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141.
Summary The blood supply of duck muscle spindles from the extensor pollicis and the extensor digitorum comminis wing muscles has been studied by light and electron microscopy. Capillaries usually accompany the nerve bundle that innervates the spindle, approaching at an oblique angle around the midequatorial region. Capillaries may run for some distance along the surface of the outer capsule, or penetrate partially into the outer capsule and lie between layers of the capsule cell processes. Some capillaries also penetrate the outer capsule, running into the periaxial space and continuing further towards the polar region. They have been shown to be in close contact with intrafusal muscle fibres, from the juxta-equatorial to the polar region, but have not been encountered among sensory terminals in the mid-equatorial region. 相似文献
142.
Abstract We investigated the expression of important Actinobacillus pleuropneumoniae surface polysaccharides, namely, capsular polysaccharides (CPS) and lipopolysaccharides (LPS), after growth under iron-restricted conditions. Iron restriction did not seem to affect the production of CPS, as determined by labelling with a monoclonal antibody (mAb) against the serotype l K-antigen and flow cytometry analysis, and also as determined by electron microscopy. SDS-PAGE revealed that the LPS profiles of these cells were also unaffected by iron restriction. Using flow cytometry analysis, however, we observed that binding of mAb against serotype 1 O-antigen was altered in cells of A. pleuropneumoniae serotype l reference strain (4074) grown under iron-restricted conditions. This strain exhibited two subpopulations with distinct patterns of reactivity with the mAb against the O-antigen. When strain 4074 was grown under iron-restricted conditions, a shift from one cell subpopulation (moderately fluorescent) to another cell subpopulation (highly fluorescent, thus binding more antibodies) was observed. Our results indicate that growth of A. pleuropneumoniae serotype l under iron-restricted conditions did not seem to affect CPS production, but might alter, at least for the reference strain, the expression of LPS. 相似文献
143.
Chlorobium limicola UdG 6038, a green sulfur bacterium, was isolated from anoxic sediments. Cells were gram-negative, non-motile, ovoid shaped,
and contained chlorobactene and bacteriochlorophyll c as the main photosynthetic pigments. The DNA G+C content was 56.4 mol%. Ultrastructural studies revealed the presence of
abundant spinae (45–110 spinae per cell) attached to the cell wall. India-ink-stained cells observed under the optical microscope
were surrounded by a large capsule (5–11 μm total diameter). The presence of this capsule was coincident with the presence
of a large number of spinae (> 30 spinae per cell). The mucilaginous capsule was attached to the spinae without penetrating
it. In batch culture, the synthesis of spinae in strain UdG 6038 was not affected by changes in temperature, pH, salt concentration,
or illumination at physiological ranges and hence, the cells remained spined. The control of spinae production was experimentally
confirmed using a semicontinuous batch culture refed by sulfide pulsing. The culture remained at a low spination level (>
30 spinae per cell) only when the duration of sulfide starvation between pulses was less than 5 h. After longer sulfide starvation
periods, the cells remained spined (more than 38 ± 6.3 spinae per cell). This observation supports the idea that the duration
of sulfide limitation in the culture plays a key role in controlling the spination process in strain C. limicola UdG 6038. Chlorobium spinae may play an eco-physiological role in buoyancy capacity and adhesion of sulfur globules to the cells in natural environments
where sulfide concentrations are expected to be highly variable.
Revision received: 13 November 1995 / Accepted: 19 January 1996 相似文献
144.
A capsule and slime were visualized electronmicroscopically in Rhodopseudomonas capsulata strain St. Louis (=ATCC 23782) and strain Sp 11 after pre-incubation of the cells in the homologous O/K antisera. The slime consists of loosely associated material surrounding the cell in irregular distribution. The capsule is directly adjacent to the cell wall and has a constant thickness of 75–85 nm in strain St. Louis and 30–40 nm in strain Sp 11. The capsule has a fibrillar fine-structure with radial orientation to the cell surface. In contrast to the slime, it is not removed from the cells by washing with saline.An acidic polysaccharide fraction was obtained from both strains by cetavlon fractionation of hot phenol-water extracts. The composition is strain-specific: the relative amounts of the common sugars found, i.e. rhamnose, galactose, glucose, glucosamine and galacturonic acid are different, the fraction from strain Sp 11 contains additionally fucose, 3-amino-3,6-dideoxygalactose, an unknown amino sugar and an unknown acidic component. Whether the polysaccharides of these fractions are in fact the slime or capsular substances remains to be established. 相似文献
145.
Mark W. Platt Joseph Scaletti Norberto CorreaJr. 《FEMS immunology and medical microbiology》1994,9(3):245-251
Abstract A Group B Streptococcus Type III (GBS) mutant which, when grown in Todd Hewitt broth (THB), does not produce any detectable capsule, produced a clearly visible polysaccharide capsule when grown in human serum. We isolated cytoplasmic membranes from GBS and separated the component membrane proteins by polyacrylamide gel electrophoresis. A significant change in membrane composition was found during growth in human serum. Several unique proteins were produced on serum growth and there was both up- and down-regulation of other proteins. We measured the intracellular levels of sialic acid for a variety of GBS serotype III isolates. Interestingly, while there was little difference between the intracellular sialic levels of most isolates, the sialic acid level of COH31-15 grown in THB was over 100% higher than that of any other isolate. When grown in serum this pool was reduced to a level similar to that in other strains. The concentration of bacterial cell sialic acid was directly correlated with the sialic acid content of the serum. Exogenous sialic acid content, in concert with other serum factors, plays a role in determining the capsular size in GBS. 相似文献
146.
Background: The current study presents a fully planar wireless power transfer (WPT) scheme with the aim of providing enough power for capsule endoscopy performance. The method’s implementation on patients is more convenient than that of the previous conventional WPT plans in which a cylindrical wire coil is placed around the patient’s body. In addition to this, while using the present printed power receiver structure, the capsule’s internal space of opens up for other components such as the image sensors and data transmitting components. To improve the efficiency, a two-layer printed coil has been used as the transmitter, a two-layer printed coil as the receiver and a power coil on the transmitter side excited at 13.56 MHz.Results: Applying this method, the efficiency has increased to more than 2% for the proposed structure. Moreover, the effect of the body tissue on power efficiency has been simulated and measured and the maximum specific absorption rate (SAR) value considered for the desired system. Conclusions: The obtained results indicate that the proposed system meets the medical standards requirements. 相似文献
147.
B. E. Brooker 《Archives of microbiology》1976,111(1-2):99-104
When Leuconostoc mesenteroides NCDO 523 was grown in MRS browth, electron microscopy of cells fixed in the presence of ruthenium red showed that the cell wall was covered with a thin layer of filamentous material. When MRS-grown cells were resuspended in the same medium supplemented with 3.6% sucrose, this surface coat doubled in thickness and a number of radial thickenings appeared within it. After 3 h the filamentous component of the surface coat had disappeared leaving only the radial projections. The progressive accumulation of polymer to produce a capsule visible by light microscopy was observed in only about 20% of the population. In this minority of cells, a dense globular dextran composed of fibrillar and particulate elements was always produced in the initial stages of synthesis. After 18 h, the dextran capsule was generally composed of an inner globular and outer fibrillar layer. It appeared that the outer layer was derived from the globular dextran of the capsule by a process of dispersion. 相似文献
148.
Crowding effects of larvae on survival and development were examined for the broad-horned flour beetle, Gnathocerus cornutus (F.). The larvae matured about 3 weeks after hatching regardless of their densities, but pupation was severely hindered by crowding. There existed an upper limit for the number of the pupae produced and its mechanism was studied by a statistical analysis of the distribution patterns of pupal cells and the experiment in which glass tubes were artificially supplied in addition as pupation site. These studies show that G. cornutus larvae have a habit to construct cells for pupation and this habit leads to a contest competition for pupation site at high densities. The significance of the contest competition for population regulation was discussed comparing the results on Tribolium confusumJacqueline duVal . 相似文献
149.
Fine surface structure of enterotoxemic Escherichia coli O139:K12 strains associated with swine edema disease 总被引:1,自引:0,他引:1
The fine structure of the cell surface of seven enterotoxemic Escherichia coli (ETEEC) O139:K12 strains isolated from piglets with edema disease were examined electron microscopically using both the negative-staining
method and the freeze-substitution fixation method. Densely packed, fine fibers were observed; they consisted of a capsule
layer approximately 25 nm thick around the cell surfaces of strains 107/86, IW-2, ED-3, ED-43, and ED-61, all of which have
a capacity to adhere strongly to HEp-2 cells. In contrast, no such structure was observed on the surface of strains RK-O139
or ED-1, both of which adhere only weakly to HEp-2 cells. These results suggest that the capsule structure might be associated
with the ability to adhere to HEp-2 cells and, as a result, also potentially play some role in ETEEC infection.
Received: 29 April 1996 / Accepted: 13 August 1996 相似文献