Tg (9 HSA-MYC), a homozygous lethal insertion in the mouse

Transgenic mice generated with different DNA sequences were surveyed for possible homozygous mutant phenotypes. We found an embryonic lethal mutation in the transgenic mouse strain (MT-MYC12.4) containing the human c-myc gene. Embryos homozygous for the transgene die shortly after implantation. The strain MT-MYC12.4 carries approximately 50 tandem copies of the recombinant plasmid sequence. The 3 flanking sequence has been cloned and analyzed. It contains a unique sequence that has been conserved during evolution and maps to Chromosome (Chr) 9. This mutant has been designated Tg 9 (HSA-MYC).     

Effects of Physicochemical Factors on the Adhesion to Cellulose Avicel of the Ruminal Bacteria Ruminococcus flavefaciens and Fibrobacter succinogenes subsp. succinogenes

Ruminococcus flavefaciens adhered instantly to cellulose, while Fibrobacter succinogenes had the highest percentage of adherent cells after about 25 min of contact between bacteria and cellulose. Adhesion of R. flavefaciens was unaffected by high concentrations of sugars (5%), temperature, pH, oxygen, metabolic inhibitors, and lack of Na⁺. In contrast, the attachment was affected by the removal of divalent cations (Mg²⁺ and Ca²⁺), the presence of cellulose derivatives (methylcellulose and hydroxyethylcellulose), and cystine. Adhesion of F. succinogenes was sensitive to low and high temperatures, high concentrations of glucose and cellobiose (5%), hydroxyethylcellulose (0.1%), redox potential, pH, lack of monovalent cations, and the presence of an inhibitor of membrane ATPases or lasalocid and monensin. Cells of F. succinogenes heated at 100°C no longer were adherent. On the other hand, adhesion was insensitive to the lack of divalent cations (Mg²⁺ and Ca²⁺), the presence of 2,4-dinitrophenol, tetrachlorosalicylanilide, or inhibitors of the electron transfer chains. Adhesion of F. succinogenes seems to be related to the metabolic functions of the cell. External proteins and/or cellulases themselves might play a part in the attachment process. Several mechanisms are probably involved in the adhesion of R. flavefaciens, the main one being the interaction between the large glycocalyx and the divalent cations Ca²⁺ and Mg²⁺. Hydrophobic bonds and enzymes may also be involved.     

Effects of light,phosphate, and oxygen on ethylene formation and conidiation in surface cultures ofpenicillium cyclopium westling

Penicillium cyclopium growing in a surface culture with 2-ketoglutarate or glutamate as a sole carbon source produced ethylene in two phases. The first peak of ethylene production (EP 1) was associated with aerial mycelium growth whereas the second peak of ethylene production (EP 2) occurred with formation and maturation of conidia. Conidiation was induced by blue light between 120 and 172 h after the culture was started and depended on the presence of a carbon source at the stage of conidiophore initiation. Exogenous phosphate content dropper rapidly before the onset of conidiation. The EP 2 was connected with conidiation via this drop. Addition of phosphate prior to the conidiophore initiation and during conidiation inhibited EP 2 without affecting conidiation, but conidia lacked a green pigment and their germination ability decreased by 905. Exogenous ethylene did not restore normal development. The EP 2 in asporogenic cultures was evoked by incubation in the dark and by phosphate removal. The EP 2 and conidiation were accompanied by an increased oxygen consumption. The EP 1 yield of ethylene depended only on biomass growth and was unaffected by any treatment mentioned above.     

A mathematical model of growth and alkaloid production in the submerged culture of Claviceps purpurea

A mathematical model of the batch cultivation of Claviceps purpurea was formulated. The main attention was devoted to the effect of exocellular and intracellular phosphate on the growth of the mycelium and production of clavine alkaloid under experimental conditions without limitation by carbon and nitrogen sources. The method of nonlinear regression was used ot predict the optional technological regime of the phosphate addition in the batch culture at different time intervals of additions.     

Comparaison entre des Crustacésa Céphalon isolé, a propos d'un beau matériel de syncarides du paléozoïque implications phylogéniques

Are the Eumalacostraca issued from a model of Crustacea which the carapace would have disapeared later on in some of them, and persisted in others, or from one without carapace that some of its decendants would have acquired? In the two instances this ancestor would goes far back, seeing that, already, in the Devonian, Syncarida, Stomatopoda, Phyllocarida and Eocarida were differenciated. With regard to the preliminary survey on a fine material of Syncarida from the Stephanian of the region of Autun, comparisons between two models of Crustaceans from which the cephalon includes only sensorial and gnathal segments, without adjunction of any thoracic metamere, allow to specify the notion of carapace, and to surround the question. The great oldness of the origin of the phyla possessing or not possessing a carapace seems to exclude the hypothesis of a passing over from one model to the other and suggests a representation of the common ancestor which have to be searched in the Cambrian period.     

Mechanosensitive Adaptation of E-Cadherin Turnover across adherens Junctions

In the natural and technological world, multi-agent systems strongly depend on how the interactions are ruled between their individual components, and the proper control of time-scales and synchronization is a key issue. This certainly applies to living tissues when multicellular assemblies such as epithelial cells achieve complex morphogenetic processes. In epithelia, because cells are known to individually generate actomyosin contractile stress, each individual intercellular adhesive junction line is subjected to the opposed stresses independently generated by its two partner cells. Contact lines should thus move unless their two partner cells mechanically match. The geometric homeostasis of mature epithelia observed at short enough time-scale thus raises the problem to understand how cells, if considered as noisy individual actuators, do adapt across individual intercellular contacts to locally balance their time-average contractile stress. Structural components of adherens junctions, cytoskeleton (F-actin) and homophilic bonds (E-cadherin) are quickly renewed at steady-state. These turnovers, if they depend on forces exerted at contacts, may play a key role in the mechanical adaptation of epithelia. Here we focus on E-cadherin as a force transducer, and we study the local regulation and the mechanosensitivity of its turnover in junctions. We show that E-cadherin turnover rates match remarkably well on either side of mature intercellular contacts, despite the fact that they exhibit large fluctuations in time and variations from one junction to another. Using local mechanical and biochemical perturbations, we find faster turnover rates with increased tension, and asymmetric rates at unbalanced junctions. Together, the observations that E-cadherin turnover, and its local symmetry or asymmetry at each side of the junction, are mechanosensitive, support the hypothesis that E-cadherin turnover could be involved in mechanical homeostasis of epithelia.     

Salt Content Impacts Food Preferences and Intake among Children

Decreasing dietary sodium intake, which can be achieved by reducing salt content in food, is recommended. Salt contributes to the taste of foods and makes them more enjoyable. Whether a food is liked or disliked is an important determinant of food intake, especially among children. However, the role of salt in children''s food acceptance has received little attention. The impact of salt content on children''s hedonic rating and intake of two foods was investigated in children. Using a within-subject crossover design, we recruited 75 children (8–11 years) to participate in five lunches in their school cafeteria. The target foods were green beans and pasta. The added salt content was 0, 0.6 or 1.2 g/100 g. The children''s intake (g) of all lunch items was measured. The children provided their hedonic rating of the food, a preference ranking and a saltiness ranking in the laboratory. Children could rank the foods according to salt content, and they preferred the two saltier options. A food-specific effect of salt content on intake was observed. Compared to the intermediate level (0.6 g salt/100 g), not adding salt decreased green bean intake (−21%; p = 0.002), and increasing the salt content increased pasta intake (+24%; p<0.0001). Structural Equation Modeling was used to model the relative weights of the determinants of intake. It showed that the primary driver of food intake was the child''s hunger; the second most important factor was the child''s hedonic rating of the food, regardless of its salt content, and the last factor was the child''s preference for the particular salt content of the food. In conclusion, salt content has a positive and food-specific effect on intake; it impacted food preferences and intake differently in children. Taking into account children''s preferences for salt instead of their intake may lead to excessive added salt.     

Generation of an Fsp1 (fibroblast‐specific protein 1)‐Flpo transgenic mouse strain

Recombination systems represent a major breakthrough in the field of genetic model engineering. The Flp recombinases (Flp, Flpe, and Flpo) bind and cleave DNA Frt sites. We created a transgenic mouse strain ([Fsp1‐Flpo]) expressing the Flpo recombinase in fibroblasts. This strain was obtained by random insertion inside mouse zygotes after pronuclear injection. Flpo expression was placed under the control of the promoter of Fsp1 (fibroblast‐specific protein 1) gene, whose expression starts after gastrulation at Day 8.5 in cells of mesenchymal origin. We verified the correct expression and function of the Flpo enzyme by several ex vivo and in vivo approaches. The [Fsp1‐Flpo] strain represents a genuine tool to further target the recombination of transgenes with Frt sites specifically in cells of mesenchymal origin or with a fibroblastic phenotype.     

New preparation techniques for molecular and in‐situ analysis of ancient organic micro‐ and nanostructures

Organic microfossils preserved in three dimensions in transparent mineral matrices such as cherts/quartzites, phosphates, or carbonates are best studied in petrographic thin sections. Moreover, microscale mass spectrometry techniques commonly require flat, polished surfaces to minimize analytical bias. However, contamination by epoxy resin in traditional petrographic sections is problematic for the geochemical study of the kerogen in these microfossils and more generally for the in situ analysis of fossil organic matter. Here, we show that epoxy contamination has a molecular signature that is difficult to distinguish from kerogen with time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). This contamination appears pervasive in organic microstructures embedded in micro‐ to nano‐crystalline carbonate. To solve this problem, a new semi‐thin section preparation protocol without resin medium was developed for micro‐ to nanoscale in situ investigation of insoluble organic matter. We show that these sections are suited for microscopic observation of Proterozoic microfossils in cherts. ToF‐SIMS reveals that these sections are free of pollution after final removal of a <10 nm layer of contamination using low‐dose ion sputtering. ToF‐SIMS maps of fragments from aliphatic and aromatic molecules and organic sulfur are correlated with the spatial distribution of organic microlaminae in a Jurassic stromatolite. Hydrocarbon‐derived ions also appeared correlated with kerogenous microstructures in Archean cherts. These developments in analytical procedures should help future investigations of organic matter and in particular, microfossils, by allowing the spatial correlation of microscopy, spectroscopy, precise isotopic microanalyses, and novel molecular microanalyses such as ToF‐SIMS.