scholarly journals Evidence for the existence of lipid-diffusion barriers in the equatorial segment of human spermatozoa

1994 ◽  
Vol 304 (1) ◽  
pp. 211-218 ◽  
Author(s):  
E G J M Arts ◽  
S Jager ◽  
D Hoekstra
Keyword(s):  
Lateral Diffusion ◽  
Distribution Patterns ◽  
Human Spermatozoa ◽  
Membrane Domains ◽  
Prolonged Incubation ◽  
Bivalent Cations ◽  
Lipid Diffusion ◽  
The Stability ◽  
Fluorescent Lipid Analogues ◽  
Fluorescent Lipid

Liposomes consisting of negatively charged phospholipids interact almost exclusively with the equatorial segment (ES) of human spermatozoa provided the cells have undergone the acrosome reaction (AR) [Arts, Kuiken, Jager and Hoekstra (1993) Eur. J. Biochem. 217, 1001-1009]. Using fluorescently tagged liposomes, this interaction can be observed by fluorescence microscopy, showing either a diffuse fluorescence in the ES region (pattern ESd, presumably reflecting membrane-incorporated lipids as a result of fusion) or a punctate fluorescence (pattern ESp, representing adhering liposomes). These distribution patterns remain unchanged during prolonged incubation, up to 40 min. Not only do these observations suggest the existence of fairly specific liposomal binding sites, associated with the ES region, but also that a barrier to lipid lateral diffusion seems to exist in the ES membrane. Using liposomes that contain fluorescent lipid analogues in either both leaflets or in the inner leaflet only, we demonstrate that this putative barrier entails both membrane leaflets. Treatment with EDTA caused fluorescence to spread from the ES towards other membrane domains. Since only spermatozoa displaying pattern ESd were affected by the chelator, the randomization was not caused by EDTA-induced fusion activity. Therefore, this observation provides further evidence that in spermatozoa displaying pattern ESd the fluorescent lipid analogues were incorporated in the ES membrane as a result of fusion. Furthermore, these experiments support the view of the existence of a transmembranous block to lipid lateral diffusion in the ES, the stability of which may be governed by bivalent cations.

The organization of cell surface membrane domains

1989 ◽  
Vol 47 ◽  
pp. 804-805
Author(s):  
Michael Edidin
Keyword(s):  
Cell Surface ◽  
Membrane Lipids ◽  
Surface Membrane ◽  
Lateral Diffusion ◽  
Cell Types ◽  
Membrane Domains ◽  
Membrane Biology ◽  
Morphological Polarity ◽  
Discrete Domains ◽  
Membrane Components

Cell surface membranes are based on a fluid lipid bilayer and models of the membranes' organization have emphasised the possibilities for lateral motion of membrane lipids and proteins within the bilayer. Two recent trends in cell and membrane biology make us consider ways in which membrane organization works against its inherent fluidity, localizing both lipids and proteins into discrete domains. There is evidence for such domains, even in cells without obvious morphological polarity and organization [Table 1]. Cells that are morphologically polarised, for example epithelial cells, raise the issue of membrane domains in an accute form.The technique of fluorescence photobleaching and recovery, FPR, was developed to measure lateral diffusion of membrane components. It has also proven to be a powerful tool for the analysis of constraints to lateral mobility. FPR resolves several sorts of membrane domains, all on the micrometer scale, in several different cell types.

Uptake and intracellular transport pathways of fluorescent lipid analogues inAmoeba proteus (Rhizopoda: Amoebida)

PROTOPLASMA ◽  
1996 ◽  
Vol 193 (1-4) ◽  
pp. 91-104 ◽  
Author(s):  
P. -M. Topf ◽  
M. Theis ◽  
W. Stockem
Keyword(s):  
Intracellular Transport ◽  
Transport Pathways ◽  
Fluorescent Lipid Analogues ◽  
Fluorescent Lipid

scholarly journals The lateral diffusion of lipid probes in the surface membrane of Schistosoma mansoni.

1986 ◽  
Vol 103 (3) ◽  
pp. 807-818 ◽  
Author(s):  
M Foley ◽  
A N MacGregor ◽  
J R Kusel ◽  
P B Garland ◽  
T Downie ◽  
...  
Keyword(s):  
Schistosoma Mansoni ◽  
Fluorescence Recovery After Photobleaching ◽  
Surface Membrane ◽  
Biological Significance ◽  
Lateral Diffusion ◽  
Asymmetric Distribution ◽  
Normal Surface ◽  
Membrane Blebs ◽  
Fluorescent Lipids ◽  
Fluorescent Lipid Analogues

The technique of fluorescence recovery after photobleaching was used to measure the lateral diffusion of fluorescent lipid analogues in the surface membrane of Schistosoma mansoni. Our data reveal that although some lipids could diffuse freely others exhibited restricted lateral diffusion. Quenching of lipid fluorescence by a non-permeant quencher, trypan blue, showed that there was an asymmetric distribution of lipids across the double bilayer of mature parasites. Those lipids that diffused freely were found to reside mainly in the external monolayer of the outer membrane whereas lipids with restricted lateral diffusion were located mainly in one or more of the monolayers beneath the external monolayer. Formation of surface membrane blebs allowed us to measure the lateral diffusion of lipids in the membrane without the influence of underlying cytoskeletal structures. The restricted diffusion found on the normal surface membrane of mature parasites was found to be released in membrane blebs. Quenching of fluorescent lipids on blebs indicated that all probes were present almost entirely in the external monolayer. Juvenile worms exhibited lower lateral diffusion coefficients than mature parasites: in addition, the lipids partitioned into the external monolayer. The results are discussed in terms of membrane organization, cytoskeletal contacts, and biological significance.

Effect of cholesterol on lateral diffusion of fluorescent lipid probes in native hippocampal membranes

2006 ◽  
Vol 143 (1-2) ◽  
pp. 11-21 ◽  
Author(s):  
Thomas J. Pucadyil ◽  
Amitabha Chattopadhyay
Keyword(s):  
Lateral Diffusion ◽  
Fluorescent Lipid Probes ◽  
Fluorescent Lipid

Selection of Positions by Drift-Feeding Salmonids in Dominance Hierarchies: Model and Test for Arctic Grayling (Thymallus arcticus) in Subarctic Mountain Streams, Interior Alaska

1992 ◽  
Vol 49 (10) ◽  
pp. 1999-2008 ◽  
Author(s):  
Nicholas F. Hughes
Keyword(s):  
Bottom Topography ◽  
Lateral Diffusion ◽  
Distribution Patterns ◽  
Mountain Stream ◽  
Physical Habitat ◽  
Dominance Hierarchies ◽  
Arctic Grayling ◽  
Drift Feeding ◽  
Stream Salmonids ◽  
Thymallus Arcticus

In this work I describe a model to predict position choice by each individual in a dominance hierarchy of drift-feeding stream salmonids. This is an adaptation of Hughes and Dill's model (1990. Can. J. Fish. Aquat. Sci. 47: 2039–2048) of position choice by solitary fish. I have included the effect that prey consumption, lateral diffusion of drifting invertebrates, and entry of invertebrates into the drift have on the density of prey downstream of feeding fish and the restrictions that dominant fish place on freedom of choice by their subordinates. l assume that each fish chooses the most profitable position that its rank in the hierarchy will allow. There was an encouraging match between the distribution patterns predicted by the model and the distribution patterns actually adopted by Arctic grayling (Thymallus arcticus) in two pools of a mountain stream. This result suggests that Arctic grayling locate and rank positions based on their profitability. The predictions of reduced models, and the location of positions in relation to bottom topography and current flow, suggest that the physical habitat forms the template for distribution patterns by determining the location and ranking of the most profitable positions.

scholarly journals A bidirectional antagonism between aPKC and Yurt regulates epithelial cell polarity

2014 ◽  
Vol 204 (4) ◽  
pp. 487-495 ◽  
Author(s):  
Clémence L. Gamblin ◽  
Émilie J.-L. Hardy ◽  
François J.-M. Chartier ◽  
Nicolas Bisson ◽  
Patrick Laprise
Keyword(s):  
Epithelial Cell ◽  
Cell Polarity ◽  
Cell Polarization ◽  
Membrane Domains ◽  
Epithelial Cell Polarity ◽  
Kinase C ◽  
The Stability ◽  
Regulatory Loop ◽  
Late Stages ◽  
Apical Localization

During epithelial cell polarization, Yurt (Yrt) is initially confined to the lateral membrane and supports the stability of this membrane domain by repressing the Crumbs-containing apical machinery. At late stages of embryogenesis, the apical recruitment of Yrt restricts the size of the apical membrane. However, the molecular basis sustaining the spatiotemporal dynamics of Yrt remains undefined. In this paper, we report that atypical protein kinase C (aPKC) phosphorylates Yrt to prevent its premature apical localization. A nonphosphorylatable version of Yrt dominantly dismantles the apical domain, showing that its aPKC-mediated exclusion is crucial for epithelial cell polarity. In return, Yrt counteracts aPKC functions to prevent apicalization of the plasma membrane. The ability of Yrt to bind and restrain aPKC signaling is central for its role in polarity, as removal of the aPKC binding site neutralizes Yrt activity. Thus, Yrt and aPKC are involved in a reciprocal antagonistic regulatory loop that contributes to segregation of distinct and mutually exclusive membrane domains in epithelial cells.

scholarly journals Lateral diffusion of the PH-20 protein on guinea pig sperm: evidence that barriers to diffusion maintain plasma membrane domains in mammalian sperm

1987 ◽  
Vol 104 (4) ◽  
pp. 917-923 ◽  
Author(s):  
AE Cowan ◽  
DG Myles ◽  
DE Koppel
Keyword(s):  
Plasma Membrane ◽  
Guinea Pig ◽  
Domain Boundary ◽  
Lateral Diffusion ◽  
Fold Increase ◽  
Membrane Domains ◽  
Mammalian Sperm ◽  
Acrosomal Membrane ◽  
Percent Recovery ◽  
Lipid Probe

PH-20 protein on the plasma membrane (PH-20PM) is restricted to the posterior head of acrosome-intact guinea pig sperm. During the exocytotic acrosome reaction the inner acrosomal membrane (IAM) becomes continuous with the posterior head plasma membrane, and PH-20PM migrates to the IAM. There it joins a second population of PH-20 protein localized to this region of the acrosomal membrane (PH-20AM) (Cowan, A.E., P. Primakoff, and D.G. Myles, 1986, J. Cell Biol. 103:1289-1297). To investigate how the localized distributions of PH-20 protein are maintained, the lateral mobility of PH-20 protein on these different membrane domains was determined using fluorescence redistribution after photobleaching. PH-20PM on the posterior head of acrosome-intact sperm was found to be mobile, with a diffusion coefficient and percent recovery typical of integral membrane proteins (D = 1.8 X 10(-10) cm2/s; %R = 73). This value of D was some 50-fold lower than that found for the lipid probe 1,1-ditetradecyl 3,3,3',3'-tetramethylindocarbocyanine perchlorate (C14diI) in the same region (D = 8.9 X 10(-9) cm2/s). After migration to the IAM of acrosome-reacted sperm, this same population of molecules (PH-20PM) exhibited a 30-fold increase in diffusion rate (D = 4.9 X 10(-9) cm2/s; %R = 78). This rate was similar to diffusion of the lipid probe C14diI in the IAM (D = 5.4 X 10(-9) cm2/s). The finding of free diffusion of PH-20PM in the IAM of acrosome-reacted sperm supports the proposal that PH-20 is maintained within the IAM by a barrier to diffusion at the domain boundary. The slower diffusion of PH-20PM on the posterior head of acrosome-intact sperm is also consistent with localization by barriers to diffusion, but does not rule out alternative mechanisms.

Unprotected freezing of human spermatozoa exerts a detrimental effect on their oocyte activating capacity and chromosome integrity

Zygote ◽  
1996 ◽  
Vol 4 (04) ◽  
pp. 263-268 ◽  
Author(s):  
Andrei V. Rybouchkin ◽  
Paul De Sutter ◽  
Marc Dhont
Keyword(s):  
Assisted Reproduction ◽  
Detrimental Effect ◽  
Chromosomal Abnormalities ◽  
Ethanol Solution ◽  
Human Spermatozoa ◽  
Physical Factors ◽  
Reproductive Characteristics ◽  
Chromosome Integrity ◽  
The Stability ◽  
Mammalian Spermatozoa

SummaryThe influence of unprotected freezing of mammalian spermatozoa on their oocyte activating capacity and chromosome integrity is unknown. However, this type of sperm treatment has been used in assisted reproduction by intracytoplasmic sperm injection in cattle and humans. The mouse oocyte injection test was used to analyse the influence of unprotected freezing of human spermatozoa on their reproductive characteristics. Mouse oocytes were microinjected with intact human spermatozoa or spermatozoa treated with two cycles of unprotected freeze-thawing. Oocytes surviving the injection were either cultured without further treatment or exposed to ethanol solution to induce parthenogenetic activation. Both injected and activated oocytes were used for sperm chromosome analysis. The results revealed a significant reduction in oocyte activating capacity and a tenfold increase in the incidence of structural chromosomal abnormalities in human spermatozoa treated by unprotected freezing. We conclude that unprotected freezing of human spermatozoa has a detrimental effect on their reproductive characteristics. Our data also provide a new perspective on the stability of mammalian spermatozoa to physical factors and demonstrate the importance of detailed analysis of the stability of sperm structures for successful development of new approaches in assisted reproduction.

scholarly journals Cyanobacteria bloom: selective filter for zooplankton?

2015 ◽  
Vol 75 (1) ◽  
pp. 165-174 ◽  
Author(s):  
NAST Mello ◽  
PM Maia-Barbosa
Keyword(s):  
Species Composition ◽  
Hydrological Cycle ◽  
Diversity Index ◽  
Zooplankton Community ◽  
Distribution Patterns ◽  
Distinct Species ◽  
Zooplankton Community Structure ◽  
Β Diversity ◽  
Cyanobacteria Blooms ◽  
The Stability

The Ibirité reservoir is an urban and eutrophic environment, with regular occurrences of cyanobacteria blooms. The reservoir is warm monomict and remains stratified most of the year, circulating in the dry season (winter). During the hydrological cycle of October/07 to October/08 there were four scenarios with different environmental conditions, which influenced the structure of the zooplankton community, as confirmed in a previous study. Changes in the zooplankton community structure between the scenarios were studied, aiming at analyzing the stability and persistence of this community. The Spearman’s coefficient of correlation was used to measure the stability; the persistence was evaluated through a cluster analysis and changes in community composition were estimated by the "temporal" β diversity index. Considering the distribution patterns of abundance, the community was stable only in the transition between scenarios 1 and 2 (n = 30, r = 0.71, p = 0.00001), when there were no cyanobacteria blooms. The persistence of zooplankton between the scenarios was low, showing a distinct species composition for each scenario. The highest variations in species composition, observed by the values of temporal β diversity index, were the transitions between scenarios 3-0 (1.45) and 0-1 (1.05), and the lowest variations occurred in the transition between scenarios 1-2 (0.57). The results suggest that the cyanobacteria blooms at Ibirité reservoir are be acting as "selective filters", and are, thus, disturbances with sufficient ability to change the structure of the zooplankton community. Keywords Urban Reservoir, zooplankton, bloom of cyanobacteria, stability, persistence.

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