Aberrant crypt foci in colorectal carcinogenesis. Cell and crypt dynamics

Aberrant crypt foci (ACF) have been identified on the colonic mucosal surface of rodents treated with colon carcinogens and of humans after methylene-blue staining and observation under a light microscope. Several lines of evidence strongly suggest that ACF with certain morphological, histological, cell kinetics, and genetic features are precursor lesions of colon cancer both in rodents and in humans. Thus, ACF represent the earliest step in colorectal carcinogenesis. This paper has the main purpose of reviewing the evidence supporting this view, with particular emphasis on cell and crypt dynamics in ACF. ACF have been used as intermediate biomarkers of cancer development in animal studies aimed at the identification of colon carcinogens and chemopreventive agents. Recently, evidence has also shown that ACF can be effectively employed in chemopreventive studies also in humans

Modelling the Spatio-Temporal Cell Dynamics Reveals Novel Insights on Cell Differentiation and Proliferation in the Small Intestinal Crypt

We developed a slow structural relaxation model to describe cellular dynamics in the crypt of the mouse small intestine. Cells are arranged in a three dimensional spiral the size of which dynamically changes according to cell production demands of adjacent villi. Cell differentiation and proliferation is regulated through Wnt and Notch signals, the strength of which depends on the local cell composition. The highest level of Wnt activity is associated with maintaining equipotent stem cells (SC), Paneth cells and common goblet-Paneth cell progenitors (CGPCPs) intermingling at the crypt bottom. Low levels of Wnt signalling area are associated with stem cells giving rise to secretory cells (CGPCPs, enteroendocrine or Tuft cells) and proliferative absorptive progenitors. Deciding between these two fates, secretory and stem/absorptive cells, depends on Notch signalling. Our model predicts that Notch signalling inhibits secretory fate if more than 50% of cells they are in contact with belong to the secretory lineage. CGPCPs under high Wnt signalling will differentiate into Paneth cells while those migrating out from the crypt bottom differentiate into goblet cells. We have assumed that mature Paneth cells migrating upwards undergo anoikis. Structural relaxation explains the localisation of Paneth cells to the crypt bottom in the absence of active forces. The predicted crypt generation time from one SC is 4–5 days with 10–12 days needed to reach a structural steady state. Our predictions are consistent with experimental observations made under altered Wnt and Notch signalling. Mutations affecting stem cells located at the crypt floor have a 50% chance of being propagated throughout the crypt while mutations in cells above are rarely propagated. The predicted recovery time of an injured crypt losing half of its cells is approximately 2 days

Detection and imaging of city’s underground void by GPR

2017 9th International Workshop on Advanced Ground Penetrating Radar [IWAGPR], 28-30 June 2017, Edinburgh, UK.202305 bckwAccepted ManuscriptOthersHong Kong Polytechnic UniversityPublishe

A blind test of nondestructive underground void detection by Ground Penetrating Radar (GPR)

202305 bckwAccepted ManuscriptOthersHong Kong Polytechnic UniversityPublishe

GPR surveys and excavation ground-truthing at the San Tau backbeach site, Hong Kong

2016 16th International Conference on Ground Penetrating Radar (GPR), 13-16 June 2016, Hong Kong, China202305 bckwAccepted ManuscriptSelf-fundedPublishe

Exploring utility system SDI – Managerial and technical perspectives

202305 bckwAccepted ManuscriptRGCPublishe

GPR surveys and excavation ground-truthing at the San Tau Backbeach Site, Hong Kong

16th International Conference of Ground Penetrating Radar, GPR 2016, Hong Kong, 13-16 June 2016This paper presents the results of an archaeological fieldwork project conducted by a pro-geophysics archaeologist (Atha) and two 'archaeo-curious' GPR specialists (Chang and Lai) at the San Tau backbeach site in Hong Kong. Previous small-scale test pitting suggested that the site might be a locally unique Tang dynasty cemetery, with probable later (Northern Song) activity, but grave definition was problematic and the cemetery's wider extent remained unknown. However, the fine-grained, relatively homogenous background appeared ideal for GPR. A two-stage approach was used: a 400MHz antenna was applied in an initial prospection survey, while both 400MHz and 900MHz were used in a second campaign of higher-resolution intra-site analytical survey. The GPR results identified many 'targets' and proved decisive in locating and discriminating both Tang dynasty graves and overlying Northern Song pits. Based on the results of GPR surveys and excavation ground-truthing, it seems the site may in total contain several hundred Tang burials, significant among which were several co-aligned 'warrior burials' with iron weapons and tools. Reference to site records of object types (metallic or non-metallic) and sizes shows that the very different slice images by 400MHz and 900MHz GPR are best explained by the radar footprints in First Fresnel zone (FFZ), which is a function of object depth, antenna frequency, GPR wave velocity in soil, and two-way travel time of the objects' reflections. The findings indicate that GPR is in general highly effective on sandy coastal sites, and in particular can provide useful estimates of the size and character of buried archaeological features and artefacts. Based on our findings, more routine application in local archaeology is therefore strongly recommended.Department of Land Surveying and Geo-Informatic

GPR imaging criteria

Title on author’s file: An Empirical Study of GPR 3D Imaging Criteria202305 bckwAccepted ManuscriptSelf-fundedPublishe