A SEM–study of Listerella paradoxa (Myxomycetes)

Apart from the presence of a capillitium, the fructifications of Listerella paradoxa Jahn resemble those of some species of Licea Schrad. Similarities exist in general appearance, mode of dehiscence, structure of peridium, and sculpturing of spores. The capillitium of Listerella is attached near the margins of the peridial lobes, and the moniliform threads are extensions from pillars from which the threads sometimes break. Aberrant capillitial outgrowths may be reminiscent of the processes bordering the peridial lobes in Licea. Although mostly found on podetia of the lichen genus Cladonia, Listerella may also occur on other substrates. A large–spored specimen developed on an oak leaf in California falls within the intraspecific variation of L. paradoxa. LwtereWa–resembling species of Licea may also occur on Cladonia. An x–ray analysis did not reveal any Ca or other elements with an atomic weight equal to or above that of Na in peridium, capillitium and spores of L. paradoxa , nor in peridium, peridial protuberances and spores of Licea pusilla Schrad.     

Formation of bundles of microfilaments during spreading of fibroblasts on the substrate

Electron microscopy was used to study the sites of formation of bundles of parallel microfilaments in the early stages of spreading of normal mouse embryo fibroblasts on the substrate. Bundles of microfilaments were not found in suspended cells. Contact of the surface of spherical cells with the substrate was not sufficient for the formation of bundles: these bundles were not seen near the under surface of cells that were already attached to the substrate but had not yet developed cytoplasmic outgrowths at their periphery. Peripheral cytoplasmic outgrowths (microspikes and lamellar processes) attached to the substrate were found to be the only sites of localization of the first bundles of microfilaments seen in the spreading cells. It is suggested that surface and/or cytoplasm of the newly-formed peripheral cytoplasmic outgrowth may have some special properties necessary for the initiation of the development of microfilament bundles.     

红托鬼笔黄水病病原鬼笔复膜孢酵母侵染过程的组织学观察

红托鬼笔黄水病是一种由鬼笔复膜孢酵母引起的致灾性土传病害,极难防治。本研究通过探索获得高质量红托鬼笔组织石蜡切片技术的基础上,对幼担子果生长期病原接种后第8、16、24、32、40、48和72h进行组织取样,利用Van-clear透明剂制备石蜡切片,观察病原的侵染过程,以健康的幼担子果做对照。结果表明：健康的红托鬼笔包被表面菌丝呈管状,与包被中部菌丝结构无明显差异。而接种病原后第8h时,即可观察到病原细胞和假丝形成,包被表面菌丝萎缩、褐变,病原细胞通过菌丝间隙向内扩散和侵染,侵染速度18.14μm/h。接种后32 h包被表面菌丝大量降解,主要是病原细胞和假丝存在,此时病原可以侵染至包被中部菌丝组织。接种后40 h幼担子果表面分泌黄色渗出物液滴,包被表面开始溃烂,病原侵染至幼担子果包被胶质层,并不断向内侵染。本研究采用石蜡切片法对黄水病病原的侵染过程进行了组织学观察,为其致病机制和病害综合防治研究提供借鉴。     

Morphology and ultrastructure of the plasmodiocarpous species Licea variabilis and L. retiformis (Myxomycetes)

Licea variabilis and L. retiformis are odd members of the genus Licea in so far as they form plasmodiocarpous fructifications and do not possess protoplasmodia. Differences between the two species are found in the sculpturing of the inner surface of the peridium, in the ornamentation of the spore wall, and in the internal structure of the spore wall. Certain characteristics indicate a closer affinity of L. retiformis to the sporangiate species of Licea than to L. variabilis. Spherical bodies attached to the inner surface of the peridium in L. retiformis appear to be an integral part of the peridium and may be homologous with ornamentations seen in L. biforis.     

Perianth development inAngophora and the bloodwood Eucalypts (Myrtaceae)

The petals ofAngophora flowers are compound structures consisting of two morphologically distinct components that develop along separate morphogenetic pathways. These two components are also evident in the corolline parts of the bloodwood eucalypts. In occasional flowers ofAngophora and some bloodwoods, several adjacent corolline primordia may become continuous due to interprimordial growth, but the petals are mostly free at anthesis. In other bloodwood eucalypt species all the primordia in the corolline whorl become continuous at some stage in development, resulting in an operculum that is anatomically unresolvable into its original petaline parts. The varying degrees of this continuity that are evident within individual trees (and even within single flowers) suggests that operculum formation is an epigenetic event that is determined by morphogenetic processes within the flower. It is suggested that these may relate to differing rates of growth in different regions of the bud.     

Histomorphological analysis of the osteophytic appositions in patients with lumbar lateral recess syndrome

Patients with lumbar lateral recess syndrome (LRS) can be successfully cured by removing osseous excrescences that grow on the peripheral edge of articular surface of the facet joint. They cause narrowing of the lateral recess and compress a root of the spinal nerve. Their appearance is related to the instability of respective dynamic vertebral segment. The aim of this study was to analyze the osteophytic composition morphohistochemically and elucidate cellular processes that lead to this new formation appearance. It is necessary to find a possible causative-consequential relation between the osteophyte and instability. The ideal object to explore was the osteophyte in the lateral recess because it had to be removed during operative treatment. The group of 30 patients with clinical feature of LRS was chosen. Each patient had clinically verified LRS with consequential radiculopathy. Bony outgrowths were removed surgically and analyzed by histological and immunohistochemical methods: toluidine blue, Goldner trichrome, TRAP, indirect peroxidase with antibodies against BMP 3 and BMP 7. The outgrowths that caused lateral recess stenosis were composed of fibrous and hyaline cartilage and cancellous bone. The changes in cartilage and bone, and occurrence of intramembranous bone formation in sense of enlargement of trabeculae, leads to the conclusion that marginal osteophytic formations could be an adaptation to changed conditions in the dynamic vertebral segment and an attempt to stabilize this segment by enlargement of articular surface.     

Functional activity of ciliated outgrowths from cultured human nasal and tracheal epithelia

Primary cultures of respiratory epithelium were produced as outgrowths from human fetal and adult tracheal and nasal polyp explants. Video recordings of the epithelial cell outgrowths were carried out after 5 days of culture and the ciliary beating frequency was analyzed by using a video technique. Uniform fields of differentiated ciliated cells were observed near the edge of the explant. In the transition region of the outgrowth from the explant to the outgrowth periphery, isolated ciliated cells were present, as well as cells with fused cilia. The ciliary beating frequency of the outgrowth of well-differentiated ciliated cells (13.5 +/- 1.4 Hz) was significantly higher (p less than 0.001) than the beating frequency of both the explant (11.9 +/- 0.7 Hz) and the ciliated cells with fused cilia (9.8 +/- 1.7 Hz). The same differentiation stages and functional activities were observed in the outgrowth cultures, whatever their origin. These in vitro models are comparable with each other and therefore could be useful for studying the ciliogenesis and functional activity of the human respiratory epithelium.     

THE MORPHOLOGY OF HYOLITHIDS AND ITS FUNCTIONAL IMPLICATIONS

Abstract:  The exceptionally preserved hyolithids Gompholites striatulus , Maxilites robustus , Maxilites snajdri and Maxilites sp. are described with particular emphasis on helen and muscle scar morphology. These two aspects of hyolithid morphology have remained controversial. In life position, each helen curved ventrally. When the operculum closed the aperture of the conch, each helen was locked at the commissure slit with its dorsal edge tilted forward. Inside the conch, it was held in the dorsal apertural plane and clear of the inner surface of the operculum. Previously unidentified muscle scars are described from both the operculum and the conch. Dorsal scars on the conch aperture held muscles directed to the operculum. Comparative study of the muscle insertion pattern indicates that hyolithids did not have serially arranged muscles and that all hyolithids may have had a common skeleto-muscular system. The arrangement of the muscle scars with respect to the helens suggests that the latter were capable of relatively complex movements and could have been used to propel the organism over the substrate. The general morphology and orientation of the helens suggests that in addition they functioned to stabilize the organism on the sea-floor.     

Scleroderma stellatum versus Scleroderma bermudense: the status of Scleroderma echinatum and the first record of Veligaster nitidum from the Virgin Islands

The type of Scleroderma stellatum from Brazil exhibits a sharp echinulate, dark brown peridium, and the type of S. bermudense from Bermuda has a peridium that is loosely woven and fibrillose, whitish to pale brownish. These characters indicate two independent species. This information is contrary to that of Guzmán in 1970, who interpreted S. bermudense to be a synonym of S. stellatum based on the similar spores. Scleroderma echinatum from Borneo and Panama, as recently discussed by Guzmán and Ovrebo, also has an echinulate, dark brown peridium and is a synonym of S. stellatum. All these fungi have a stellate dehiscence. New records of S. bermudense from the Greater Antilles and Mexico's Pacific Coast, and Veligaster nitidum from Virgin Islands also are discussed.     

Quantitation of in vitro ciliated cell growth through image analysis

Summary Ciliated cell cultures can be produced in outgrowths from explants of human respiratory epithelium. An image analysis technique was develope to quantify the percentage of active ciliated cells present in these cultures. The subtraction 2 by 2 of five successive video images of the cultures, followed by the addition of the resulting images, allowed the determinaton of the culture surface covered by ciliated cells. The percentage of this surface varied according to the regions of the explant (27.7% in the outgrowth near the explant and 4.1% at the periphery of the outgrowth). High variations were observed within the same region of an outgrowth, as well as from one outgrowth to another. However, maximal differentiation was observed after 4 d of culture. The quantitation techniques described in the present work might be useful for studying in vitro the respiratory epithelial injury and the subsequent repair processes. This work was supported by CEB-INSERM and SYNTHELABO-INSERM grants.     

Dissymmetry in the structure and dimensions of the temporal operculum of the cerebral hemispheres

In 130 cerebral preparations of children and mature persons external structure and dimensions of the temporal operculum, pertaining to the posterior speech cerebral area, have been studied. A great variability in the operculum form, in the number of tertial sulci situating on it, in its linear dimensions and superficial area has been stated. Final dimensions of the temporal operculum are formed in early childhood and have no sex differences. During all age periods, there is a pronounced left-sided tendency in dimensional asymmetry of the temporal operculum dimensions; their predominance in the left side is noticed in more than 70%. No correlation between the operculum surface and the brain mass is revealed, as well as between its surface and the surface of transversal temporal gyri. The left-sided predominance in the length of the lateral sulcus is observed nearly as often as the left-sided prevalence of the temporal operculum, but in a number of cases their asymmetry has an opposite direction. This should be taken into consideration at diagnosing the dominant hemisphere by means of the intravital arteriography and when certain neurosurgical interventions are performed.     

Timing of development of the middle ear of Anura (Amphibia)

Summary The opercularis system and tympanum-stapes complex of the anuran middle ear develop at different times relative to metamorphosis. In early larvae, the fenestra ovalis is represented by a large lateral opening in the otic capsule filled with connective tissue. At later larval stages, but well before metamorphosis, a cartilaginous operculum begins to form at the posterior margin of the fenestra ovalis, and proceeds to expand to fill all except the anterior part of the fenestra. The opercularis muscle forms along with the levator scapulae superior muscle at the anteromedial edge of the developing suprascapular cartilage of the shoulder girdle. The muscle fibers extend anteroventrally towards the operculum and otic capsule, and, just before emergence of the forelimbs, that portion that will form the opercularis muscle inserts on the lateral surface of the operculum. At this stage, when the metamorphosing frogs first show terrestrial habits, the opercularis system is complete and presumably functional. Timing of development of the tympanum-stapes complex is more variable. The stapes begins as a cartilaginous condensation in the anterior part of the fenestra ovalis, and develops laterally to eventually contact the epidermis and dermis that together will form the tympanum. Meanwhile a middle ear cavity and tympanic annulus form to complete the complex. In several species, especially those that metamorphose at a smaller body size, the tympanum-stapes complex is quite incomplete by the end of metamorphosis, and in Hyla crucifer it takes about 60 days to fully develop. The presence of a complete opercularis system by the start of terrestrial activity is consistent with an hypothesized seismic function of the system. The independent timing of development of the opercularis system and tympanum-stapes complex does not support functional hypotheses linking the opercularis system with modulation of responsiveness of the tympanum-stapes complex to aerial sound. Newly metamorphosed frogs with poorly developed tympanum-stapes complexes are presumably either insensitive to aerial sound or employ alternate mechanisms for transmission of sound energy to the inner ear, possibly involving the opercularis system.     

Ultrastructural Study of the Encystation and Excystation Processes in Naegleria sp.

ABSTRACT. An important aspect of the biology of Naegleria sp. is the differentiation processes that occur during encystation and excystation. We studied these using both fluorescence and transmission electron microscopy techniques. In the initial stages of encystation, the cisternae of the endoplasmic reticulum became densely filled with a fibrillar material. Vesicles with a similar content that appeared to be derived from the cisternae were also observed in close contact with the plasma membrane. As encystation progressed, the fibrillar material became localized on the surface of the amoeba. An irregular compaction was observed in some areas of the cyst wall, which contained thin extensions of the cyst wall fibrillar material. Completely formed cysts had two to three ostioles, each sealed by an operculum. The operculum contained two areas in which a differential compaction of the fibrillar structure was observed. When excystation was induced, small dense granules (DGs), which were in close contact with fibrillar material were observed in the cyst cytoplasm and in the peritrophic space. During excystation, the more compact component of the operculum moves to enable the pseudopod of the emerging trophozoite to penetrate the ostiole. Vacuoles containing a fibrillar material, probably derived from the cyst wall, were observed in the cytoplasm of the pseudopodia. Our results provide a platform for further studies using biochemical markers to investigate the origin of the cyst wall as well as the role of DGs during excystation in Naegleria .     

Characteristic properties of fluctuating particle fluxes near the last closed flux surface in the course of lower hybrid heating and during a transition into the improved confinement mode in the FT-2 tokamak

Results are presented from experimental studies of the time behavior of the transport processes in the edge plasma of the FT-2 tokamak during auxiliary lower hybrid heating when an internal transport barrier and then an external transport barrier form in the plasma. An analysis of the data on turbulent particle transport in the edge plasma shows that the radial electric field generated inside the plasma column during auxiliary heating plays an important role in both the formation of a transport barrier and the suppression of anomalous transport at the plasma periphery in the postheating phase of the discharge. The mechanism for the formation of a negative radial electric field E _r near the last closed flux surface after the end of the lower hybrid heating pulse is considered. Fluctuation spectra of the particle density and poloidal electric field are presented that characterize the process of suppression of microturbulence at the plasma periphery. The experimental data were obtained with the use of movable multielectrode Langmuir probes.     

Surface topology and structural integrity of the Theromyzon tessulatum (Annelida: Hirudinea: Glossiphoniidae) cocoon

Cocoons secreted by the aquatic leech Theromyzon tessulatum comprise a tubular, membranous ovoid, sealed at each end by a glue‐like substance, called an operculum. Scanning electron microscopy showed surface features of the T. tessulatum cocoon that included a circuitous bulge, cups that conformed to the shape of embryos, relief folds that radiated from opercula, and asymmetric distributions of protuberances on the upper aspect of the cocoon surface. The structural integrity of the T. tessulatum cocoon was assessed after exposure to a variety of denaturing conditions (e.g., extreme heat, detergents, acids). Although both the fibrous cocoon membrane and opercula were strikingly resilient, the membrane/operculum boundary appeared to be the weakest structural component of the cocoon, consistent with its functional role as an escape hatch for juvenile leeches. The operculum itself was more sensitive to denaturation than the cocoon membrane, and thus was probably the source of a major protein component isolated from the T. tessulatum cocoon (i.e., Tcp; Theromyzon cocoon protein). J. Morphol., 2008. © 2008 Wiley‐Liss, Inc.     

Developmental role of dpp in the gastropod shell plate and co-option of the dpp signaling pathway in the evolution of the operculum

The operculum is a novel structure in gastropod molluscs. Because the operculum shows notable similarities to the shell plate, we asked whether there were an evolutionary link between these two secretory organs. We found that some of the genes involved in shell-field development are expressed in the operculum, such as dpp and grainyhead, whereas engrailed and Hox1 are not. Specific knockdown of dpp by injection of double-stranded RNA (dsRNA) resulted in malformation of the shell plate. The shell plate was smaller due to failure of activation of cell proliferation in the shell-field margin. The expressions of grainyhead and chitin synthase 1 in the shell field margin were suppressed by dpp-dsRNA. However, matrix secretion was not completely abolished, and the expressions of ferritin, engrailed or Hox1 were not affected by dpp-dsRNA, indicating that dpp is partly involved in the developmental pathway for shell matrix secretion. We also present evidence that dpp performs a key role in operculum development. Indeed, dpp-dsRNA impaired matrix secretion in the operculum as well as expression of grainyhead. Based on these observations that dpp is important for development of both the shell plate and operculum, we conclude that co-option of dpp to the posterior part of the foot contributed to the innovation of the operculum in gastropods.     

MORPHOGENESIS OF THE SPORANGIUM OF COMATRICHA

Goodwin , Donna C. (State U. Iowa, Iowa City.) Morphogenesis of the sporangium of Comatricha. Amer. Jour. Bot. 48(2): 148–154. IIlus. 1961.—Three species of the myxomycete genus, Comatricha, were studied: Comatricha nigra, C. fimbriata, and C. elegans. The sporangia developed on living bark of Ulmus americana in moist chamber. The hypothallus is formed under the homogeneous protoplasmic mass of the sporangial initial. The fibrous threads of the hypothallus bend upward, lengthening at the apices to become the fibers of the stalk and columella. The undifferentiated protoplasm is carried upward as the stalk elongates. When the columella has attained its mature height, threads bend out from the columella and grow toward the periphery of the sporangium. These threads form the capillitium. Simultaneous with the appearance of the capillitial initials, the peridium, a delicate membrane, forms. After the capillitium is mature, the protoplast cleaves into many cells, the future spores. The peridium evanesces early in the stage of spore maturation. Cellulose is present in the stalk, capillitium, and spore walls but is not found in the peridium or hypothallus. The capillitium of these species follows a developmental pattern designated as the “Comatricha-type” by Ross (1957) from a study of Comatricha typhoides. The taxonomic implications of the sporangial developmental pattern are discussed.     

The development of growth lines on articulate brachiopods

Three types of growth lines are recognised on articulate brachiopod shells: (1) very fine diurnal growth lines formed by calcite increments at the shell margin, (2) seasonal growth lines, formed by inward reflection (doubling back) of the mantle edge, seen as concentric steps on the shell surface and marked by re-orientation of growth vectors evidenced by secondary shell fibres, (3) disturbance lines, formed by abrupt regression of the mantle edge, also seen as concentric steps on the shell surface, but indicated by a dislocation in the shell fabric. Lamellose and spinose ornaments of the sort seen in Tegulorhynchia are essentially genetically controlled. Periodic outgrowths from the outer mantle lobe secrete frills of primary shell that project from the shell surface and form short hollow spines where they cross the radial ornament. In longitudinal section spine formation is seen to involve gradual increase in the rate of secretion of primary shell followed by retraction, and often collapse, of the mantle outgrowth, accompanied by regression. Reflection of the mantle edge usually follows spine formation.     

The presence of an embryonic opercular flap in amniotes

The operculum is a large flap consisting of several flat bones found on the side of the head of bony fish. During development, the opercular bones form within the second pharyngeal arch, which expands posteriorly and comes to cover the gill-bearing arches. With the evolution of the tetrapods and the assumption of a terrestrial lifestyle, it was believed that the operculum was lost. Here, we demonstrate that an embryonic operculum persists in amniotes and that its early development is homologous with that of teleosts. As in zebrafish, the second pharyngeal arch of the chick embryo grows disproportionately and comes to cover the posterior arches. We show that the developing second pharyngeal arch in both chick and zebrafish embryos express orthologous genes and require shh signalling for caudal expansion. In amniotes, however, the caudal edge of the expanded second arch fuses to the surface of the neck. We have detailed how this process occurs and also demonstrated a requirement for thyroid signalling here. Our results thus demonstrate the persistence of an embryonic opercular flap in amniotes, that its fusion mirrors aspects of amphibian metamorphosis and gives insights into the origin of branchial cleft anomalies in humans.