Calcium fluctuations drive morphological patterning at the onset of Hydra morphogenesis

Morphogenesis in animal development involves significant morphological transitions leading to the emerging body plan of a mature animal. Understanding how the collective physical processes drive robust morphological patterning requires a coarse-grained description of the dynamics and the characterization of the underlying fields. Here I show that calcium spatial fluctuations serve as an integrator field of the electrical-mechanical processes of morphogenesis in whole-body Hydra regeneration and drive the morphological dynamics. We utilize external electric fields to control the developmental process and study a critical transition in morphogenesis, from the initial spheroidal shape of the tissue to an elongated cylindrical shape defining the body plan of a mature animal. Morphogenesis paused under external voltage is associated with a significant increase of the calcium activity compared with the activity supporting normal development. The enhanced calcium activity is characterized by intensified spatial fluctuations, extended spatial correlations across the tissue and faster temporal fluctuations. In contrast, the normal morphogenesis process is characterized by relatively moderate calcium fluctuation activity and restrained spatial correlations. Long-range communication however, is essential for development. Blocking gap-junctions halts morphogenesis by suppressing the long-range electrical communication, severely reducing the overall calcium activity and enhancing its localization in the tissue. Normal calcium activity is resumed following the wash of the blocker drug, leading to a morphological transition characterizing a normal regeneration process and the emergence of a mature animal. Our methodology of controlling morphogenesis by a physical electric field allows us to gain a global statistical view of the dynamics. It shows that the normalized calcium spatial fluctuations exhibit a universal shape distribution, across tissue samples and conditions, suggesting the existence of a global constrain over these fluctuations. Studying the correlations in space and time of the calcium fluctuation field at the onset of morphogenesis opens a new vista on this process and paints a picture of development analogous to a dynamical phase transition.

Osteohistology of the hadrosauroid (Dinosauria: Ornithopoda) from Labirinta cave, Bulgaria: An example of insular dwarfism or simply young giant?

The hadrosauroid remains from Kajlâka Formation (Upper Maastrichtian) limestones of the Labirinta Cave, NW Bulgaria, are most interesting for their small size but without paleohistological data it was not possible to affirm whether they belong to young individual/s or to small-sized mature animal/s. To elucidate their histology and ontogenetic state, 6 associated cortical fragments and one partial diaphysis were sectioned and studied. Thin-sections reveal cortex build of highly vascularized tissues of the woven-parallel complex. Vascularization patterns are somewhat intermediate between those of derived hadrosauroids and non-hadrosauroid ornithopods, yet characterized by thick sequences of laminar bone. Bone tissue matrix consists largely of parallel-fibered or lamellar bone tissue. Cortical tissues are affected by processes of secondary remodeling that locally results in dense Haversian tissue reaching the subperiosteal cortex. No growth marks or external fundamental system are observed in any of the specimens. The transition from bone tissues with predominantly longitudinally oriented osteons to true laminar bone, the thickness of the latter, the extensive secondary bone remodeling and Haversian tissue with at least 3 generations of secondary osteons, as well as the presence of endosteal bone in one of studied specimens all suggest that the material pertains to animal/s at a late sub-adult ontogenetic stage. The high presence of parallel-fibered and lamellar tissues in the cortex indicates significantly slower growth rates in comparison with similarly sized but ontogenetically younger derived hadrosauroids. The osteohistology of the Bulgarian hadrosauroid reveals yet another example of dinosaurian insular dwarfism in latest Cretaceous European archipelago.

Thalidomide-type teratogenicity: structure–activity relationships for congeners

Unravelling the molecular basis of thalidomide embryotoxicity, which is remarkably species-specific, is challenging in view of its low toxicity in the mature animal.

Implications of finding a ceratopsian horncore in the Danek bonebed

In connection with the excavation of the Danek Bonebed in 2011, a half-metre long, well preserved right ceratopsian orbital horncore was recovered. The horncore belongs to the taphonomic group of larger, heavier elements from the bonebed. So far, no other ceratopsian elements have been identified from the bonebed. Ceratopsids from the Horseshoe Canyon Formation of southern Alberta include Anchiceratops, Arrhinoceratops, Eotriceratops, and Pachyrhinosaurus. The size, proportions, and gently anterolaterally procurving morphology of the horncore indicates that it is from a chasmosaurine ceratopsid. There is weak morphological information to suggest that it may represent Anchiceratops ornatus, which is the most common chasmosaurine at this stratigraphic level. The base of the specimen has been hollowed out by a sinus system, which in conjunction with its large size indicates it is probably from a mature animal. The rarity of ceratopsian remains in this and other hadrosaur bonebeds suggests horned dinosaurs were excluded from anywhere that was occupied by herds of large numbers of Edmontosaurus.

On the Role of Autonomous Control in Organ Development

Developmental biology (“development” for short) deals with how the mature animal or plant results from a single fertilized cell. This paper is concerned with one aspect of development, morphogenesis—the formation of complex shapes from simpler ones. In particular, this paper focuses on organ development and illustrates the central role that mechanical feedback plays in effecting the final shape of various organs. The first aim of this paper is to illustrate how self-governing autonomous control systems can lead to the development of organs such as the heart. Although feedback plays a key role in these processes, the field is largely unexplored by controls engineers; hence, the second aim of this paper is to introduce mechanical feedback during development to controls engineers and suggest avenues for future research.

Reduction of the bull: cow ratio in the Brazilian Pantanal

This work was conducted to study alternatives for reduction of the bull:cow ratio in the Brazilian lowland and, therefore, lower the production costs for the local beef cattle industry. The ratios 1:10, 1:25, and 1:40 were used in native pastures with a mean stocking rate of 0.27 mature animal unit per hectare over two consecutive breeding seasons. Statistical analysis did not show any effect (P>0.05) of year (P = 0.2097), animal category (P = 0.0773), bull:cow ratio (0.8134) on reproductive performance. However, the pregnancy rate in a multiple bull system was higher (P = 0.0228) than in the individual bull system. An evaluation of the economic impact of this management system in the extensive Lowland herds showed that at the ratio of 1:10 the bulls were sub utilized.

Development of GP-2 and five zymogens in the fetal and young pig: biochemical and immunocytochemical evidence of an atypical zymogen granule composition in the fetus.

To uncover the mechanisms involved in the biogenesis of secretory granules, we studied development of the exocrine pancreas in the pig from the fetus up to the mature animal by following the enzyme activities and expression (Northern blot) of five zymogens and GP-2, the major protein of the granule membrane. Fetal pancreas mainly contained chymotrypsinogen and barely detectable amounts of amylase, trypsin, lipase, and elastase. GP-2 was not notably expressed before the Day 21 of life. Ultrastructural examination of the fetal tissue embedded in Epon with osmium postfixation or in Lowicryl at -20 degrees C without postfixation showed dense granules with an irregular shape but also showed that most granules had uncondensed contents, with the aspect of immature granules, or had a dense core surrounded by light material. With immunogold cytochemistry, the concentration of chymotrypsinogen was directly associated with the acquisition of electron density by the granule matrix. These observations suggest that fetal granules have a slower rhythm of zymogen condensation and an irregular shape that could be due to the particular composition of the matrix and the absence of GP-2. We conclude that, in the exocrine pancreas, secretory granules can be formed under various conditions, even with a matrix containing a ratio of components very different from that of the normal mature animal.