Neuron and glia generating progenitors of the mammalian enteric nervous system isolated from foetal and postnatal gut cultures

Cultures of dissociated foetal and postnatal mouse gut gave rise to neurosphere-like bodies, which contained large numbers of mature neurons and glial cells. In addition to differentiated cells, neurosphere-like bodies included proliferating progenitors which, when cultured at clonal densities, gave rise to colonies containing many of the neuronal subtypes and glial cells present in the mammalian enteric nervous system. These progenitors were also capable of colonising wild-type and aganglionic gut in organ culture and had the potential to generate differentiated progeny that localised within the intrinsic ganglionic plexus. Similar progenitors were also derived from the normoganglionic small intestine of mice with colonic aganglionosis. Our findings establish the feasibility of expanding and isolating early progenitors of the enteric nervous system based on their ability to form distinct neurogenic and gliogenic structures in culture. Furthermore, these experiments provide the rationale for the development of novel approaches to the treatment of congenital megacolon (Hirschsprung's disease) based on the colonisation of the aganglionic gut with progenitors derived from normoganglionic bowel segments.     

Salmonella InvG forms a ring-like multimer that requires the InvH lipoprotein for outer membrane localization

Salmonella species translocate virulence effector proteins from the bacterial cytoplasm into mammalian host cells by means of a type III secretion apparatus, encoded by the pathogenicity island-1 (SPI-1). Little is known about the assembly and structure of this secretion apparatus, but the InvG protein is essential and could be an outer membrane secretion channel for the effector proteins. We observed that in recombinant Escherichia coli , the yield of InvG was enhanced by co-expression of InvH, and showed that mutation of invH decreased the level of InvG in wild-type Salmonella typhimurium . In E. coli , InvG alone was able to form an SDS-resistant multimer, but InvG localization to the outer membrane was dependent upon InvH, a lipoprotein itself located in the outer membrane, and no other SPI-1 specific protein. InvG targeted to the outer membrane by InvH became accessible to extracellular protease. InvG and InvH did not, however, appear to form a stable complex. Electron microscopy of InvG membrane protein purified from E. coli revealed that it forms an oligomeric ring-like structure with inner and outer diameters, 7 nm and 15 nm respectively.     

Characterization of the subunits of purine nucleoside phosphorylase from cultured normal human fibroblasts

In previous communications we have demonstrated that the subunits of normal human erythrocyte purine nucleoside phosphorylase can be resolved into four major (1–4) and two minor (1p and 2p) components with the same molecular weight but different apparent isoelectric points (and net ionic charge). The existence of subunits with different charge results in a complex isoelectric focusing pattern of the native erythrocytic enzyme. In contrast, the isoelectric focusing pattern of the native enzyme obtained from cultured human fibroblasts is simpler. The multiple native isoenzymes obtained from human erythrocytes and human brain have isoelectric points ranging from 5.0 to 6.4 and from 5.2 to 5.8, respectively, whereas cultured human fibroblasts have two major native isoenzymes with apparent isoelectric points of 5.1 and 5.6.Purine nucleoside phosphorylase has been purified at least a hundredfold from ³⁵S-labeled cultured human fibroblasts. A two-dimensional electrophoretic analysis of the denatured purified normal fibroblast enzyme revealed that it consists mainly of subunit 1 (90%) with small amounts of subunits 2 (10%) and 3 (1%). This accounts for the observed differences between the native isoelectric focusing and the electrophoretic patterns of the erythrocyte and fibroblast enzymes. The purine nucleoside phosphorylase subunit 1 is detectable in the autoradiogram from a two-dimensional electrophoretic analysis of a crude, unpurified extract of ³⁵S-labeled cultured normal human fibroblasts. The fibroblast phosphorylase coincides with the erythrocytic subunit 1 of the same enzyme, and the cultured fibroblasts of a purine nucleoside phosphorylase deficient patient (patient I) lack this protein component, genetically confirming the identity of the purine nucleoside phosphorylase subunit in cultured fibroblasts.This work was supported by a grant from the National Institute of Arthritis, Metabolism, and Digestive Diseases, National Institutes of Health, United States Public Health Service. L. J. G. is supported by a fellowship from the National Institute of Child Health and Human Development. D. W. M. is an Investigator, Howard Hughes Medical Institute.     

Elk-1 is a novel protein-binding partner for FAK, regulating phagocytosis in medfly hemocytes

Focal adhesion kinase (FAK) and its downstream signaling targets, mitogen-activated protein kinase (MAPKs), are implicated in the process of phagocytosis by insect hemocytes. The goal of this study was to explore further the signaling pathways underlining the process of phagocytosis. The combination of bioinformatics, biochemical, and immunofluorescence approaches strongly support the expression of Elk-1-like protein in medfly hemocytes. Elk-1 is phosphorylated in E. coli or latex beads-challenged hemocytes and osmotic loading experiments as well as flow cytometry analysis demonstrated that Elk-1-like protein regulates the uptake of bacteria. RNA interference (RNAi) and pharmacological inhibitors show that the signaling for Elk-1 phosphorylation is transmitted via FAK/Src and MAPKs pathways. Furthermore, confocal analysis clearly shows that FAK and the phosphorylated FAK at Y397 are localized in the nucleus and cytoplasm, whereas, the phosphorylated Elk-1-like protein is exclusively localized in the nucleus. Finally, co-immunoprecipitation and reciprocal co-immunoprecipitation analysis demonstrated the association of low molecular weight protein bands recognized by FAK antibodies, with Elk-1 or phospho-Elk-1 at ser 383 and confocal microscopy specifies that this association occurs only in the nucleus. These results are strongly supporting that Elk-1-like protein is a novel protein-binding partner for FAK, a finding that significantly broadens the potential functioning of FAK and Elk-1 generally. Evidently, the complex participates in the process of phagocytosis in medfly hemocytes.     

Is there any potential link among caspase-8, p-p38 MAPK and bcl-2 in clear cell renal cell carcinomas? A comparative immunohistochemical analysis with clinical connotations

Background

Management of endometrial precancerous lesions has been of much debate due to inconsistencies in their classification, natural history and histologic diagnosis. Endometrial hyperplasia constitutes a wide range of histomorphologic features associated with high intra and interobserver diagnostic variability. Although traditional microscopic diagnosis is by far the most applicable method and the gold standard for histomorphologic diagnosis, digitized image analysis has been used as a powerful adjunct to maximize the histologic data retrieval and to add some detailed objective criteria for correct diagnosis in difficult cases.

Methods

A series of 100 endometrial curettage specimens with diagnosis of endometrial hyperplasia or well differentiated adenocarcinoma were blindly reviewed by 5 pathologists; their intra and interobserver reproducibility determined and further compared to the objective morphometric data i.e. D-score and volume percent of stroma (VPS).

Results

The results were assessed using the weighted kappa statistics. Mean intraobserver kappa value was 0.8690 (99.44% agreement). Mean interobserver kappa values by diagnostic category were: simple hyperplasia without atypia: 0.7441; complex hyperplasia without atypia: 0.3379; atypical hyperplasia: 0.3473, and well-differentiated endometrioid carcinoma: 0.6428; with a kappa value of 0.5372 for all cases combined. Interobserver agreement was in substantial rate for simple hyperplasia (SH) and well differentiated adenocarcinoma (WDA) but was in fair limit for complex hyperplasia (CH) and atypical hyperplasia (AH). Intraobserver agreement was almost perfect. The specimens were divided in two groups according to the computerized morphometric analysis: Endometrial Hyperplasia (EH) ( D Score ≥ 1 or VPS ≥ 55%) and Endometrial Intraepithelial Neoplasia (EIN) (D-Score < 1 or VPS < 55%). Morphometric findings were closely compatible with routine WHO classification made by one expert pathologist; however; diagnosis of (CH) and (AH) made by other pathologists were not concordant with morphometric data.

Conclusion

It may be necessary to make some revisions in WHO classification for endometrial hyperplasia and precancerous lesions.     

Exercise as a model to study redox homeostasis in blood: the effect of protocol and sampling point

Twenty males ran either on a level treadmill (nonmuscle-damaging condition) or on a downhill treadmill (muscle-damaging condition). Blood and urine samples were collected before and after exercise (immediately after, 1h, 4h, 24h, 48h, and 96h). The following assays were performed: F(2)-isoprostanes in urine, protein carbonyls in plasma, glutathione, superoxide dismutase, glutathione peroxidase, and catalase in erythrocytes. The main finding was that monophasic redox responses were detected after nonmuscle-damaging exercise compared to the biphasic responses detected after muscle-damaging exercise. Based on these findings, muscle-damaging exercise may be a more appropriate experimental model to induce physiological oxidative stress.     

Peptidoglycan N-acetylglucosamine deacetylases from Bacillus cereus, highly conserved proteins in Bacillus anthracis

The genomes of Bacillus cereus and its closest relative Bacillus anthracis contain 10 polysaccharide deacetylase homologues. Six of these homologues have been proposed to be peptidoglycan N-acetylglucosamine deacetylases. Two of these genes, namely bc1960 and bc3618, have been cloned and expressed in Escherichia coli, and the recombinant enzymes have been purified to homogeneity and further characterized. Both enzymes were effective in deacetylating cell wall peptidoglycan from the Gram(+) Bacillus cereus and Bacillus subtilis and the Gram(-) Helicobacter pylori as well as soluble chitin substrates and N-acetylchitooligomers. However, the enzymes were not active on acetylated xylan. These results provide insight into the substrate specificity of carbohydrate esterase family 4 enzymes. It was revealed that both enzymes deacetylated only the GlcNAc residue of the synthetic muropeptide N-acetyl-D-glucosamine-(beta-1,4)-N-acetylmuramyl-L-alanine-D-isoglutamine. Analysis of the constituent muropeptides of peptidoglycan from B. subtilis and H. pylori resulting from incubation of the enzymes BC1960 and BC3618 with these polymers and subsequent hydrolysis by Cellosyl and mutanolysin, respectively, similarly revealed that both enzymes deacetylate GlcNAc residues of peptidoglycan. Kinetic analysis toward GlcNAc(2-6) revealed that GlcNAc4 was the favorable substrate for both enzymes. Identification of the sequence of N-acetychitooligosaccharides (GlcNAc(2-4)) following enzymatic deacetylation by using 1H NMR revealed that both enzymes deacetylate all GlcNAc residues of the oligomers except the reducing end ones. Enzymatic deacetylation of chemically acetylated vegetative peptidoglycan from B. cereus by BC1960 and BC3618 resulted in increased resistance to lysozyme digestion. This is the first biochemical study of bacterial peptidoglycan N-acetylglucosamine deacetylases.     

The canonical NF-κB pathway differentially protects normal and human tumor cells from ROS-induced DNA damage

DNA damage responses (DDR) invoke senescence or apoptosis depending on stimulus intensity and the degree of activation of the p53-p21(Cip1/Waf1) axis; but the functional impact of NF-κB signaling on these different outcomes in normal vs. human cancer cells remains poorly understood. We investigated the NF-κB-dependent effects and mechanism underlying reactive oxygen species (ROS)-mediated DDR outcomes of normal human lung fibroblasts (HDFs) and A549 human lung cancer epithelial cells. To activate DDR, ROS accumulation was induced by different doses of H(2)O(2). The effect of ROS induction caused a G2 or G2-M phase cell cycle arrest of both human cell types. However, ROS-mediated DDR eventually culminated in different end points with HDFs undergoing premature senescence and A549 cancer cells succumbing to apoptosis. NF-κB p65/RelA nuclear translocation and Ser536 phosphorylation were induced in response to H(2)O(2)-mediated ROS accumulation. Importantly, blocking the activities of canonical NF-κB subunits with an IκBα super-repressor or suppressing canonical NF-κB signaling by IKKβ knock-down accelerated HDF premature senescence by up-regulating the p53-p21(Cip1/Waf1) axis; but inhibiting the canonical NF-κB pathway exacerbated H(2)O(2)-induced A549 cell apoptosis. HDF premature aging occurred in conjunction with γ-H2AX chromatin deposition, senescence-associated heterochromatic foci and beta-galactosidase staining. p53 knock-down abrogated H(2)O(2)-induced premature senescence of vector control- and IκBαSR-expressing HDFs functionally linking canonical NF-κB-dependent control of p53 levels to ROS-induced HDF senescence. We conclude that IKKβ-driven canonical NF-κB signaling has different functional roles for the outcome of ROS responses in the contexts of normal vs. human tumor cells by respectively protecting them against DDR-dependent premature senescence and apoptosis.     

Enteric nervous system progenitors are coordinately controlled by the G protein-coupled receptor EDNRB and the receptor tyrosine kinase RET

The enteric nervous system (ENS) in vertebrates is derived mainly from vagal neural crest cells that enter the foregut and colonize the entire wall of the gastrointestinal tract. Failure to completely colonize the gut results in the absence of enteric ganglia (Hirschsprung's disease). Two signaling systems mediated by RET and EDNRB have been identified as critical players in enteric neurogenesis. We demonstrate that interaction between these signaling pathways controls ENS development throughout the intestine. Activation of EDNRB specifically enhances the effect of RET signaling on the proliferation of uncommitted ENS progenitors. In addition, we reveal novel antagonistic roles of these pathways on the migration of ENS progenitors. Protein kinase A is a key component of the molecular mechanisms that integrate signaling by the two receptors. Our data provide strong evidence that the coordinate and balanced interaction between receptor tyrosine kinases and G protein-coupled receptors controls the development of the nervous system in mammals.