To follow the dynamics of meiosis in the model plant Arabidopsis, we have established a live cell imaging setup to observe male meiocytes. Our method is based on the concomitant visualization of microtubules (MTs) and a meiotic cohesin subunit that allows following five cellular parameters: cell shape, MT array, nucleus position, nucleolus position, and chromatin condensation. We find that the states of these parameters are not randomly associated and identify 11 cellular states, referred to as landmarks, which occur much more frequently than closely related ones, indicating that they are convergence points during meiotic progression. As a first application of our system, we revisited a previously identified mutant in the meiotic A-type cyclin TARDY ASYNCHRONOUS MEIOSIS (TAM). Our imaging system enabled us to reveal both qualitatively and quantitatively altered landmarks in tam, foremost the formation of previously not recognized ectopic spindle- or phragmoplast-like structures that arise without attachment to chromosomes.

Little is known how patterns of cross-over (CO) numbers and distribution during meiosis are established. Here, we reveal that cyclin-dependent kinase A;1 (CDKA;1), the homolog of human Cdk1 and Cdk2, is a major regulator of meiotic recombination in Arabidopsis. Arabidopsis plants with reduced CDKA;1 activity experienced a decrease of class I COs, especially lowering recombination rates in centromere-proximal regions. Interestingly, this reduction of type I CO did not affect CO assurance, a mechanism by which each chromosome receives at least one CO, resulting in all chromosomes exhibiting similar genetic lengths in weak loss-of-function cdka;1 mutants. Conversely, an increase of CDKA;1 activity resulted in elevated recombination frequencies. Thus, modulation of CDKA;1 kinase activity affects the number and placement of COs along the chromosome axis in a dose-dependent manner.

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23Meiosis is essential for sexual reproduction and key to the generation of genetic 24 diversity. To reveal the robustness of meiocyte differentiation and progression 25 through meiosis, we have here established a live cell imaging setup to follow the 26 dynamics of individual male meiocytes in Arabidopsis. Our method is based on the 27 concomitant visualization of microtubules and a meiotic cohesion subunit that 28 allowed following five cellular parameters: cell shape, nucleus position, nucleolus 29 position, chromatin condensation and microtubule array. We find that the states of 30 these parameters are not randomly associated and identify 11 states, referred to as 31 landmarks, that occur much more frequently than closely related states, indicating 32 that they are convergent points of meiotic progression. With this, the here-presented 33 landmark system represents a novel method to analyze meiosis not only allowing a 34 high-temporal dissection but also providing new criteria to evaluate mutants or 35 environmental effects on meiosis. 36 37 38 First, we selected inflorescences and removed all but one young flower 128 primordium presumably containing meiotic stages as indicated by its round shape 129 and an approximate diameter of 0.4-0.6 mm ( Figure 1B), corresponding to stage 9 of 130 flower development (Smyth et al., 1990). Next, the upper sepal was removed giving 131 access to two of the six anthers since the petals are shorter than the anthers at this 132 floral stage. Finally, the bud along with the pedicel and a few millimeters of the stem 133 was embedded into Arabidopsis Apex Culture Medium (ACM) and stabilized with a 134 drop of agarose ( Figure 1A,B). In agreement with the previous analysis of the SAM, 135 we found that the flower buds stayed alive on the ACM medium for up to seven days 136 during which flowers grew and developed normally ( Figure 1C). 137Imaging was performed with an up-right confocal laser scanning microscopy 138 equipped with a water immersion objective. The entire flower bud was submerged in 139 water and the objective was brought into direct contact with the sample (Figure 1A).

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Am Universitätskrankenhaus Erlangen (4 Kliniken, ca. 1000 Betten) werden seit 1. 1. 1970 die stationären Patienten zentral mit Hilfe eines Prozeßrechners Siemens 305 aufgenommen. Alle Patientendaten werden im Dialogverkehr zwischen Blattschreibern und Rechner eingegeben. Korrekturmöglichkeiten und formale Prüfungen sind im Programm enthalten. Die Patienten-Datei baut sich aus fest numerierten Plattenspeicherfeldern auf, die einer »Patienten-Nr.« entsprechen. Aufgrund der fehlergeprüften Daten werden obligatorisch und ohne besondere Anforderung für Verwaltungs- und ärztliche Zwecke zahlreiche Arbeitsmittel über Schnelldrucker ausgedruckt.

Objective: We present the operational organization and daily workflow of our Hamburg model and the results of the years 2007–2011 concerning donation of corneas, musculoskeletal and, since 2010, cardiovascular tissues. Methods: Each of the about 3,600 deceased every year undergoes an evaluation process by two coordinators on duty, the tissue coordinator and the family coordinator. All donation connected issues are carried out within the standardized protocols of a quality management system and documented in a special data base. Two catamnestic surveys evaluated the satisfaction of donor families retrospectively. The inclusion rate for cornea donation was 23% and for musculoskeletal donation 10%, with a decrease after the 75 years age restriction of musculoskeletal donors in 2011 defined by the contracting tissue bank German Institute for Cell and Tissue Replacement gGmbH (DIZG), Berlin. Results: Since 2007 1,268 corneas were explanted altogether, reflecting an increasing explantation rate from 156 (University Medical Center Hamburg-Eppendorf (UMC: 9) in 2007 up to 304 (UMC: 52) in 2011. Overall 173 musculoskeletal donors (5 years) and 11 cardiovascular donors (2 years) spent tissues. The consent rate was much higher. The evaluation of the families reflected a positive feedback for the guiding of the donation process. Conclusion: Forensic institutes can act as an interface between donors and recipients without neglecting forensic investigations. They are uniquely positioned to recognize potential donors. In addition, the contact with a physician of the forensic institute may help families during the mourning phase.

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