Busulphan is active against neuroblastoma and medulloblastoma xenografts in athymic mice at clinically achievable plasma drug concentrations.
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High-dose busulphan-containing chemotherapy regimens have shown high response rates in children with relapsed or refractory neuroblastoma, Ewing's sarcoma and medulloblastoma. However, the anti-tumour activity of busulfan as a single agent remains to be defined, and this was evaluated in athymic mice bearing advanced stage subcutaneous paediatric solid tumour xenografts. Because busulphan is highly insoluble in water, the use of several vehicles for enteral and parenteral administration was first investigated in terms of pharmacokinetics and toxicity. The highest bioavailability was obtained with busulphan in DMSO administered i.p. When busulphan was suspended in carboxymethylcellulose and given orally or i.p., the bioavailability was poor. Then, in the therapeutic experiments, busulphan in DMSO was administered i.p. on days 0 and 4. At the maximum tolerated total dose (50 mg kg(-1)), busulphan induced a significant tumour growth delay, ranging from 12 to 34 days in the three neuroblastomas evaluated and in one out of three medulloblastomas. At a dose level above the maximum tolerated dose, busulphan induced complete and partial tumour regressions. Busulphan was inactive in a peripheral primitive neuroectodermal tumour (PNET) xenograft. When busulphan pharmacokinetics in mice and humans were considered, the estimated systemic exposure at the therapeutically active dose in mice (113 microg h ml(-1)) was close to the mean total systemic exposure in children receiving high-dose busulphan (102.4 microg h ml(-1)). In conclusion, busulphan displayed a significant anti-tumour activity in neuroblastoma and medulloblastoma xenografts at plasma drug concentrations which can be achieved clinically in children receiving high-dose busulphan-containing regimens. (+info)
The evaluation of hypersensitivity tests in cattle after foot-and-mouth disease vaccination.
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The response to passive cutaneous anaphylaxis, dermal hypersensitivity and intravenous provocation tests has been compared in 30, 40, 31 and 24 cattle injected with foot-and-mouth disease vaccine 0, 1, 2 and 3 times respectively, using vaccine components and other substances as test materials. Reaginic antibodies demonstrated by passive cutaneous anaphylaxis in goats, were directed against BHK 21 cell extracts (20), hydroxypropylmethylcellulose (3) and an unidentified vaccine component (3), and distributed in 0, 5, 19 and 75 per cent of the cattle vaccinated 0, 1, 2 and 3 times. None of the animals showed clinical signs of allergy after vaccination. When BHK 21 cell extract was injected intradermally a significant correlation was noted between the development of large weals and the presence of reagins although the size of the weals was not correlated with the reagin titres. In the case of hydroxypropylmethylcellulose a similar trend was evident. The majority of cattle with large dermal weals possessed reagins but the number of reactions was too small for statistical evaluation. Dermal reactions to sodium penicillin, sodium carboxymethylcellulose, saponin and whole vaccine occurred in both unvaccinated and vaccinated cattle but BHK 21 cell lysate and normal bovine serum provoked weals which increased in frequency according to the number of vaccinations experienced. Intravenous hydroxypropylmethylcellulose elicited a response in all the animals previously injected with certain batches of vaccine but cell extract intravenously produced a clinical response in half the tested animals which was uncorrelated with the results of the passive cutaneous anaphylaxis or dermal hypersensitivity tests. (+info)
Identification of a ribosomal protein essential for peptidyl transferase activity.
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Extraction with 2 M lithium chloride removes a group of proteins (LiC1 SP) from 50S ribosomal subunits. Both the LiC1 SP and the resulting cores, which contain the remaining proteins as well as 5S and 23S RNA, lack peptidyl transferase activity, as measured by the "fragment reaction". Activity can be restored to the LiC1 cores by reconstitution with LiC1 SP under conditions of high temperature and high ionic strength. The LiC1 SP proteins were fractionated by carboxymethyl-cellulose and Sephadex G-100, and the individual fractions were tested by this reconstitution system. Of the 18 ribosomal proteins found in the LiC1 SP, only L16 is essential for reconstitution of peptidyl transferase activity. (+info)
Bacterial cell surface display of an enzyme library for selective screening of improved cellulase variants.
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The bacterial surface display method was used to selectively screen for improved variants of carboxymethyl cellulase (CMCase). A library of mutated CMCase genes generated by DNA shuffling was fused to the ice nucleation protein (Inp) gene so that the resulting fusion proteins would be displayed on the bacterial cell surface. Some cells displaying mutant proteins grew more rapidly on carboxymethyl cellulose plates than controls, forming heterogeneous colonies. In contrast, cells displaying the nonmutated parent CMCase formed uniform tiny colonies. These variations in growth rate were assumed to result from altered availability of glucose caused by differences in the activity of variant CMCases at the cell surface. Staining assays indicate that large, rapidly growing colonies have increased CMCase activity. Increased CMCase activity was confirmed by assaying the specific activities of cell extracts after the expression of unfused forms of the variant genes in the cytoplasm. The best-evolved CMCases showed about a 5- and 2.2-fold increase in activity in the fused and free forms, respectively. Sequencing of nine evolved CMCase variant genes showed that most amino acid substitutions occurred within the catalytic domain of the enzyme. These results demonstrate that the bacterial surface display of enzyme libraries provides a direct way to correlate evolved enzyme activity with cell growth rates. This technique will provide a useful technology platform for directed evolution and high-throughput screening of industrial enzymes, including hydrolases. (+info)
Extracellular glycanases of Rhizobium leguminosarum are activated on the cell surface by an exopolysaccharide-related component.
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Rhizobium leguminosarum secretes two extracellular glycanases, PlyA and PlyB, that can degrade exopolysaccharide (EPS) and carboxymethyl cellulose (CMC), which is used as a model substrate of plant cell wall cellulose polymers. When grown on agar medium, CMC degradation occurred only directly below colonies of R. leguminosarum, suggesting that the enzymes remain attached to the bacteria. Unexpectedly, when a PlyA-PlyB-secreting colony was grown in close proximity to mutants unable to produce or secrete PlyA and PlyB, CMC degradation occurred below that part of the mutant colonies closest to the wild type. There was no CMC degradation in the region between the colonies. By growing PlyB-secreting colonies on a lawn of CMC-nondegrading mutants, we could observe a halo of CMC degradation around the colony. Using various mutant strains, we demonstrate that PlyB diffuses beyond the edge of the colony but does not degrade CMC unless it is in contact with the appropriate colony surface. PlyA appears to remain attached to the cells since no such diffusion of PlyA activity was observed. EPS defective mutants could secrete both PlyA and PlyB, but these enzymes were inactive unless they came into contact with an EPS(+) strain, indicating that EPS is required for activation of PlyA and PlyB. However, we were unable to activate CMC degradation with a crude EPS fraction, indicating that activation of CMC degradation may require an intermediate in EPS biosynthesis. Transfer of PlyB to Agrobacterium tumefaciens enabled it to degrade CMC, but this was only observed if it was grown on a lawn of R. leguminosarum. This indicates that the surface of A. tumefaciens is inappropriate to activate CMC degradation by PlyB. Analysis of CMC degradation by other rhizobia suggests that activation of secreted glycanases by surface components may occur in other species. (+info)
Some general methods of preparing affinity columns.
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Some general methods of covalent coupling of nucleotides, especially derivatized nucleotides, polynucleotides and cofactors to insoluble polymers are described in this paper. Wherever necessary individual methods also carry some information on the binding of enzymes to the same polymers to serve as a guide to the efficiency of the coupling methods. (+info)
Biochemical characterization of MI-ENG1, a family 5 endoglucanase secreted by the root-knot nematode Meloidogyne incognita.
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A beta-1,4-endoglucanase named MI-ENG1, homologous to the family 5 glycoside hydrolases, was previously isolated from the plant parasitic root-knot nematode Meloidogyne incognita. We describe here the detection of the enzyme in the nematode homogenate and secretion and its complete biochemical characterization. This study is the first comparison of the enzymatic properties of an animal glycoside hydrolase with plant and microbial enzymes. MI-ENG1 shares many enzymatic properties with known endoglucanases from plants, free-living or rumen-associated microorganisms and phytopathogens. In spite of the presence of a cellulose-binding domain at the C-terminus, the ability of MI-ENG1 to bind cellulose could not be demonstrated, whatever the experimental conditions used. The biochemical characterization of the enzyme is a first step towards the understanding of the molecular events taking place during the plant-nematode interaction. (+info)
Cloning and sequencing of cel5Z gene from Erwinia chrysanthemi PY35.
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The phytopathogenic bacterium Erwinia chrysanthemi (Ech) secretes multiple isozymes of plant cell wall disrupting enzymes such as pectate lyase and endoglucanases. We cloned genomic DNA from Ech PY35 digested with Sau3AI and ligated into pBluescript II SK+. One of the E. coli XL1-blue clones had the ability to hydrolyze carboxymethyl cellulose and polygalacturonic acid. By subsequent subcloning from this 2.9 kb fragment, we obtained a 2.0 kb (pPY401), designated cel5Z, which had the activity of hydrolyzation of carboxymethyl cellulose. The cel5Z gene had an open reading frame (ORF) of 1,281 bp starting with an ATG start codon and followed by a TAA stop codon, encoding 426 amino acids with a signal peptide of 41 amino acids. Since the deduced amino acid sequence of this protein was very similar to that of CelE of Pseudomonas fluorescens, and had the conserved region, VIYEIYNEPL, it belonged to the glycoside hydrolase family 5 of EC 3.2.1.4. The molecular mass of Cel5Z protein from E. coli XL1-blue, as analyzed by CMC-SDS-PAGE, appeared to be 42 kDa. The optimum pH was 6, and the optimum temperature was about 40 degrees C for its enzymatic activity. (+info)