合浦珠母贝鳃的显微与超微结构

合浦珠母贝(Pinctada fucata)是典型的滤食性瓣鳃类动物,也是我国重要的海水珍珠养殖贝类。本研究用光学显微镜、扫描电镜和透射电镜观察了合浦珠母贝鳃的显微和超微结构。结果表明,合浦珠母贝鳃结构属于异丝鳃型,左右两侧各2个鳃瓣,每个鳃瓣由内鳃瓣和外鳃瓣组成。鳃瓣由主鳃丝和普通鳃丝构成,主鳃丝在鳃瓣中主要起支架作用,每2根主鳃丝之间的9～12根普通鳃丝由"簇内连接"(intrabunchial junction)相连成簇。普通鳃丝之间通过"丝间连接"(interfilament junction)相连,丝间连接的上皮细胞与普通鳃丝的扁平细胞结构一样,为鳃的呼吸上皮。丝间连接的存在扩大了鳃的表面积,这种结构有助于进行气体交换。主鳃丝和普通鳃丝表面有前纤毛和侧纤毛,与食物运送和气体交换有关。普通鳃丝表面的纤毛为典型的"9+2"型微管结构。     

Scanning electron microscopy of the gills of a freshwater catfish,Rita Rita

Variations in the gross morphology and surface architecture of the gill filaments and secondary lamellae of a freshwater catfish (Rita rita) have been investigated using scanning electron microscopy. Heterogeneity of the gill has been correlated with the distribution of lamellar water-flow at different regions of a gill filament. Higher lamellar water flow (cc/pore/cmH₂O/sec) was estimated for the middle region of the filaments. The filaments are covered with epithelial cells whose surface is provided with well-developed microridges. The lamellae are generally covered with microvillous epithelial cells. The variations in surface architecture of the gill filaments and secondary lamellae have been correlated with their probable functions.     

Gross morphology and surface ultrastructure of the gills of Odontesthes argentinensis (Actinopterygii, Atherinopsidae) from a Southwestern Atlantic coastal lagoon

Odontesthes argentinensis was collected from Mar Chiquita Coastal Lagoon, the Southernmost coastal Atlantic Lagoon of Argentina. The morphology of the gills was analyzed by scanning electron microscopy. The morphology of the superficial structures of the gill filaments and pharyngeal region of the gill arch was discussed and related to their functional aspects. The gills arches are structurally similar to those of other teleosts and bring out the osmoregulatory capacity of this species. The epithelium that covers the surface of the filaments and the pharyngeal region of the gill arch is formed by polygonal pavement cells with conspicuous microridges. These folds in the membrane are not denoted in the epithelium of the respiratory lamellae. Apical crypts of chloride cells are present on the afferent and interlamellar filament surfaces, but are absent elsewhere on the gill arch. The highest density of mucous cells is observed into the gill filament and the pharyngeal region which indicates the existence of a protective strategy of the respiratory lamellae and the pharynx. The epithelium of the gill arches and the rakers is studded with spines. There are taste buds along the whole pharyngeal region that may be associated with their participation in tasting at this zone.     

Exceptional preservation of a novel gill grade in large Cretaceous inoceramids: systematic and palaeobiological implications

Organised mineralised structures observed in large inoceramids (valves on a metre scale) from the Late Albian, Toolebuc Formation, Australia (Inoceramus sutherlandi McCoy, 1865), and the Santonian, Niobrara Formation, USA (Platyceramus sp.), were investigated using variable pressure scanning electron microscope (SEM) with energy‐dispersive X‐ray spectroscopy (EDX), X‐ray microcomputed tomography (micro‐CT) and X‐ray diffraction (XRD) analyses. These indicate that the structures comprised a phosphate framework of aligned tubes and shallow troughs overlain perpendicularly by evenly spaced structures. In the Toolebuc Inoceramus, these are U‐shaped cross‐structures, whilst in the Niobrara Platyceramus, they comprise bundled fibre elements. Comparison with modern bivalves indicates that the observed phosphatised structures represent soft‐tissue preservation of the gills, as suggested in earlier publications. The tubes and troughs are remnants of a filamental support framework comprising ordinary and primary filaments, whilst the U‐shaped cross‐structures (I. sutherlandi) and fibrous bands (Platyceramus) represent preserved longitudinal gill musculature. Internal perforate and strand‐like fabric observed on the internal surface of some Platyceramus tubular structures suggests that the framework comprised collagen. The presence of primary and ordinary filaments in numerous unusually large plicae, in at least two lamellae, indicates that the gill structures were heterorhabdic. Each plica has at least 40 ordinary filaments, an exceptional number when compared with the maximum of 20 present in modern heterorhabdic gills. The absence of incontrovertible interfilament junctions makes it difficult to say whether inoceramids were filibranch, pseudolamellibranch or eulamellibranch. However, structures that are best attributed to intraplical junctions between filaments suggest the Inoceramidae had gills akin to those of pseudolamellibranch bivalves, although their unusually large number of filaments per plica is more reminiscent of homorhabdic eulamellibranch gills. The general form of the gill is similar to that described in some other pteriomorphs, most specifically Pteria. However, it has more complex junctions and interconnections, although these are not as intricate or pervasive as those observed in the pseudolamellibranch Ostreidae. The connections and well‐developed filament framework allowed the gill to reach its unusually large size, supporting the large size of these inoceramid species. The unusually large size of the gill and its components indicate that the organism fed on the larger suspended organic particles in the water column. It would also have been capable of processing large volumes of water quickly, leading to greater potential for food accumulation and with likely implications for respiratory efficiency. This may help explain the common association of inoceramids with oxygen‐deficient palaeoenvironments, particularly as the general structure of the inoceramid gill is very different to that observed in the commonest extant chemosymbiotic bivalves.     

A possible cause of termination of cell growth in the cellular slime mold Dictyostelium discoideum.

The gill ctenidium growth tip of the lamellibranch mollusc Aequipecten irradians recapitulates the temporal development of ciliated gill filaments and related structures in a spatial fashion. This “meristematic” relationship has allowed a study of basal body formation and ciliogenesis in adjacent cells of gill filament papillae at stages of progressively more advanced relative development. Basal bodies appear to originate quite rapidly, subsequent to the appearance of a complex of dense granules, quite reminiscent of the “condensation forms” or “procentriole precursors” typically seen in vertebrate ciliogenesis. Unlike basal body generation in higher forms, that in Aequipecten shows no obvious organized intermediate stages. During ciliation, randomly-oriented, nearly complete procentrioles are found concomitantly with actively-functioning basal bodies. Cilia formation in more advanced, already-ciliated cells is again preceded by the presence of granular complexes. Ciliogenesis in this mollusc thus shares with certain lower forms the property of very rapid basal body formation but, like many higher forms, it is preceded by the formation of a granular precursor complex, presumably consisting of particulate microtubule protein.     

Tissue damage and leukocytic infiltration following attachment of the mite Unionicola intermedia to the gills of the bivalve mollusc Anodonta anatina

Unionicola intermedia lives as a parasite in the gill region of Anodonta anatina. It attaches to the gills of its host by means of the pedipalps which cause displacement, rupture, and erosion of the gill epithelium. The pedipalps are sunk deeply into the underlying connective tissue of the gills and produce a leukocytic infiltration into the damaged area and a consequent edema of the gill filaments.     

鲤鳃表面结构扫描电镜研究

鲤的鳃丝表面显示了由三边形一六边形不等的表皮细胞,呈现出各种图案式的结构。     

γ-Tubulin has a conserved intrinsic property of self-polymerization into double stranded filaments and fibrillar networks

γ-Tubulin is essential for microtubule nucleation and also plays less understood roles in nuclear and cell-cycle-related functions. High abundancy of γ-tubulin in acentrosomal Arabidopsis cells facilitated purification and biochemical characterization of large molecular species of γ-tubulin. TEM, fluorescence, and atomic force microscopy of purified high molecular γ-tubulin forms revealed the presence of linear filaments with a double protofilament substructure, filament bundles and aggregates. Filament formation from highly purified γ-tubulin free of γ-tubulin complex proteins (GCPs) was demonstrated for both plant and human γ-tubulin. Moreover, γ-tubulin associated with porcine brain microtubules formed oligomers. Experimental evidence on the intrinsic ability of γ-tubulin to oligomerize/polymerize was supported by conservation of α- and β-tubulin interfaces for longitudinal and lateral interactions for γ-tubulins. STED (stimulated emission depletion) microscopy of Arabidopsis cells revealed fine, short γ-tubulin fibrillar structures enriched on mitotic microtubular arrays that accumulated at polar regions of acentrosomal spindles and the outer nuclear envelope before mitosis, and were also present in nuclei. Fine fibrillar structures of γ-tubulin representing assemblies of higher order were localized in cell-cycle-dependent manner at sites of dispersed γ-tubulin location in acentrosomal plant cells as well as at sites of local γ-tubulin enrichment after drug treatment. Our findings that γ-tubulin preserves the capability of prokaryotic tubulins to self-organize into filaments assembling by lateral interaction into bundles/clusters help understanding of the relationship between structure and multiple cellular functions of this protein species and suggest that besides microtubule nucleation and organization, γ-tubulin may also have scaffolding or sequestration functions.     

Gill remodelling during terrestrial acclimation in the amphibious fish Polypterus senegalus

Fishes are effectively weightless in water due to the buoyant support of the environment, but amphibious fishes must cope with increased effective weight when on land. Delicate structures such as gills are especially vulnerable to collapse and loss of surface area out of water. We tested the ‘structural support’ hypothesis that amphibious Polypterus senegalus solve this problem using phenotypically plastic changes that provide mechanical support and increase stiffness at the level of the gill lamellae, the filaments, and the whole arches. After 7 d in terrestrial conditions, enlargement of an inter-lamellar cell mass filled the water channels between gill lamellae, possibly to provide structural support and/or reduce evaporative water loss. Similar gill remodelling has been described in several other actinopterygian fishes, suggesting this may be an ancestral trait. There was no change in the mechanical properties or collagen composition of filaments or arches after 7 days out of water, but 8 months of terrestrial acclimation caused a reduction in gill arch length and mineralized bone volume. Thus, rather than increasing the size and stiffness of the gill skeleton, P. senegalus may instead reduce investment in supportive gill tissue while on land. These results are strikingly similar to the evolutionary trend of gill loss that occurred during the tetrapod invasion of land, raising the possibility that genetic assimilation of gill plasticity was an underlying mechanism.     

Interspecific variations in the surface ultrastructure of the gills of freshwater mullets

SEM studies were made on the gills of freshwater mullets,Rhinomugil corsula andSicamugil cascasia, to correlate surface ultrastructure of various gill units with their probable functions. Two types of lamellated gill rakers of the former fish are suited for plankton feeding and the short, stumpy and transversely beaded gill rakers of the latter reflect the varied food and feeding habit of the fish.R. corsula has numerous mucous glands on the epithelium covering the gill arch and gill filaments,S. cascasia has fewer. In accordance with the differences in the density and distribution of the mucous glands, the microridged epithelial cells also show variations in their architectural plan. In both species the epithelium of the secondary lamellae is smooth, probably an adaptation for better gaseous exchange.     

Description of a new species of Anuretes (Copepoda: Caligidae) from Kerala

A new species ofAnuretes collected from the gills ofDiagramma crassispinum Day at Cape Comorin, India, is described in detail. The carapace of the three females obtained was folded ventrally likeHermilius on the gill filaments.     

Microhabitats of gill parasites (Monogenea and copepoda) of teleosts (Scomberoides spp.)

Ramasamy P., Ramalingam K., Hanna R. E. B. and Halton D. W. 1985. Microhabitat of gill parasites (Monogenea and Copepoda) of teleosts (Scomberoides spp.). International Journal for Parasitology15: 385–397. The parasites Vallisia indica, Allodiscocotyla chorinemi, Heterapta chorinemi, and Dionchus remorae exhibited site specificity on the gills of Scomberoides commersonianus, S. tol, S. lysan and S. tala, whereas the copepod Caligus sp. did not. Observations on site preference revealed microhabitat differences along the length of gill filaments, along the anterio-posterior axis of the gill, between external and internal gill filaments and on different gill arches. Site preference varied with parasite density on each gill and host. An interspecific association test between pairs of species revealed, in some cases, a positive association, and in other cases a negative association. There were apparently no association? between certain pairs of species. A comparison of intensity within pairs of parasite species infecting the same host revealed either an inverse or a direct correlation. The numerical dominance and prevalence of parasites differed on each host species. This study indicates that intra- and interspecific competition may occur among the gill parasites. The direction and speed of ventilation water-currents and certain intrinsic factors of the parasite themselves may determine their microhabitat restriction on the gills.     

Gross structure and dimensions of the gill in an air-breathing estuarine goby,Pseudapocryptes lanceolatus

The gills of the air-breathing estuarine goby,Pseudapocryptes lanceolatus, are reduced owing to the development of a specialized organ of O₂ uptake from air. In the first gill arch, the filaments of the outer hemibranch are reduced to nearly one-half in comparison to those of its inner hemibranch. A smaller number of secondary lamellae per mm (27.6) occurring on one side of the gill filament reduces the gill surface area. A bilogarithmic plot of the gill area and the body weight indicates a curve with two significantly different components, one (b = 0.924) related to the fish weighing up to 6 g and the other (b = 0.405) to the fish weighing 8 g and above.     

Studies on the gill ciliation of the American oyster Crassostrea virginica (Gmelin)

Latero-frontal, para-latero-frontal, and frontal ciliary tracts on the gill filaments of Crassostrea virginica (Gmelin) were studied with light microscopy and scanning electron microscopy. Latero-frontal cirri are complex structures composed of varying numbers of paired cilia. The multiple pairs of cilia which constitute a single cirrus are closely appressed for a portion of their length; they then branch laterally from the central axis in a plume-like fashion. Latero-frontal cirri of adjacent gill filaments create a filtration sieve which should be capable of retaining particles smaller than 1 μm in diameter. Para-latero-frontal cilia are short, closely spaced cilia arranged as a staggered row along the frontal side of each tract of latero-frontal cirri. Latero-frontal cirri and para-latero-frontal cilia occur on ordinary, principal, and transitional gill filaments. Frontal ciliary tracts of ordinary filaments are divided into a central, ventrally directed coarse tract, flanked on either side by a dorsally directed fine ciliary tract. The coarse tract is covered by cirri which are comprised of five to eight cilia, while the fine frontal tracts are made up of individually functioning cilia. The frontal ciliary tracts of principal and transitional filaments bear only dorsally directed fine cilia. The unique direction of effective beat of the coarse frontal cirri of ordinary filaments, in combination with the action of fine frontal cilia and the strategic location of mucus producing cells, is used to describe a possible mechanism for the sorting of filtered particles.     

Constitutive aggregates of intermediate-sized filaments of the vimentin and cytokeratin type in cultured hepatoma cells and their dispersal by butyrate

Cloned hepatoma cells ($\text{72}\text{22}$) derived from the liver of a rat treated with the carcinogen, diethylnitrosamine, exhibit a genetically stable, large, acentric, juxtanuclear, hyaline aggregate of loosely packed intermediate-sized (7–11 nm) filaments, interspersed with variable but minor amounts of microtubules, polyribosomes and membranous structures. Immunofluorescence microscopy shows that the these filaments react specifically with antibodies to bovine prekeratin and to murine vimentin. The aggregates contain aster-like foci common to the arrangement of both tonofilament-like and vimentin-containing intermediate-sized filaments, although both filament systems show different fibrillar patterns in other cytoplasmic regions. While the cytokeratin filament system is not significantly altered during exposure to colcemid, the vimentin in the abnormal aggregate is rearranged during such treatment into extensive and complex perinuclear ‘whorls’ of filaments. Treatment of the cells with butyrate results in a markedly flattened, hepatocyte-like morphology, a reappearance of typical actin-containing ‘cables’, and a progressive disintegration of the filament aggregate concomitant with a normal display of filaments of both the cytokeratin and vimentin type. The results show that (i) some cells contain aggregates consisting of two different types of intermediate-sized filaments oriented onto a common focal center; (ii) such an abnormal filament arrangement is clonally stable; (iii) the vimentin-type filaments contained in such aggregates are still susceptible to the action of antimitotic drugs and can be rearranged into characteristic perinuclear whorls; and (iv) this abnormal aggregate of intermediate filaments can be reverted to normal patterns upon treatment of the cells with butyrate.     

Gill‐derived glands in species of Astyanax (Teleostei: Characidae)

The presence of a gill‐derived gland is herein reported for the first time in males of species of Astyanax and related genera; they are described through histological cuts and SEM. The gill‐derived glands described for the Characidae, when fully developed, present a similar structure in different species. The main external feature of gill‐derived glands is the fusion of anteriormost gill filaments on the ventral branch of first gill arch. This fusion is caused by squamous stratified epithelial tissue that covers adjacent filaments, forming a series of chambers. In the region where the gill‐derived gland develops, the secondary lamellae of the gill filaments are much reduced or completely atrophied being characterized by the presence of glandular cells forming nests.     

Simultaneous labelling of microtubules and fibrillar bundles in tobacco BY-2 cells by the anti-intermediate filament antibody,ME 101

Summary In previous studies on plant cells, antibodies directed against intermediate filaments (IFs) have shown that IF antigens are distributed in one of two quite distinct forms. The first co-distributes with each of the four microtubule arrays (cortical, preprophase band, spindle and phragmoplast), while the second form is associated with cytoplasmic paracrystalline fibrillar bundles (FBs) of 10 nm filaments. Conditions allowing one form to be labelled with antibody have generally proved unsuitable for labelling of the other; this has prevented the simultaneous visualization of the two forms of IF antigen in plants and the study of any possible physical relationships between them at the electron microscopic level. In this paper, we show that ME 101, which recognizes an epitope in the N-terminal portion of all classes of intermediate filaments, stains both forms of plant IF antigen simultaneously in tobacco suspension cells using immunofluorescence or immunogold labelling techniques. These cells contain in their cortex short (ca. l m) fibrillar bundles which stain with ME 101. These bundles appear to be independent of the microtubule-associated epitope which stains in a continuous linear manner with ME 101. When protoplasts are either cleaved open on grids or sequentially extracted with detergents prior to critical point drying, the short fibrillar bundles are specifically labelled by ME 101 tagged with colloidal gold. ME 101 also co-distributed with underlying linear filaments, which appeared to be microtubules. In addition to these structures, the cortex also contains a meshwork of variably-sized fine filaments but these are not labelled with ME 101 nor with an antibody raised against the plant cytoskeleton, which recognizes cytokeratin 8. These results confirm that the fibrillar bundles and the microtubule-associated form of plant IF antigens are present simultaneously rather than experimentally-interconvertible, and that they appear to be physically unconnected.Abbreviations DAPI 4,6-diamidino-2-phenylindole - FB fibrillar bundle - FITC fluorescein isothiocyanate - IF intermediate filaments - MTSB microtubule stabilizing buffer - TBS Tris-buffered-saline     

波纹唇鱼鳃丝的光镜、扫描和透射电镜观察

应用光学显微镜、扫描电镜和透射电镜对波纹唇鱼(Cheilinus undulatus)鳃的组织结构、表面形态特征及鳃小片超微结构进行了观察.结果表明,波纹唇鱼有3对全鳃,1对半鳃和1对伪鳃,鳃丝呈梳状紧密排列在鳃弓上,鳃小片紧密地镶嵌排列在鳃丝两侧,入鳃动脉、出鳃动脉和鳃小片毛细血管网组成鳃的血液系统.鳃丝非呼吸区分布...     

Amyloid fibrils of glucagon characterized by high-resolution atomic force microscopy

Glucagon solutions at pH 2.0 were subjected to mechanical agitation at 37 degrees C in the presence of a hydrophobic surface to explore the details of aggregation and fiber formation. High-resolution intermittent-contact atomic force microscopy performed in solution revealed the presence of aggregates after 0.5 h; however, longer agitation times resulted in the formation of fibrillated structures with varying levels of higher-order assembly. Height, periodicity, and amplitude measurements of these structures allowed the identification of four distinct fiber types. The most elementary fiber form, designated a filament, self-associates in a specific wound fashion to produce protofibrils composed of two filaments. Subsequent self-assembly of these filaments and protofibrils leads to two well-defined fibrillar motifs, termed Type I and Type II. Atomic force microscopy imaging of pH 2.8 glucagon solutions not agitated or exposed to elevated temperature revealed the presence of amorphous aggregates before the formation of fibrillar structures similar to those seen at pH 2.0. Time-course solution Fourier transform infrared spectroscopy and thioflavin T binding studies suggested that glucagon aggregation and fibril formation were associated with the development of beta-sheet structure. The results of these studies are used to describe a possible mechanism for glucagon aggregation and fibrillation that is consistent with a hierarchical assembly model proposed for amyloid fibril formation.     

Morphology and Ultrastructure of the Intestine in a Plant-Parasitic Nematode,Tylenchorhynchus dubius

An unusual feature of the intestine in Tylenchorhynchus dubius is the presence, within the intestinal cytoplasm, of an extensive system of fibrillar bundles consisting of thin (14 nm diam) filaments and thick (70-90 nm diam), rod-like elements arranged in closely packed arrays. The larger of the fibrillar bundles, for which the term "intestinal fasciculi" is proposed, are evident in whole mounts and apparently correspond to the lateral or sinuous canals described in some other tylenchids. The nature and function of fasciculi are not known, but some possibilities are considered. Fasciculi were found in at least seven other species of Tylenchorhynchus. The intestinal cytoplasm also contains the usual sub cellular organelles and large amounts of reserve materials in the form of particulate glycogen and three types of globules. The surface of the cells bordering the lumen is elaborated into numerous microvilli which have central filaments and often bear regular external projections. Although terminal bars delimit the apical margins between cells, the frequent lack of complete lateral boundaries and extensive length of the fasciculi indicate that the intestinal epithelium is a multinucleate mosaic or syncytium.