Collenchyma cells have thickened primary cell walls and provide mechanical support during plant growth. During their development, these cells elongate and their walls thicken considerably. We used ...microscopy and synchrotron small-angle X-ray scattering to study changes in the orientations of cellulose microfibrils that occur during development in the walls of collenchyma cells present in peripheral strands in celery (Apium graveolens) petioles. Transmission electron microscopy showed that the walls consisted of many lamellae (polylamellate), with lamellae containing longitudinally oriented cellulose microfibrils alternating with microfibrils oriented at higher angles. The lamellae containing longitudinally oriented microfibrils predominated at later stages of development. Nevertheless, transmission electron microscopy of specially stained, oblique sections provided evidence that the cellulose microfibrils were ordered throughout development as crossed-polylamellate structures. These results are consistent with our synchrotron small-angle X-ray scattering results that showed the cellulose microfibrils become oriented increasingly longitudinally during development. Some passive reorientation of cellulose microfibrils may occur during development, but extensive reorientation throughout the wall would destroy ordered structures. Atomic force microscopy and field emission scanning electron microscopy were used to determine the orientations of newly deposited cellulose microfibrils. These were found to vary widely among different cells, which could be consistent with the formation of crossed-polylamellate structures. These newly deposited cellulose microfibrils are deposited in a layer of pectic polysaccharides that lies immediately outside the plasma membrane. Overall, our results show that during development of collenchyma walls, the cellulose microfibrils become increasingly longitudinal in orientation, yet organized, crossed-polylamellate structures are maintained.
Collenchyma serves as a mechanical support tissue for many herbaceous plants. Previous work based on solid-state NMR and immunomicroscopy suggested collenchyma cell walls (CWs) may have similar ...polysaccharide compositions to those commonly found in eudicotyledon parenchyma walls, but no detailed chemical analysis was available. In this study, compositions and structures of cell wall polysaccharides of peripheral collenchyma from celery petioles were investigated.
This is the first detailed investigation of the cell wall composition of collenchyma from any plant. Celery petioles were found to elongate throughout their length during early growth, but as they matured elongation was increasingly confined to the upper region, until elongation ceased. Mature, fully elongated, petioles were divided into three equal segments, upper, middle and lower, and peripheral collenchyma strands isolated from each. Cell walls (CWs) were prepared from the strands, which also yielded a HEPES buffer soluble fraction. The CWs were sequentially extracted with CDTA, Na
CO
, 1 M KOH and 4 M KOH. Monosaccharide compositions of the CWs showed that pectin was the most abundant polysaccharide with homogalacturonan (HG) more abundant than rhamnogalacturonan I (RG-I) and rhamnogalacturonan II (RG-II), followed by cellulose, and other polysaccharides, mainly xyloglucans, with smaller amounts of heteroxylans and heteromannans. CWs from different segments had similar compositions, but those from the upper segments had slightly more pectin than those from the lower two segments. Further, the pectin in the CWs of the upper segment had a higher degree of methyl esterification than the other segments. In addition to the anticipated water-soluble pectins, the HEPES-soluble fractions surprisingly contained large amounts of heteroxylans. The CDTA and Na
CO
fractions were rich in HG and RG-I, the 1 M KOH fraction had abundant heteroxylans, the 4 M KOH fraction was rich in xyloglucan and heteromannans, and cellulose was predominant in the final residue. The structures of the xyloglucans, heteroxylans and heteromannans were deduced from the linkage analysis and were similar to those present in most eudicotyledon parenchyma CWs. Cross polarization with magic angle spinning (CP/MAS) NMR spectroscopy showed no apparent difference in the rigid and semi-rigid polysaccharides in the CWs of the three segments. Single-pulse excitation with magic-angle spinning (SPE/MAS) NMR spectroscopy, which detects highly mobile polysaccharides, showed the presence of arabinan, the detailed structure of which varied among the cell walls from the three segments.
Celery collenchyma CWs have similar polysaccharide compositions to most eudicotyledon parenchyma CWs. However, celery collenchyma CWs have much higher XG content than celery parenchyma CWs. The degree of methyl esterification of pectin and the structures of the arabinan side chains of RG-I show some variation in the collenchyma CWs from the different segments. Unexpectedly, the HEPES-soluble fraction contained a large amount of heteroxylans.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Every leader has human resource management and development responsibilities. Using a behavioural science perspective, Developing High Performance Leaders will enable leaders throughout the various ...business sectors to increase the yield on their organization's human capital and help their team members achieve their goals.
In this instructive book, Philip Harris centres his teaching around five key aspects of the leadership process:
human behaviour and performance
communications
cultural influences
organizational relations
change management
A selection of strategies to take forward into practice are offered to the reader and the text is organized with a view to the leader sharing the learning obtained from this volume. For personal or group growth, each chapter is framed in terms of four "I's": Introduction, Input, Interaction and Instrumentation, to provide an ideal framework for any adult education endeavour.
Developing High Performance Leaders is for all human resource development professionals, supervisors, managers and executives concerned with the career development of themselves and their team.
RIP1 regulates cell death and inflammation and is believed to play an important role in contributing to a variety of human pathologies, including immune-mediated inflammatory diseases and cancer. ...While small-molecule inhibitors of RIP1 kinase have been advanced to the clinic for inflammatory diseases and CNS indications, RIP1 inhibitors for oncology indications have yet to be described. Herein we report on the discovery and profile of GSK3145095 (compound 6). Compound 6 potently binds to RIP1 with exquisite kinase specificity and has excellent activity in blocking RIP1 kinase-dependent cellular responses. Highlighting its potential as a novel cancer therapy, the inhibitor was also able to promote a tumor suppressive T cell phenotype in pancreatic adenocarcinoma organ cultures. Compound 6 is currently in phase 1 clinical studies for pancreatic adenocarcinoma and other selected solid tumors.
The cell walls of forage chicory (
Cichorium intybus
) leaves are known to contain high proportions of pectic polysaccharides. However, little is known about the distribution of pectic ...polysaacharides among walls of different cell types/tissues and within walls. In this study, immunolabelling with four monoclonal antibodies was used to map the distribution of pectic polysaccharides in the cell walls of the laminae and midribs of these leaves. The antibodies JIM5 and JIM7 are specific for partially methyl-esterified homogalacturonans; LM5 and LM6 are specific for (1→4)-β-galactan and (1→5)-α-arabinan side chains, respectively, of rhamnogalacturonan I. All four antibodies labelled the walls of the epidermal cells with different intensities. JIM5 and JIM7, but not LM5 or LM6, labelled the middle lamella, tricellular junctions, and the corners of intercellular spaces of ground, xylem and phloem parenchyma. LM5, but not LM6, strongly labelled the walls of the few sclerenchyma fibres in the phloem of the midrib and lamina vascular bundles. The LM5 epitope was absent from some phloem parenchyma cells. LM6, but not LM5, strongly labelled the walls of the stomatal guard cells. The differential distribution of pectic epitopes among walls of different cell types and within walls may reflect the deposition and modification of these polysaccharides which are involved in cell wall properties and cell development.
We describe preparations of plant cell walls and polysaccharides obtained from plant cell walls that are added to food products for two purposes: as modifiers of food texture and/or as dietary fibres ...with potential health benefits. Although a number of different types of plant cell walls occur, only some are presently exploited. Commercial 'fibre preparations' range from those containing mostly primary walls to those containing mostly lignified secondary walls from which much of the lignin and non-cellulosic polysaccharides have been removed. Preparations of cell-wall polysaccharides are obtained from the following sources: cellulose mostly from secondary walls of cotton and wood, pectin from primary walls of dicotyledons, and (1rightward arrow3),(1rightward arrow4)-β-glucans and arabinoxylans from primary walls of cereal grains. Preparations of galactomannans, xyloglucans and the pectic polysaccharide rhamnogalacturonan I are obtained from non-lignified secondary walls of certain leguminous seeds. The compositions, functionalities, uses and possible health benefits of these different preparations are discussed.
Infrared spectroscopy coupled with partial least squares (PLS) regression has been shown to be a rapid alternative to wet chemical analytical methods for determining the cell-wall compositions of ...wood. Both near infrared (NIR) spectroscopy, and mid-infrared spectroscopy with attenuated total reflectance Fourier transform infrared (ATR FTIR) sampling, coupled with PLS regression, can be used to quickly and accurately predict the lignin contents and monosaccharide compositions of milled wood. However, milling wood can be time consuming and laborious. In this study we demonstrate that PLS-1 models built using NIR and ATR FTIR spectra of milled
Pinus radiata
wood, with different sized wood particles and different moisture contents, can rapidly and accurately predict the cell-wall compositions of solid wood. A robust assessment of the prediction accuracy was conducted using a separate test set of solid wood samples with both ‘smooth’ and ‘rough’ surface finishes. The lowest standard error (SE) values for most of the compositional predictions were obtained for the ‘rough’ solid wood samples, using PLS-1 models built from NIR spectra of ‘large’ milled wood particles (0.422 mm) with ambient moisture content. The SE achieved for NIR spectroscopy prediction of lignin for the ‘rough’ solid wood was 1.91%, and for the monosaccharides, arabinose (0.37%), xylose (1.25%), galactose (2.00%), mannose (1.54%), and 4-
O
-methyl glucuronic acid (0.24%). The powerful combination of NIR spectroscopy with PLS regression offers an attractive method for rapid prediction of cell-wall compositions of solid wood samples, thus avoiding milling. In addition, this technique highlights the different levels of these cell-wall components in opposite and compressed regions in solid wood.
When examining patients with sports-related and exercise-related injuries, a thorough knowledge of anatomy is vital in order to make an accurate diagnosis and work out an effective treatment plan. In ...this helpful, practical book, a professional anatomist and a sports physiotherapist have combined their expertise to give a detailed explanation of the structural and functional anatomy of the back. The book includes descriptions and images of the relevant anatomy, and sample clinical problems (with model answers) throughout.
Little is known about the effects of treatment attrition on juvenile recidivism, particularly with regard to community-based treatment. Compounding this gap in the literature is a lack of studies ...that have disaggregated recidivism offense type or type of treatment attrition. These distinctions are believed to have both theoretical implications for understanding recidivism and practical implications for engaging youths in community-based programs. The current study analyzes a sample of 5,517 male juvenile offenders adjudicated within Philadelphia between 1996 and 2002 to determine the effects of treatment attrition, either due to dropping out or expulsion, on juvenile recidivism, distinguished in terms of property, violent, or drug offenses. Results indicate that voluntarily dropping out of treatment significantly increases the likelihood of recidivism through drug and property offending, while expulsion from treatment significantly increases the likelihood of a violent recidivism offense, suggesting that the causes of treatment attrition and reoffending may be related.
We investigate the reach of the LHC Run 2 and that of a future circular hadron collider with up to 100 TeV center of mass energy for the exploration of potential dark matter sectors. These dark ...sectors are conveniently and broadly described by simplified models. The simplified models we consider provide microscopic descriptions of interactions between the standard model partons and the dark sector particles mediated by the four basic types of (s-channel) messenger fields: scalar, pseudoscalar, vector or axial-vector. Our analysis extends and updates the previously available results for the LHC at 8 and 14 TeV to 100 TeV for models with all four messenger types. We revisit and improve the analysis at 14 TeV, by studying a variety of analysis techniques, concluding that the most discriminating variables correspond to the missing transverse energy and the azimuthal angle between jets in the final state. Going to 100 TeV, the limits on simplified models of dark matter are enhanced significantly, in particular for heavier mediators and dark sector particles, for which the available phase space at the LHC is restricted. The possibility of a 100 TeV collider provides an unprecedented coverage of the dark sector basic parameters and a unique opportunity to pin down the particle nature of dark matter and its interactions with the standard model.
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