Variable Regions of PI4P 5-Kinases Direct PtdIns(4,5)P2 Toward Alternative Regulatory Functions in Tobacco Pollen Tubes

The apical plasma membrane of pollen tubes contains different PI4P 5-kinases that all produce phosphatidylinositol-4,5-bisphosphate [PtdIns(4,5)P2] but exert distinct cellular effects. In the present example, overexpression of Arabidopsis AtPIP5K5 or tobacco NtPIP5K6-1 caused growth defects previously attributed to increased pectin secretion. In contrast, overexpression of Arabidopsis AtPIP5K2 caused apical tip swelling implicated in altering actin fine structure in the pollen tube apex. AtPIP5K5, NtPIP5K6-1, and AtPIP5K2 share identical domain structures. Domains required for correct membrane association of the enzymes were identified by systematic deletion of N-terminal domains and subsequent expression of fluorescence-tagged enzyme truncations in tobacco pollen tubes. A variable linker region (Lin) contained in all PI4P 5-kinase isoforms of subfamily B, but not conserved in sequence, was recognized to be necessary for correct subcellular localization of AtPIP5K5, NtPIP5K6-1, and AtPIP5K2. Deletion of N-terminal domains including the Lin domain did not impair catalytic activity of recombinant AtPIP5K5, NtPIP5K6-1, or AtPIP5K2 in vitro; however, the presence of the Lin domain was necessary for in vivo effects on pollen tube growth upon overexpression of truncated enzymes. Overexpression of catalytically inactive variants of AtPIP5K5, NtPIP5K6-1, or AtPIP5K2 did not influence pollen tube growth, indicating that PtdIns(4,5)P2 production rather than structural properties of PI4P 5-kinases was relevant for the manifestation of growth phenotypes. When Lin domains were swapped between NtPIP5K6-1 and AtPIP5K2 and the chimeric enzymes overexpressed in pollen tubes, the chimeras reciprocally gained the capabilities to invoke tip swelling or secretion phenotypes, respectively. The data indicate that the Lin domain directed the enzymes into different regulatory contexts, possibly contributing to channeling of PtdIns(4,5)P2 at the interface of secretion and actin cytoskeleton

MINI REVIEW: ASSESSING TECHNICAL SKILLS IN YOUTH ATHLETES USING SPORTS BIOMECHANICAL METHODS

Since technical skills are suggested to play a crucial role in talent identification and development (TID) programs, sports biomechanical assessment methods could gain in importance within this field. This systematic mini review provides a brief overview of the biomechanical approaches used so far to assess technical skills and the respective findings in the context of TID. Our results show that few studies have used biomechanical approaches to identify or develop talented young athletes but those doing so found promising results. On the basis of those studies and given the advancements in technologies, we discuss possible obstacles and the potential of biomechanical assessment methods for motion and technique analysis in the context of talent research

The influence of ambient lighting on the detection of small contrast elements in digital dental radiographs

Objectives: The aim of this study was to evaluate the effect of ambient light on the detection of contrast elements in digital dental radiographs. Materials and methods: A high-contrast standardized digital radiograph of an aluminum step wedge containing 32 boreholes of different depth was cut into 40 isometric images. Images were presented at random on a 17-in cathode ray tube (CRT) monitor at different ambient background illuminations of 0, 50, 200, and 500lx. Twenty observers stated twice their blinded decision whether or not they could perceive a dark spot on a five-point confidence scale. Areas (Az) under receiver operating characteristic curves were calculated and compared between the four different ambient illuminations using the Friedman test. Statistical significance was set at p < 0.05. Overall agreement was estimated determining the intraclass correlation coefficient. Results: The Az values (0.735 for 0lx, 0.728 for 50lx, 0.735 for 200lx, and 0.788 for 500lx) did not significantly differ (p = 0.796) between the four ambient lighting levels. Conclusions: The detection of small contrast features in digital dental radiographs on a CRT monitor seems to be comparable over a wide range of ambient background illumination. Clinical relevance: The ambient light in dental offices of <500lx may not negatively impact the diagnostic performance of digital dental radiograph

Community Health Workers to Improve Antenatal Care and PMTCT Uptake in Dar es Salaam, Tanzania: A Quantitative Performance Evaluation

Background: Home visits by community health workers (CHW) could be effective in identifying pregnant women in the community before they have presented to the health system. CHW could thus improve the uptake of antenatal care (ANC), HIV testing, and prevention of mother-to-child transmission (PMTCT) services. Methods: Over a 16-month period, we carried out a quantitative evaluation of the performance of CHW in reaching women early in pregnancy and before they have attended ANC in Dar es Salaam, Tanzania. Results: As part of the intervention, 213 CHW conducted more than 45,000 home visits to about 43,000 pregnant women. More than 75% of the pregnant women identified through home visits had not yet attended ANC at the time of the first contact with a CHW and about 40% of those who had not yet attended ANC were in the first trimester of pregnancy. Over time, the number of pregnant women the CHW identified each month increased, as did the proportion of women who had not yet attended ANC. The median gestational age of pregnant women contacted for the first time by a CHW decreased steadily and significantly over time (from 21/22 to 16 weeks, P-value for test of trend <0.0001). Conclusions: A large-scale CHW intervention was effective in identifying pregnant women in their homes early in pregnancy and before they had attended ANC. The intervention thus fulfills some of the conditions that are necessary for CHW to improve timely ANC uptake and early HIV testing and PMTCT enrollment in pregnancy