scholarly journals Structure of native cellulose microfibrils, the starting point for nanocellulose manufacture

2017 ◽  
Vol 376 (2112) ◽  
pp. 20170045 ◽  
Author(s):  
Michael C. Jarvis
Keyword(s):  
Higher Plants ◽  
Cellulose Microfibrils ◽  
New Horizons ◽  
Nanofibrillar Cellulose ◽  
Starting Point ◽  
Anionic Polysaccharides ◽  
Dicotyledonous Plants ◽  
The Mean

There is an emerging consensus that higher plants synthesize cellulose microfibrils that initially comprise 18 chains. However, the mean number of chains per microfibrilin situis usually greater than 18, sometimes much greater. Microfibrils from woody tissues of conifers, grasses and dicotyledonous plants, and from organs like cotton hairs, all differ in detailed structure and mean diameter. Diameters increase further when aggregated microfibrils are isolated. Because surface chains differ, the tensile properties of the cellulose may be augmented by increasing microfibril diameter. Association of microfibrils with anionic polysaccharides in primary cell walls and mucilages leads toin vivomechanisms of disaggregation that may be relevant to the preparation of nanofibrillar cellulose products. For the preparation of nanocrystalline celluloses, the key issue is the nature and axial spacing of disordered domains at which axial scission can be initiated. These disordered domains do not, as has often been suggested, take the form of large blocks occupying much of the length of the microfibril. They are more likely to be located at chain ends or at places where the microfibril has been mechanically damaged, but their structure and the reasons for their sensitivity to acid hydrolysis need better characterization.This article is part of a discussion meeting issue ‘New horizons for cellulose nanotechnology’.

In vitro and in vivo polysaccharides assembly: ultrastructural and cytochemical study of growing plant cell wall components.

1978 ◽  
Vol 36 (2) ◽  
pp. 434-435
Author(s):  
D. Reis ◽  
B. Vian ◽  
J. C. Roland
Keyword(s):  
Cell Wall ◽  
Self Assembly ◽  
Plant Cell Wall ◽  
Higher Plants ◽  
Three Dimensional ◽  
Cytochemical Study ◽  
Wall Components

Wall morphogenesis in higher plants is a problem still open to controversy. Until now the possibility of a transmembrane control and the involvement of microtubules were mostly envisaged. Self-assembly processes have been observed in the case of walls of Chlamydomonas and bacteria. Spontaneous gelling interactions between xanthan and galactomannan from Ceratonia have been analyzed very recently. The present work provides indications that some processes of spontaneous aggregation could occur in higher plants during the formation and expansion of cell wall.Observations were performed on hypocotyl of mung bean (Phaseolus aureus) for which growth characteristics and wall composition have been previously defined.In situ, the walls of actively growing cells (primary walls) show an ordered three-dimensional organization (fig. 1). The wall is typically polylamellate with multifibrillar layers alternately transverse and longitudinal. Between these layers intermediate strata exist in which the orientation of microfibrils progressively rotates. Thus a progressive change in the morphogenetic activity occurs.

Relationship between the gas production profiles of mixtures of hay and maize and the patterns of rumen fermentation observed in sheep fed those mixtures

1998 ◽  
Vol 1998 ◽  
pp. 63-63
Author(s):  
C. Rymer ◽  
D.I. Givens
Keyword(s):  
Growth Rate ◽  
Feed Intake ◽  
Rumen Fermentation ◽  
Gas Production ◽  
Post Feeding ◽  
Molar Proportion ◽  
Rumen Ph ◽  
The Mean

The gas production (GP) technique has been developed to assess dynamics of ruminant digestion. Relationships have been observed between a feed's GP profile and in vivo parameters such as digestibility (Khazaal et al., 1993), feed intake and growth rate (Blümmel and Ørskov, 1993), and in situ degradability (Sileshi et al., 1997). However, there are few studies which relate GP data to the in vivo pattern of rumen fermentation (in terms of the rate of pH decline 2 h post-feeding and the mean rumen pH, concentration of total VFA and molar proportion of individual VFA). The object of this experiment was to determine whether such a relationship existed between a feed's GP profile and the pattern of rumen fermentation observed in animals fed that feed.

scholarly journals Implantation in Coronary Circulation Induces Morphofunctional Transformation of Radial Grafts From Muscular to Elastomuscular

Circulation ◽  
2005 ◽  
Vol 112 (9_supplement) ◽  
Author(s):  
Mario Gaudino ◽  
Francesco Prati ◽  
Eugenio Caradonna ◽  
Carlo Trani ◽  
Francesco Burzotta ◽  
...  
Keyword(s):  
Internal Thoracic Artery ◽  
Coronary Circulation ◽  
Ultrasound Examination ◽  
Artery Bypass ◽  
Elastic Tissue ◽  
The Media ◽  
The Mean ◽  
Muscular Architecture

Background— The purpose of this research was to investigate the in vivo morphofunctional changes induced in the radial artery (RA) by its use as coronary artery bypass conduit by comparing the morphological features and vasoreactivity of the native RA versus the coronary RA graft in the same patient. Methods and Results— Ten years after surgery, 10 patients were submitted to intravascular ultrasound examination of the RA graft of the controlateral (in situ) RA and of the internal thoracic artery (ITA) graft and to vasoactive challenges with acetylcholine and serotonin. Quantitative angiographic assessment showed that the mean diameter of the RA coronary grafts was significantly larger than that of the in situ RA and of the ITA (2.89±0.40 mm RA grafts, 2.14±0.52 mm in situ RA, 2.25±0.53 mm ITA grafts; P <0.001). The in situ RA demonstrated a typical muscular architecture, whereas RA coronary grafts showed a clear reduction of the thickness of the medial layer and had a less well-defined muscular component of the media with interposition of elastic tissue. Serotonin endovascular infusion elicited a strong spastic reaction in in situ RAs; the same challenge induced only moderate constriction in RA and ITA coronary grafts. Conclusions— Implantation in the coronary circulation leads to major anatomic and vasoreactive modifications of the RAs that tend to lose the morphofunctional features of a muscular conduit and assume those of an elastomuscular artery, such as the ITA.

Thrombopoietin responsiveness reflects the number of doublings undergone by megakaryocyte progenitors

Blood ◽  
2004 ◽  
Vol 104 (8) ◽  
pp. 2291-2298 ◽  
Author(s):  
Jean-Michel Paulus ◽  
Najet Debili ◽  
Frédéric Larbret ◽  
Jack Levin ◽  
William Vainchenker
Keyword(s):  
Dose Response ◽  
Receptor Density ◽  
Response Curves ◽  
Age Model ◽  
Normal Human ◽  
The Mean ◽  
Dose Response Curves

Abstract To assess the variation of thrombopoietin (TPO) responsiveness associated with megakaryocyte (MK) progenitor amplification, TPO dose-response curves were obtained for normal human, single-cell plated CD34+CD41+ cells. The number of MKs per well was determined in situ and expressed as number of doublings (NbD). Dose-response curves of the mean frequency of clones of each size versus log TPO concentration showed highly significant differences in the TPO concentration needed for half-maximum generation of clones of different sizes (TPO50): 1.89 ± 0.51 pg/mL for 1 MK clones; 7.75 ± 0.81 pg/mL for 2 to 3 MK clones; 38.5 ± 5.04 pg/mL for 4 to 7 MK clones, and 91.8 ± 16.0 pg/mL for 8 to 15 MK clones. These results were consistent with a prediction of the generation-age model, because the number of previous doublings in vivo was inversely correlated with the number of residual doublings in vitro. TPO responsiveness decreased in vitro by a factor of 3.5 per doubling, reflecting the recruitment of progressively more ancestral progenitors. In support of this hypothesis, the more mature CD34+CD41+CD42+ cell fraction had a lower TPO50 (P &lt; .001), underwent fewer NbD (P &lt; .001), and expressed a 2.8-fold greater median Mpl receptor density (P &lt; .001) than the CD34+CD41+CD42– fraction. Progenitors that have completed their proliferative program have maximum factor responsiveness and are preferentially induced to terminal differentiation.

scholarly journals In vivo Fluorometric Measurement of Changes in Cytosolic Free Calcium from the Cat Cortex during Anoxia

1988 ◽  
Vol 8 (3) ◽  
pp. 367-374 ◽  
Author(s):  
Daisuke Uematsu ◽  
Joel H. Greenberg ◽  
Martin Reivich ◽  
Sei Kobayashi ◽  
Andrea Karp
Keyword(s):  
Intracellular Free Calcium ◽  
Ultraviolet Rays ◽  
Free Calcium ◽  
Acetoxymethyl Ester ◽  
New Approach ◽  
Electrical Failure ◽  
Electrocorticogram Ecog ◽  
The Mean

A new approach to assess the mean changes in intracellular free calcium [Ca2+]i directly from the cortex in situ is described along with the [Ca2+]i changes during nitrogen anoxia. Following incision of the dura and part of the pia-arachnoid membrane, quin2 acetoxymethyl ester, 100 μ M in artificial CSF, was superfused for 60 min onto the cat cortex. A small cortical area was irradiated with ultraviolet rays (350/30 nm) and the changes in the fluorescence and reflectance were recorded microfluorometrically at 506 and 366 nm, respectively. The net change in the quin2-Ca2+ fluorescence was calculated after correction for the hemodynamic artifact and subtraction of the basal NADH change. The quin2-Ca2+ fluorescence began to increase significantly (48.0 ± 13.4 units; p < 0.05) 20 s prior to the isoelectric electrocorticogram (ECoG) and remained elevated during nitrogen anoxia. It decreased steeply 7.3 ±1.7 s prior to the recovery of the ECoG activity after the animal was reoxygenated. Thus, the changes in the intracellular free calcium preceded those of the ECoG during a reversible anoxic insult, suggesting that the increase in the [Ca2+]i might be related to the electrical failure during anoxia.

Relationship between the gas production profiles of mixtures of hay and maize and the patterns of rumen fermentation observed in sheep fed those mixtures

1998 ◽  
Vol 1998 ◽  
pp. 63-63 ◽  
Author(s):  
C. Rymer ◽  
D.I. Givens
Keyword(s):  
Growth Rate ◽  
Feed Intake ◽  
Rumen Fermentation ◽  
Gas Production ◽  
Post Feeding ◽  
Molar Proportion ◽  
Rumen Ph ◽  
The Mean

The gas production (GP) technique has been developed to assess dynamics of ruminant digestion. Relationships have been observed between a feed's GP profile and in vivo parameters such as digestibility (Khazaal et al., 1993), feed intake and growth rate (Blümmel and Ørskov, 1993), and in situ degradability (Sileshi et al., 1997). However, there are few studies which relate GP data to the in vivo pattern of rumen fermentation (in terms of the rate of pH decline 2 h post-feeding and the mean rumen pH, concentration of total VFA and molar proportion of individual VFA). The object of this experiment was to determine whether such a relationship existed between a feed's GP profile and the pattern of rumen fermentation observed in animals fed that feed.

Parthenogenetic development of mouse embryos in vivo

Development ◽  
1973 ◽  
Vol 30 (3) ◽  
pp. 547-560
Author(s):  
Anna Witkowska
Keyword(s):  
Electric Shock ◽  
Implantation Rate ◽  
Mouse Embryos ◽  
Somite Stage ◽  
Advanced Embryo ◽  
Parthenogenetic Development ◽  
Implantation Sites ◽  
The Mean

CBA-p and CBA-T6T6 females were mated with vasectomized males of A strain and early in the morning the eggs were activated in situ with the electric shock of 30, 40 and 50 V. Females were killed between the 5th and the 10th day of pregnancy and the implantation sites were studied histologically or their content was examined under the dissecting microscope. Of the uterine horns, 43·6% contained at least one implantation and the mean number of implantations per horn was 0·76. Altogether 152 implantations were collected. The implantation rate was twice as high in older females (12 weeks and over) as in young ones (6–8 weeks). The number of living embryos decreased with every day so that on the 9th and 10th day only 2 out of 86 embryos were alive (2·3%). With one exception all embryos which were alive at the time of examination were retarded in development for approximately 1 day. The most advanced embryo was at the 8-somite stage. Two attempts aimed at increasing the synchrony between the embryos and the uterus at the time of implantation (activation immediately after delayed mating and transfer of 4·5-day embryos to 3·5-day uterus) did not improve the survival of embryos after implantation.

scholarly journals Activation of cyclic electron flow by hydrogen peroxide in vivo

2015 ◽  
Vol 112 (17) ◽  
pp. 5539-5544 ◽  
Author(s):  
Deserah D. Strand ◽  
Aaron K. Livingston ◽  
Mio Satoh-Cruz ◽  
John E. Froehlich ◽  
Veronica G. Maurino ◽  
...  
Keyword(s):  
Redox Regulation ◽  
Higher Plants ◽  
Electron Flow ◽  
Cyclic Electron Flow ◽  
Glycolate Oxidase ◽  
Half Time ◽  
Redox Modulation ◽  
In Situ Production

Cyclic electron flow (CEF) around photosystem I is thought to balance the ATP/NADPH energy budget of photosynthesis, requiring that its rate be finely regulated. The mechanisms of this regulation are not well understood. We observed that mutants that exhibited constitutively high rates of CEF also showed elevated production of H2O2. We thus tested the hypothesis that CEF can be activated by H2O2 in vivo. CEF was strongly increased by H2O2 both by infiltration or in situ production by chloroplast-localized glycolate oxidase, implying that H2O2 can activate CEF either directly by redox modulation of key enzymes, or indirectly by affecting other photosynthetic processes. CEF appeared with a half time of about 20 min after exposure to H2O2, suggesting activation of previously expressed CEF-related machinery. H2O2-dependent CEF was not sensitive to antimycin A or loss of PGR5, indicating that increased CEF probably does not involve the PGR5-PGRL1 associated pathway. In contrast, the rise in CEF was not observed in a mutant deficient in the chloroplast NADPH:PQ reductase (NDH), supporting the involvement of this complex in CEF activated by H2O2. We propose that H2O2 is a missing link between environmental stress, metabolism, and redox regulation of CEF in higher plants.

Three-Dimensional Subcellular Organization of Hepatocytes in Intact Liver: Simultaneous Visualization of Cytoskeletal and Membrane Markers by Confocal Microscopy

1996 ◽  
Vol 54 ◽  
pp. 288-289
Author(s):  
Greg V. Martin ◽  
Ann L. Hubbard
Keyword(s):  
Three Dimensional ◽  
Integral Membrane Proteins ◽  
Polarized Secretion ◽  
Microscope Images ◽  
Computer Aided ◽  
Intracellular Organelles ◽  
Cytoskeletal Elements ◽  
Simultaneous Visualization

The microtubule (MT) cytoskeleton is necessary for many of the polarized functions of hepatocytes. Among the functions dependent on the MT-based cytoskeleton are polarized secretion of proteins, delivery of endocytosed material to lysosomes, and transcytosis of integral plasma membrane (PM) proteins. Although microtubules have been shown to be crucial to the establishment and maintenance of functional and structural polarization in the hepatocyte, little is known about the architecture of the hepatocyte MT cytoskeleton in vivo, particularly with regard to its relationship to PM domains and membranous organelles. Using an in situ extraction technique that preserves both microtubules and cellular membranes, we have developed a protocol for immunofluorescent co-localization of cytoskeletal elements and integral membrane proteins within 20 µm cryosections of fixed rat liver. Computer-aided 3D reconstruction of multi-spectral confocal microscope images was used to visualize the spatial relationships among the MT cytoskeleton, PM domains and intracellular organelles.

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