Freeze-fracture analysis of endothelial cell membranes in rabbit carotid arteries subjected to short-term atherogenic stimuli

1988 ◽  
Vol 56 (1) ◽  
pp. 413-417 ◽  
Author(s):  
H. Mühleisen ◽  
H. Wolburg ◽  
E. Betz
1993 ◽  
Vol 101 (6) ◽  
pp. 510-516 ◽  
Author(s):  
D J Hazen-Martin ◽  
J H Todd ◽  
M A Sens ◽  
W Khan ◽  
J E Bylander ◽  
...  

Author(s):  
A. Tonosaki ◽  
M. Yamasaki ◽  
H. Washioka ◽  
J. Mizoguchi

A vertebrate disk membrane is composed of 40 % lipids and 60 % proteins. Its fracture faces have been classed into the plasmic (PF) and exoplasmic faces (EF), complementary with each other, like those of most other types of cell membranes. The hypothesis assuming the PF particles as representing membrane-associated proteins has been challenged by serious questions if they in fact emerge from the crystalline formation or decoration effects during freezing and shadowing processes. This problem seems to be yet unanswered, despite the remarkable case of the purple membrane of Halobacterium, partly because most observations have been made on the replicas from a single face of specimen, and partly because, in the case of photoreceptor membranes, the conformation of a rhodopsin and its relatives remains yet uncertain. The former defect seems to be partially fulfilled with complementary replica methods.


1972 ◽  
Vol 53 (1) ◽  
pp. 148-163 ◽  
Author(s):  
Daniel S. Friend ◽  
Norton B. Gilula

Extensive cell contacts which resemble septate junctions occur between cells in the three major zones of the rat adrenal cortex. Characteristically, they extend between small intercellular canaliculi and the periendothelial space, frequently interrupted by gap junctions and rarely by desmosomes. Zonulae occludentes have not been identified in the adrenal cortex. Along this distinctive cell contact, the cell membranes of apposing cells are separated by 210–300 a bisected by irregularly spaced 100–150-A extracellular particles which are often circular in profile. In lanthanum preparations, these particles appear to form a continuous chain throughout the intercellular space and are visualized as an alveolate structure in sections parallel to the plane of the cell membrane. The cell membrane in the area of septate-like contact does not differ from nonjunctional areas of the cell membrane in freeze-fracture replicas. The cell contact retains its integrity after cell dispersion and after the separation of cell membranes from disrupted cells. The intercellular particles also persist after brief extraction in lipid solvents. Besides adherence, possible functions of this adrenal contact include maintenance of the width of the extracellular space, the provision of channels between intercellular canaliculi and the bloodstream, and utilization as cation depots. Similar structures are also present between adrenal cortical cells of several other species and between interstitial cells of the testis. This type of cell contact may, in fact, be a typical feature of steroid-hormone-secreting tissues in vertebrates.


1978 ◽  
Vol 8 (3) ◽  
pp. 325-335 ◽  
Author(s):  
Ronald S. Weinstein ◽  
Jena K. Khodadad ◽  
Theodore L. Steck

1983 ◽  
Vol 60 (1) ◽  
pp. 137-156
Author(s):  
L.A. Hufnagel

A freeze-fracture analysis of early neogenesis of somatic and oral cilia of Tetrahymena was conducted using exponentially grown cultures and also cells induced to undergo oral reorganization. In this report, presumptive ciliary domains (PCDs), sites of future outgrowth of somatic cilia, are identified and their membrane structure is described in detail. The fairy ring, an array of membrane particles that occurs within the PCD and appears to be a precursor of the ciliary necklace, is described. A sequence of early stages in the formation of the ciliary necklace of somatic cilia is deduced from topographical information and membrane particle arrangements and numbers. Evidence is presented that basal bodies are seated at the cell surface prior to initiation of necklace assembly and a possible role for the basal body in necklace assembly is suggested. In dividing cells, new oral cilia grow out prior to orientation of cilia-parasomal sac complexes relative to cell axes. In dividing cells and during oral reorganization, new cilia also develop prior to their alignment into membranelles. Thus, growth of cilia is independent of their spatial orientation. Fairy rings were not observed during oral reorganization. During cell division, proliferation of new cilia is accompanied by the formation of a network of junctions between a cortical system of membranous cisternae, the cortical ‘alveoli’. These interalveolar junctions may serve as tracks for early positioning and orientation of new oral basal bodies.


1984 ◽  
Vol 4 (2) ◽  
pp. 241-249 ◽  
Author(s):  
Albert Gjedde ◽  
Ove Christensen

Tracer studies on facilitated diffusion across the blood–brain barrier lead to the calculation of Michaelis-Menten constants that describe the rate of transport. However, the barrier consists of two endothelial cell membranes, and the relevance of single Michaelis-Menten constants in relation to the two cell membranes is unknown. We have formulated a model of two endothelial cell membranes and show that the measured Michaelis-Menten constants are simple functions of the properties of the individual membranes when transport across the endothelium is rapid ( P1 > 10−6 cm s−1). We also show that the Michaelis-Menten constants determined in tracer experiments describe facilitated diffusion in the steady state only if the two membranes have similar transport properties. As an application of this observation, we have examined three experimental studies that measure glucose transport in the steady state and show that the Michaelis-Menten constants for glucose transport calculated from the tracer experiments are equal to the constants calculated from the steady-state experiments. We conclude that the luminal and abluminal membranes of brain capillary endothelial cells have equal glucose transport properties.


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