No abstract

Mammary gland development starts in utero with one or several pairs of mammary rudiments (MRs) budding from the surface ectodermal component of the mammalian embryonic skin. Mice develop five pairs, numbered MR1 to MR5 from pectoral to inguinal position. We have previously shown that Gli3Xt-J/Xt-J mutant embryos, which lack the transcription factor Gli3, do not form MR3 and MR5. We show here that two days after the MRs emerge, Gli3Xt-J/Xt-J MR1 is 20% smaller, and Gli3Xt-J/Xt-J MR2 and MR4 are 50% smaller than their wild type (wt) counterparts. Moreover, while wt MRs sink into the underlying dermis, Gli3Xt-J/Xt-J MR4 and MR2 protrude outwardly, to different extents. To understand why each of these five pairs of functionally identical organs has its own, distinct response to the absence of Gli3, we determined which cellular mechanisms regulate growth of the individual MRs, and whether and how Gli3 regulates these mechanisms. We found a 5.5 to 10.7-fold lower cell proliferation rate in wt MRs compared to their adjacent surface ectoderm, indicating that MRs do not emerge or grow via locally enhanced cell proliferation. Cell-tracing experiments showed that surface ectodermal cells are recruited toward the positions where MRs emerge, and contribute to MR growth during at least two days. During the second day of MR development, peripheral cells within the MRs undergo hypertrophy, which also contributes to MR growth. Limited apoptotic cell death counterbalances MR growth. The relative contribution of each of these processes varies among the five MRs. Furthermore, each of these processes is impaired in the absence of Gli3, but to different extents in each MR. This differential involvement of Gli3 explains the variation in phenotype among Gli3Xt-J/Xt-J MRs, and may help to understand the variation in numbers and positions of mammary glands among mammals.

No abstract

The inability to effectively track data in cloud computing environments is becoming one of the top concerns for cloud stakeholders. This inability is due to two main reasons. Firstly, the lack of data tracking tools built for clouds. Secondly, current logging mechanisms are only designed from a systemcentric perspective. There is a need for data-centric logging techniques which can trace data activities (e.g. file creation, edition, duplication, transfers, deletions, etc.) within and across all cloud servers. This will effectively enable full transparency and accountability for data movements in the cloud. In this paper, we introduce S2Logger, a data event logging mechanism which captures, analyses and visualizes data events in the cloud from the data point of view. By linking together atomic data events captured at both file and block level, the resulting sequence of data events depicts the cloud data provenance records throughout the data lifecycle. With this information, we can then detect critical data-related cloud security problems such as malicious actions, data leakages and data policy violations by analysing the data provenance. S2Logger also enables us to address the gaps and inadequacies of existing system-centric security tools.