Summary The lenses of albino rats were studied after freeze-drying with scanning electron microscopic technique.The multilamellated lens capsule is covered by adhering fibers in the equatorial region but looks otherwise almost smooth. The cuboidal, polyhedronal cells on the anterior surface of the lens are characterized by their complex interdigitations and their paucity of extracellular space. The cortical polyhedronal, mostly hexagonal lens fibers have several processes interconnecting neighbouring cells. The plasma membrane appears slightly undulated. It is covered by extracellular material. There is a well-delimited extracellular space between the lens fibers in the cortical layer. The results are discussed in relation to previous studies based upon light and electron microscopy.Supported by grants from the Swedish Medical Research Council (B70-12X-2543-02) and Magn. Bergwalls Stiftelse. 相似文献
Abstract Streptococcus suis capsular type 2 has a capsule rich in sialic acid (NANA). Sialic acid, known to be an antiphagocytic factor for many bacterial species, inhibits the activation of the alternative complement pathway. The role of capsular NANA in virulence, resistance to phagocytosis and intracellular survival of S. suis capsular type 2 was evaluated. In general, a low concentration of NANA was observed for all the S. suis strains tested. In addition, no difference could be found in NANA concentrations between strains of different virulence degrees. Sialic acid concentration increased in the virulent strain 89–1591 and the avirulent strain 90–1330 after in vivo growth with an increased capsular material thickness compared to growth in vitro. No significant difference could be found in the phagocytosis rate by porcine blood monocytes of either strain and strain 89–1591 treated with sialidase or the sialic acid-binding lectin from Sambucus nigra (SNA I). Intracellular survival of strain 89–1591 decreased after treatments with sialidase or lectin, becoming comparable to that of strain 90–1330. Finally, no difference could be seen in virulence using a murine model, even if strain 89–1591 was treated with the enzyme or the lectin. Thus, NANA does not seem to be a critical virulence factor for S. suis capsular type 2. 相似文献
Only 4% of 600 particles slid on or adhered to buccopharyngeal surfaces of Oreochromis esculentus . Only a minute quantity of mucus was visible during feeding (0·6% of 68 224 video frames; 30 frames s–1), and very few particles were retained in this mucus. Filtration by mucus entrapment on the branchial arches is rejected as a mechanism of particle retention in this species. Since particles contacted the branchial arches infrequently, and the inter–raker spaces are too large to retain particles less than approximately 50 μm, sieving by gill rakers as a particle retention mechanism is rejected also. Unlike the suspension–feeding congener O. niloticus, O. esculentus does not use branchial arches to retain food particles by sieving or by mucus entrapment. 相似文献
The capsule polysaccharide-protein-peptidoglycan complex (insoluble in boiling sodium dodecyl sulfate and hot phenol-water) from cell envelopes of Rhodobacter capsulatus St. Louis was characterized. Hydrofluoric, hydrochloric acid or alkaline hydrolysis solubilized the polysaccharide moiety, whereas the protein-peptidoglycan moiety remained insoluble. On treatment of the protein-peptidoglycan moiety with lysozyme, the protein with peptidoglycan-residues bound was solubilized. It showed a single, broad peptide band (Mr=about 17,000) on sodium dodecyl sulfate polyacrylamide gel-electrophoresis. The same protein was obtained by lysozyme digestion (without preceding hydrofluoric or hydrochloric acid treatment) of the protein-peptidoglycan complex of the phage-resistant mutant Rhodobacter capsulatus St. Louis RC1-, in which the capsule polysaccharide is present in a free form. A protein-peptidoglycan complex was isolated also from the capsulefree Rhodobacter capsulatus 37b4. Covalent binding between the protein and peptidoglycan moieties is likely for all three strains as is the lipoprotein nature of the protein moiety. The polysaccharide moiety of the complete complex from the wild-type Rhodobacter capsulatus St. Louis was at least partly removable from the complex in the presence of high salt concentrations or ethylene diamine tetraacetate. A specific amino acid pattern (with Ser, Gly, Glu, and Ala dominating) remained constantly associated with the capsule polysaccharide moiety independent of the separation procedure.Abbreviations A2pm
diaminopimelic acid
- Cetavlon
cetyltrimethyl-ammonium bromide
- EDTA
ethylene-diaminetetraacetate, disodium salt
- HF
hydrofluoric acid
- HPLC
high-performance liquid chromatography
- PAGL
polyacrylamide gel-electrophoresis
- SDS
sodium dodecyl sulfate
- TCA
trichloroacetic acid 相似文献
Hyperspectral imaging (HSI) is a technology with high potential in the field of non‐invasive detection of cancer. However, in complex imaging situations like HSI of the larynx with a rigid endoscope, various image interferences can disable a proper classification of cancerous tissue. We identified three main problems: i) misregistration of single images in a HS cube due to patient heartbeat ii) image noise and iii) specular reflections (SR). Consequently, an image pre‐processor is developed in the current paper to overcome these image interferences. It encompasses i) image registration ii) noise removal by minimum noise fraction (MNF) transformation and iii) a novel SR detection method. The results reveal that the pre‐processor improves classification performance, while the newly developed SR detection method outperforms global thresholding technique hitherto used by 46%. The novel pre‐processor will be used for future studies towards the development of an operational scheme for HS‐based larynx cancer detection.
RGB image of the larynx derived from the hyperspectral cube and corresponding specular reflections ( a ) manually segmented and ( b ) detected by a novel specular reflection detection method. 相似文献
A portable electro‐immobilization and laparoscopy system is described that is suitable for sex determination, gonadal biopsy and immediate release of largemouth bass Micropterus salmoides. Continuous direct current at a power density of 52·2 µW cm?1 for 2 min was sufficient to immobilize fish for surgery, but induced a mild, transient hypokalaemia and hyperglycaemia. Insertion of a 4·8 mm laparoscopic instrument set through the urogenital pore provided access to the gonads for examination and biopsy with mild tissue trauma. 相似文献
This light and electron microscope study reveals considerable uniformity in hornwort stomata morphology and density in contrast to common spatial and developmental abnormalities in tracheophytes and mosses. Stomata arise from a median longitudinal division of sporophyte epidermal cells morphologically indistinguishable from their neighbours apart from the retention of a single chloroplast whilst those in the other epidermal cells fragment. Chloroplast division and side-by-side repositioning of the two daughter chloroplasts determines the division plane in the stomatal mother cell. The nascent guard cells contain giant, starch-filled chloroplasts which subsequently divide and, post aperture opening, regain their spherical shape. Accumulation of wall material over the guard cells and of wax rodlets lining the pores follows opening. While the majority of stomata are bilaterally symmetrical those lining the dehiscence furrows display dextral and sinistral asymmetry due to differential expansion of the adjacent epidermal cells.
The ubiquity of open stomata suggests that these never close with the maturational wall changes rendering movement extremely unlikely. These structural limitations, a liquid-filled stage in the ontogeny of the intercellular spaces, and spores already at the tetrad stage when stomata open, suggest that their primary role is facilitating sporophyte desiccation leading to dehiscence and spore dispersal rather than gaseous exchange. Stomata ontogeny and very low densities, like those in Devonian fossils, suggest either ancient origins at a time when atmospheric carbon dioxide levels were much greater than today or a function other than gaseous exchange regulation. We found no evidence for stomatal homology between hornworts, mosses and tracheophytes. 相似文献
Cryptococcus neoformans (C. neoformans) is an opportunistic fungal pathogen that mainly infects immunocompromised individuals such as AIDS patients. Although cell surface receptors for recognition of C. neoformans have been studies intensively, cytoplasmic recognition of this pathogen remains unclear. As an important detector of pathogen infection, inflammasome can sense and get activated by infection of various pathogens, including pathogenic fungi such as Candida albicans and Aspergillus fumigatus. Our present study showed that acapsular C. neoformans (cap59Δ) activated the NLRP3-, but not AIM2-nor NLRC4- inflammasome. During this process, viability of the fungus was required. Moreover, our in vivo results showed that during the pulmonary infection of cap59Δ, immune cell infiltration into the lung and effective clearance of the fungus were both dependent on the presence of NLRP3 inflammasome. In summary, our data suggest that the capsule of C. neoformans prevents recognition of the fungus by host NLRP3 inflammasome and indicate that manipulation of inflammasome activity maybe a novel approach to control C. neoformans infection. 相似文献