering the left lateral surface. Cryptopharynx minutus spec. nov. can be recognized by its small body length (30–50μm), seven to 15 dikinetids in intrabuccal kinety, and two to five macronuclei. Based on our comparison, we believe that Cryptopharynx sp. 1 described by Foissner in 1996 represents a population of C. minutus spec. nov.

Affinities and Taphonomy of a Cambrian Discoid from Guizhou, South China

Disc-like fossils from siltstones of the Taozichong Formation (Cambrian) in the Qingzhen area, Guizhou, South China are reported here. They are similar to some Ediacaran and Phanerozoic discoidal fossils, and assigned to Tirasiana? disciformis? Palij, 1976. Based on the study of 43 specimens, dewatering or fluid escape structures, soft-sediment loading, scratch circles or other inorganic origins are ruled out, and the fossil is interpreted as a discoidal body fossil of unknown affinities rather than trace fossils. Energy-dispersive X-ray spectroscopy and elemental mapping analyses reveal that the discoid fossils contain higher concentrations of C, Fe, and P than the surrounding matrix, indicating the possible presence of pyrite, apatite, and organic carbon as a result of authigenic mineralization in association with decay and early diagenetic processes. The possible presence of extracellular polymeric substance suggests that the discs were surrounded by thin microbial mats composed primarily of extracellular polymeric substances, which facilitated their fossilization by promoting conditions that are favorable to secondary mineral precipitation. The new specimens provide useful information about the phylogenetic affinities of these early discoidal fossils and help us to better understand the taphonomic modes of non-biomineralizing organisms in Ediacara-type and Burgess Shale-type biotas.

1176 LATTICE BOLTZMANN SIMULATION OF MOTION OF RED BLOOD CELLS IN CONSTRICTED PIPE FLOWS

The lattice Botlzmann method (LBM) for two-phase flows containing a deformable body with a viscoelastic membrane is improved to simulate circular pipe flows by incorporation of the immersed boundary method. The method is applied to the motion of a biconcave discoidal body in pressure-driven pipe flows. The validation of the red blood cell (RBC) model is demonstrated by investigating the relation between the deformation index and terminal streamwise velocity of the RBC in circular pipe flow. In addition, the behavior of a biconcave discoidal body in constricted pipe flows is simulated under various geometrical conditions. These results indicate that the present method is applicable to simulation of the motion of RBCs in microscale capillary blood vessels.

Ovarian development in the Amazonian red discus, Symphysodon discus Heckel (Osteichthyes: Cichlidae)

The Neotropical red discus fish, Symphysodon discus, originates from the Amazonian basin and has a discoid body. Although this species is popularly used in aquaria and is exported as an ornamental fish, it has not been intensively studied. The purpose of this work was to study the morphological and histological aspects of the ovarian development in the red discus. Forty females of S. discus of varying body sizes and different stages of gonadal development were used in this study. The ovaries were weighed and examined macroscopically in order to observe the maturation stages. Histological staining of hematoxilin-eosin was used for microscopic observations of the ovaries. Macroscopic observations showed immature, maturing, mature and partially spent stages of ovarian development. Microscopic examination of the ovaries revealed five stages and five phases of ovarian development. The ovaries of the mature females showed all the different phases of oocyte development, indicating the multiple spawning habit of this species.

Petrography and Geochemistry of the Eugui Magnesite Deposit(Western Pyrenees, Spain): Evidence for the Development of a PeculiarZebra Banding by Dolomite Replacement

The Eugui-Asturreta magnesite deposit (Western Pyrenees, Spain) forms a discoidal body with a maximum thickness of 130 m, located within a folded Namurian carbonate sequence. The magnesite rocks are composed of lens-shaped crystals (max 8 cm) arranged in black and white bands (zebra structure). The morphology and textural characteristics of magnesite and the structural relationships between magnesite and dolostone host rocks indicate that magnesite replaced the host dolostone. The magnesite crystals replaced the host dolostones, growing perpendicularly from stylolites and meeting between two adjacent stylolite sets. The portions of the crystals close to the stylolites are black colored because they incorporated carbonaceous matter and clay laminations of the replaced dolostone (incorporative growth), whereas the crystal terminations are white because impurities have been displaced and lie at an intercrystalline position and into the meeting zone (displacive growth). These texture differentiations could be interpreted by changes in the ratios of dolomite dissolution versus magnesite precipitation due to increasing amounts of Ca released during the replacement process. Late dolomite is commonly pseudomorphous after magnesite crystals. Dolostone host rocks and magnesite show similar Mn, Al, and K contents. The host dolostones have a lower average FeO content (0.24 wt %) than magnesite (1.82 wt %) and than later dolomite after magnesite (1.04 wt %). The black magnesite bands with a low percentage of impurities show REE contents and patterns similar to those of the relatively pure dolostone host rocks, suggesting an origin by metasomatic replacement. The white magnesite bands display REE contents similar, but slightly lower in LREE, to those of the host dolostones, as would be expected by magnesite replacing dolomite. REE patterns of dolomite after magnesite are very similar to those of magnesite, suggesting that REE behaved conservatively during the replacment of magnesite by dolomite and that the process has been induced by fluids impoverished in REE and equilibrated with the carbonate sequence. The petrography and geochemistry of the Eugui magnesite indicate that the deposit originated by metasomatic replacement of a dolostone precursor promoted by fluids moving through stylolite and bedding planes. Sedimentary, structural, textural, and geochemical relics of the replaced dolostones are preserved in the magnesite rocks. The peculiar textural characteristics of the magnesite represent replacement features and cannot be interpreted by diagenetic or metamorphic recrystallization of an original marine microcrystalline magnesite deposit.

The first named Ediacaran body fossil, Aspidella Terranovica

Aspidella terranovica Billings, 1872 was first described from the late Neoproterozoic Fermeuse Formation (St. John's Group) on the Avalon Peninsula of eastern Newfoundland, approximately 1km stratigraphically above the famous Ediacaran biota at Mistaken Point, and several kilometres below the base of the Cambrian. Aspidella has been reinterpreted perhaps more than any other Precambrian taxon, and has variously been regarded as a fossil mollusc or ‘medusoid’, a gas escape structure, a concretion, or a mechanical suction mark. Our studies indicate that Aspidella includes a wide variety of preservational morphs varying from negative hyporeliefs with a raised rim and ridges radiating from a slit (Aspidella‐type preservation), to flat discs with a central boss and sharp outer ring (Spriggia preservation), to positive hyporeliefs with concentric ornamentation (Ediacaria preservation). Specimens occur in a continuum of sizes, with preservational styles dependent on the size of the specimen and the grain size of the host lithology; the elongation of specimens is tectonic. Aspidella is confirmed as a body fossil from observations of complex radial and concentric ornamentation, mutually deformed borders in clusters of specimens, and occurrence on the same bedding planes as certain distinctive Ediacaran taxa. Aspidella is indistinguishable from, and has priority over, several of the most common genera of late Neoproterozoic discoidal body fossils worldwide. Similar fossils from Australia are interpreted as holdfasts of frond‐like organisms. The density of specimens in the Aspidella beds suggests levels of benthic biomass in the Neoproterozoic that could rival those of modern marine communities. The serial growth forms, PalaeopascichnusIntrites, Neonereites renariusYelovichnus, associated with Aspidella, are interpreted as body fossils of unknown affinities rather than trace fossils. A new, trilobed, Ediacaran body fossil, Triforillonia costellae gen. et sp. nov., is described from the Aspidella beds of the Fermeuse Formation.

Characterisation of a family of Schistosoma japonicum proteins related to dynein light chains

Dynein light chains (DLC) are components of dynein, an enzyme complex involved in various aspects of microtubule-based motility. We report here the molecular cloning and sequencing of cDNAs encoding a family of DLC-like polypeptides (SjcDLC1–5) from the human bloodfluke Schistosoma japonicum with open reading frames of 87–104 amino acids and deduced molecular masses ranging from 10.5 to 12.3 kDa. Two-dimensional Western blot analysis confirmed the presence of several S. japonicum DLC isoforms with differing p I values and molecular sizes. We also describe the molecular characterisation, genomic organisation and expression of clone SjcDLC1, and the immunological characterisation and localisation of its encoded protein. Northern blot analysis of adult worm RNA indicated SjcDLC1 is encoded by a single message of approximately 650 bp and Southern analysis suggested one SjcDLC1 gene exists in the S. japonicum genome. Immunolocalisation studies demonstrated that the SjcDLC1 protein is present in the tegument of the adult and cercarial stages of S. japonicum. SjcDLC1 and the other SjcDLC may function in the transport of specialised organelles, comprising membranous and discoid bodies, through the tegument to the schistosome-unique heptalaminate tegumental membrane at the external surface of the adult worm. As a consequence, they may provide novel targets for anti-schistosome vaccine and/or drug development.

Scolex Glands Associated with the Rostella in Three Species of the Dilepididae (Cestoda: Cyclophyllidea)

AbstractThe microanatomy, fine structure and cytochemistry of scolex glands of Vitta riparia, Angularella beemaand Trichocephaloidis megalocephalaare examined by light and electron microscopy. Cytochemical tests include PAS, mercury bromphenol blue and performic acid‐alcian blue for light microscopy and periodic acid‐thiocarbohydrazide‐OsO4 for electron microscopy. The scolex glands are organized in two spatially isolated syncytia, one located in the rostellum, the other in the rostellar sac. The cytoplasm of the gland syncytia is characterized by a high affinity for haematoxylin. Cytochemical tests indicate the presence of moderate amounts of glycoprotein in the glands. A specialized type of secretion—dark oval or ovoid bodies with diameter 0.3–0.5 μm are observed by EM in both the rostellum glands and the rostellar‐sac glands of V. ripariaand T. megalocephala, and in the rostellar‐sac gland of A. beema. The rostellum gland of A. beemaproduces larger dark oval bodies measuring up to 0.9 μm. Lipid droplets are also observed in the glandular cytoplasm. Some tegumental cytons containing discoid bodies are found between the glandular perikarya. The glandular products and the lipid droplets are secreted via the rostellar tegument. © 1997 Published by Elsevier Science Ltd on behalf of The Royal Swedish Academy of Sciences.

Schistosoma mansoni:The Glucose Transport Protein SGTP4 Is Present in Tegumental Multilamellar Bodies, Discoid Bodies, and the Surface Lipid Bilayers

Schistosomes metabolize large quantities of glucose obtained from the host serum by facilitated diffusion through the tegument. Here we have used rabbit antibodies affinity purified against the carboxyl terminus of a facilitated glucose transporter, SGTP4, to localize the antigen in both schistosomula and adults. By ultrastructural immunocytochemical analysis, SGTP4 was localized to both lipid bilayers that cover the tegumental surface of adults and schistosomula. In the inner bilayer of adults, SGTP4 was apparently oriented with the carboxyl terminus on the internal side of the bilayer. SGTP4 was also present in the discoid and multilamellar bodies in adults and the membranous bodies in schistosomula. Finally, the affinity purified antibodies against SGTP4 bound nonspecifically to the head glands and postacetabular glands in schistosomula. The localization of the antigen in the two surface lipid bilayers suggests that SGTP4 may be responsible for transporting glucose from mammalian host serum into the tegument.

Localization of a 24-Kilodalton Glycoprotein in Adult Schistosoma mansoni Using Immunofluorescence and Immunoelectron Microscopy

Studies on schistosome protective immune responses have focused mainly on antigens of the parasite's syncytial surface. One of the characterized schistosome antigens, a 24-kDa glycoprotein, has been considered important in mechanisms of immune evasion by the parasites. In the present study, using affinity-purified antibodies to the 24-kDa protein for immunofluorescence and immunoelectron microscopy, we demonstrated an association of the 24-kDa antigen with the discoid bodies (the major syncytial inclusion bodies; DBs) and the surface membrane complex (most likely the apical plasma membrane) of adult Schistosoma mansoni. This is consistent with previous observations that the 24-kDa antigen appeared to be localized to the syncytial membrane and DB fractions. The present results also support the suggestion that the DBs are the precursor organelles of the apical plasma membrane.

Ultrastructural studies on the plerocercoid ofSpirometra erinacei in experimental sparganosis

The gland cell and the tegument of the Spirometra erinacei plerocercoid following parasite migration in hamsters were observed by electron microscopy. Gland cells released secretory granules mainly into the frontal pit during each stage of migration. The density of the perinuclear secretory granules decreased markedly just after parasite penetration through the host intestinal wall. Therefore, gland cells seem to play an essential role in penetration. During migration in the host, lipid-like droplets appeared in the subtegumental cells and tegument and increased in number and size during migration in the abdominal cavity, but they had disappeared from plerocercoids recovered from subcutaneous tissues. Myelin-like bodies also occurred in the tegument, subtegumental cells and medullary matrix; they were released directly through the tegument into the frontal pit. Discoidal bodies gathered in the distal part of the tegument, where filamentous microtriches appeared in regions from which microtriches had been peeled off during penetration.

Tegumental Ca-stimulated adenosine triphosphatase activity in adult Schistosoma mansoni worms

A Ca-stimulated ATPase activity (pH 9.5) associated with the tegumental membrane enriched (TME) fraction of Schistosoma mansoni adults was partially inhibited by NAP-taurine or by increasing concentrations of chlorpromazine; endogenous calmodulin was found associated with the TME fraction. A similar activity (pH 8.6) was histochemically visualized within the tegument of fixed worms on the cytoplasmic leaflet of both the double surface membrane and the basement membrane; this reaction was inhibited by 1 microM chlorpromazine and it was also observed on the inner side of double membrane vesicles present in the TME fraction. No ATPase activity could be seen at alkaline pH with added Mg or Na/K ions. Without ATP, the addition of external Ca to the fixed worms induced the appearance of lead precipitates on the tegumental discoid bodies; this reaction was inhibited by molybdate and not by chlorpromazine. The intrategumentary regulation of calcium by the systems described and the possible use of phenothiazines against schistosomes are discussed.

Effects of Serotonin (5HT) and Complement C 3 on the Synthesis of the Surface Membrane Precursors of Adult Schistosoma mansoni

The syncytial surface epithelium of Schistosoma mansoni plays an important role in immune evasion. This syncytium is covered by an unusual double-membrane complex consisting of an apical plasma membrane (APM) and an overlying envelope (En) that have been shown to have different rates of synthesis and turnover. It has been suggested that discoid bodies (DBs) and multilamellar bodies (MLBs), the major syncytial inclusion bodies of schistosomes, may be the precursors of the APM and En, respectively. In this ultrastructural study, we examined the effects of serotonin (5HT) and complement C3, which have been shown to stimulate synthesis and turnover of the APM and En, respectively, on the synthesis of DBs and MLBs in vitro. With short-time incubations (20 or 40 min), 5HT stimulated the synthesis of the DBs by 2-fold, whereas C3 accelerated synthesis of the MLBs by 2-fold. Furthermore, when microtubules within the cytoplasmic connections between the syncytium and the underlying cell bodies (the site of membrane synthesis) were disrupted with colchicine, the DBs and MLBs synthesized in response to 5HT or C3 accumulated in the cell bodies. This suggests that the transport of the organelles to the syncytium is dependent upon the microtubules but not the signaling mechanism in response to 5HT or C3. These observations also support the suggestion that the DBs and MLBs are synthesized in subsyncytial cell bodies and serve as precursors of the APM and En, respectively. The rapid synthetic response to 5HT and C3 is also consistent with rapid synthesis and turnover of the APM/En, as suggested by previous studies.