Effect of volume of porogens on the porosity of PLGA scaffolds in pH-controlled environment

Poly(lactic-co-glycolic acid) (PLGA) is a well-studied biodegradable polymer used in drug delivery and other medical applications such as in tissue regeneration. It is often necessary to impart porosity within the scaffold (microparticles) in order to promote the growth of tissue during the regeneration process. Sodium chloride and ammonium bicarbonate have been extensively used as porogens in the generation of porous microstructure. In this study, we compared the effect of volumes (250?μl, 500?μl and 750?μl) of two porogens, sodium chloride (1.71 M) and ammonium bicarbonate (1.71 M), on the porosity of PLGA microparticles.     

Diagnostic reproducibility of tumour budding in colorectal cancer: a multicentre,multinational study using virtual microscopy

Puppa G, Senore C, Sheahan K, Vieth M, Lugli A, Zlobec I, Pecori S, Wang L M, Langner C, Mitomi H, Nakamura T, Watanabe M, Ueno H, Chasle J, Conley S A, Herlin P, Lauwers G Y & Risio M
(2012) Histopathology  61, 562–575 Diagnostic reproducibility of tumour budding in colorectal cancer: a multicentre, multinational study using virtual microscopy Aims: Despite the established prognostic relevance of tumour budding in colorectal cancer, the reproducibility of the methods reported for its assessment has not yet been determined, limiting its use and reporting in routine pathology practice. Methods and results: A morphometric system within telepathology was devised to evaluate the reproducibility of the various methods published for the assessment of tumour budding in colorectal cancer. Five methods were selected to evaluate the diagnostic reproducibility among 10 investigators, using haematoxylin and eosin (H&E) and AE1‐3 cytokeratin‐immunostained, whole‐slide digital scans from 50 pT1–pT4 colorectal cancers. The overall interobserver agreement was fair for all methods, and increased to moderate for pT1 cancers. The intraobserver agreement was also fair for all methods and moderate for pT1 cancers. Agreement was dependent on the participants’ experience with tumour budding reporting and performance time. Cytokeratin immunohistochemistry detected a higher percentage of tumour budding‐positive cases with all methods compared to H&E‐stained slides, but did not influence agreement levels. Conclusions: An overall fair level of diagnostic agreement for tumour budding in colorectal cancer was demonstrated, which was significantly higher in early cancer and among experienced gastrointestinal pathologists. Cytokeratin immunostaining facilitated detection of budding cancer cells, but did not result in improved interobserver agreement.     

Pyrosequencing: applicability for studying DNA damage‐induced mutagenesis

Site‐specifically modified DNAs are routinely used in the study of DNA damage‐induced mutagenesis. These analyses involve the creation of DNA vectors containing a lesion at a pre‐determined position, DNA replication, and detection of mutations at the target site. The final step has previously required the isolation of individual DNA clones, hybridization with radioactively labeled probes, and verification of mutations by Sanger sequencing. In the search for an alternative procedure that would allow direct quantification of sequence variants in a mixed population of DNA molecules, we evaluated the applicability of pyrosequencing to site‐specific mutagenesis assays. The progeny DNAs were analyzed that originated from replication of N⁶‐(deoxy‐D‐erythro‐pentofuranosyl)‐2,6‐diamino‐3,4‐dihydro‐4‐oxo‐5‐N‐methylformamidopyrimidine (MeFapy‐dG)‐containing vectors in primate cells, with the lesion being positioned in the 5′‐GCNGG‐3′ sequence context. Pyrosequencing detected ～8% G to T transversions and ～3.5% G to A transitions, a result that was in excellent agreement with frequencies previously measured by the standard procedure (Earley LF et al. [2013]: Chem Res Toxicol 26:1108–1114). However, ～3.5% G to C transversions and ～2.0% deletions could not be detected by pyrosequencing. Consistent with these observations, the sensitivity of pyrosequencing for measuring the single deoxynucleotide variants differed depending on the deoxynucleotide identity, and in the given sequence contexts, was determined to be ～1–2% for A and T and ～5% for C. Pyrosequencing of other DNA isolates that were obtained following replication of MeFapy‐dG‐containing vectors in primate cells or Escherichia coli, identified several additional limitations. Collectively, our data demonstrated that pyrosequencing can be used for studying DNA damage‐induced mutagenesis as an effective complementary experimental approach to current protocols. Environ. Mol. Mutagen. 55:601–608, 2014. © 2014 Wiley Periodicals, Inc.