ABSTRACT
Objective To obtain antibiotic-resistant mutants producing metabolites with antitumor activity from wild-type actinomycete strains without antitumor activity. Methods An actinomycete strain L35-1 was used as an initial strain for obtaining antibiotic-resistant mutants, which is a marine-derived wild-type strain without antitumor activity with an inhibition rate of 2.8% at the 1000 μg/ml of high sample concentration on K562 cells. The antibiotic-resistant mutants both from auto-mutagenesis and chemical mutagen-induced mutagenesis were selected by single colony isolation on antibiotic-containing plates according to the method for obtaining drug-resistant mutants in ribosome engineering. The antitumor activity was assayed by the MTT method using K562 cells for the mutants with aqueous acetone extracts of the whole broth of their fermentation.Results A total of 114 neomycin-resistant (ner) and 68 streptomycin-resistant (str) mutants, all from auto-mutagenesis, was obtained on drug-containing plates. Among them, the 7 ner and 3 str mutants appeared to be bioactive with an inhibition rate above 20% at the 100 μg/ml sample concentration on K562 cells. On the other hand, 41 str and 32 ner mutants from DES-induced mutagenesis and 46 ner mutants from NTG-induced mutagenesis were obtained by mutagen-induced mutation coupled with the single colony isolation on antibiotic-containing plates, among which, one str mutant from DES-induced mutagenesis and one ner mutant from NTG-induced mutagenesis were bioactive with an inhibition rate over 20% at the 100 μg/ml sample concentration on K562 cells. Conclusions The present result has revealed that the wild-type actinomycete strains without bioactivity might become a great source initial strains to obtain bioactive mutants by drug-resistant mutation technique.
ABSTRACT
<p><b>OBJECTIVE</b>To develop the method and investigate the value of the application of multislice helical computed tomography (CT) in the maxillofacial distraction osteogenesis.</p><p><b>METHODS</b>Twelve cases of maxillofacial distraction osteogenesis (3 in zygoma, 2 in maxilla, and 7 in mandible) were scanned by the multislice helical CT, then the reconstruction of three dimensional and fault image and the relative measurement were carried out to study the effect of distraction and osteogenesis.</p><p><b>RESULTS</b>The three dimensional image provided clear and high resolution stereoscopic view that the effect of distraction osteogenesis could be evaluated easily and exactly. The fault image could be set up in private computer by Mimics and the measurements, such as distance, thickness and density, could be performed as expected. The effect of 12 cases was satisfied, and the average distracted distance was 16.73 mm.</p><p><b>CONCLUSION</b>Basing on multislice helical CT scanning, the high resolution image reconstruction and relative measurement data could be obtained which could meet the need of clear and direct observation. Its application in the maxillofacial distraction osteogenesis is expecting and promising.</p>
Subject(s)
Humans , Imaging, Three-Dimensional , Mandible , Maxilla , Osteogenesis, Distraction , Tomography, Spiral Computed , Tomography, X-Ray ComputedABSTRACT
<p><b>OBJECTIVE</b>To study the possibility of segmental maxillary regeneration by arced distraction osteogenesis of zygoma.</p><p><b>METHODS</b>The distraction of zygoma with the internal arced devices was performed in 2 dogs to simulate the reconstruction of maxillary defect. The zygoma was distracted about 12 mm, and the process of new bone formation was studied by histology and scanning electron microscopy.</p><p><b>RESULTS</b>The transport disk was distracted about 12 mm around the arc. After 8 weeks of consolidation, the density of new bone was close to that of normal bone.</p><p><b>CONCLUSIONS</b>The segmental maxillary regeneration by arced distraction osteogenesis of zygoma is possible.</p>