Early innervation of abdominal swimmeret muscles in developing lobsters.

The swimmerets in the abdomen of the lobster Homarus americanus are paired external appendages whose back and forth propulsive movements are brought about largely by a group of power and return stroke muscles located in the lateral abdominal cavity. We find functional innervation of these muscles by several excitatory axons and a single inhibitor in embryonic and stage 1 larval lobsters before the external appendages are even formed. This early innervation is via a few nerve bundles in which branches of the motor axons are intertwined in a complex manner. As the swimmerets develop to maturity in later larval and juvenile stages, the innervation consisting usually of several excitor and a single inhibitor synaptic terminals becomes localized to individual muscles. Patterned synaptic activity in these muscles was not seen in the embryonic and larval stages but has been shown in early juvenile stages, when it coincides with the onset of rhythmic movement of the swimmerets. Consequently, such early innervation of the swimmeret muscles may be influential in establishing the central circuitry for the generation of patterned activity, a possibility that was discounted in a previous study (Proc. Natl. Acad. Sci. USA, 70:954-958).     

Origin of archosaurian integumentary appendages: the bristles of the wild turkey beard express feather-type beta keratins

The discovery that structurally unique "filamentous integumentary appendages" are associated with several different non-avian dinosaurs continues to stimulate the development of models to explain the evolutionary origin of feathers. Taking the phylogenetic relationships of the non-avian dinosaurs into consideration, some models propose that the "filamentous integumentary appendages" represent intermediate stages in the sequential evolution of feathers. Here we present observations on a unique integumentary structure, the bristle of the wild turkey beard, and suggest that this non-feather appendage provides another explanation for some of the "filamentous integumentary appendages." Unlike feathers, beard bristles grow continuously from finger-like outgrows of the integument lacking follicles. We find that these beard bristles, which show simple branching, are hollow, distally, and express the feather-type beta keratins. The significance of these observations to explanations for the evolution of archosaurian integumentary appendages is discussed.     

Martinssonia elongata gen. et sp.n., a crustacean-like euarthropod from the Upper Cambrian 'Orsten' of Sweden

A tiny arthropod, with five growth stages, is described. Three of the instars are metanauplius-like larvae, having unsegmented bodies and four pairs of appendages. The largest stage, with a length of about 1.5 mm, may still be immature. Its body is divided into three tagmata. The cephalon, including five appendiculate segments, h a projecting forehead with a rostral spine and a small shield with a joint between fourth and fifth segments. Eyes are absent. The trunk is composed of seven annular segments, the anterior two with appendages. The caudal end is a long pleotelson-like segment with the anus on its ventral surface. There are seven pairs of appendages: uniramous antennulae, composed of few tubular podomeres; four pairs of biramous postantennular, almost homeomorphic cephalic appendages; two pairs on the trunk, the anterior pair being similar to the cephalic appendages except for the exopodite, the posterior being much smaller, uniramous and apparently rudimentary. Martinssonia was probably benthic, feeding on detritic particles which it stirred up from the bottom. Besides various crustacean-like features, the new form reveals structures different from Crustacea as well as from all other known arthropodan groups. Martinssonia presumably is a descendant of an euarthropodan group, originating from the crustacean branch long before reaching the eucrustacean level of evolution.     

Antigenic Properties of Bacteriophage φ29 Structural Proteins

Serological methods and electron microscopy were used to study the structural proteins of the small Bacillus subtilis bacteriophage phi29. This virus has a large number of fibers attached at both ends of its prolate head. A complex neck assembly is comprised of 12 symmetrically arranged appendages as the outer component. Head fibers, neck appendages, and the head surface bind anti-phi29 antibodies. Immune sera absorbed with defective lysates of suppressor-sensitive (sus) mutants have been used to determine the genetic control of neck appendages production. Studies on the serum-blocking power of lysates defective in different tail components showed that appendages contain the main serum-blocking protein. This finding suggests an essential role of the neck appendages in phage adsorption or DNA injection.     

Postembryonic development of Tisbe gracilis (T. Scott) (Copepoda, Harpacticoida)

All six naupliar and five copepodite stages of Tisbe gracilis (T. Scott, 1895) are described. A key for the identification of the nauplius stages is given. The oral appendages of all copepodite stages are described. Sexual dimorphism is visible from the copepodite IV stage on.     

Phosphatocopine ostracodes with preserved appendages from the Upper Cambrian of Sweden

Mülkr. Klaus 1. 1979 01 IS: Phosphatocopine ostracodes with preserved appendages from the Upper Cambrian of Sweden. Lethaia . Vol. 12. pp. 1–27. Oslo. ISSN 0024–1164.
More than 400 specimens of phosphatocopine ostracodes. representing different moult stages of Vestrogothia. Falites and Hesslandona have been recovered, with body and appendage structures preserved in minute detail. from anthraconites in the Upper Cambrian of Sweden and drift boulders deriving from that area. The secondary phosphatization of these structures, leading to preservation. is extensively discussed. It comprises even the inner lamella, but the abdomen is not preserved. Hypostome and lower lip are well developed. The large antennula is composed of a basipodite with probably two podomeres and a long exopodite with up to 18 podomeres bearing long spines, forming a natatory organ, and a broad endopodite of two to three podomeres. The biramous organization of the antennula is a unique, most primitive feature of phylogenetic significance. The antennae and up lo four additional pairs of appendages are also biramous and similar to the antennulae, not yet differentiated for specialized functions. Only the last pair is uniramous, but a second branch may have developed in subsequent moult stages not represented in the material. The movement of food into the mouth was achieved by the endites of antennulae and antennae, a function transferred backwards to other appendages during the course of ostracode phylogeny and reflected in ontogenetic trends among Recent ostracodes. The phosphatocopines were nectobenthic, filtering plankton feeders.     

Structure of the centriolar complex in the hepatocytes of intact and regenerating mouse live

The structure of the cellular center in polyploid hepatocytes of intact and regenerating liver of adult mice has been studied. It was shown that the structure of the centriolar complex depends on stages of the cellular cycle. No pericentriolar structures (such as satellites, appendages and others) and cytoplasmic microtubules were found in the centriolar complex within G0-period. The satellites and appendages are formed in the half of the centrioles within G1-period. The microtubules can branch off some satellites; the daughter centrioles begin to form within S-period; there are diplosomes in the cells within G2-period, some mother centrioles are surrounded with the fine fibrillar halo. It is concluded that the structure of the centriolar complex within G0-period is distinguished by that within G1-period. The structure of the centriolar complex in polyploid hepatocytes has the same feature of reorganization in certain interphase periods of the cell cycle as in diploid cells of some cultured cells and the thyroid epithelium.     

A Light and Electron Microscopical Study of Trichoduboscqia epeori Léger (Microspora: Duboscqiidae)1

Trichoduboscqia epeori Léger was found to parasitize nymphs of the mayfly Rhithrogena iridina Kolenati in southwest Germany for a new host record. It was studied by light and electron microscopy. The pansporoblast membrane is evaginated at several points, usually four, to produce long needle-like appendages >20 μm in length with a resilient inner core superficially resembling collagen, which is thought to maintain their orientation. It is suggested that the pansporoblast appendages may play a role in host infection. The structure and ultrastructure of developmental stages are recorded for the first time. Apart from the pansporoblast appendages, the ultrastructure of T. epeori conforms to the general pattern seen in many other pansporoblastic Microspora. Typically 16 spores are produced per pansporoblast but 32-spore pansporoblasts were also found, and the taxonomic significance of this is discussed.     

Genetic basis of skin appendage development

Morphogenesis of hair follicles, teeth, and mammary glands depends on inductive epithelial-mesenchymal interactions mediated by a conserved set of signalling molecules. The early development of different skin appendages is remarkably similar. Initiation of organogenesis is marked by the appearance of a local epithelial thickening, a placode, which subsequently invaginates to produce a bud. These early developmental stages require many of the same genes and signalling circuits and consequently alterations in them often cause similar phenotypes in several skin appendages. After the bud stage, these organs adopt diverse patterns of epithelial growth, reflected in the usage of more divergent genes in each.     

Larval leg integrity is maintained by Distal-less and is required for proper timing of metamorphosis in the flour beetle, Tribolium castaneum

The dramatic transformation from a larva to an adult must be accompanied by a coordinated activity of genes and hormones that enable an orchestrated transformation from larval to pupal/adult tissues. The maintenance of larval appendages and their subsequent transformation to appendages in holometabolous insects remains elusive at the developmental genetic level. Here the role of a key appendage patterning gene Distal-less (Dll) was examined in mid- to late-larval stages of the flour beetle, Tribolium castaneum. During late larval development, Dll was expressed in appendages in a similar manner as previously reported for the tobacco hornworm, Manduca sexta. Removal of this late Dll expression resulted in disruption of adult appendage patterning. Intriguingly, earlier removal resulted in dramatic loss of structural integrity and identity of larval appendages. A large amount of variability in appendage morphology was observed following Dll dsRNA injection, unlike larvae injected with dachshund dsRNA. These Dll dsRNA-injected larvae underwent numerous supernumerary molts, which could be terminated with injection of either JH methyltransferase or Methoprene-tolerant dsRNA. Apparently, the partial dedifferentiation of the appendages in these larvae acts to maintain high JH and, hence, prevents metamorphosis.     

The nauplius stages of the cirripede Tetraclita squamosa rufotincta Pilsbry

The nauplius stages of the cirripede Tetraclita squamosa rufotincta Pilsbry from Elat have been cultured and described. There are the usual six larval stages followed by the cypris but the increase in size during development is small compared with many other species. This small increase compares favourably with other species having very large embryos containing an excess of yolk and which do not take external food during larval development. The setation of the larval appendages is less than in other species and on the antenna and mandible does not increase after stage III. It is suggested that the lack of setation, coupled with a reduced development of the labrum, may be a consequence of the lack of a necessity for this species to feed externally during its planktonic life.     

Mechanical performance of aquatic rowing and flying

Aquatic flight, performed by rowing or flapping fins, wings or limbs, is a primary locomotor mechanism for many animals. We used a computer simulation to compare the mechanical performance of rowing and flapping appendages across a range of speeds. Flapping appendages proved to be more mechanically efficient than rowing appendages at all swimming speeds, suggesting that animals that frequently engage in locomotor behaviours that require energy conservation should employ a flapping stroke. The lower efficiency of rowing appendages across all speeds begs the question of why rowing occurs at all. One answer lies in the ability of rowing fins to generate more thrust than flapping fins during the power stroke. Large forces are necessary for manoeuvring behaviours such as accelerations, turning and braking, which suggests that rowing should be found in slow-swimming animals that frequently manoeuvre. The predictions of the model are supported by observed patterns of behavioural variation among rowing and flapping vertebrates.     

Appendage activity recordings of the sub-Antarctic copepod Drepanopus pectinatus in relation to its feeding behaviour

Summary Movements of the cephalic appendages of nauplii (stages 3 and 4), copepodites (stage 4) and adult female Drepanopus pectinatus were investigated using a computerized micro-impedance unit. Direct measurements and visual observations of the behaviour of restrained copepods were made in the presence of filtered seawater, naturally occurring phytoplankton of different sizes, prefiltered extracts of phytoplankton and seston. The normal appendage movements recorded in filtered seawater were similar for adult females and copepodites. Traces for nauplii were different compared with those of the two other developmental stages. Appendage movements were modified when adult females were offered particles of different sizes and extracts of phytoplankton, showing significant changes in the frequency of the limb beats in relation to each stimulus. Impedance traces distinguished between activity of copepod appendages related to feeding and to swimming such as: flicking, stroking, jerking, combing, handling and rejecting particles. Prolonged recordings of restrained females in association with visual observations suggested that the activity of the mandibular palp was related to gut fullness and peristaltic movements, and to fecal pellet formation and evacuation. These results indicated that D. pectinatus is an intermittent beater responding to the physical and chemical characteristics of food.     

An interpretation of the morphology and evolution of the cone and shoot of Equisetum

Evidence is presented from new observations in morphological, anatomical and numerical fields which supports the view that in Equisetum the units of which the vegetative and fertile axes are composed are serially homologous throughout the shoot. Though greatly different in their modern morphology, these differences can be accounted for by the evolutionary specialization of each from a once common type of unit. The structure of the primitive unit is most closely approached today by that of the fertile axis of Equisetum , especially in the construction of its vascular system. A relationship also exists between the appendages borne from the units of each of the two axes—the leaves and sporangiophores. The evidence, however, fails to support the widely held notion that sporangiophore and leaf are wholly homologous. Instead, only part of the Equisetum sporangiophore (the stalk plus the upper half of its peltate head) is homologous with the modern leaf. Based on this interpretation, a new schematic sequence of evolutionary stages is simultaneously proposed for both the axes and appendages of the type seen in Equisetum. Evidence from the fossil record, as well as from the structure of living Equisetum , is cited in support of the outline of evolutionary morphology proposed.     

Three new dicyemids from Octopus sasakii (Mollusca: Cephalopoda: Octopoda)

Three new species of dicyemid mesozoan are described from Octopus sasakii Taki, 1942, collected from Tosa Bay and Kii Strait in Japan. Dicyema shimantoense n. sp. is a medium-size species that reaches about 3,000 microm in length, and lives in folds of the renal appendages. The vermiform stages are characterized by having 22 peripheral cells, a conical calotte, and an axial cell that extends to the base of the propolar cells. Infusoriform embryos consist of 37 cells; a single nucleus is present in each urn cell, and the refringent bodies are solid. Dicyema codonocephalum n. sp. is also a medium-size species that reaches about 2,000 microm in length. It too lives in folds of the renal appendages. The vermiform stages are characterized by having 17-22 peripheral cells, an elongated calotte, and an axial cell that extends to the middle of propolar cells. Infusoriform embryos consist of 37 cells; a single nucleus is present in each urn cell, and the refringent bodies are solid. Dicyemennea pileum n. sp. is a medium species that reaches about 2,000 microm in length. It attaches to the surface of the renal appendages. The vermiform stages are characterized by having 23 peripheral cells, a disc-shaped calotte, and an axial cell that extends to the propolar cells. An anterior abortive axial cell is absent in vermiform embryos. Infusoriform embryos consist of 38 cells; 2 nuclei are present in each urn cell, and the refringent bodies are liquid. These are the first dicyemids to be described from Octopus sasakii.     

Embryonic and postembryonic neurogenesis in the ventral nerve cord of the freshwater crayfish Cherax destructor.

Previous studies of neurogenic activity in the thoracic neuromeres of indirect developing crustaceans indicated that the temporal patterns of neurogenesis can be correlated with the appearance of the thoracic appendages during larval and metamorphic development. To test further the idea that the temporal patterns of neurogenesis in crustaceans are related to their life histories, we examined neurogenesis in the ventral nerve cord of a direct developing crustacean, the freshwater crayfish Cherax destructor, whose life history contains neither larval stages nor metamorphoses. Neurogenesis was examined using the in vivo incorporation of bromodeoxyuridine into DNA. During late embryonic development the thoracic neuromeres of the crayfish contain arrays of mitotically active neuroblasts similar to those previously described in the spider crab and lobster. The arrays in the crayfish abdomen are, however, greatly reduced compared with those of the thorax. On hatching, both the thoracic and abdominal appendages of C. destructor are capable of movement. The pleopods, however, do not beat rhythmically until the second postembryonic stage whereas the pereiopods are not used in coordinated walking movements until the third stage. An examination of the time course of neurogenesis in the ventral nerve cord revealed that neurogenic activity in each neuromere ceases during or before the moult to the developmental stage in which its segmental appendage is first used in coordinated movements. These findings indicate that the patterns of neurogenesis in crustaceans are indeed related to the maturation of the segmental appendages and, in particular, to the maturation of motor behaviours.     

Partial co-option of the appendage patterning pathway in the development of abdominal appendages in the sepsid fly Themira biloba

The abdominal appendages on male Themira biloba (Diptera: Sepsidae) are complex novel structures used during mating. These abdominal appendages superficially resemble the serially homologous insect appendages in that they have a joint and a short segment that can be rotated. Non-genital appendages do not occur in adult pterygote insects, so these abdominal appendages are novel structures with no obvious ancestry. We investigated whether the genes that pattern the serially homologous insect appendages have been co-opted to pattern these novel abdominal appendages. Immunohistochemistry was used to determine the expression patterns of the genes extradenticle (exd), Distal-less (Dll), engrailed (en), Notch, and the Bithorax Complex in the appendages of T. biloba during pupation. The expression patterns of Exd, En, and Notch were consistent with the hypothesis that a portion of the patterning pathway that establishes the coxopodite has been co-opted to pattern the developing abdominal appendages. However, Dll was only expressed in the bristles of the developing appendages and not the proximal–distal axis of the appendage itself. The lack of Dll expression indicates the absence of a distal domain of the appendage suggesting that sepsid abdominal appendages only use genes that normally pattern the base of segmental appendages.     

Non-alcoholic fatty liver disease (NAFLD)--a novel common aspect of the metabolic syndrome

Non-alcoholic fatty liver disease (NAFLD) is emerging as one of the most common liver disorders claiming the urgent attention of both medical professionals and the public sphere because of the imminent epidemic of advanced liver injury that appendages epidemic of obesity. Recent research reveals simple triglyceride accumulation in hepatocytes (i.e., liver steatosis) frequently becoming complicated by inflammation (i.e., non-alcoholic steatohepatitis, or NASH) that may progress into more advanced stages of the disease including cirrhosis or, eventually, hepatocellular carcinoma. The exact mechanisms of the progression of NAFLD into overt NASH and advanced disease stages are largely unknown. There is urgent need in terms of both intensive research pursuits and effective practical measures to deal with this common threat.