Fate and plasticity of the endoderm in the early chick embryo

In vertebrates, the endoderm is established during gastrulation and gradually becomes regionalized into domains destined for different organs. Here, we present precise fate maps of the gastrulation stage chick endoderm, using a method designed to label cells specifically in the lower layer. We show that the first population of endodermal cells to enter the lower layer contributes only to the midgut and hindgut; the next cells to ingress contribute to the dorsal foregut and followed finally by the presumptive ventral foregut endoderm. Grafting experiments show that some migrating endodermal cells, including the presumptive ventral foregut, ingress from Hensen's node, not directly into the lower layer but rather after migrating some distance within the middle layer. Cell transplantation reveals that cells in the middle layer are already committed to mesoderm or endoderm, whereas cells in the primitive streak are plastic. Based on these results, we present a revised fate map of the locations and movements of prospective definitive endoderm cells during gastrulation.     

A comparison of random vs. chemotaxis-driven contacts of T cells with dendritic cells during repertoire scanning

Generating adaptive immunity after infection or immunization requires physical interactions within a lymph node (LN) T-zone between antigen-bearing dendritic cells (DCs) that arrive from peripheral tissues and rare cognate T cells entering via high endothelial venules (HEVs). This interaction results in activation of cognate T cells, expansion of that T cell lineage and their exit from the LN T-zone via efferent lymphatics (ELs). How antigen-specific T cells locate DCs within this complex environment is controversial, and both random T cell migration and chemotaxis have been proposed. We developed an agent-based computational model of a LN that captures many features of T cell and DC dynamics observed by two-photon microscopy. Our simulations matched in vivo two-photon microscopy data regarding T cell speed, short-term directional persistence of motion and cell motility. We also obtained in vivo data regarding density of T cells and DCs within a LN and matched our model environment to measurements of the distance from HEVs to ELs. We used our model to compare chemotaxis with random motion and showed that chemotaxis increased total number of T cell DC contacts, but decreased unique contacts, producing fewer activated T cells. Our results suggest that, within a LN T-zone, a random search strategy is optimal for a rare cognate T cell to find its DC match and maximize production of activated T cells.     

A novel stereotactic frame for real PET-guided biopsies: A preclinical proof-of-concept

Purpose: To design, build and test a stereotactic device that allows PET image-guided biopsies to be performed. Methods: An initial prototype consisting of four main pieces, one of which contains radioactive markers to make it visible in the PET images, was built using a 3D printer. Once the device is mounted, a spherical coordinate system is built with the entrance needle point in the skin as the origin of coordinates. Two in-house software programs, namely getCoord.ijm, which obtains the spherical coordinates of the tumour tissue to be biopsied, and getNeedle.ijm, which virtualizes the inner needle tip once the puncture has taken place, were written. This prototype was tested on an FDG-doped phantom to characterize both the accuracy of the system and the procedure time. Results: Up to 11 complete biopsy procedures were conducted. The mean total procedure time was less than 20 min, which is less than the procedure time of conventional standard CT-guided biopsies. The overall accuracy of the system was found to be 5.0 ± 1.3 mm, which outperforms the criterion used in routine clinical practice when targeting tumours with a diameter of 10 mm. Conclusions: A stereotactic frame to conduct real PET image-guided biopsies has been designed and built. A proof-of-concept was performed to characterize the system. The procedure time and accuracy of the system were found to meet the current needs of physicians performing biopsies.     

Identification of identical TCRs in primary melanoma lesions and tumor free corresponding sentinel lymph nodes

It is generally believed that priming of efficient T-cell responses takes place in peripheral lymphoid tissues. Although this notion has been rigidly proven for infectious diseases, direct evidence for lymph node priming of in vivo T-cell responses against tumors is still lacking. In the present study, we conducted a full and nonbiased comparison of T-cell clonotypes in melanoma lesions and corresponding sentinel lymph nodes. Whereas most tumor lesions comprised a high number of T-cell clonotypes, only a small number of clonally expanded T cells were detected in the draining lymph nodes. Comparative clonotype mapping demonstrated the presence of identical T-cell clonotypes in the tumors and the respective sentinel lymph nodes, only when tumor cells were present in the latter. However, taking advantage of clonotype specific PCR amplification, TCR sequences representing clonally expanded T cells at the tumor site could be detected in the lymph nodes draining the tumors even in the absence of tumor cells. Evidence for the tumor-specific characteristics of these cells was obtained by in situ staining with peptide/HLA class I complexes demonstrating the presence of MART-1/HLA-A2- and MAGE-3/HLA-A2-reactive T cells at the tumor site, as well as in the draining lymph node. Our data indicate that T-cell responses to melanoma are primed in the sentinel lymph node by cross presentation of tumor antigens by dendritic cells.     

How Does The AJCC/TNM Staging System Eighth Edition Perform in Thyroid Cancer at A Major Middle Eastern Medical Center?

ObjectiveThe American Joint Committee on Cancer tumor node metastasis (TNM) staging system eighth edition (TNM-8) for differentiated thyroid cancer (DTC) has been introduced as a replacement for tumor node metastasis staging system seventh edition (TNM-7). We present the first study from a Middle Eastern population comparing these 2 versions of the TNM staging system.MethodsWe compared TNM-8 with TNM-7 in 701 patients with DTC seen during a 3-year period with a median age of 37 years (6-83) and a female-to-male ratio of 558 (79.6%) to 143 (20.4%).ResultsThe number (%) of patients within each stage in TNM-7 and TNM-8, respectively, are as follows: stage I = 503 (71.6%) and 583 (83.2%), stage II = 52 (7.4%) and 81 (11.4%), stage III = 53 (7.6%) and 6 (0.9%), and stage IV = 93 (13.2%) and 31 (4.6%). Overall, 172 patients (24.5%) were downstaged in TNM-8 compared to that in TNM-7, as follows: 26, 30, and 24 patients from stages II, III, and IV in TNM-7 to stage I in TNM-8; 23 and 32 patients from TNM-7 stages III and IV to TNM-8 stage II; 6 patients from stage IVa in TNM-7 to stage III in TNM-8; and 31 patients from stage IVc in TNM-7 to stage IVb in TNM-8. TNM-7 and TNM-8 predicted the long-term outcome well (median follow-up, 7.9 years), but Kaplan-Meier analysis showed better separation of cancer-specific survival in TNM-8 compared to TNM-7.ConclusionsCompared with TNM-7, TNM-8 approximately downstaged a quarter of DTC patients and was more robust in separating the outcome of different stages over time.