The microscopic anatomy and ultrastructure of the contractile vessel in the sipunculan Themiste hexadactyla (Satô, 1930) (Sipuncula: Sipunculidea)

The microscopic anatomy and ultrastructure of the contractile vessel of the sipunculan Themiste hexadactyla (Satô, 1930) from Vostok Bay (the Sea of Japan) were studied by histological and electron microscope methods. The ultrastructural features of the internal (endothelium) and external (coelothelium) lining of the contractile vessel are described and illustrated. Numerous macromolecular filters, the so-called “double diaphragms,” were found in the external coelothelium facing the cavity of the trunk coelom. This suggests a possible filtration from the tentacular coelom into the trunk coelom though the contractile vessel wall. The microscopic peculiarities of the main tube of the contractile vessel and its numerous lateral branches twining around several internal organs are described in detail. The contractile vessel is polyfunctional: it can act as the main reservoir for the cavity fluid during the withdrawal of the tentacular crown and performs the functions of the distribution system in sipunculans.     

Internal anatomy and ultrastructure of the male reproductive organization of the Sesarmid crab Muradium tetragonum (1798)—(Decapoda: Brachyura)

Sesarmid crab, Muradium tetragonum, considered a key detritus consumer plays a significant role in the nutrient cycling and energy flow in most of the mangrove environments. Morphological and ultrastructural organization of the M. tetragonum male reproductive system are characterized through transmission electron microscopic studies. Adult males (3.2–4.2 cm) with dark violet carapace and white-tipped cheliped were procured alongside the coastal areas of Tanjavur district, Tamil Nadu, India. The morphological analysis highlights the male gonads to be bilaterally symmetrical and anterolaterally located inside the cephalothorax. A pair of elongated testes lying attached to the hypodermis of the carapace leads to a long highly coiled vas deferens categorized into three distinct regions (Proximal vas deferens, Middle vas deferens and distal vas deferens) structurally and functionally with Posterior vas deferens receiving sac-like accessory glands. It gets followed by an ejaculatory duct and ends with the penile papillae at the coxae's base of the fifth peripod. Structural modifications were observed in the ultrastructure of vas deferens envisage (considering) its functional role in storing spermatophores, active absorption and assisting the secretory activity. Spermatophores, witnessed as spherical bodies are bounded by a dense double wall. Aflagellate, immotile and spherical spermatozoa that measuring 3.6 μm in diameter encompasses a complex acrosome cupped by a nucleus. Moreover, perforatorium and the extending nuclear arms with chromatin, as displayed in the experimental organism M. tetragonum, are in synergy with that of certain brachyurans as specified in the study. Hence, the current study assessing the morphology and ultrastructure parameters of the male gonads could be useful in understanding the physiology of sexual maturation, annual cyclic changes, tracing the phylogenetic relationship among species and enhancing the brood-stock management.     

The pen and the sword: recovering the disciplinary identity of physiology and anatomy before 1800: II: Old anatomy—the sword

Following the exploration of the disciplinary identity of physiology before 1800 in the previous paper of this pair, the present paper seeks to recover the complementary identity of the discipline of anatomy before 1800. The manual, artisanal character of anatomy is explored via some of its practitioners, with special attention being given to William Harvey and Albrecht von Haller. Attention is particularly drawn to the important role of experiment in anatomical research and practice—which has been misread by historians as physiological experiment. Although scientific status was claimed by some practitioners for the discipline, the knife remained the tool of the discipline. Finally the differences between the teleological assumptions underlying anatomy, and the ‘argument from design’ or natural theology are explored.     

Structure and ultrastructure of the silk glands and spinneret of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

This study provides comprehensive documentation of silk production in the pest moth Helicoverpa armigera from gland secretion to extrusion of silk thread. The structure of the silk glands, accessory structures and extrusion apparatus are reported. The general schema of the paired silk glands follows that found for Lepidoptera. Morphology of the duct, silk press, muscle attachments and spigot are presented as a three-dimensional reconstruction and the cuticular crescent-shaped profile of the silk press is demonstrated in both open and closed forms with attendant muscle blocks, allowing advances in our knowledge of how the silk press functions to regulate the extrusion of silk. Growth of the spigot across instars is documented showing a distinctive developmental pattern for this extrusion device. Its shape and structure are related to use and load-bearing activity.     

Characterization of C₃--C₄ intermediate species in the genus Heliotropium L. (Boraginaceae): anatomy, ultrastructure and enzyme activity

Photosynthetic pathway characteristics were studied in nine species of Heliotropium (sensu lato, including Euploca), using assessments of leaf anatomy and ultrastructure, activities of PEP carboxylase and C₄ acid decarboxylases, and immunolocalization of ribulose 1·5‐bisphosphate carboxylase/oxygenase (Rubisco) and the P‐subunit of glycine decarboxylase (GDC). Heliotropium europaeum, Heliotropium calcicola and Heliotropium tenellum are C₃ plants, while Heliotropium texanum and Heliotropium polyphyllum are C₄ species. Heliotropium procumbens and Heliotropium karwinskyi are functionally C₃, but exhibit ‘proto‐Kranz’ anatomy where bundle sheath (BS) cells are enlarged and mitochondria primarily occur along the centripetal (inner) wall of the BS cells; GDC is present throughout the leaf. Heliotropium convolvulaceum and Heliotropium greggii are C₃–C₄ intermediates, with Kranz‐like enlargement of the BS cells, localization of mitochondria along the inner BS wall and a loss of GDC in the mesophyll (M) tissue. These C₃–C₄ species of Heliotropium probably shuttle photorespiratory glycine from the M to the BS tissue for decarboxylation. Heliotropium represents an important new model for studying C₄ evolution. Where existing models such as Flaveria emphasize diversification of C₃–C₄ intermediates, Heliotropium has numerous C₃ species expressing proto‐Kranz traits that could represent a critical initial phase in the evolutionary origin of C₄ photosynthesis.     

The effect of salinity acclimation on the ultrastructure of the gills of Gammarus oceanicus (Segerstråle, 1947) (Crustacea: Amphipoda)

Summary Acclimation to low salinity induces changes in the ultrastructure of the gill cells of the marine euryhaline amphipod, Gammarus oceanicus. The gills are composed of a single cell type. In 100% artificial sea water, these cells contain moderate numbers of mitochondria which are randomly distributed in the cytoplasm. The plasma membrane is extensively invaginated at the apical, lateral, and basal surfaces. Acclimation to 20% artificial sea water induces a further invagination at the apical cell membrane to form an elaborate apical labyrinth. The extracellular spaces between the folds in the basal cell membrane dilate to 1500 Å or more. Mitochondria are more abundant and in many cells they undergo a change in conformation. The mitochondria are crowded into thin leaflets of cytoplasm between the dilated basal invaginations or into the narrow space between apical and basal cell membranes. Consequently, they lie in close contact with the plasma membrane over much of their surface.Supported in part by grants from the United States Public Health Service, 5 RO1 AM13455-03 and PHS FR-07085-04, and by a grant from the National Research Council of Canada administered by Dr. G. P. Morris.     

The ultrastructure of the trophic cells of the protostelidPlanoprotθstelium aurantium

Summary The protostelidPlanoprotostelium aurantium Olive andStoianovitch has trophic cells which are either amoebae or flagellates. The general morphology and ultrastructure are consistent with what has been reported for otherEumycetozoa (protostelids, myxomycetes, and dictyostelids). The flagellar apparatus structure has the same basic pattern as that of other flagellate eumycetozoans. It shares with all these an anteriorly directed flagellum and centriole and microtubule arrays (MTA) 2–4. Unlike more primitive species which have two centrioles per flagellar apparatus,P. aurantium has only one. Also, the flagellar apparatus is independent of the nucleus inP. aurantium, not linked to it as in the primitive species. These features are useful in explaining the differences in swimming behavior betweenP. aurantium and biflagellate species. Evidence is presented to show thatP. aurantium is closely related to the non-flagellateProtostelium mycophaga Olive andStoianovitch.This research represents part of a Ph.D. dissertation presented to the University of North Carolina.     

The ultrastructure of the “difference factor” in the myelin

Summary Electron-microscopic studies of peripheral nerves as prepared by the freezeetching method show the myelin lamella to be 185 Å thick. This is the same dimension found by x-ray diffraction analysis of natural myelin. In contrast to the appearance of osmiumfixed material, the cytoplasmic surfaces of the paired membranes in the myelin lamella are apposed to two fine, separate lines, while the outer membrane sides are fused into a broader single line. The finding of a decidedly different structure for the outer and for the inner membrane surfaces appears to be the cause of the difference factor.This work was supported by the Swiss National Foundation (Nr. 4065). — Acknowledgement: We thank the Balzers AG. (9496 Balzers, Fürstentum Liechtenstein) for providing us with the High Vakuum Device.     

Interaction of force transmission and sarcomere assembly at the muscle-tendon junctions of carp (Cyprinus carpio): ultrastructure and distribution of titin (connectin) and α-actinin

At muscle-tendon junctions of red and of white axial muscle fibres of carp, new sarcomeres are found adjacent to existing sarcomeres along the bundles of actin filaments that connect the myofibrils with the junctional sarcolemma. As the filament bundles that transmit force to the junction originate proximal to new sarcomeres, they probably relieve these new sarcomeres from premature loading. In red fibres, these filament bundles are long (up to 20 m) and dense, permitting light-microscopical immunohistochemistry (double reactions: anti-titin or anti--actinin and phalloidin). New sarcomeres have clear I bands; their A band lengths are similar to those of older sarcomeres and the thick filaments lie in register. T tubules are found at the distal side of new sarcomeres but terminal Z lines are absent. The late addition of -actinin suggests that -actinin mainly has a stabilizing role in sarcomere formation. The presence of titin in the terminal fibre protrusions is in agreement with its supposed role in sarcomere formation, viz. the integration of thin and thick filaments. The absence of a terminal Z line from sarcomeres with well-registered A bands suggests that this structure is not essential for the anchorage of connective (titin) filaments.     

Retinal ultrastructure of the dorsal eye region of Pararge aegeria (Linné) (Lepidoptera: Satyridae)

We examined the fine structure of dorsal rim ommatidia of the compound eye of Pararge aegeria (Lepidoptera: Satyridae) and compared them with ommatidia of the large dorsal region described by Riesenberg (1983 Diploma, University of Munich). 1. The ommatidia of the dorsal rim show morphological specializations known to be typical of the perception of polarized light: (a) the dumb-bell-shaped rhabdoms contain linearly aligned rhabdomeres with only 2 orthogonally arranged microvilli orientations. The rhabdoms are composed of the rhabdomeres of 9 receptor cells, 8 of which are radially arranged. The rhabdomeres of receptor cells VI and V5, as well as D2, D4, D6 and D8 are dorsoventrally aligned, whereas the rhabdomeres of the cells H3 and H7 are perpendicular to them. The rhabdomere of the bilobed 9th retinula cell lies basally and is dorsoventrally aligned, where retinula cell VI and V5 are already axonal. (b) There is no rhabdomeric twist, and (c) the rhabdoms are rather short. 2. However, in the ommatidia of the large dorsal region, only 2 retinula cells (H3 and H7) are suitable for perception of polarized light. 3. Lucifer yellow and horse radish peroxidase were used as tracers to visualize the projections of retinula cell axons of the dorsal rim area and the large dorsal region into the optic neuropils (lamina and medulla). Two receptors (VI and V5) from both the dorsal rim area and the large dorsal region, have long visual fibres projecting into the medulla. The 7 remaining retinula cells of both eye regions, including those that meet the structural requirements for detection of polarized light in the large dorsal region, terminate in the lamina (short visual fibres). These results provide a starting point for further studies to reveal the possible neuronal pathways by which polarized light may be processed.     

The cytology,histochemistry, and ultrastructure of the cell types found in the digestive gland of the slug,Agriolimax reticulatus (Müller)

Summary Four cell types have been identified in the digestive glands from light and electron microscope studies. The possible functions of each cell type are discussed.Thin cells are undifferentiated. Calcium cells contain spherules of calcium salts which have a characteristic ultrastructure. Different protein granules are found apically. Digestive cells are present as two distinct forms. One form is believed to be absorbing food material and digesting it intracellularly, and the other form is a secreting cell. Both forms contain green and yellow granules and histochemistry shows these granules to be distinct. Protein granules also occur apically.Excretory cells are distinguished by having a large central vacuole containing excretory granules. Histochemistry shows these granules, like the yellow granules of digestive cells, to be composed mainly of lipofuscin.It is suggested that digestive cells form excretory cells.     

Commentary: The Rôle of Toxicology in Prevention and Precaution

Advocates of the Precautionary Principle have recently called for a “new science” to support the goals of precaution-based environmental and occupational health policy. While much attention has been given to epidemiology, the evidentiary science most relevant to precaution, or prevention, is toxicology. Opportunities for enhancing the rôle of toxicology in public policy must consider current biases in the field. Thus, rather than a “new science,” advocates for change should focus upon ensuring that current scientific methods are appropriate and that interpretations of scientific data are accurate.     

The physico-chemical “anatomy” of the tautomerization through the DPT of the biologically important pairs of hypoxanthine with DNA bases: QM and QTAIM perspectives

The biologically important tautomerization of the Hyp·Cyt, Hyp*·Thy and Hyp·Hyp base pairs to the Hyp*·Cyt*, Hyp·Thy* and Hyp*·Hyp* base pairs, respectively, by the double proton transfer (DPT) was comprehensively studied in vacuo and in the continuum with a low dielectric constant (ε?=?4) corresponding to hydrophobic interfaces of protein–nucleic acid interactions by combining theoretical investigations at the B3LYP/6-311++G(d,p) level of QM theory with QTAIM topological analysis. Based on the sweeps of the energetic, electron-topological, geometric and polar parameters, which describe the course of the tautomerization along the intrinsic reaction coordinate (IRC), it was proved that the tautomerization through the DPT is concerted and asynchronous process for the Hyp·Cyt and Hyp*·Thy base pairs, while concerted and synchronous for the Hyp·Hyp homodimer. The continuum with ε?=?4 does not affect qualitatively the course of the tautomerization reaction for all studied complexes. The nine key points along the IRC of the Hyp·Cyt?Hyp*·Cyt* and Hyp*·Thy?Hyp·Thy* tautomerizations and the six key points of the Hyp·Hyp?Hyp*·Hyp* tautomerization have been identified and fully characterized. These key points could be considered as electron-topological “fingerprints” of concerted asynchronous (for Hyp·Cyt and Hyp*·Thy) or synchronous (for Hyp·Hyp) tautomerization process via the DPT. It was found, that in the Hyp*·Cyt*, Hyp·Thy*, Hyp·Hyp and Hyp*·Hyp* base pairs all H-bonds are significantly cooperative and mutually reinforce each other, while the C2H…O2 H-bond in the Hyp·Cyt base pair and the O6H…O4 H-bond in the Hyp*·Thy base pair behave anti-cooperatively, i.e., they become weakened, while two others become strengthened.     

C3−C4 Intermediate species in the genus Flaveria: leaf anatomy,ultrastructure, and the effect of O2 on the CO2 compensation concentration

Leaf anatomical, ultrastructural, and CO₂-exchange analyses of three closely related species of Flaveria indicate that they are C₃–C₄ intermediate plants. The leaf mesophyll of F. floridana J.R. Johnston, F. linearis Lag., and F. chloraefolia A. Gray is typical of that in dicotyledonous C₃ plants, but the bundle sheath cells contain granal, starch-containing chloroplasts. In F. floridana and F. chloraefolia, the chloroplasts and numerous associated mitochondria are arranged largely centripetally, as in the closely related C₄ species, F. brownii A.M. Powell. In F. linearis, fewer mitochondria are present and the chloroplasts are more evenly distributed throughout the bundle sheath cytosol. There is no correlation between the bundle sheath ultrastructure and CO₂ compensation concentration. () values of these C₃–C₄ intermediate Flaveria species. At 21% O₂ and 25°C, for F. chloraefolia, F. linearis, and F. floridana is 23–26, 14–19, and 8–10 l CO₂ l^-1, respectively. The O₂ dependence of is the greatest for F. chloraefolia and F. linearis (similar to that for C₃–C₄ intermediate Panicum and Moricandia species) and the least for F. floridana, whose O₂ response is identical to that for F. brownii from 1.5 to 21% O₂, but greater at higher pO₂. The variation in leaf anatomy, bundle sheath ultrastructure, and O₂ dependence of among these Flaveria species may indicate an active evolution in the pathway of photosynthetic carbon metabolism within this genus.Abbreviations CO₂ compensation concentration - IRGA infrared gas analysis Published as Paper No. 7068, Journal Series, Nebraska Agricultural Experiment Station     

Comparative anatomy of the heart–glomerulus complex of Cephalodiscus gracilis (Pterobranchia): structure,function, and phylogenetic implications

Cephalodiscus gracilis Harmer, 1905 is a semi-sessile deuterostome that shares with fish-like chordates pharyngeal gill slits and a dorsally situated brain. In order to reveal structures potentially homologous among deuterostomes and to infer their functional roles, we investigated the axial complex, associated blood vessels and structures of C. gracilis using transmission electron microscopy, light microscopy, and digital 3D reconstructions. We describe the smooth, bipartite cephalic shield retractor muscles that originate as solid compact muscles and fan out to traverse the protocoel as individual muscle cells. The axial complex consists of a cap-shaped coelomic sac, the pericardium that surrounds the central heart. The pericardium is constituted of myoepithelial cells, with the cells facing the heart being thicker and richer in myofilaments. A prominent dorsal median blood vessel opens into the heart, which gives rise to a short median ventral vessel that opens into the paired glomeruli connected to the ventral side of the stomochord. The tip of the curved stomochord rests precisely above the connection of the dorsal median vessel with the heart, a position that would allow the stomochord to function as a valve facilitating unidirectional blood flow. Glomeruli are lined by podocytes of the spacious protocoel and are considered to be the site of ultrafiltration. Two pairs of blood vessels enter the median dorsal blood vessel from the tentacles. The median dorsal blood vessel is separated from the brain by a thin basement membrane. This arrangement is consistent with the hypothesis that blood vessels in the tentacles increase oxygen supply for the brain. Based on detailed similarities, the heart–glomerulus complex of C. gracilis is considered homologous with the heart–glomerulus complex in Rhabdopleura spp., and Enteropneusta, and the axial complex in Echinodermata. In addition, we hypothesize homology to the excretory complex including Hatschek’s nephridium in Cephalochordata. Thus, the heart–glomerulus complex does not support a sister-group relationship between Echinodermata and Hemichordata, whereas the organization of the cephalic shield retractor muscles is consistent with the evolution of pterobranchs within enteropneusts.