scholarly journals FRACTURE FACES OF OSMOTICALLY DISRUPTED ZONULAE OCCLUDENTES

1974 ◽  
Vol 62 (2) ◽  
pp. 344-350 ◽  
Author(s):  
James B. Wade ◽  
Morris J. Karnovsky
Keyword(s):  
Essential Role ◽  
Cell Attachment ◽  
Freeze Fracture ◽  
Toad Urinary Bladder ◽  
Mucosal Epithelium ◽  
Zonulae Occludentes ◽  
Ringer’S Solution ◽  
Zonula Occludens ◽  
A Site

Exposing the mucosal epithelium of the toad urinary bladder to 240 mM urea in Ringer's solution is known to cause a dramatic increase in the permeability of the zonulae occludentes and the appearance of distended, bubble-like compartments within these junctions. Examination of such osmotically disrupted junctions with the freeze-fracture technique reveals that these bubbles result from a distention of the compartments existing within the meshwork of interconnecting fibrils characteristic of the zonulae occludentes in this epithelium. Frequent discontinuities in the meshwork of fibrils are also found after osmotic disruption of the junction. These observations indicate the essential role of these fibrils in maintaining the characteristic properties of the zonula occludens as a site of cell-to-cell attachment and as a permeability seal.

Reciprocity and Just Conduct in War

2020 ◽  
pp. 81-104
Author(s):  
Neil C. Renic
Keyword(s):  
Essential Role ◽  
Just War ◽  
Structural Risk ◽  
Just War Tradition ◽  
A Site

This chapter locates the role of reciprocal risk within the Just War Tradition. This begins with the ‘conventionalist’ account of the moral right to kill. The chapter then considers the most recent challenge to this position in the form of Just War ‘revisionism’. Following this, it will examine the more consequentialist approach of ‘contractarianism’. The chapter will demonstrate that within all three of these approaches, an assumption of war as a site of reciprocal structural risk plays an essential role in the permissiveness of inter-combatant violence. The chapter then explores the tension between the coherence of these justifications and conditions of radical asymmetry.

scholarly journals Essential Role of the Oocyte in Estrogen Amplification of Follicle-Stimulating Hormone Signaling in Granulosa Cells

Endocrinology ◽  
2005 ◽  
Vol 146 (8) ◽  
pp. 3362-3367 ◽  
Author(s):  
Fumio Otsuka ◽  
R. Kelly Moore ◽  
Xia Wang ◽  
Shweta Sharma ◽  
Tomoko Miyoshi ◽  
...  
Keyword(s):  
Mrna Expression ◽  
Granulosa Cells ◽  
Essential Role ◽  
Primary Cultures ◽  
The Novel ◽  
Camp Production ◽  
Lh Receptor ◽  
Cell Responses ◽  
A Site

Abstract The establishment of dominant ovarian follicles that are capable of ovulating fertilizable oocytes is a fundamental determinant of female fertility. This process is governed by pituitary gonadotropins as well as local ovarian factors. Within the follicle, estrogen acts in an autocrine/paracrine manner to enhance FSH action in the granulosa cells. These effects include the augmentation of P450aromatase expression and estradiol production. This feed-forward effect of estrogen is believed to play a key role in follicle dominance. Here we found the essential role of the oocyte in this physiological process using primary cultures of rat granulosa cells. In the presence, but not absence, of oocytes, estrogen amplified FSH-stimulated increases in mRNA expression of P450aromatase, FSH receptor, LH receptor, and inhibin α-, βA-, and βB-subunits as well as cAMP production. Thus, oocytes mediate the estrogen enhancement of FSH action in the granulosa cells. In comparison with FSH, cotreatment with estrogen and oocytes failed to amplify the stimulatory effects of forskolin or 8-bromoadenosine-cAMP on granulosa cell responses including P450aromatase mRNA expression and cAMP production, indicating that estrogen/oocytes amplify FSH action at a site upstream of adenylate cyclase. These findings support the novel conclusion that communication between the oocyte and granulosa cells plays a crucial role in mediating estrogen action during FSH-dependent folliculogenesis.

Cytochalasin B inhibition of toad bladder apical membrane responses to ADH

1988 ◽  
Vol 255 (4) ◽  
pp. C526-C530 ◽  
Author(s):  
J. B. Wade ◽  
W. A. Kachadorian
Keyword(s):  
Water Permeability ◽  
Cytochalasin B ◽  
Apical Membrane ◽  
Freeze Fracture ◽  
Toad Urinary Bladder ◽  
Osmotic Gradient ◽  
Osmotic Water ◽  
Structural Responses ◽  
Freeze Fracture Electron Microscopy

The possible role of actin microfilaments in antidiuretic hormone (ADH)-induced increases in apical membrane water permeability was investigated in studies that evaluate inhibition by cytochalasin B of both permeability and membrane structural responses in the toad urinary bladder. Experiments were carried out in the absence of a transepithelial osmotic gradient to eliminate possible flow-induced distortions of the response. Measurements of osmotic water permeability after a brief tissue fixation with glutaraldehyde show that cytochalasin B reduces the permeability response to ADH by approximately one-third. Freeze-fracture electron microscopy indicates that the intramembrane particle aggregates, previously found to correlate closely with ADH-induced permeability, are reduced by about the same extent (28%) under these conditions. However, the frequency of apical membrane fusion events was not affected by cytochalasin B treatment. These results suggest that cytochalasin B treatment in the absence of an osmotic gradient alters the ADH-induced permeability through an effect on apical membrane aggregate frequency.

scholarly journals The Roles of Sodium and Potassium Ions in the Generation of the Electro-Olfactogram

1968 ◽  
Vol 51 (4) ◽  
pp. 552-578 ◽  
Author(s):  
Sadayuki F. Takagi ◽  
Gordon A. Wyse ◽  
Harunobu Kitamura ◽  
Katsuhiro Ito
Keyword(s):  
Essential Role ◽  
Ringer Solution ◽  
The Other ◽  
Potassium Ions ◽  
Ionic Mechanism ◽  
Ringer’S Solution ◽  
Sodium And Potassium

In order to clarify whether or not the electronegative olfactory mucosal potentials (EOG) are generator potentials, the effects of changed ionic enviroment were studied. The EOG decreased in amplitude and in some cases nearly or completely disappeared, when Na+ in the bathing Ringer solution was replaced by sucrose, Li+, choline+, tetraethylammonium+ (TEA), or hydrazine. In the K+-free Ringer solution, the negative EOG's initially increased and then decreased in amplitude. In Ringer's solution with increased K+, the negative EOG's increased in amplitude. When K+ was increased in exchange for Na+ in Ringer's solution, the negative EOG's decreased, disappeared, and then reversed their polarity (Fig. 6). Next, when the K+ was replaced by equimolar sucrose, Li+, choline+, TEA+, hydrazine, or Na+, the reversed potentials recovered completely only in Na+-Ringer's solution, but never in the other solutions. Thus, the essential role of Na+ and K+ in the negative EOG's was demonstrated. Ba++ was found to depress selectively the electropositive EOG, but it hardly decreased and never increased the negative EOG. Hence, it is concluded that Ba++ interferes only with Cl- influx, and that the negative EOG's are elicited by an increase in permeability of the olfactory receptive membrane to Na+ and K+, but not to Cl-. From the ionic mechanism it is inferred that the negative EOG's are in most cases composites of generator and positive potentials.

scholarly journals FRACTURE FACES OF ZONULAE OCCLUDENTES FROM "TIGHT" AND "LEAKY" EPITHELIA

1973 ◽  
Vol 58 (2) ◽  
pp. 390-400 ◽  
Author(s):  
Philippa Claude ◽  
Daniel A. Goodenough
Keyword(s):  
Urinary Bladder ◽  
Large Fraction ◽  
Distal Tubule ◽  
Morphological Data ◽  
Physiological Data ◽  
Toad Urinary Bladder ◽  
Leaky Epithelia ◽  
Zonulae Occludentes ◽  
Zonula Occludens ◽  
Variable Morphology

Epithelia vary with respect to transepithelial permeability. In those that are considered "leaky", a large fraction of the passive transepithelial flux appears to follow the paracellular route, passing across the zonulae occludentes and moving down the intercellular clefts. In "tight" epithelia, the resistance of the paracellular pathway to passive flux is greatly increased. To see whether differences in the morphology of the zonula occludens could contribute to this variability in leakiness among epithelia, replicas of zonulae occludentes in freeze-fractured material from a variety of tight and leaky epithelia were examined. The junctions appear as a branching and anastomosing network of strands or grooves on the A and B membrane fracture faces, respectively. It was found that the zonula occludens from a "very leaky" epithelium, the proximal convoluted tubule of the mouse kidney, is extremely shallow in the apical-basal direction, consisting in most places of only one junctional strand. In contrast, the "very tight" frog urinary bladder exhibits a zonula occludens that is relatively deep (>0.5 µm) in the apical-basal direction, and consists of five or more interconnected junctional strands interposed between luminal and lateral membrane surfaces. Epithelia of intermediate permeabilities exhibited junctions with intermediate or variable morphology. Toad urinary bladder, mouse stomach, jejunum, and distal tubule, rabbit gallbladder, and Necturus kidney and gallbladder were also examined, and the morphological data from these epithelia were compared to physiological data from the literature.

Role of vesicular transport in ADH-stimulated aggregate delivery

1988 ◽  
Vol 255 (5) ◽  
pp. C641-C652 ◽  
Author(s):  
G. Ding ◽  
N. Franki ◽  
J. Bourguet ◽  
R. M. Hays
Keyword(s):  
Electron Microscopy ◽  
Freeze Fracture ◽  
Toad Urinary Bladder ◽  
Supporting Evidence ◽  
Tubular Structures ◽  
Luminal Membrane ◽  
Transmission Electron ◽  
Intermediate Storage ◽  
Particle Delivery

It has been assumed from studies in toad bladder that antidiuretic hormone (ADH)-stimulated particle delivery to the luminal membrane is mediated by particle-carrying tubular structures (aggrephores). We report studies in frog and toad urinary bladder showing that vesicles, rather than aggrephores, appear to play the major role in particle delivery in the frog and that vesicle and aggrephore delivery proceed in parallel in the toad. Our principal evidence for this view is that in the frog, transmission electron microscopy shows virtually no fused aggrephores. Supporting evidence includes the following. 1) Freeze-fracture studies show that the diameters of fusion events delivering particles can be quite small, indicating that they are formed by fused vesicles rather than fused aggrephores. 2) A significant population of small fusion events is also seen in the toad, along with larger fusion events related to both aggrephores and large vesicles. 3) Surface aggregate areas in both species are small, consistent with vesicular delivery. 4) Freeze-fracture replicas indicate delivery from shallow pits. We propose a system of transport of particles in which aggrephores act largely as intermediate storage organelles in the frog and as storage and fusion organelles in the toad.

Role of PKC isozymes in water transport in toad urinary bladder

1991 ◽  
Vol 49 ◽  
pp. 302-303
Author(s):  
A.J. Mia ◽  
L.X. Oakford ◽  
T. Yorio
Keyword(s):  
Urinary Bladder ◽  
Apical Membrane ◽  
Membrane Surface ◽  
Protein A ◽  
Cell Types ◽  
Leukemic Cells ◽  
Toad Urinary Bladder ◽  
Pkc Isozymes ◽  
Antibody Labeling

Protein kinase C (PKC) isozymes, when activated, are translocated to particulate membrane fractions for transport to the apical membrane surface in a variety of cell types. Evidence of PKC translocation was demonstrated in human megakaryoblastic leukemic cells, and in cardiac myocytes and fibroblasts, using FTTC immunofluorescent antibody labeling techniques. Recently, we reported immunogold localizations of PKC subtypes I and II in toad urinary bladder epithelia, following 60 min stimulation with Mezerein (MZ), a PKC activator, or antidiuretic hormone (ADH). Localization of isozyme subtypes I and n was carried out in separate grids using specific monoclonal antibodies with subsequent labeling with 20nm protein A-gold probes. Each PKC subtype was found to be distributed singularly and in discrete isolated patches in the cytosol as well as in the apical membrane domains. To determine if the PKC isozymes co-localized within the cell, a double immunogold labeling technique using single grids was utilized.

Freeze-fracture observations on changes in the distribution of Filipin-sterol complexes during epididymal maturation and capacitation of boar spermatozoa

1990 ◽  
Vol 48 (3) ◽  
pp. 90-91
Author(s):  
N. Seki ◽  
Y. Toyama ◽  
T. Nagano
Keyword(s):  
Plasma Membrane ◽  
Essential Role ◽  
Freeze Fracture ◽  
Final Concentration ◽  
Freeze Fracturing ◽  
Physiological Conditions ◽  
Epididymal Maturation ◽  
Cacodylate Buffer ◽  
Sperm Membrane ◽  
Boar Spermatozoa

It is believed that i ntramembra.nous sterols play an essential role in membrane stability and permeability. To investigate the distribution changes of sterols in sperm membrane during epididymal maturation and capacitation, filipin has been used as a cytochemical probe for the detection for membrane sterols. Using this technique in combination with freeze fracturing, we examined the boar spermatozoa under various physiological conditions.The spermatozoa were collected from: 1) caput, corpus and cauda epididymides, 2) sperm rich fraction of ejaculates, and 3)the uterus 2hr after natural coition. They were fixed with 2.5% glutaraldehyde in 0.05M cacodylate buffer (pH 7.4), and treated with the filipin solution (final concentration : 0.02.0.05%) for 24hr at 4°C with constant agitation. After the filipin treatment, replicas were made by conventional freeze-fracture technique. The density of filipin-sterol complexes (FSCs) was determined in the E face of the plasma membrane of head regions.

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