Simulations reveal that different responses to cell crowding determine the expansion of p53 and Notch mutant clones in squamous epithelia

During ageing, normal epithelial tissues progressively accumulate clones carrying mutations that increase mutant cell fitness above that of wild-type cells. Such mutants spread widely through the tissues, yet despite this cellular homeostasis and functional integrity of the epithelia are maintained. Two of the genes most commonly mutated in human skin and oesophagus are p53 and Notch1 , both of which are also recurrently mutated in cancers of these tissues. From observations taken in human and mouse epithelia, we find that clones carrying p53 and Notch pathway mutations have different clone dynamics which can be explained by their different responses to local cell crowding. p53 mutant clone growth in mouse epidermis approximates a logistic curve, but feedbacks responding to local crowding are required to maintain tissue homeostasis. We go on to show that the observed ability of Notch pathway mutant cells to displace the wild-type population in the mouse oesophageal epithelium reflects a local density feedback that affects both mutant and wild-type cells equally. We then show how these distinct feedbacks are consistent with the distribution of mutations observed in human datasets and are suggestive of a putative mechanism to constrain these cancer-associated mutants.

The measure of spatial position within groups that best predicts predation risk depends on group movement

Both empirical and theoretical studies show that an individual's spatial position within a group can impact the risk of being targeted by predators. Spatial positions can be quantified in numerous ways, but there are no direct comparisons of different spatial measures in predicting the risk of being targeted by real predators. Here, we assess these spatial measures in groups of stationary and moving virtual prey being attacked by three-spined sticklebacks ( Gasterosteus aculeatus ). In stationary groups, the limited domain of danger best predicted the likelihood of attack. In moving groups, the number of near neighbours was the best predictor but only over a limited range of distances within which other prey were counted. Otherwise, measures of proximity to the group's edge outperformed measures of local crowding in moving groups. There was no evidence that predators preferentially attacked the front or back of the moving groups. Domains of danger without any limit, as originally used in the selfish herd model, were also a poor predictor of risk. These findings reveal that the collective properties of prey can influence how spatial position affects predation risk, via effects on predators' targeting. Selection may therefore act differently on prey positioning behaviour depending on group movement.

The measure of spatial position within groups that best predicts predation risk depends on group movement

Both empirical and theoretical studies show that an individual's spatial position within a group can impact the risk of being targeted by predators. Spatial positions can be quantified in numerous ways, but there are no direct comparisons of different spatial measures in predicting the risk of being targeted by real predators. Here we assess these spatial measures in groups of stationary and moving virtual prey being attacked by three-spined sticklebacks (Gasterosteus aculeatus). In stationary groups, the limited domain of danger best predicted the likelihood of attack. In moving groups, the number of near neighbours was the best predictor but only over a limited range of distances within which other prey were counted. Otherwise, measures of proximity to the group's edge outperformed measures of local crowding in moving groups. There was no evidence that predators preferentially attacked the front or back of the moving groups. Domains of danger without any limit, as originally used in the selfish herd model, were also a poor predictor of risk. These findings reveal that the collective properties of prey can influence how spatial position affects predation risk, via effects on predators' targeting, hence selection may act differently on prey positioning behaviour depending on group movement.

Deep point spread function photometric catalog of the VVV survey data

Context. The Vista Variables in the Vía Láctea (VVV) survey has performed a multi-epoch near-infrared imaging of the inner Galactic plane. High-fidelity photometric catalogs are needed to utilize the data. Aims. We aim at producing a deep, point spread function (PSF) photometric catalog for the VVV survey J-,H-, and Ks-band data. Specifically, we aim to take advantage of multiple epochs of the survey to reach high limiting magnitudes. Methods. We developed an automatic PSF-fitting pipeline based on the DaoPHOT algorithm and performed photometry on the stacked VVV images in J, H, and Ks bands. Results. We present a PSF photometric catalog in the Vega system that contains about 926 million sources in the J, H, and Ks filters. About 10% of the sources are flagged as possible spurious detections. The 5σ limiting magnitudes of the sources with high reliability are about 20.8, 19.5, and 18.7 mag in the J, H, and Ks bands, respectively, depending on the local crowding condition. Our photometric catalog reaches on average about one magnitude deeper than the previously released PSF DoPHOT photometric catalog and includes less spurious detections. There are significant differences in the brightnesses of faint sources between our catalog and the previously released one. The likely origin of these differences is in the different photometric algorithms that are used; it is not straightforward to assess which catalog is more accurate in different situations. Our new catalog is beneficial especially for science goals that require high limiting magnitudes; our catalog reaches such high magnitudes in fields that have a relatively uniform source number density. Overall, the limiting magnitudes and completeness are different in fields with different crowding conditions.

Bilateral Molariform Mandibular Second Premolars

Macrodontia is a rare dental anomaly that refers to teeth that appear larger than normal. Generalised macrodontia can be associated with certain medical conditions and syndromes. This case report presents clinical and radiographic findings of isolated bilateral macrodontia in a 14-year-old child. The patient was referred to the clinic with local crowding of maxillary and mandibular teeth. Radiographic findings revealed the presence of impacted macrodont mandibular second premolar on one side and erupted macrodontic premolar on the other side and their distinct morphological appearance, characterized by large, multitubercular, and molariform crowns and tapering, single roots.

Isolated bilateral macrodontia of mandibular second premolars: A case report

ABSTRACTIsolated bilateral macrodontia of mandibular second premolars is an extremely rare dental anomaly with only 5 cases reported to date. This case report presents clinical and radiographic findings of isolated bilateral macrodontia in a 12-year-old child. The patient was referred to the clinic with local crowding of mandibular posterior teeth. Radiographic findings revealed the presence of impacted macrodont mandibular second premolars and their distinct morphological appearance, characterized by large, multitubercular, molariform crowns, and tapering, single roots. Following surgical removal of the impacted premolars, orthodontic therapy was initiated to correct the malocclusion. Along with the features and treatment of this rare anomaly, this case report also illustrates the benefits, in terms of treatment planning and surgical technique, of supplementing conventional radiography with cone-beam computed tomography to localize the macrodont premolars and accurately establish their relationship with the neighboring roots and anatomic structures. (Eur J Dent 2012;6:330-334)

Deviation of Mass-Density Allometry in Ramet Populations of Switchgrass

We studied a ramet population of switchgrass, caespitose in appearance, and proved the absence of density-dependent mortality. We present a deviation of mass-density allometry based on spatially explicit densities along the vertical space of the population. The number of ramets in the mean-ramet-height space explains the variation in the average weight of whole ramets (M) more accurately, with an asymptote towards critical self-thinning trajectory for such a mass-density relationship. With the development of size heterogeneity, a ‘vertical packing’ process appears in the population. We define the process as a similar ‘self-thinning’ trajectory, through the initial crowding of ramets in the mean-ramet-height space and continued transferring into the upper space and the lower space. The process presents a possibly competitive mechanism of self-thinning, local-competition-driving size deviation and vertical space packing. Here, log10 (M) = 2.91 - 1.25 log10 (NL). Local crowding degree (NL) is the number of ramets per unit area (m2) in the mean-ramet-height space class. Similar ‘self-thinning’ occurs in the ramet population, but it just indicates how those ramets escape out of the mean-ramet-height space class, and therefore how the mean weight of whole ramets increases. Self-thinning should be the result of local competition among effective number of individuals in a population, rather than apparent crowding degree presented by whole individuals. The critical mass-density allometry based on whole individuals should be only a special case.