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  • 1
    Keywords: Life sciences ; Cell Biology ; Microbiology ; Plant science ; Botany ; Aerospace engineering ; Astronautics ; Life sciences ; Cell Biology ; Aerospace Technology and Astronautics ; Microbiology ; Plant Sciences ; Springer eBooks
    Description / Table of Contents: Chapter 1: Gravity Sensing, Graviorientation and Microgravity -- Chapter 2: Methods for Gravitational Biology Research -- Chapter 3: Gravitaxis in Flagellates and Ciliates -- Chapter 4: Gravitropism in Tip-Growing Rhizoids and Protonemata of Characean Algae -- Chapter 5: Gravitropism in Fungi, Mosses and Ferns -- Chapter 6: Gravitropism in Higher Plants: Cellular Aspects -- Chapter 7: Gravitropism in Higher Plants: Molecular Aspects -- Chapter 8: Bioregenerative Life Support Systems in Space Research
    Abstract: This book summarizes what is currently known about gravity sensing and response mechanisms in microorganisms, fungi, lower and higher plants; starting from the historical eye-opening experiments from the 19th century up to today’s extremely rapid advancing cellular, molecular and biotechnological research. All forms of life are constantly exposed to gravity and it can be assumed that almost all organisms have developed sensors and respond in one way or the other to the unidirectional acceleration force,this books shows us some of these different ways. The book is written for plant biologists and microbiologists as well as scientists interested in space and gravitational biology
    Pages: XVII, 122 p. 36 illus., 24 illus. in color. : online resource.
    ISBN: 9783319938943
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  • 2
    ISSN: 1615-6102
    Keywords: Actin microfilaments ; Characean protonemata ; Gravitropism ; Microtubules ; Mitosis ; Photomorphogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The reorganization of the actin and microtubule (MT) cytoskeleton was immunocytochemically visualized by confocal laser scanning microscopy throughout the photomorphogenetic differentiation of tip-growing characean protonemata into multicellular green thalli. After irradiating dark-grown protonemata with blue or white light, decreasing rates of gravitropic tip-growth were accompanied by a series of events leading to the first cell division: the nucleus migrated towards the tip; MTs and plastids invaded the apical cytoplasm; the polar zonation of cytoplasmic organelles and the prominent actin patch at the cell tip disappeared and the tip-focused actin microfilaments (MFs) were reorganized into a homogeneous network. During prometaphase and metaphase, extranuclear spindle microtubules formed between the two spindle poles. Cytoplasmic MTs associated with the apical spindle pole decreased in number but did not disappear completely during mitosis. The basal cortical MTs represent a discrete MT population that is independent from the basal spindle poles and did not redistribute during mitosis and cytokinesis. Preprophase MT bands were never detected but cytokinesis was characterized by higher-plant-like phragmoplast MT arrays. Cytoplasmic actin MFs persisted as a dense network in the apical cytoplasm throughout the first cell division. They were not found in close contact with spindle MTs, but actin MFs were clearly coaligned along the MTs of the early phragmoplast. The later belt-like phragmoplast was completely depleted of MFs close to the time of cell plate fusion except for a few actin MF bundles that extended to the margin of the growing cell plate. The cell plate itself and young anticlinal cell walls showed strong actin immunofluorescence. After several anticlinal cell divisions, basal cells of the multicellular protonema produced nodal cell complexes by multiple periclinal divisions. The apical-dome cell of the new shoot which originated from a nodal cell becomes the meristem initial that regularly divides to produce a segment cell. The segment cell subsequently divides to produce a single file of alternating internodal cells and multicellular nodes which together form the complexly organized characean thallus. The actin and MT distribution of nodal cells resembles that of higherplant meristem cells, whereas the internodal cells exhibit a highly specialized cortical system of MTs and streaming-generating actin bundles, typical of highly vacuolated plant cells. The transformation from the asymmetric mitotic spindle of the polarized tip-growing protonema cell to the symmetric, higher-plant-like spindle of nodal thallus cells recapitulates the evolutionary steps from the more primitive organisms to higher plants.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2048
    Keywords: Key words: Actin ; Cytochalasin D ; Mastoparan ; Phosphatidylinositol-4 ; 5-bisphosphate ; Profilin ; Tip growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The continuously changing polar cytoplasmic organization during initiation and tip growth of root hairs is reflected by a dynamic redistribution of cytoskeletal elements. The small G-actin binding protein, profilin, which is known to be a widely expressed, potent regulator of actin dynamics, was specifically localized at the tip of root hairs and co-distributed with a diffusely fluorescing apical cap of actin, but not with subapical actin microfilament (MF) bundles. Profilin and actin caps were present exclusively in the bulge of outgrowing root hairs and at the apex of elongating root hairs; both disappeared when tip growth terminated, indicating a tip-growth mechanism that involves profilin-actin interactions for the delivery and localized exocytosis of secretory vesicles. Phosphatidylinositol-4,5-bisphosphate (PIP2), a ligand of profilin, was localized almost exclusively in the bulge and, subsequently, formed a weak tip-to-base gradient in the elongating root hairs. When tip growth was eliminated by the MF-disrupting inhibitor cytochalasin D, the apical profilin and the actin fluorescence were lost. Mastoparan, which is known to affect the PIP2 cycle, probably by stimulating phospholipases, caused the formation of a meshwork of distinct actin MFs replacing the diffuse apical actin cap and, concomittantly, tip growth stopped. This suggests that mastoparan interferes with the PIP2-regulated profilin-actin interactions and hence disturbs conditions indispensable for the maintenance of tip growth in root hairs.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Planta 199 (1996), S. 443-450 
    ISSN: 1432-2048
    Keywords: Chara (rhizoids, protonemata) ; Gravitropism ; Growth centre ; Statoliths ; Polarity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Centrifugal accelerations of 50–250 g were applied to rhizoids of Chara globularis Thuill. at stimulation angles (α) of 5–90° between the acceleration vector and the rhizoid axis. After the start of centrifugation, the statoliths were pressed asymmetrically onto the centrifugal flank of the apical cell wall. In contrast to the well-known bending (by bowing) under 1 g, the rhizoids responded in two distinct phases. Following an initial phase of sharp bending (by bulging), which is similar to the negatively gravitropic response of Chara protonemata, rhizoids stopped bending and, in the second phase, grew straight in directions clearly deviating from the direction of acceleration. These response angles (β) between the axis of the bent part of the rhizoid and the acceleration vector were strictly correlated with the g-level of acceleration. The higher the acceleration the greater was β. Except for the sharp bending, the shape and growth rate of the centrifuged rhizoids were not different from those of gravistimulated control rhizoids at 1 g. These results indicate that gravitropic bending of rhizoids during enhanced accelerations (5° ≤ α ≤ 90°) is caused not only by subapical differential flank growth, as it is the case at 1 g, but also by the centripetal displacement of the growth centre as was recently discussed for the negative gravitropism of Chara protonemata. A hypothesis for cytoskeletally mediated polar growth is presented based on data from positive gravitropic bending of Chara rhizoids at 1 g and from the anomalous gravitropic bending of rhizoids compared with the negatively gravitropic bending of Chara protonemata. The data obtained are also relevant to a general understanding of graviperception in higher-plant organs.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Planta 203 (1997), S. S11 
    ISSN: 1432-2048
    Keywords: Key words:Chara (rhizoids ; protonemata) ; Cytoske leton ; Gravitropism ; Moss protonemata ; Statoliths ; Tip-growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Unicellular tip-growing cells are excellent experimental systems in which to study gravitropism because cell extension, gravity sensing and the gravity response are all confined to the apical dome. Thus various approaches can be used to determine the distinct steps of the short gravitropic signal-transduction chain, which lacks a signal-transmission phase between the gravity-sensing cells and the competent responding target cells. Single-cell systems readily allow in-vivo observation of cellular processes during gravistimulation at 1 g, centrifugation, clinostatting and in microgravity, as well as permitting fluorescence labeling. Such diverse studies have revealed fascinating information on the mechanism of gravitropic tip growth, especially on the important role of the cytoskeleton in the positioning of the statoliths and in organizing and adjusting the Spitzenkörper. A hypothesis explaining the negative and positive gravitropism of Chara rhizoids and Chara protonemata has been put forward, which emphasizes the role of the actin cytoskeleton in the process of gravitropic tip-growth. Differences in the gravitropic responses of single-cell systems, however, reflect a diversity of gravitropic mechanisms, and represent an example of parallel evolution.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-2048
    Keywords: Key words:Chara (rhizoid ; protonema) ; Calcium ; Calcium channel ; Fluorescent-dihydropyridine ; Gravitropic tip growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The localization of cytoplasmic free calcium and a dihydropyridine (DHP) receptor, a putative calcium channel, was recorded during the opposite graviresponses of tip-growing Chara rhizoids and Chara protonemata by using the calcium indicator Calcium Crimson and a fluorescently labeled dihydropyridine (FL-DHP). In upward (negatively gravitropically) growing protonemata and downward (positively gravitropically) growing rhizoids, a steep Ca2+ gradient and DHP receptors were found to be symmetrically localized in the tip. However, the localization of the Ca2+ gradient and DHP receptors differed considerably during the gravitropic responses upon horizontal positioning of the two cell types. During the graviresponse of rhizoids, a continuous bowing downward by differential flank growth, the Ca2+ gradient and DHP receptors remained symmetrically localized in the tip at the centre of growth. However, after tilting protonemata into a horizontal position, there was a drastic displacement of the Ca2+ gradient and FL-DHP to the upper flank of the apical dome. This displacement occurred after the apical intrusion and sedimentation of the statoliths but clearly before the change in the growth direction became evident. In protonemata, the reorientation of the growth direction started with the appearence of a bulge on that site of the upper flank which was predicted by the asymmetrically displaced Ca2+ gradient. With the upward shift of the cell tip, which is suggested to result from a statolith-induced displacement of the growth centre, the Ca2+ gradient and DHP receptors became symmetrically relocalized in the apical dome. No major asymmetrical rearrangement was observed during the following phase of gravitropic curvature which is characterized by slower rates of bending. Labeling with FL-DHP was completely inhibited by a non-fluorescently labeled dihydropyridine. From these results it is suggested that FL-DHP labels calcium channels in rhizoids and protonemata. In rhizoids, positive gravitropic curvature is caused by differential growth limited to the opposite subapical flanks of the apical dome, a process which does not involve displacement of the growth centre, the calcium gradient or calcium channels. In protonemata, however, it is proposed that a statolith-induced asymmetrical relocalization of calcium channels and the Ca2+ gradient precedes, and might mediate, the rearrangement of the centre of growth, most likely by the displacement of the Spitzenkörper, to the upper flank, which results in the negative gravitropic reorientation of the growth direction.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-2048
    Keywords: Key words: Actin microfilament ; Characean algae (rhizoids ; protonemata) ; Gravitropism ; Microtubule ; Microinjection ; Tip growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The organization of the microtubule (MT) and actin microfilament (MF) cytoskeleton of tip-growing rhizoids and protonemata of characean green algae was examined by confocal laser scanning microscopy. This analysis included microinjection of fluorescent tubulin and phallotoxins into living cells, as well as immunofluorescence labeling of fixed material and fluorescent phallotoxin labeling of unfixed material. Although the morphologically very similar positively gravitropic (downward growing) rhizoids and negatively gravitropic (upward growing) protonemata show opposite gravitropic responses, no differences were detected in the extensive three-dimensional distribution of actin MFs and MTs in both cell types. Tubulin microinjection revealed that in contrast to internodal cells, fluorescent tubulin incorporated very slowly into the MT arrays of rhizoids, suggesting that MT dynamics are very different in tip-growing and diffusely expanding cells. Microtubules assembled from multiple sites at the plasma membrane in the basal zone, and a dense subapical array emerged from a diffuse nucleation centre on the basal side of the nuclear envelope. Immunofluorescence confirmed these distribution patterns but revealed more extensive MT arrays. In the basal zone, short branching clusters of MTs form two cortical hemicylinders. Subapical, axially oriented MTs are distributed in equal density throughout the peripheral and inner cytoplasm and are closely associated with subapical organelles. Microtubules, however, are completely absent from the apical zones of rhizoids and protonemata. Actin MFs were found in all zones of rhizoids and protonemata including the apex. Two files of axially oriented bundles of subcortical actin MFs and ring-like actin structures in the streaming endoplasm of rhizoids were detected in the basal zones by microinjection or rhodamine-phalloidin labeling. The subapical zone contains a dense array of mainly axially oriented actin MFs that co-distribute with the subapical MT array. In the apex, actin MFs form thicker bundles that converge into a remarkably distinct actin patch in the apical dome, whose position coincides with the position of the endoplasmic reticulum aggregate in the centre of the Spitzenkörper. Actin MFs radiate from the actin patch towards the apical membrane. Together with results from previous inhibitor studies (Braun and Sievers, 1994, Eur J Cell Biol 63: 289–298), these results suggest that MTs have a stabilizing function in maintaining the polar cytoplasmic and cytoskeletal organization. The motile processes, however, are mediated by actin. In particular, the actin cytoskeleton appears to be involved in the structural and functional organization of the Spitzenkörper and thus is responsible for controlling cell shape and growth direction. Despite the similar structural arrangements of the actin cytoskeleton, major differences in the function of actin MFs have been observed in rhizoids and protonemata. Since actin MFs are more directly involved in the gravitropic response of protonemata than of rhizoids, the opposite gravitropism in the two cell types seems to be based mainly on different properties and activities of the actin cytoskeleton.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract For walled plant cells, the immunolocalization of actin microfilaments, also known as F-actin, has proved to be much trickier than that of microtubules. These difficulties are commonly attributed to the high sensitivity of F-actin to aldehyde fixatives. Therefore, most plant studies have been accomplished using fluorescent phallotoxins in fresh tissues. Nevertheless, concerns regarding the questionable ability of phallotoxins to bind the whole complement of F-actin necessitate further optimization of actin immunofluorescence methods. We have compared two procedures: (1) formaldehyde fixation and (2) rapid freezing and freeze substitution (cryofixation), both followed by embedding in low-melting polyester wax. Actin immunofluorescence in sections of garden cress (Lepidium sativum L.) root gave similar results with both methods. The compatibility of aldehydes with actin immunodetection was further confirmed by the freeze-shattering technique that does not require embedding after aldehyde fixation. It appears that rather than aldehyde fixation, some further steps in the procedures used for actin visualization are critical for preserving F-actin. Wax embedding, combined with formaldehyde fixation, has proved to be also suitable for the detection of a wide range of other antigens.
    Type of Medium: Electronic Resource
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  • 9
    Publication Date: 2020-05-05
    Description: Children are commonly exposed to second-hand smoke (SHS) in the domestic environment or inside vehicles of smokers. Unfortunately, prenatal tobacco smoke (PTS) exposure is still common, too. SHS is hazardous to the health of smokers and non-smokers, but especially to that of children. SHS and PTS increase the risk for children to develop cancers and can trigger or worsen asthma and allergies, modulate the immune status, and is harmful to lung, heart and blood vessels. Smoking during pregnancy can cause pregnancy complications and poor birth outcomes as well as changes in the development of the foetus. Lately, some of the molecular and genetic mechanisms that cause adverse health effects in children have been identified. In this review, some of the current insights are discussed. In this regard, it has been found in children that SHS and PTS exposure is associated with changes in levels of enzymes, hormones, and expression of genes, micro RNAs, and proteins. PTS and SHS exposure are major elicitors of mechanisms of oxidative stress. Genetic predisposition can compound the health effects of PTS and SHS exposure. Epigenetic effects might influence in utero gene expression and disease susceptibility. Hence, the limitation of domestic and public exposure to SHS as well as PTS exposure has to be in the focus of policymakers and the public in order to save the health of children at an early age. Global substantial smoke-free policies, health communication campaigns, and behavioural interventions are useful and should be mandatory.
    Print ISSN: 1661-7827
    Electronic ISSN: 1660-4601
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
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  • 10
    Publication Date: 2020-04-02
    Description: Although the big tobacco companies offer the same cigarette brands across countries, little is known about the potential regional differences of the particulate matter (PM) emissions of apparently equal brands. PM emissions of three cigarette brands (Marlboro Gold, Winston Red resp. Classic, Parliament Platinum resp. Night Blue) from the United Arab Emirates (UAE) and Germany were analysed. Second-hand smoke was produced in a 2.88 m3 measuring cabin by an automatic environmental tobacco smoke emitter. PM size fractions PM10, PM2.5, and PM1 were detected in real-time using laser aerosol spectrometry. Depending on the PM fraction Marlboro cigarettes from UAE showed 33%–35% higher PM amounts. Moreover, Winston cigarettes from UAE showed distinctly higher PM values (28–31%) than the German counterparts. The “lighter” Parliament from UAE emitted 3%–9% more PM than the German one. The measured mean PM10 values laid between 778 and 1163 µg/m3 (mean PM2.5: 777–1161 µg/m3; mean PM1: 724–1074 µg/m3). That means smoking in enclosed rooms causes massive PM burden. The PM emission of equal or similar tobacco products from different countries can differ distinctly. Hence, the declaration of PM emission values, besides nicotine, tar, and carbon monoxide amounts, should be obligatory worldwide. Furthermore, complete information about the ingredients and production processes of tobacco products should be provided to health officials and the public. This can help to minimise or ban substances or product designs that make smoking even more harmful, and to enhance the awareness of the risks of smoking.
    Print ISSN: 1661-7827
    Electronic ISSN: 1660-4601
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
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