Effet des souches arctiques de Rhizobium sur la structure des nodules du sainfoin (Onobrychis viciifolia) et de légumineuses arctiques (Astragalus et Oxytropis spp.)

1989 ◽  
Vol 67 (11) ◽  
pp. 3164-3168 ◽  
Author(s):  
Danielle Prévost ◽  
L. M. Bordeleau ◽  
H. Antoun
Keyword(s):  
Internal Structure ◽  
Lipid Droplets ◽  
The Arctic ◽  
Rhizobium Strain ◽  
Indeterminate Growth ◽  
Onobrychis Viciifolia ◽  
Nodule Shape ◽  
Membrane Envelope

Rhizobium strain N31, isolated from the arctic legume Astragalus alpinus, nodulates sainfoin (Onobrychis viciifolia) as efficiently as strain SM-2, isolated from sainfoin. Nodule shape and tissue arrangement of 70-day-old plants infected by these two strains were examined. Sainfoin nodules formed by either strain N31 or SM-2 were cylindrical, with indeterminate growth, and similar to those found on arctic legumes. However, in the active symbiotic zone of sainfoin nodules, bacteroids of strain N31 were pleiomorphic or spherical and found individually or in groups of three, surrounded by the membrane envelope, whereas the bacteroids of strain SM-2 were elongated and enclosed in clusters of 3 to 12 by each membrane envelope. Thus, arctic strain N31 affects the internal structure of sainfoin nodules. Nodules of arctic legumes A. alpinus, Oxytropis maydelliana, and Oxytropis arctobia, infected with either strain N31 or SM-2, contained lipid droplets, while sainfoin nodules did not show such characteristics. This phenomenon seems specific to arctic legumes and it is not influenced by the origin of the nodulating strain.

Effect of temperature on succinate transport by an arctic and a temperate strain of rhizobia

1993 ◽  
Vol 39 (10) ◽  
pp. 907-911 ◽  
Author(s):  
Pierre C. Bigwaneza ◽  
Danielle Prévost ◽  
Lucien M. Bordeleau ◽  
Hani Antoun
Keyword(s):  
Transport System ◽  
Cold Adaptation ◽  
Proton Motive Force ◽  
The Arctic ◽  
Transport Systems ◽  
Effect Of Temperature ◽  
Rhizobium Strain ◽  
Onobrychis Viciifolia ◽  
Carbonyl Cyanide ◽  
Similar Kinetic

The effect of temperature on the succinate transport system was studied in the arctic Rhizobium strain N31 (isolated from Astragalus alpinus) and in the temperate strain SM2 (isolated from Onobrychis viciifolia). Only one inducible succinate transport system was found in the two strains as indicated by the linear Eadie–Hofstee plot obtained at 10, 15, and 25 °C. The transport of succinate was not affected by arsenate, but was inhibited by carbonyl cyanide m-chlorophenylhydrazone, KCN, and iodoacetate, implying an active process, a proton motive force, and essential sulfhydryl groups in the system. At 25 °C the apparent Km and Vmax values observed were 6.7 and 7.4 μM and 40.8 and 27.9 nmol∙min−1∙mg protein−1 for strains N31 and SM2, respectively. Similar kinetic parameters for succinate transport at 25 °C were obtained with the cells of both strains grown at 10 or 25 °C. However, when transport was measured at 10 °C the Km and Vmax values obtained with strain SM2 were higher for cells cultured at 10 °C than for those cultured at 25 °C, suggesting that this temperate strain might be more affected by low growth temperature than the arctic strain N31. The succinate transport systems in the two strains were affected by temperature in a similar fashion, as indicated by similar Arrhenius plots of Vmax showing a discontinuity at 20 °C and by comparable apparent energy of activation values. These observations suggest that the cold adaptation of strain N31 is not related to a cold adaptation of the succinate carrier.Key words: arctic, Rhizobium, succinate, symbiosis, transport.

Structural characteristics and development of sea ice in the western Ross Sea

1993 ◽  
Vol 5 (1) ◽  
pp. 63-75 ◽  
Author(s):  
M. O. Jeffries ◽  
W. F. Weeks
Keyword(s):  
Sea Ice ◽  
Internal Structure ◽  
Ross Sea ◽  
Ice Cores ◽  
Arctic Sea Ice ◽  
Weddell Sea ◽  
The Arctic ◽  
Ice Thickness ◽  
Pack Ice ◽  
Western Ross Sea

The internal structure of ice cores from western Ross Sea pack ice floes showed considerable diversity. Snow-ice formation made a small, but significant contribution to ice growth. Frazil ice was common and its growth clearly occurred during both the pancake cycle and deformation events. Congelation ice was also common, in both its crystallographically aligned and non-aligned varieties. Platelet ice was found in only one core next to the Drygalski Ice Tongue, an observation adding to the increasing evidence that this unusual ice type occurs primarily in coastal pack ice near ice tongues and ice shelves. The diverse internal structure of the floes indicates that sea ice development in the Ross Sea is as complex as that in the Weddell Sea and more complex than in the Arctic. The mean ice thickness at the ice core sites varied between 0.71 m and 1.52 m. The thinnest ice generally occurred in the outer pack ice zone. Regardless of latitude, the ice thickness data are further evidence that Antarctic sea ice is thinner than Arctic sea ice.

Glucose transport by an arctic and a temperate strain of rhizobia

1991 ◽  
Vol 37 (2) ◽  
pp. 105-109 ◽  
Author(s):  
Pierre C. Bigwaneza ◽  
Danielle Prévost ◽  
Lucien M. Bordeleau ◽  
Hani Antoun
Keyword(s):  
Key Words ◽  
Glucose Transport ◽  
Transport System ◽  
High Energy ◽  
The Arctic ◽  
Transport Systems ◽  
High Energy Phosphate ◽  
Rhizobium Species ◽  
Onobrychis Viciifolia ◽  
Active Mechanism

Glucose transport was studied in two strains of Rhizobium species effective on sainfoin (Onobrychis viciifolia), the arctic strain N31 isolated from Astragalus alpinus and the temperate strain SM2 isolated from sainfoin. The two strains had comparable glucose transport systems with a biphasic kinetics, indicating the presence of a high- and low-affinity transport system. Apparent Km and Vmax values for the high- and low-affinity transport systems were, respectively, 4.7 and 53.4 μM and 12.7 and 58.9 nmol∙min−1∙mg protein−1 with N31 and 2.6 and 72.6 μM and 10.1 and 64.6 nmol∙min−1∙mg protein−1 with SM2. Glucose transport systems were inhibited by 2,4-dinitrophenol, KCN, azide, and N-ethylmaleimide. NaF did not affect glucose transport, while arsenate showed partial inhibition of the low-affinity transport system with strain N31. These results suggest an active mechanism of transport that is dependent on an energized membrane but does not directly utilize high-energy phosphate compounds. In the two strains, glucose transport is constitutive and repressed by succinate, and it is glucose specific. Key words: Arctic, glucose, Rhizobium, symbiosis, transport.

Transitions in the internal structure of lipid droplets during fat digestion

Soft Matter ◽  
2011 ◽  
Vol 7 (2) ◽  
pp. 650-661 ◽  
Author(s):  
Stefan Salentinig ◽  
Laurent Sagalowicz ◽  
Martin E. Leser ◽  
Concetta Tedeschi ◽  
Otto Glatter
Keyword(s):  
Internal Structure ◽  
Lipid Droplets ◽  
Fat Digestion

scholarly journals Cells of matter and life – towards understanding the internal structure and spatial patchiness of particles and plankton distribution in the Arctic fjords

2021 ◽  
Author(s):  
Emilia Trudnowska ◽  
Katarzyna Dragańska-Deja ◽  
Sławomir Sagan ◽  
Katarzyna Błachowiak-Samołyk
Keyword(s):  
Water Column ◽  
Internal Structure ◽  
Temporal Distribution ◽  
Distribution Patterns ◽  
Atlantic Water ◽  
The Arctic ◽  
Size Fractions ◽  
Spatio Temporal ◽  
Plankton Distribution ◽  
Arctic Fjords

Abstract. Nothing is homogenous, neither the oceans, nor the distribution pattern of particles and plankton, both in the water column and within their patches. Here we analyse and map the spatio-temporal distribution patterns and the internal structure of 94 patches of various size fractions of particles and plankton studied in two Arctic fjords over six summer seasons. Observed patches generally occupied only the minor part of the studied upper water column (on average 12 %), and frequently occurred as multi-fraction forms. They varied among years and regions in terms of their position in a water column, size, shape, and structure. Consequently, we propose completely novel insight into their internal structure, by classifying them according to their shapes and the location of their cores. We distinguished seven types of patches: Belt, Triangle, Diamond, Flare, Fingers, Flag, and Rosette. The observed increasing role of the smallest size fractions (steepening size spectra slopes) over years implies that Atlantic water advection played the crucial role on compositional dynamics on temporal scale. The recurring feature of the elevated concentrations of particles and plankton near glacier fronts suggest that it, together with local biological production, is the strongest mechanism generating patchiness on the local scale. Even though we significantly extended our comprehension of the phenomenon of patchiness, it still remains an ambiguous matter, when, why, and if the mechanistic or ecological forcing prevails in shaping the patterns of particles and plankton distribution. Regardless of the mechanism, our results show that particles and plankton are not purely dye-like passive objects and that the type of their structuring in a water column may have only short term and local validity.

Ultrastructural Cytopiasmic Changes of Adrenal Cortex During Pregnancy

1969 ◽  
Vol 27 ◽  
pp. 298-299
Author(s):  
T. M. Murad ◽  
Karen Israel ◽  
Jack C. Geer
Keyword(s):  
Adrenal Gland ◽  
Steroid Hormones ◽  
Adrenal Cortex ◽  
Lipid Droplets ◽  
Plasma Cholesterol ◽  
Adrenal Steroids ◽  
Dynamic Changes ◽  
Cortical Cells ◽  
Acetyl Coenzyme A ◽  
Adrenal Cortical Cells

Adrenal steroids are normally synthesized from acetyl coenzyme A via cholesterol. Cholesterol is also shown to enter the adrenal gland and to be localized in the lipid droplets of the adrenal cortical cells. Both pregnenolone and progesterone act as intermediates in the conversion of cholesterol into steroid hormones. During pregnancy an increased level of plasma cholesterol is known to be associated with an increase of the adrenal corticoid and progesterone. The present study is designed to demonstrate whether the adrenal cortical cells show any dynamic changes during pregnancy.

X-ray microtomography

1988 ◽  
Vol 46 ◽  
pp. 998-999
Author(s):  
H.W. Deckman ◽  
B.F. Flannery ◽  
J.H. Dunsmuir ◽  
K.D' Amico
Keyword(s):  
Computed Tomography ◽  
Internal Structure ◽  
Imaging Technique ◽  
Three Dimensional ◽  
Tissue Structure ◽  
Individual Element ◽  
X Ray ◽  
Non Invasive ◽  
Panoramic Imaging ◽  
Three Dimensional Images

We have developed a new X-ray microscope which produces complete three dimensional images of samples. The microscope operates by performing X-ray tomography with unprecedented resolution. Tomography is a non-invasive imaging technique that creates maps of the internal structure of samples from measurement of the attenuation of penetrating radiation. As conventionally practiced in medical Computed Tomography (CT), radiologists produce maps of bone and tissue structure in several planar sections that reveal features with 1mm resolution and 1% contrast. Microtomography extends the capability of CT in several ways. First, the resolution which approaches one micron, is one thousand times higher than that of the medical CT. Second, our approach acquires and analyses the data in a panoramic imaging format that directly produces three-dimensional maps in a series of contiguous stacked planes. Typical maps available today consist of three hundred planar sections each containing 512x512 pixels. Finally, and perhaps of most import scientifically, microtomography using a synchrotron X-ray source, allows us to generate maps of individual element.

Morphometric SEM study of the effects of ACTH on endothelial fenestrae in the rat adrenal cortex

1984 ◽  
Vol 42 ◽  
pp. 234-235
Author(s):  
J. Curtis ◽  
K. S. Schwartz ◽  
R. P. Apkarian
Keyword(s):  
Anterior Pituitary ◽  
Lipid Droplets ◽  
Adrenocorticotropic Hormone ◽  
Unit Area ◽  
High Density Lipoproteins ◽  
Capillary Endothelium ◽  
Zona Fasciculata ◽  
Sem Study ◽  
Saline Vehicle ◽  
Scanning Electron

A scanning electron microscope (SEM) study was made of the effect of adrenocorticotropic hormone (ACTH) on the size and numbers of fenestrae/unit area in the capillary endothelium of the zona fasciculata (ZF) of the rat adrenal. The stimulatory effect of ACTH on cholesterol uptake via high density lipoproteins in the rat and evidence for the secretion of glucocorticoids by exocytosis of lipid droplets described by Rhodin suggest that endothelial change may accompany these transport phenomena.Twelve rats received two Dexamethasone (DEX) ip injections (25 μg DEX/100 g body wt.), the first at 8 PM and the second at 8 AM the next day, to inhibit the release of endogenous ACTH by the anterior pituitary. The animals were then divided into two groups. Six animals received only saline vehicle and six rats received ACTH (100 ng/100 g body wt.).

The internal structure of medullated wool

1984 ◽  
Vol 42 ◽  
pp. 388-389
Author(s):  
Leo Barish
Keyword(s):  
Light Microscopy ◽  
Internal Structure ◽  
Wool Fiber ◽  
Guard Hair ◽  
Bright Field ◽  
Wool Fibers ◽  
Thin Skin ◽  
Air Pockets

Although most of the wool used today consists of fine, unmedullated down-type fibers, a great deal of coarse wool is used for carpets, tweeds, industrial fabrics, etc. Besides the obvious diameter difference, coarse wool fibers are often medullated.Medullation may be easily observed using bright field light microscopy. Fig. 1A shows a typical fine diameter nonmedullated wool fiber, Fig. IB illustrates a coarse fiber with a large medulla. The opacity of the medulla is due to the inability of the mounting media to penetrate to the center of the fiber leaving air pockets. Fig. 1C shows an even thicker fiber with a very large medulla and with very thin skin. This type of wool is called “Kemp”, is shed annually or more often, and corresponds to guard hair in fur-bearing animals.

Sign in / Sign up

Export Citation Format

Share Document