Traditionally, cartilage is stained by alcian blue using acidic conditions to differentiate tissue staining. The acidic conditions are problematic when one wishes to stain the same specimen for mineralized bone with alizarin red, because acid demineralizes bone, which negatively affects bone staining. We have developed an acid-free method to stain cartilage and bone simultaneously in zebrafish larvae. This method has the additional advantage that PCR genotyping of stained specimens is possible.

A two-color acid-free cartilage and bone stain for zebrafish larvae.

The slime polysaccharides produced by Pseudomonas aeruginosa isolated from a variety of human infections were investigated. Slime production in culture seemed optimal when adequate amounts of carbohydrate were present and under conditions of either high osmotic pressure or inadequate protein supply. The polysaccharides produced by the organisms were similar to each other, to the slime of Azotobacter vinelandii, and to seaweed alginic acids. They were composed of beta-1,4-linked d-mannuronic acid residues and variable amounts of its 5-epimer l-guluronic acid. All bacterial polymers contained o-acetyl groups which are absent in the alginates. The polysaccharides differed considerably in the ratio of mannuronic to guluronic acid content and in the number of o-acetyl groups. The particular composition of the slime was not found to be characteristic for the disease process from which the mucoid variants of P. aeruginosa were obtained.

Production and Characterization of the Slime Polysaccharide of Pseudomonas aeruginosa

Bovine articular chondrocytes cultured in agarose gel comprise a heterogeneous population when judged by morphological and histochemical criteria. The purpose of the present experiments was to compare, under the same conditions of culture, sub-populations of chondrocytes derived from different depths of articular cartilage. Sub-populations of chondrocytes were cultured separately following their isolation from slices of articular cartilage cut from successive depths of the tissue. Chondrocytes derived from superficial and deep zones differed significantly in morphology, rate of proliferation, and activity in secreting a proteoglycan-rich extracellular matrix. The differences are sufficient to account for the heterogeneity observed in cultures of the entire cell population, and the correlate well with known variations with depth in morphology and histochemistry of intact articular cartilage. These results demonstrate that articular chondrocytes continue in culture to express metabolic differences which reflect their original anatomical location; such differences may have important functional significance.

Differences between sub-populations of cultured bovine articular chondrocytes. I. Morphology and cartilage matrix production

Synthesis and turnover of proteoglycans by human and bovine adult articular chondrocytes cultured in alginate beads.

Dentin Sialophosphoprotein Knockout Mouse Teeth Display Widened Predentin Zone and Develop Defective Dentin Mineralization Similar to Human Dentinogenesis Imperfecta Type III

The application of the “critical electrolyte concentration” (CEC) concept to the differentiation of acidic glycosaminglycans (mucopolysaccharides) is described. Alcian Blue 8GX stains with increasing selectivity as increasing amounts of magnesium chloride are incorporated into the dye solution. Model experiments with pure polyanions, or artifically carboxylated, phosphorylated and sulphated liver sections, showed that binding of dye to carboxylate or phosphate groups ceased at low electrolyte concentrations (< 0.3M) whereas dye continued to be held by sulphate ester groups at concentrations five to ten times as high. The similarity to the well established cetylpyridinium system for polyanion fractionation is discussed. Sections of tissues chosen to contain predominantly or characteristically carboxylated mucins, and/or sulphate ester polyanions showed a staining pattern entirely similar to the model sections. Goblet cell mucin in rat ileum stained at < 0.4M MgCl2, Cartilage at < 0.6M MgCl2, mast cells at < 0.75M, and corneal stroma at < 1.0M. These results are in agreement with the known contents of sialo-mucin, chondroitin sulphate, heparin and keratansulphate, respectively. The conditions in which this principle can be used in a practical technique are described.

Differential staining of acid glycosaminoglycans (mucopolysaccharides) by Alcian blue in salt solutions

1.

A two-step PAS method for acid mucopolysaccharides containing 1∶4 linked uronio acid (e.g. chondroitin sulphate) is described. A primary oxidation with sodium periodate oxidises rapidly reacting substrates. The aldehydes are reduced with aqueous sodium borohydride to Schiff-negative materials. A secondary, longer, oxidation step produces aldehyde from the slowly reacting acid mucopolysaccharides, which are demonstrated with Schiff.




2.

The distribution of stain in the two-step PAS method in rabbit liver, human lung and nasal septal cartilage is as predicted from model experiments.




3.

This, the first chemical method for localising acid mucopolysaccharides, is compared with “critical electrolyte concentration” techniques using Alcian blue for the same purposes. Preliminary data presented here show that both sets of results are compatible.

Periodate oxidation of acid polysaccharides

During peptidoglycan recycling (PR) bacteria can recover extracellular fragments of peptidoglycan (PGN) liberated by peptidoglycan turnover (PT) during cell growth and division, and reuse them in cell wall biosynthesis or central carbon metabolism. In Gram-negative bacteria, PR has been well studied, and functions in the induction of resistance to certain classes of antibiotics, and in host-pathogen interaction. However, while Gram-negative cell envelope architecture allows for highly efficient PR, Gram-positive bacteria, which lack an outer cell membrane and are instead enclosed by a glycopolymer layer, can shed large quantities of PGN-derived material to the external environment during growth. Nonetheless, the occurrence of PR was recently demonstrated in several Gram-positive bacteria, including the Gram-positive bacterial pathogen Staphylococcus aureus, and its potential adaptive functions are largely unexplored. Given the known roles of PR in Gram-negative bacteria, and that Gram-positive bacteria include several important human pathogens, we asked what role PR may play during Gram-positive pathogen-host interaction. Using the model insect host Drosophila melanogaster, we demonstrate that S. aureus mutants impaired in extracellular PGN hydrolysis (Δatl) and PGN fragment uptake (ΔmurP) show differential virulence compared to their wild-type counterpart. This was linked to increased activation of the D. melanogaster Toll-cascade by spent supernatant from the Δatl mutant. Thus, we propose that S. aureus, and potentially other Gram-positive bacteria, may use extracellular PGN degradation during PT to simultaneously process PGN fragments for recycling and for immune evasion, while recovery and metabolism of peptidoglycan fragments during PR may play more subtle roles in determining virulence. Author summary PGN is a key component of the bacterial cell wall, forming a stress-bearing sacculus surrounding the cell and providing cell shape. During growth and division, the sacculus is dynamically degraded and remodelled to ensure daughter cell separation, resulting in PT. PGN fragments released during PT can be recovered and reutilised by the cell during PR. In Gram-negative pathogens, PR is linked to antibiotic resistance, virulence and modulation of host immune recognition. In Gram-positive bacteria, PR was only recently observed. Here, we explore the roles of PT and PR in host-pathogen interaction in S. aureus, a Gram-positive pathogen of significant clinical relevance. Disruption of PT in S. aureus affected host-pathogen interaction through altering host recognition of shed PGN fragments and PR through modulation of PGN fragment recovery. This improves our understanding of the biology of this important pathogen and may aid development of novel therapeutic approaches to treat S. aureus infections.

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J. Dorling

Papers

Differential staining of acid glycosaminoglycans (mucopolysaccharides) by Alcian blue in salt solutions

Periodate oxidation of acid polysaccharides

Analysis of the influence of peptidoglycan turnover and recycling on host-pathogen interaction in the Gram-positive pathogen Staphylococcus aureus