Solubility and disintegration of a glass ionomer cement

ABSTRACT

The mechanism of erosion of a glass ionomer cement (PR Scell) was studied using two experimental procedures: discs of dental cement were immersed in distilled water under unrenewed conditions as defined by ISO standard or under continuously running distilled water to simulate the oral environment. Both experiments suggest that erosion is important and highly correlated to the cryolithe material included in the formulation of this cement.     

Origins of bone repair in the armour of fossil fish: response to a deep wound by cells depositing dentine instead of dermal bone

The outer armour of fossil jawless fishes (Heterostraci) is, predominantly, a bone with a superficial ornament of dentine tubercles surrounded by pores leading to flask-shaped crypts (ampullae). However, despite the extensive bone present in these early dermal skeletons, damage was repaired almost exclusively with dentine. Consolidation of bone, by dentine invading and filling the vascular spaces, was previously recognized in Psammolepis and other heterostracans but was associated with ageing and dermal shield wear (reparative). Here, we describe wound repair by deposition of dentine directly onto a bony scaffold of fragmented bone. An extensive wound response occurred from massive deposition of dentine (reactionary), traced from tubercle pulp cavities and surrounding ampullae. These structures may provide the cells to make reparative and reactionary dentine, as in mammalian teeth today in response to stimuli (functional wear or damage). We suggest in Psammolepis, repair involved mobilization of these cells in response to a local stimulatory mechanism, for example, predator damage. By comparison, almost no new bone is detected in repair of the Psammolepis shield. Dentine infilling bone vascular tissue spaces of both abraded dentine and wounded bone suggests that recruitment of this process has been evolutionarily conserved over 380 Myr and precedes osteogenic skeletal repair.     

Gastrulation of Gastrotheca riobambae in comparison with other frogs

Blastopore formation, the embryonic disk, archenteron and notochord elongation, and Brachyury expression in the marsupial frog Gastrotheca riobambae was compared with embryos of Xenopus laevis and of the dendrobatids Colostethus machalilla and Epipedobates anthonyi. In contrast with X. laevis embryos, the blastopore closes before elongation of the archenteron and notochord in the embryos of G. riobambae and of the dendrobatid frogs. Moreover, the circumblastoporal collar (CBC) thickens due to the accumulation of involuted cells. An embryonic disk, however, is formed only in the G. riobambae gastrula. We differentiate three gastrulation patterns according to the speed of development: In X. laevis, elongation of the archenteron and notochord begin in the early to mid gastrula, whereas in the dendrobatids C. machalilla and E. anthonyi the archenteron elongates at mid gastrula and the notochord elongates after gastrulation. In G. riobambae, only involution takes place during gastrulation. Archenteron and notochord elongation occur in the post gastrula. In the non-aquatic reproducing frogs, the margin of the archenteron expands anisotropically, resulting in an apparent displacement of the CBC from a medial to a posterior location, resembling the displacement of Hensen's node in the chick and mouse. The differences detected indicate that amphibian gastrulation is modular.     

Size of genetic bottlenecks leading to virus fitness loss is determined by mean initial population fitness.

Genetic bottlenecks are important events in the genetic diversification of organisms and colonization of new ecological niches. Repeated bottlenecking of RNA viruses often leads to fitness losses due to the operation of Muller's ratchet. Herein we use vesicular stomatitis virus to determine the transmission population size which leads to fitness decreases of virus populations. Remarkably, the effective size of a genetic bottleneck associated with fitness loss is greater when the fitness of the parental population increases. For example, for starting virus populations with low fitness, population transfers of five-clone-to-five-clone passages resulted in a fitness increase. However, when a parental population with high fitness was transferred, 30-clone-to-30-clone passages were required simply to maintain fitness values.     

N,N-dimethyl-thioamphetamine and methyl-thioamphetamine, two non-neurotoxic substrates of 5-HT transporters, have scant in vitro efficacy for the induction of transporter-mediated 5-HT release and currents

We studied two non-neurotoxic amphetamine derivatives (methyl-thioamphetamine, MTA and N,N- dimethylMTA, DMMTA) interacting with serotonin (5-HT) transporters (SERTs) with affinities comparable to that of p- Cl-amphetamine (pCA). The rank order for their maximal effects in inducing both [³H]5-HT release from rat brain synaptosomes or hSERT-expressing HEK-293 cells, and currents in hSERT-expressing oocytes, was pCA >> MTA ≥ DMMTA. A correlation between drug-induced release and currents is also strengthened by the similar bell shape of the dose–response curves. Release experiments indicated that MTA and DMMTA are SERT substrates although MTA is taken up by HEK-293 cells with a V _max 40% lower than pCA. The weak effects of MTA and DMMTA in vitro might therefore be due to their properties as 'partial substrates' on the mechanisms, other than translocation, responsible for currents and/or release. After either local or systemic in vivo administration, MTA and DMMTA release 5-HT in a manner comparable to pCA. These findings confirm that the neurotoxic properties of some amphetamine derivatives are independent of their 5-HT-releasing activity in vivo . It is worth noting that only those amphetamine derivatives with high efficiency in inducing 5-HT release and currents in vitro have neurotoxic properties.     

The novel nucleotide 4KNTP, in high concentrations in erythrocytes of renal failure children: a comparison with accumulation of other putative precursors in the plasma

We have measured the concentrations of metabolites related to the turnover of NAD, which accumulate in the blood of children with renal failure. One is a novel nucleotide, identified as the N1-riboside triphosphate of 4-pyridone-3-carboxamide (4PYTP), also described as 4KNTP, which accumulates in the erythrocytes in parallel with renal failure.     

Effects of cage beddings on microsomal oxidative enzymes in rat liver

The purpose of the present studies was to evaluate the effects of some commercially available cage beddings on rat liver microsomal cytochrome P-450-dependent drug-metabolizing enzyme, ethylmorphine N-demethylase, and the carcinogen-metabolizing enzyme, benzo(a)pyrene hydroxylase. Sprague-Dawley rats were housed in cages containing cedar chip, corncob or heat-treated pinewood bedding for 3 weeks. Control rats were housed in cages on wire bottom floors containing no bedding material. Rats housed in cages containing cedar chip showed 18, 46 and 49% increases in liver cytochrome P-450 content, ethylmorphine N-demethylase and benzo(a)pyrene hydroxylase activities, respectively. The liver enzyme activities of rats housed in cages containing corncob bedding were similar to those obtained with control rats. In contrast, the pinewood-bedded rats showed a 21% decrease in ethylmorphine N-demethylase activity without affecting cytochrome P-450 content and benzo(a)pyrene hydroxylase activity. Hexobarbital-induced sleep times of the variously bedded rats were similar to those of control animals. These data suggest that the commercial bedding materials differ in their abilities to affect liver microsomal enzymes. Thus, interlaboratory variability in basal enzyme activities reported in the literature may be partly due to bedding materials used in the animal's cages.     

Validation of a 1DL earliness per se (eps) flowering QTL in bread wheat (Triticum aestivum)

Vernalization, photoperiod and the relatively poorly defined earliness per se (eps) genes regulate flowering in plants. We report here the validation of a major eps quantitative trait locus (QTL) located on wheat 1DL using near isogenic lines (NILs). We used four independent pairs of NILs derived from a cross between Spark and Rialto winter wheat varieties, grown in both the field and controlled environments. NILs carrying the Spark allele, defined by QTL flanking markers Xgdm111 and Xbarc62, consistently flowered 3–5 days earlier when fully vernalized relative to those with the Rialto. The effect was independent of photoperiod under field conditions, short days (10-h light), long days (16-h light) and very long days (20-h light). These results validate our original QTL identified using doubled haploid (DH) populations. This QTL represents variation maintained in elite north-western European winter wheat germplasm. The two DH lines used to develop the NILs, SR9 and SR23 enabled us to define the location of the 1DL QTL downstream of marker Xgdm111. SR9 has the Spark 1DL arm while SR23 has a recombinant 1DL arm with the Spark allele from Xgdm111 to the distal end. Our work suggests that marker assisted selection of eps effects is feasible and useful even before the genes are cloned. This means eps genes can be defined and positionally cloned in the same way as the photoperiod and vernalization genes have been. This validation study is a first step towards fine mapping and eventually cloning the gene directly in hexaploid wheat.     

Biological control of snails exerted byEuglandina rosea (Ferussac) in Bermuda

Résumé Cet article relate un essai de lutte biologique effectué aux Bermudes contre deux Gastéropodes nuisibles:Rumina decollata (Linné) (Achatinidae) etOtata lactea Muller (Helicidae) au moyen du mollusque carnivoreEuglandina rosea (Ferussac). 845Euglandina, ont été libérés dans l'?le en 1958 et 1960. Dès 1962, il était évident que l'opération se soldait par un succès complet contreOtata mais par un échec contreRumina. 500Euglandina ont été récoltés en quelques jours aux Bermudes et expédiés à l'?le Maurice, à Hong-kong, Nord-Bornéo et les Bahamas pour de semblables essais.