N Nanninga's research while affiliated with University of Amsterdam and other places

... A similar phenomenon seemed to occur with the variable visibility in freeze fractures of the E. coli nucleoid: the latter could not always be distinguished, probably due to ice crystal formation. These problems and, in addition, the difference in nucleoid appearance between osmium tetroxide and glutaraldehyde fixed [4] led Nanninga to stimulate the development of a confocal scanning light microscope [5,6], which promised to bridge the gap in resolution between electron and light microscopy. ...

... For instance, the differences in global cell wall architecture between Gram-positive or Gram-negative microorganisms is reflected also in their surface consitituents and properties ( Popescu and Doyle, 1996;Beveridge, 2001). The structure and properties of the bacterial cell wall have been reviewed in detail before by Roger et al. (1978), Beveridge (1981), Schockman and Barrett (1983), Cooper (1991), Nanninga et al. (1992), Höltje (1998), andBeveridge (1999). ...

... Thus, in the strain used, the C period is distributed over two subsequent cell cycles. Because cell length can be used as a measure of time in a steadystate culture, we could calculate the expected number of oriC, ftsQAZ and minB DNA regions per cell length from the determined C and D periods (Nanninga et al., 1982 and references therein). Assuming that replication proceeds at a constant rate, we expected two oriC regions, two ftsQAZ regions and one minB region in newborn cells; these numbers double before the next cell division. ...

... Phragmoplast correction has been observed in bean, maize, and onion cells where imaging experiments revealed tilted spindles (e.g. >50% in maize epidermal cells), but normal final division orientations (Cleary and Smith, 1998;Oud and Nanninga, 1992;Palevitz, 1986). In onion guard mother cells, live cell imaging demonstrated correction of oblique spindle and phragmoplast angles occurs as the cell plate expands along the location previously marked by the PPB (Palevitz, 1986). ...

... The degree of MSA was determined by counting the number of cells that possessed mating structures after visualizing the papillae by immunofluorescence (m). reaction involves the elongation of the outer microtubules, which results in a rounding of the flagellar tip, and the accumulation of fibrous material (Mesland et al., 1980; EIzenga et al., 1982). FTA was induced in gametes of both mating types by WGA, but the process was less complete than during sexual agglutination. ...

... To determine if the DDGR seen with mec treatment was due to mec itself or the inhibition of PBP2, we used a temperaturesensitive mutant of PBP2 (PBP2ts) 39 . At temperatures >40 o C, the PBP2ts mutant grows slowly, and the cells are round, while at the permissive temperature (30 o C) the cells grow as rods. ...

... But first, we must obtain an estimate of underlying length distribution for the glycan strands in the cylindrical region of the cell by combining Obermann and Höltje's data for minicells with their data for wild-type cells. To do this, we follow Obermann and Höltje in estimating that 2/9 of the PG in whole cells is polar PG while the remaining 7/9 of the PG is cylindrical PG; this estimated partitioning was based on surface measurements of isolated murein sacculi (59). Using these estimates, we subtracted a suitably weighted version of the minicell (polar) length distribution from the wild-type (whole cell) length distribution to yield the estimated length distribution for the cylindrical PG from 1 to 30 DS units. ...

... Reports of a less rigid chromatin state, due in part to the lack and/or absence of chromatin remodeling markers, in undifferentiated cells has been reported (Keohane et al., 1996;Francastel et al., 2000;Lee et al., 2004;. In normal somatic cells, centromeres are mostly found nearer to the nuclear periphery or around nucleoli, and also often by the CT periphery (Weierich et al., 2003;Gilchrist et al., 2004), although this may depend on the stage of the cell cycle (Ferguson et al., 1992;Weimer et al., 1992;Hulspas et al., 1994). Previous reports have found that in human cells during differentiation, centromeres tend to move nearer to the nuclear periphery (Salníková et al., 2000;Bártová et al., 2001;Galiová et al., 2004;Horáková et al., 2010), or relocate more centrally (Bártová et al., 2008) to the heterochromatin surrounding nucleoli, and cluster together in chromo-centromeres (Alcobia et al., 2000;Beil et al., 2002). ...

... Although diffraction limit is surpassed in fluorescence imaging (Sheppard, 1988;Hell & Wichmann, 1994;Gustafsson, 2000;), resolution improvement in other conventional optical techniques such as reflection and other modalities are constantly attempted (Ploem, 1975;Brakenhoff et al., 1979;Koerten et al., 1979;1980;Cox et al., 1982a;Cox et al., 1982b;Brakenhoff et al., 1984;Cornelesetenvelde et al., 1989;Prins et al., 1993;Brakenhoff & Muller, 1996;Prins et al., 2006;Azeredo et al., 2016;Ploem & Prins, 2017;Sivaguru et al., 2017b;Sivaguru et al., 2018a). Superresolution techniques such as stimulated emission and depletion (Hell & Wichmann, 1994), structured illumination (Gustafsson, 2000), Airyscan (Sheppard, 1988;Huff, 2015) and PALM/STORM (Betzig et al., 2006) have recently been commercialised to go beyond diffraction limit of resolution in biological samples labelled with fluorescent targets. ...

... The above new possibilities led us to design a computer-controlled confocal microscope (van der Voort et al., 1985 [165]). Essential is the use of pinholes, that is, an illuminated pinhole is focused on to the specimen. ...