Mechanical and biochemical characterization of cartilage explants in serum-free culture

Allografts of articular cartilage are both used clinically for tissue-transplantation procedures and experimentally as model systems to study the physiological behavior of chondrocytes in their native extracellular matrix. Long-term maintenance of allograft tissue is challenging. Chemical mediators in poorly defined culture media can stimulate cells to quickly degrade their surrounding extracellular matrix. This is particularly true of juvenile cartilage which is generally more responsive to chemical stimuli than mature tissue. By carefully modulating the culture media, however, it may be possible to preserve allograft tissue over the long-term while maintaining its original mechanical and biochemical properties. In this study juvenile bovine cartilage explants (both chondral and osteochondral) were cultured in both chemically defined medium and serum-supplemented medium for up to 6 weeks. The mechanical properties and biochemical content of explants cultured in chemically defined medium were enhanced after 2 weeks in culture and thereafter remained stable with no loss of cell viability. In contrast, the mechanical properties of explants in serum-supplemented medium were degraded by ( approximately 70%) along with a concurrent loss of biochemical content (30-40% GAG). These results suggest that long-term maintenance of allografts can be extended significantly by the use of a chemically defined medium.     

Isolation of elastin from bovine auricular cartilage.

Clostridium histolyticum collagenase (clostridiopeptidase A, EC 3.4.24.3), purified by affinity chromatography, was applied to the isolation of insoluble elastin from bovine auricular cartilage. The low level of N-terminal residues (2.8 mol per 10⁶g of protein) present in this preparation indicated the almost complete lack of hydrolytic damage caused by the isolation procedure. The amino acid composition of the preparation showed an overall two-fold increase in polar residues, and a 20% reduction in valine, when compared to those of aortic and ligamentum nuchae elastin, while the concentration of cross-links was almost identical in the three preparations. Analysis of peptides, isolated by gel-exclusion chromatography after digestion of auricular elastin with elastase (pancreatopeptidase E, EC 3.4.21.11) in the presence of sodium dodecyl sulfate, revealed elevated levels of polar residues in all fractions examined, with no correlation between the concentration of these amino acids and that of the lysine-derived cross-links. Comparison of auricular and ligamentum nuchae elastin by fingerprint analysis of their elastase digests also suggested that the two proteins were compositionally distinct. Finally, treatment of auricular elastin with either trypsin or chymotrypsin produced no significant reduction in the level of polar residues. It is concluded that elastin exhibits tissue-related compositional variability.     

The zebrafish erythropoietin: functional identification and biochemical characterization

In the present study, the zebrafish epo cDNA was cloned. The encoded protein displays 90%, 55% and 32% identity to the Epo from carp, fugu and human, respectively. Through RT-PCR, the expression of zepo mRNA was mainly in the heart and liver. In the COS-1 cell transfection experiments, the recombinant zEpo-HA protein was efficiently secreted into the culture medium as a glycoprotein and the carbohydrate moiety can be cleaved by the treatment of peptide-N-glycosidase F (PNGase F). Using the morpholino approach, we showed that zepo morphants displayed severe anemia leading to high mortality during development. Such an effect can be significantly rescued by zepo RNA. Furthermore, in the absence of functional zEpo, the expression of specific markers for adult globin genes, such as alphaA1- and betaA1-globin, but not the embryonic betae1-globin, was affected.     

Uronema marinum: identification and biochemical characterization of phosphatidylcholine-hydrolyzing phospholipase C

Phosphatidylcholine (PC)-specific phospholipase D (PC-PLD) and phosphatidylcholine (PC)-specific phospholipase C (PC-PLC) activities have been detected in Uronema marinum. Partial purification of PC-PLC revealed that two distinct forms of PC-PLC (named as mPC-PLC and cPC-PLC) were existed in membrane and cytosol fractions. The two PC-PLC enzymes showed the preferential hydrolyzing activity for PC with specific activity of 50.4 for mPC-PLC and 28.3 pmol/min/mg for cPC-PLC, but did not hydrolyze phosphatidylinositol or phosphatidylethanolamine. However, the biochemical characteristics and physiological roles of both enzymes were somewhat different. mPC-PLC had a pH optimum in the acidic region at around, pH 6.0, and required approximately 0.4 mM Ca2+ and 2.5 mM Mg2+ for maximal activity. cPC-PLC had a pH optimum in the neutral region at around, pH 7.0, and required 1.6 mM Ca2+ and 2.5 mM Mg2+ for maximal activity. cPC-PLC, but not mPC-PLC, showed a dose-dependent inhibitory effect on the luminal-enhanced chemiluminescence (CL) responses and the viability of zymosan-stimulated phagocytes of olive flounder, indicating that cPC-PLC may contribute to the parasite evasion against the host immune response. Our results suggest that U. marinum contains PC-PLD as well as two enzymatically distinct PC-PLC enzymes, and that mPC-PLC may play a role in the intercellular multiplication of U. marinum and cPC-PLC acts as a virulence factor, serving to actively disrupt the host defense mechanisms.     

In silico identification and biochemical characterization of novel inhibitors of NQO1

From in silico docking and COMPARE analysis, novel inhibitors of human NAD(P)H quinone oxidoreductase (NQO1) have been identified from the NCI compound database, the most potent of which has an observed IC₅₀ of 0.7 μM. The inhibitors exhibit a diverse range of scaffolds. The ability of docking calculations to predict experimentally determined binding affinities for NQO1 is discussed, considering the influence of target flexibility and scoring function.     

D-Ala5 analog of the elastin polypentapeptide. Physical characterization

The D-Ala5 analog, (L-Val1-L X Pro2-Gly3-L X Val4-D-Ala5) of the polypentapeptide (PPP) of elastin is synthesized and characterized by a series of physical methods. Carbon-13 and proton nuclear magnetic resonance spectroscopies are used to verify purity and, by means of solvent dependence of peptide C-O chemical shift and of temperature dependence of peptide NH chemical shift, to establish by comparison with the PPP of elastin the presence and increased stability of the Type II Pro2-Gly3 beta-turn. The temperature dependence of aggregation in water to form a viscoelastic phase called the coacervate is reported for several concentrations. Comparison of carbon-13 nuclear magnetic resonance spectra obtained under identical conditions for the coacervate states of the PPP of elastin and the D-Ala5 analog shows the effect of replacing the Gly5 residue by a D-Ala5 residue to be one of greatly restricting mobility of the polypeptide chain. Scanning electron micrographs, of the coacervate alone and of the coacervate cross-linked and compounded to a Dacron fabric before and after stress-strain studies, are reported which show the D-Ala5 PPP matrix to rupture during the stresses of drying and of stretching while wet. Thus, the effect of adding a methyl moiety to the Gly5 residue of the PPP of elastin is to decrease markedly the mobility of the polypeptide chain and to destroy elasticity. The results are presented as a test of the proposed librational entropy mechanism of elasticity of the PPP of elastin.     

The biochemical content of articular cartilage: an original MRI approach

The MR aspect of articular cartilage, that reflects the interactions between protons and macromolecular constituents, is affected by the intrinsic tissue structure (water content, the content of matrix constituents, collagen network organization), imager characteristics, and acquisition parameters. On the T1-weighted sequences, the bovine articular cartilage appears as an homogeneous tissue in high signal intensity, whatever the age of animals considered, whereas on the T2-weighted sequences, the articular bovine cartilage presents variations of its imaging pattern (laminar appearance) well correlated to the variations of its histological and biochemical structure. The T2 relaxation time measurement (T2 mapping), which reflects quantitatively the signal intensity variations observed on T2 weighted sequences, is a way to evaluate more precisely the modifications of cartilage structure during the aging and maturation processes (rat's study). This technique so far confined to experimental micro-imagers is now developed on clinical imagers. Consequently, it may permit to depict the early stages of osteoarthritic disease (OA) or to evaluate the chondroprotective effect of drugs.     

Immunochemical and mechanical characterization of cartilage subtypes in rabbit.

Cartilage is categorized into three general subgroups, hyaline, elastic, and fibrocartilage, based primarily on morphologic criteria and secondarily on collagen (Types I and II) and elastin content. To more precisely define the different cartilage subtypes, rabbit cartilage isolated from joint, nose, auricle, epiglottis, and meniscus was characterized by immunohistochemical (IHC) localization of elastin and of collagen Types I, II, V, VI, and X, by biochemical analysis of total glycosaminoglycan (GAG) content, and by biomechanical indentation assay. Toluidine blue staining and safranin-O staining were used for morphological assessment of the cartilage subtypes. IHC staining of the cartilage samples showed a characteristic pattern of staining for the collagen antibodies that varied in both location and intensity. Auricular cartilage is discriminated from other subtypes by interterritorial elastin staining and no staining for Type VI collagen. Epiglottal cartilage is characterized by positive elastin staining and intense staining for Type VI collagen. The unique pattern for nasal cartilage is intense staining for Type V collagen and collagen X, whereas articular cartilage is negative for elastin (interterritorially) and only weakly positive for collagen Types V and VI. Meniscal cartilage shows the greatest intensity of staining for Type I collagen, weak staining for collagens V and VI, and no staining with antibody to collagen Type X. Matching cartilage samples were categorized by total GAG content, which showed increasing total GAG content from elastic cartilage (auricle, epiglottis) to fibrocartilage (meniscus) to hyaline cartilage (nose, knee joint). Analysis of aggregate modulus showed nasal and auricular cartilage to have the greatest stiffness, epiglottal and meniscal tissue the lowest, and articular cartilage intermediate. This study illustrates the differences and identifies unique characteristics of the different cartilage subtypes in rabbits. The results provide a baseline of data for generating and evaluating engineered repair cartilage tissue synthesized in vitro or for post-implantation analysis.     

Proteoglycans of guinea-pig coastal cartilage. Fractionation and characterization.

Proteoglycans were extracted, in a yield of about 90%, from costal cartilage of young, growing guinea-pigs. Three solvents were used in sequence: 0.4 M guanidine - HCl, pH 5.8, 4 M guanidine - HCl, pH 5.8, and 4 M guanidine - HCl/0.1 M EDTA, pH 5.8. The proteoglycans were purified and fractionated by cesium chloride density gradient ultracentrifugation under associative and dissociative conditions. Gel chromatography on Sepharose 2 B of proteoglycan fractions from associative centrifugations showed the presence of both aggregated and monomer proteoglycans. The ratio of aggregates to monomers was higher in the second extract than in the other two extracts. Dissociative gradient centrifugation gave a similar distribution for proteoglycans from all three extracts. Thus, with decreasing buoyant density there were decreasing ratios of polysaccharide to protein, and of chondroitin sulfate to keratan sulfate. In addition, there was with decreasing density an increasing ratio of chondroitin 4-sulfate to chondroitin 6-sulfate. Amino acid analyses of dissociative fractions were inaccordance with previously published results. On comparing proteoglycan monomers of the three extracts, significant differences were found. Proteoglycans, extracted at low ionic strength, contained lower proportions of protein, keratan sulfate, chondroitin 6-sulfate and basic amino acids than those of the second extract. The proteoglycans of the third extract also differed from those of the other extracts. The results indicate that the proteoglycans of guinea-pig costal cartilage exist as a very polydisperse and heterogenous population of molecules, exhibiting variations in aggregation capacity, molecular size, composition of protein core, degree of substitution of the protein core, as well as variability in the type of polysaccharides substituted.     

Lysozyme in preosseous cartilage VI. Purification, characterization and localization of mammalian cartilage lysozyme

Lysozyme (mucopeptide-N-acetylmuramylhydrolase, EC 3.2.1.17) is present in mammalian cartilage. Lysozyme was isolated and purified from bovine and canine cartilage and from dog serum using various chromatographic steps and affinity chromatography on carboxymethylated chitin. Amino acid analysis of bovine cartilage lysozyme showed that it is similar to other mammalian lysozymes. Anti-canine lysozyme antibodies cross-react with calf lysozyme, but not with hen egg white or embryonic chick cartilage lysozyme. In the epiphyseal plate of the dog, 90-μm sections were analyzed for lysozyme and its was found that in the hypertrophic zone its concentration is approximately six times higher than it is in the resting zone. Using immunocytochemical techniques at the electromicroscopic level, lysozyme in the epiphyseal plate of the dog was localized extracellularly, mainly in the immediate vicinity of the chondrocytes, the territorial matrix.     

Screening and identification of polyhydroxyalkanoates producing bacteria and biochemical characterization of their possible application

Polyhydroxyalkanoates (PHAs) accumulating bacteria were isolated under various selective conditions such as pH, salt concentrations and types of heavy metal. Fifty strains of bacterial isolates were found to belong to Bacillus, Proteus, Pseudomonas, Aeromonas, Alcaligenes and Chromobacterium, based on phenotypical features and genotypic investigation. Only twenty five bacterial isolates were selected and observed for the production of PHAs. Interestingly, bacteria belonging to Firmucutes Bacillus sp. produced a high amount of PHAs. The maximum PHAs were accumulated by B. licheniformis PHA 007 at 68.80% of dry cell weight (DCW). Pseudomonas sp., Aeromonas sp., Alcaligenes sp. and Chromobacterium sp. were recorded to produce a moderate amount of PHAs, varying from 10.00-44.32% of DCW. The enzymatic activity was preliminarily analyzed by the ratio of the clear zone diameter to colony diameter. Bacillus gave the highest ratio of hydrolysis zone which corresponds to the highest hydrolytic enzyme activities. Bacillus licheniformis PHA 007 had the highest lipase and protease activity at 2.1 and 5.1, respectively. However, the highest amylase activity was observed in Bacillus sp. PHA 023 at 1.4. Determination of metabolic characteristics was also investigated to check for their ability to consume a wide range of substrates. Bacillus, Aeromonas sp. and Alcaligenes sp. had great ability to utilize a variety of substrates. To decrease high PHA cost, different sources of cheap substrates were tested for the production of PHAs. Bacillus cereus PHA 008 gave the maximal yield of PHA production (64.09% of DCW) when cultivated in anaerobically treated POME. In addition, the accumulation of PHA copolymers such as 3-hydroxyvalerate and 3-hydroxyhexanoate was also observed in Bacillus and Pseudomomas sp. strain 012 and 045, respectively. Eight of the nine isolates accumulated a significant amount of PHAs when inexpensive carbon sources were used as substrates. Here it varied from 1.69% of DCW by B. licheniformis PHA 007 to 64.09% of DCW by B. cereus PHA 008.     

Nutritional and biochemical characterization of Methanospirillum hungatii.

To ascertain its physiological similarity to other methanogenic bacteria, Methanospirillum hungatii, the type species of the genus, was characterized nutritionally and biochemically. Good growth occurred in a medium consisting of mineral salts, cysteine sulfide reducing buffer, and an H2-CO2 (80:20) atmosphere. Addition of amino acids and B vitamins stimulated growth. Cell-free extracts contained methylcobalamin-coenzyme M methyltransferase, methylreductase, and formate hydrogenlyase. Cells contained coenzyme M and coenzyme F420. Coenzyme F420 was required for formate hydrogenlyase activity. Coenzyme F420 purified from M. hungatii had identical properties to that purified from species of Methanobacterium. The physiological basis of the family Methanobacteriaceae is strengthened by these findings.     

Nutritional and biochemical characterization of Methanospirillum hungatii.

To ascertain its physiological similarity to other methanogenic bacteria, Methanospirillum hungatii, the type species of the genus, was characterized nutritionally and biochemically. Good growth occurred in a medium consisting of mineral salts, cysteine sulfide reducing buffer, and an H2-CO2 (80:20) atmosphere. Addition of amino acids and B vitamins stimulated growth. Cell-free extracts contained methylcobalamin-coenzyme M methyltransferase, methylreductase, and formate hydrogenlyase. Cells contained coenzyme M and coenzyme F420. Coenzyme F420 was required for formate hydrogenlyase activity. Coenzyme F420 purified from M. hungatii had identical properties to that purified from species of Methanobacterium. The physiological basis of the family Methanobacteriaceae is strengthened by these findings.     

Purification and biochemical characterization of an endoxylanase from Aspergillus versicolor

An endoxylanase (β-1,4-xylan xylanohydrolase, EC 3.2.1.8) was purified from the culture filtrate of a strain of Aspergillus versicolor grown on oat wheat. The enzyme was purified to homogeneity by chromatography on DEAE-cellulose and Sephadex G-75. The purified enzyme was a monomer of molecular mass estimated to be 19 kDa by SDS-PAGE and gel filtration. The enzyme was glycoprotein with 71% carbohydrate content and exhibited a pI of 5.4. The purified xylanase was specific for xylan hydrolysis. The enzyme had a K _m of 6.5 mg ml⁻¹ and a V _max of 1440 U (mg protein)⁻¹.     

Purification and biochemical characterization of an 11 000-dalton beta-bungarotoxin

The chromatographic separation and biochemical characterization of a beta-bungarotoxin is described. This toxin is isolated as the most basic eluting protein of Bungarus multicinctus venom when separated by column chromatography on CM-Sephadex C-25. The protein migrated as a single band on pH 4.3 and sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. The molecular weight of this toxin was estimated to be 10 000 +/- 1000 by analytical sedimentation analysis. This value was consistent with the electrophoretic mobility of the toxin in SDS-polyacrylamide gels. The amino acid composition of this 11 000-dalton beta-bungarotoxin was similar to that of the 22 000-dalton beta-bungarotoxin previously reported (Lee et al. (1972) J. Chromatogr. 72, 71--82; Kelly, R.B. and Brown, III, F.R. (1974) J. Neurobiol. 5, 135--150; Kondo et al. (1978) J. Biochem. Tokyo 83, 91--99), suggesting that the 11 000-dalton toxin may be one of the polypeptide chains of the larger toxin. The 11 000-dalton beta-bungarotoxin was toxic to mice when injected intravenously. Animals that received lethal doses exhibited hyperexcitability followed by ataxia, convulsions, and death. The minimum lethal dose was 0.12 microgram/g body weight. This beta-bungarotoxin exhibited Ca2+-dependent phospholipase A activity comparable to that of the 22 000-dalton beta-bungarotoxin. The enzyme exhibited phospholipid substrate specificity in the rank order of phosphatidyl-choline, phosphatidylserine, phosphatidylethanolamine, and phosphatidyl-inositol. The enzyme activity was destroyed by boiling for 3 min at pH 8.6. In addition, an enzymatically inactive quantity of the 11 000-dalton toxin, equivalent to five times the minimum lethal dose of enzymatically active toxin, was not lethal when injected into mice. To test whether phospholipase A activity is responsible for lethality, bee venom phospholipase A2 was injected into mice at similar and greater concentrations with no toxic effect. Thus, while phospholipase A activity may be required for the lethal effect of the 11 000-dalton beta-bungarotoxin, the specificity of action of the toxin is not determined by its enzyme activity.     

Purification and characterization of an acid metalloproteinase from human articular cartilage

A metalloprotease that digests cartilage proteoglycan optimally at pH 5.3 has been purified (4400-fold) to homogeneity from 20-g samples of human articular cartilage containing about 100 micrograms of enzyme. This enzyme was cleanly separated from a related neutral metalloprotease with an optimum pH of 7.2. The acid metalloprotease displays 40% of its maximum activity at pH 7.2 and so has significant activity at physiological pH. The protease is calcium-dependent and indirect evidence suggests that it may contain zinc at its active center. It occurs largely in a latent form that can be activated by aminophenylmercuric acetate. The apparent Mr of the latent form is 55,000 and of the active form, 35,000. The isoelectric point is at pH 4.9. The protease activity is inhibited by chelators, Z-phenylalanine, ovostatin, and tissue inhibitor of metalloproteinase from human articular cartilage. It differs from metalloproteinases such as enkephalinase and kidney brush-border protease in its failure to be strongly inhibited by phosphoramidon and Zincov. It cleaves the proteoglycan monomer of bovine nasal cartilage to fragments of approximately 140,000 Da. It cleaves the B chain of insulin at Ala14-Leu15 and Tyr16-Leu17. A survey of 26 cartilage extracts indicates this enzyme is elevated to about 3 times the normal level in human osteoarthritic cartilage and that the tissue inhibitor of metalloproteinase is only slightly diminished. Preliminary evidence points to the presence of a similar acid metalloprotease activity in human polymorphonuclear leukocytes.