Nucleoporin98-96 Function Is Required for Transit Amplification Divisions in the Germ Line of Drosophila melanogaster

Production of specialized cells from precursors depends on a tightly regulated sequence of proliferation and differentiation steps. In the gonad of Drosophila melanogaster, the daughters of germ line stem cells (GSC) go through precisely four rounds of transit amplification divisions to produce clusters of 16 interconnected germ line cells before entering a stereotypic differentiation cascade. Here we show that animals harbouring a transposon insertion in the center of the complex nucleoporin98-96 (nup98-96) locus had severe defects in the early steps of this developmental program, ultimately leading to germ cell loss and sterility. A phenotypic analysis indicated that flies carrying the transposon insertion, designated nup98-962288, had dramatically reduced numbers of germ line cells. In contrast to controls, mutant testes contained many solitary germ line cells that had committed to differentiation as well as abnormally small clusters of two, four or eight differentiating germ line cells. This indicates that mutant GSCs rather differentiated than self-renewed, and that these GSCs and their daughters initiated the differentiation cascade after zero, or less than four rounds of amplification divisions. This phenotype remained unaffected by hyper-activation of signalling pathways that normally result in excessive proliferation of GSCs and their daughters. Expression of wildtype nup98-96 specifically in the germ line cells of mutant animals fully restored development of the GSC lineage, demonstrating that the effect of the mutation is cell-autonomous. Nucleoporins are the structural components of the nucleopore and have also been implicated in transcriptional regulation of specific target genes. The nuclear envelopes of germ cells and general nucleocytoplasmic transport in nup98-96 mutant animals appeared normal, leading us to propose that Drosophila nup98-96 mediates the transport or transcription of targets required for the developmental timing between amplification and differentiation

Standard of disocclusion in complete dentures supported by implants without free distal ends: analysis by the finite elements method

OBJECTIVE: The occlusal patterns are key requirements for the clinical success of oral rehabilitation supported by implants. This study compared the stresses generated by the disocclusion in the canine guide occlusion (CGO) and bilateral balanced occlusion (BBO) on the implants and metallic infrastructure of a complete Brånemark protocol-type denture modified with the inclusion of one posterior short implant on each side. MATERIAL AND METHODS: A three-dimensional model simulated a mandible with seven titanium implants as pillars, five of them installed between the mental foramen and the two posterior implants, located at the midpoint of the occlusal surface of the first molar. A load of 15 N with an angle of 45º was applied to a tooth or distributed across three teeth to simulate the CGO or BBO, respectively. The commercial program ABAQUS(®) was used for the model development, before and after the processing of the data. The results were based on a linear static analysis and were used to compare the magnitude of the equivalent stress for each of the simulations. RESULTS: The results showed that the disocclusion in CGO generated higher stresses concentrated on the working side in the region of the short implant. In BBO, the stresses were less intense and more evenly distributed on the prosthesis. The maximum stress found in the simulation of the disocclusion in CGO was two times higher than that found in the simulation of the BBO. The point of maximum stress was located in the neck of the short implant on the working side. CONCLUSIONS: Under the conditions of this study, it was concluded that the BBO pattern was more suitable than CGO for the lower complete denture supported by implants without free distal ends

Clinical and laboratory passive fit assessment of implant‐supported zirconia restorations fabricated using conventional and digital workflow

Background Long-term success of implant-supported restorations can be affected by the accuracy of the prosthodontic workflow which may differ between conventional and digital techniques. Purpose The purpose was to compare the fit of two-implant-supported restorations, fabricated using conventional and digital workflows and to assess the influence of distance and angulation between the implants on the passive fit of the prosthesis. The SR test was selected to evaluate the fit of two-implant-supported zirconia restorations. Materials and Methods Forty-eight zirconia two-implant-supported restorations were fabricated according to conventional (group C, n = 24) and digital (group D, n = 24) workflows. The SR parameter was calculated as a difference of rotation angles of each screw in passive and nonpassive situations. SR values between groups C and D were compared by performing measurements intraorally, on master and control casts. Results SR intraorally in group C (16.25 +/- 15.52 degrees) was higher than it was in group D (13.85 +/- 10.78 degrees), but the difference was not statistically significant (P = .557). While measuring SR on the master cast, group C SR (6.04 +/- 7.43 degrees) had lower values than group D (13.12 +/- 13.86 degrees) (P = .0039). No statistically significant correlations were found between SR measurements and inter-implant distance or angulation. Restorations with inter-implant angle higher than 10 degrees differed significantly from those with less than 10 degrees angulation. Conclusions Digital restorations had a better fit on the control cast, which was used as a reference in this study. Angulation of more than 10 degrees between the implants could negatively affect the passive fit of the digitally fabricated restorations intraorally.</p