scholarly journals Direct Evidence for a Sugar Transport Mechanism in Isolated Vacuoles

1979 ◽  
Vol 64 (1) ◽  
pp. 61-64 ◽  
Author(s):  
Micha Guy ◽  
Leonora Reinhold ◽  
Dorit Michaeli
Keyword(s):  
Transport Mechanism ◽  
Direct Evidence ◽  
Sugar Transport

scholarly journals Energization of the Sugar Transport Mechanism in the Plasmalemma of Isolated Mesophyll Protoplasts

1980 ◽  
Vol 65 (3) ◽  
pp. 550-553 ◽  
Author(s):  
Micha Guy ◽  
Leonora Reinhold ◽  
Michaela Rahat
Keyword(s):  
Transport Mechanism ◽  
Sugar Transport ◽  
Mesophyll Protoplasts

A common pathway for sugar transport in hamster intestine

1961 ◽  
Vol 200 (1) ◽  
pp. 111-116 ◽  
Author(s):  
Charles R. Jorgensen ◽  
Bernard R. Landau ◽  
T. Hastings Wilson
Keyword(s):  
Small Intestine ◽  
Transport Mechanism ◽  
Sugar Transport ◽  
The Other ◽  
Common Pathway ◽  
In Vitro Method ◽  
Single Segment ◽  
Other Hand

The competition between different sugars for the transport mechanism of hamster small intestine was tested with an in vitro method which allowed the use of a single segment of intestine for both control and experimental periods. The transport of the test sugar d-galactose was inhibited by other sugars known to be actively absorbed by the intestine; namely, d-glucose, α-methyl-d-glucoside, i-deoxy-d-glucose, 6-deoxy-d-glucose and 3-o-methyl-d-glucose. On the other hand d-mannose and d-xylose, two sugars not actively transported, did not inhibit d-galactose absorption. In addition, sugars known to be actively absorbed produced an inhibition of transport of d-glucose and 6-deoxy-d-glucose when these were selected as test sugars. The results of these experiments are consistent with the view that all transported sugars compete for a common pathway in hamster intestine. Various hypotheses of sugar transport are discussed in light of the present data.

Na+-coupled sugar transport: membrane potential-dependent Km and Ki for Na+

1988 ◽  
Vol 255 (4) ◽  
pp. C486-C494 ◽  
Author(s):  
G. A. Kimmich ◽  
J. Randles
Keyword(s):  
Membrane Potential ◽  
Kinetic Analysis ◽  
Transport Mechanism ◽  
Transport Model ◽  
Sugar Transport ◽  
Intestinal Cells ◽  
Maximal Velocity ◽  
Phlorizin Binding ◽  
Binding Event ◽  
Inner Surface

Kinetic analysis of the characteristics of phlorizin binding and of the Na+, sugar, and potential dependence of alpha-methylglucoside (alpha-MG) influx into isolated avian intestinal cells has pointed toward two alternative models for the transport mechanism (D. Restrepo and G. A. Kimmich, J. Membr. Biol. 89: 269-280, 1986). One of these models envisions a potential-dependent Na+ binding event (Na+ well concept) as a part of the molecular mechanism. The data reported here show that the apparent Km for Na+ for sugar transport is sharply dependent on the magnitude of the membrane potential. When intracellular Na+ is absent, the maximal velocity (Vmax) achieved for sugar influx is the same with or without a potential, although Vmax is obtained at a lower Na+ concentration when a potential is imposed (interior negative). Intracellular Na+ severely inhibits the influx of sugar in the absence of a potential, but this effect is largely overcome when a potential is present. The Vmax obtained when intracellular Na+ is present is a function of the potential. These results are consistent with a transport model in which Na+ binding to the Na+-dependent sugar carrier at the extracellular surface of the membrane and debinding at the inner surface of the membrane are both potential-dependent events.

scholarly journals The Hexose efflux from the peeled grape berry

OENO One ◽  
2019 ◽  
Vol 53 (2) ◽  
Author(s):  
Predrag Nenad Božović ◽  
Suzy Rogiers ◽  
Alain Deloire
Keyword(s):  
Transport Mechanism ◽  
Sugar Transport ◽  
Inhibitory Effect ◽  
Cellular Level ◽  
Grape Berry ◽  
Sugar Accumulation ◽  
Ethanesulfonic Acid ◽  
Two Stages ◽  
Process Elements ◽  
Vacuolar Membranes

Aim: The transport of sugars into grape berry mesocarp cells across the plasma and vacuolar membranes after onset of ripening is a complex process. Elements of the sugar transport mechanism may be assessed by exposing the mesocarp cells and investigating sugar movement across the membranes. The purpose of this study was to gain insights into the nature of the transport mechanism by creating conditions conducive to hexose efflux from the peeled berry.Methods and results: The experimental technique employed was a derivate of the ‘berry-cup’ technique. The skin of ripening cv. Shiraz berries was peeled in situ and, after an initial wash, hexose efflux into a collection medium (MES buffer) was monitored. Additionally, during the period of intensive sugar accumulation (one week after veraison) and two weeks later, hexose efflux was assessed following three modifications: (i) using berries excised from the vine, (ii) using MES buffer (2-(N-morpholino)ethanesulfonic acid, pH 5.5) containing PCMBS (p-chloromercuribenzenesulfonic acid, 1mM), and (iii) using cold (10°C) or warm (40°C) MES buffer. Hexose quantities collected into the buffer were dependent on ripening stage and buffer temperature, but they were not dependent on an intact berry-to-cluster connection. The inhibitory effect of PCMBS was observed early in ripening, but not two weeks later.Conclusions: These results lead us to the conclusion that the origin of the collected hexoses was vacuolar as opposed to vascular, and that the hexose efflux mechanism is differently sensitive to PCMBS at the two stages of ripening.Significance and impact of the study: This simple technique was effective at providing insights into hexose transport within the grape berry at the cellular level.

scholarly journals Direct Evidence of Photoinduced Charge Transport Mechanism in 2D Conductive Metal Organic Frameworks

2020 ◽  
Vol 142 (50) ◽  
pp. 21050-21058
Author(s):  
James Nyakuchena ◽  
Sarah Ostresh ◽  
Daniel Streater ◽  
Brian Pattengale ◽  
Jens Neu ◽  
...  
Keyword(s):  
Charge Transport ◽  
Transport Mechanism ◽  
Direct Evidence ◽  
Metal Organic Frameworks ◽  
Charge Transport Mechanism ◽  
Metal Organic ◽  
Photoinduced Charge

The Immuno-Electron Microscopic Localization of the Mo-Fe Protein Component of Nitrogenase in Cells of Azotobacter Vinelandii

1973 ◽  
Vol 31 ◽  
pp. 574-575
Author(s):  
J. T. Stasny ◽  
R. C. Burns ◽  
R. W. F. Hardy
Keyword(s):  
Cellular Localization ◽  
Direct Evidence ◽  
Azotobacter Vinelandii ◽  
Intracellular Localization ◽  
Protein Component ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Fe Protein ◽  
Intracytoplasmic Membranes

Structure-functlon studies of biological N2-fixation have correlated the presence of the enzyme nitrogenase with increased numbers of intracytoplasmic membranes in Azotobacter. However no direct evidence has been provided for the internal cellular localization of any nitrogenase. Recent advances concerned with the crystallizatiorTand the electron microscopic characterization of the Mo-Fe protein component of Azotobacter nitrogenase, prompted the use of this purified protein to obtain antibodies (Ab) to be conjugated to electron dense markers for the intracellular localization of the protein by electron microscopy. The present study describes the use of ferritin conjugated to goat antitMo-Fe protein immunoglobulin (IgG) and the observations following its topical application to thin sections of N2-grown Azotobacter.

Structural similarity of ribosomes from E. coli and A. salina

1978 ◽  
Vol 36 (2) ◽  
pp. 242-243
Author(s):  
M. Boublik ◽  
R.M. Wydro ◽  
W. Hellmann ◽  
F. Jenkins
Keyword(s):  
Ribosomal Proteins ◽  
Direct Evidence ◽  
Structural Similarity ◽  
Carbon Support ◽  
Artemia Salina ◽  
Uranyl Acetate ◽  
Biological Assays ◽  
E Coli ◽  
And Function ◽  
Fine Carbon

Ribosomes are ribonucleoprotein particles necessary for processing the genetic information of mRNA into proteins. Analogy in composition and function of ribosomes from diverse species, established by biochemical and biological assays, implies their structural similarity. Direct evidence obtained by electron microscopy seems to be of increasing relevance in understanding the structure of ribosomes and the mechanism of their role in protein synthesis.The extent of the structural homology between prokaryotic and eukaryotic ribosomes has been studied on ribosomes of Escherichia coli (E.c.) and Artemia salina (A.s.). Despite the established differences in size and in the amount and proportion of ribosomal proteins and RNAs both types of ribosomes show an overall similarity. The monosomes (stained with 0.5% aqueous uranyl acetate and deposited on a fine carbon support) appear in the electron micrographs as round particles with a diameter of approximately 225Å for the 70S E.c. (Fig. 1) and 260Å for the 80S A.s. monosome (Fig. 2).

Effects of Vincristine on Endothelial Microtubules in the Spinal Cord

1976 ◽  
Vol 34 ◽  
pp. 58-59
Author(s):  
John L. Beggs ◽  
John D. Waggener ◽  
Wanda Miller
Keyword(s):  
Spinal Cord ◽  
Biological Activity ◽  
Horseradish Peroxidase ◽  
Transport Mechanism ◽  
Vasogenic Edema ◽  
Vesicular Transport ◽  
Close Proximity

Microtubules (MT) are versatile organelles participating in a wide variety of biological activity. MT involvement in the movement and transport of cytoplasmic components has been well documented. In the course of our study on trauma-induced vasogenic edema in the spinal cord we have concluded that endothelial vesicles contribute to the edema process. Using horseradish peroxidase as a vascular tracer, labeled endothelial vesicles were present in all situations expected if a vesicular transport mechanism was in operation. Frequently,labeled vesicles coalesced to form channels that appeared to traverse the endothelium. The presence of MT in close proximity to labeled vesicles sugg ested that MT may play a role in vesicular activity.

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