scholarly journals FOOD VACUOLE MEMBRANE GROWTH WITH MICROTUBULE-ASSOCIATED MEMBRANE TRANSPORT IN PARAMECIUM

1974 ◽  
Vol 63 (3) ◽  
pp. 904-922 ◽  
Author(s):  
Richard D. Allen
Keyword(s):  
Membrane Surface ◽  
Three Dimensional ◽  
Food Vacuole ◽  
Structural System ◽  
Digestive Vacuole ◽  
Membrane Surface Area ◽  
Vacuole Membrane ◽  
Membrane Growth ◽  
Food Vacuoles ◽  
Membrane Disk

Evidence from a morphological study of the oral apparatus of Paramecium caudatum using electron microscope techniques have shown the existence of an elaborate structural system which is apparently designed to recycle digestive-vacuole membrane. Disk-shaped vesicles are filtered out of the cytoplasm by a group of microtubular ribbons. The vesicles, after being transported to the cytostome-cytopharynx region in association with these ribbons, accumulate next to the cytopharynx before they become fused with the cytopharyngeal membrane. This fusion allows the nascent food vacuole to grow and increase its membrane surface area. The morphology of this cytostome-cytopharynx region is described in detail and illustrated with a three-dimensional drawing of a portion of this region and a clay sculpture of the oral apparatus of Paramecium. Evidence from the literature for the transformation of food vacuole membrane into disk-shaped vesicles both from condensing food vacuoles in the endoplasm and from egested food vacuoles at the cytoproct is presented. This transformation would complete a system of digestive vacuole membrane recycling.

Membrane recycling at the cytoproct of Tetrahymena

1979 ◽  
Vol 35 (1) ◽  
pp. 217-227
Author(s):  
R.D. Allen ◽  
R.W. Wolf
Keyword(s):  
Plasma Membrane ◽  
Single Cells ◽  
Tetrahymena Pyriformis ◽  
Food Vacuole ◽  
Membrane Recycling ◽  
Vacuole Membrane ◽  
Thin Section Electron Microscopy ◽  
Section Electron ◽  
Food Vacuoles ◽  
Spherical Vesicles

Exocytosis and membrane recycling at the cytoproct (cell anus) of Tetrahymena pyriformis were studied using thin-section electron microscopy. Single cells were fixed at specific times relative to the elimination of the vacuole's contents—before elimination, at elimination, 3–5 s and 10–15 s following elimination. The closed cytoproct is distinguished from other pellicular regions by a single membrane at the cell surface which is circumscribed by an electron-opaque flange that links or welds the plasma membrane to the underlying alveolar margins. Microtubules originating in the flange pass inward where they lie over, and possibly guide, the approaching food vacuoles to the cytoproct. Food facuoles near the cytoproct are also accompanied by coats of microfilaments. These microfilaments appear to be active in the channelling and endocytosis of food vacuole membrane. Upon cytoproct opening the plasma membrane and food vacuole membrane fuse. Elimination seems to be essentially passive and is accomplished by re-engulfment of the old food vacuole membrane which is constantly associated with microfilaments. Reengulfment of all the food vacuole membrane requires 10–15 s and results in a closed cytoproct. The membrane remnants embedded in microfilaments form a cluster under the closed cytoproct. At the periphery of this cluster remnants take the shape of 70–130-nm spherical vesicles or 0.2-micrometer-long flattened vesicles.

scholarly journals Three-dimensional ATUM-SEM reconstruction and analysis of hepatic endoplasmic reticulum-organelle interactions

2020 ◽  
Author(s):  
Yi Jiang ◽  
Linlin Li ◽  
Xi Chen ◽  
Jiazheng Liu ◽  
Jingbin Yuan ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
3D Reconstruction ◽  
Surface Area ◽  
Lipid Droplets ◽  
Membrane Surface ◽  
Three Dimensional ◽  
Surface Area Ratio ◽  
Intracellular Space ◽  
Membrane Surface Area ◽  
Membrane Contact Sites

AbstractThe endoplasmic reticulum (ER) is a contiguous and complicated membrane network in eukaryotic cells, and membrane contact sites (MCSs) between the ER and other organelles perform vital cellular functions, including lipid homeostasis, metabolite exchange, calcium level regulation, and organelle division. Here, we establish a whole pipeline to reconstruct all ER, mitochondria, lipid droplets, lysosomes, peroxisomes, and nuclei by automated tape-collecting ultramicrotome scanning electron microscopy (ATUM-SEM) and deep-learning techniques, which generates an unprecedented 3D model for mapping liver samples. Furthermore, the morphology of various organelles is systematically analyzed. We found that the ER presents with predominantly flat cisternae and is knitted tightly all throughout the intracellular space and around other organelles. In addition, the ER has a smaller volume-to-membrane surface area ratio than other organelles, which suggests that the ER could be more suited for functions that require a large membrane surface area. Moreover, the MCSs between the ER and other organelles are explored. Our data indicate that ER-mitochondrial contacts are particularly abundant, especially for branched mitochondria. In addition, ER contacts with lipid droplets, lysosomes, and peroxisomes are also plentiful. In summary, we design an efficient method for obtaining a 3D reconstruction of biological structures at a nanometer resolution. Our study also provides the first 3D reconstruction of various organelles in liver samples together with important information fundamental for biochemical and functional studies in the liver.

scholarly journals Digestive system membranes: freeze-fracture evidence for differentiation and flow in Paramecium.

1981 ◽  
Vol 89 (1) ◽  
pp. 9-20 ◽  
Author(s):  
R D Allen ◽  
L A Staehelin
Keyword(s):  
Digestive System ◽  
Membrane Surface ◽  
Freeze Fracture ◽  
Membrane Material ◽  
Specific Sequence ◽  
Membrane Surface Area ◽  
Vacuole Membrane ◽  
Membrane Changes ◽  
Discoidal Vesicles ◽  
Second Category

Freeze-fractured membranes of digestive vacuoles of randomly feeding Paramecium caudatum exhibit dramatic differences in intramembrane particle (IMP) number and distribution on both E- and P-fracture faces. By pulse-feeding latex spheres to cells we have demonstrated that these differences are related to the age of the digestive vacuoles, and that the membranes of such vacuoles undergo a specific sequence of changes during the digestive cycle. Young digestive vacuoles (DV-I; less than or equal to 6 min), nascent vacuoles still connected to the cytopharynx, and discoidal vesicles, from which vacuole membrane is derived, all have a highly particulate E face and a less particulate P face. As early as 3 min after feeding, a second category of digestive vacuoles (DV-II) can be recognized, which are both considerably smaller in diameter and lack particles on their E face. These findings suggest that the endocytic removal of DV-I membrane material associated with the formation of DV-II vacuoles involves a concomitant and selective removal of E-face particles, as essentially no changes are seen in the density of P-face particles on the two types of vacuoles. Beginning at 10 min the first DV-III vacuoles are encountered. These are both larger than the DV-II vacuoles and possess very prominent E-face particles, which resemble those on the E face of the numerous lysosomes bordering the digestive vacuoles. DV-III vacuoles also exhibit a substantial increase in P-face particles. These membrane changes closely parallel, and are probably correlated with, the physiological events occurring within the vacuole lumen: concentration of food, killing of prey, and digestion. Calculations of the amount of membrane removed from DV-I to form DV-II and of the increase in membrane surface area during the transition from DV-II to DV-III indicate that as much as 90% of the initial phagosome (DV-I) membrane can be removed before digestion begins. The enlargment of DV-II must be caused by fusion with adjacent lysosomes which also contribute the new populations of IMPs to the DV-III membrane. The appearance of numerous endocytic structures on older DV-III vacuoles suggests that membrane is retrieved from DV-III before defecation.

Feeding in Ciliated Protozoa

1974 ◽  
Vol 15 (2) ◽  
pp. 379-401
Author(s):  
JOHN. A. KLOETZEL
Keyword(s):  
Cell Surface ◽  
Buccal Cavity ◽  
Surface Membrane ◽  
Food Vacuole ◽  
Food Ingestion ◽  
Membrane Flow ◽  
Vacuole Membrane ◽  
Vacuole Formation ◽  
Food Vacuoles ◽  
Lamellar Material

The ciliate Euplotes is able to expend a very large amount of membrane in the formation of food vacuoles. Calculations based on the rate of ingestion of the food organism Tetrahymena indicate that an amount of food vacuole membrane equivalent to approximately 50-150% of the total Euplotes cell surface area can be produced within 5-10 min. An aggregation of osmiophilic, membrane-limited ‘pharyngeal disks’ is found packed in the cytoplasm just beneath the cell surface membrane in the region of the cell mouth and cytopharynx. These disks, which can be seen also in living cells, have average dimensions of 2 µm diameter by 100 nm thickness, and contain tightly packed layers of a thin lamellar material. Electron micrographs have revealed the apparent fusion of the limiting membrane of disks with the cell's plasma membrane at the base of the gullet. The lamellar disk contents are thereby released to the exterior medium in the buccal cavity, where they form a loosely packed layer over the surface membrane. It is postulated that the pharyngeal disks represent a repository of preformed membrane for use in food vacuole formation. The disk contents may also play a role in food ingestion, although this is not well defined at present. The myeloid content of old food vacuoles is very similar to that of nearby disks in the cytoplasm, suggesting that the disks may form by pinching from shrinking food vacuoles during the digestive cycle. Thus a cycle of membrane flow is envisaged, with the pharyngeal disks (1) coalescing with the surface membrane during food vacuole formation, (2) reforming by pinching from these food vacuoles during digestion, and (3) migrating back to the oral region to serve as a membrane store for subsequent food vacuole formation.

Practitioner-friendly design method to improve the seismic performance of RC frame buildings

2021 ◽  
pp. 875529302098801
Author(s):  
Orlando Arroyo ◽  
Abbie Liel ◽  
Sergio Gutiérrez
Keyword(s):  
Seismic Performance ◽  
Design Method ◽  
Three Dimensional ◽  
Rc Frame ◽  
Structural System ◽  
Standard Code ◽  
Frame Buildings ◽  
Rc Frame Buildings ◽  
Mathematical Justification ◽  
Story Building

Reinforced concrete (RC) frame buildings are a widely used structural system around the world. These buildings are customarily designed through standard code-based procedures, which are well-suited to the workflow of design offices. However, these procedures typically do not aim for or achieve seismic performance higher than code minimum objectives. This article proposes a practical design method that improves the seismic performance of bare RC frame buildings, using only information available from elastic structural analysis conducted in standard code-based design. Four buildings were designed using the proposed method and the prescriptive approach of design codes, and their seismic performance is evaluated using three-dimensional nonlinear (fiber) models. The findings show that the seismic performance is improved with the proposed method, with reductions in the collapse fragility, higher deformation capacity, and greater overstrength. Furthermore, an economic analysis for a six-story building shows that these improvements come with only a 2% increase in the material bill, suggesting that the proposed method is compatible with current project budgets as well as design workflow. The authors also provide mathematical justification of the method.

Intracellular distribution of lead in Tetrahymena during continuous exposure to the metal

1979 ◽  
Vol 39 (1) ◽  
pp. 383-396
Author(s):  
J.R. Nilsson
Keyword(s):  
Cell Growth ◽  
Growth Medium ◽  
Food Vacuole ◽  
Continuous Exposure ◽  
Organic Growth ◽  
Food Vacuoles ◽  
Entire Cell ◽  
Membrane Bound ◽  
Lag Period ◽  
High Concentrations

Lead acetate (0.1–0.2%) forms a precipitate with the organic growth medium. The Tetrahymena cells ingest this lead-containing precipitate and cell growth is resumed after a variable lag period. Ingested lead is observed as electron-dense material in food vacuoles. Soon after exposure, cytoplasmic lead (preserved with certain fixation only) is revealed as electron-dense particles in cilia and in a halo around digestive vacuoles. Later the lead particles pervade the entire cell but after the lag period they are confined to membrane-bound spaces. In dilute growth medium, high concentrations of lead inhibit food-vacuole formation and cell growth. Under these conditions lead is deposited in alveoli of the pellicle and is also found in autophagic vacuoles and other membrane-limited structures. The study has revealed that lead enters Tetrahymena through the membrane of digestive vacuoles and through the cell surface. The change in distribution of lead during the lag period indicates that a mechanism is activated for removal of lead into membrane-bound spaces. The final storage of lead seems to be in lysosomes.

The macrophage capacity for phagocytosis

1992 ◽  
Vol 101 (4) ◽  
pp. 907-913 ◽  
Author(s):  
G.J. Cannon ◽  
J.A. Swanson
Keyword(s):  
Surface Area ◽  
Membrane Surface ◽  
Fc Receptors ◽  
Phagocytic Capacity ◽  
Membrane Surface Area ◽  
Murine Bone Marrow ◽  
Latex Beads ◽  
Endocytic Compartments ◽  
Frustrated Phagocytosis

Murine bone marrow-derived macrophages, which measure 13.8 +/− 2.3 microns diameter in suspension, can ingest IgG-opsonized latex beads greater than 20 microns diameter. A precise assay has allowed the determination of the phagocytic capacity, and of physiological parameters that limit that capacity. Ingestion of beads larger than 15 microns diameter required IgG-opsonization, and took 30 minutes to reach completion. Despite the dependence on Fc-receptors for phagocytosis of larger beads, cells reached their limit before all cell surface Fc-receptors were occupied. The maximal membrane surface area after frustrated phagocytosis of opsonized coverslips was similar to the membrane surface area required to engulf particles at the limiting diameter, indicating that the capacity was independent of particle shape. Vacuolation of the lysosomal compartment with sucrose, which expanded endocytic compartments, lowered the phagocytic capacity. This decrease was reversed when sucrose vacuoles were collapsed by incubation of cells with invertase. These experiments indicate that the phagocytic capacity is limited by the amount of available membrane, rather than by the availability of Fc-receptors. The capacity was also reduced by depolymerization of cytoplasmic microtubules with nocodazole. Nocodazole did not affect the area of maximal cell spreading during frustrated phagocytosis, but did alter the shape of the spread cells. Thus, microtubules may coordinate cytoplasm for engulfment of the largest particles.

scholarly journals Brush border protocadherin CDHR2 promotes the elongation and maximized packing of microvilli in vivo

2019 ◽  
Vol 30 (1) ◽  
pp. 108-118 ◽  
Author(s):  
Julia A. Pinette ◽  
Suli Mao ◽  
Bryan A. Millis ◽  
Evan S. Krystofiak ◽  
James J. Faust ◽  
...  
Keyword(s):  
Functional Capacity ◽  
Brush Border ◽  
Intestinal Tract ◽  
Membrane Surface ◽  
Careful Examination ◽  
Tissue Cell ◽  
Apical Surface ◽  
Membrane Surface Area ◽  
Solute Uptake

Transporting epithelial cells optimize their morphology for solute uptake by building an apical specialization: a dense array of microvilli that serves to increase membrane surface area. In the intestinal tract, individual cells build thousands of microvilli, which pack tightly to form the brush border. Recent studies implicate adhesion molecule CDHR2 in the regulation of microvillar packing via the formation of adhesion complexes between the tips of adjacent protrusions. To gain insight on how CDHR2 contributes to brush border morphogenesis and enterocyte function under native in vivo conditions, we generated mice lacking CDHR2 expression in the intestinal tract. Although CDHR2 knockout (KO) mice are viable, body weight trends lower and careful examination of tissue, cell, and brush border morphology revealed several perturbations that likely contribute to reduced functional capacity of KO intestine. In the absence of CDHR2, microvilli are significantly shorter, and exhibit disordered packing and a 30% decrease in packing density. These structural perturbations are linked to decreased levels of key solute processing and transporting factors in the brush border. Thus, CDHR2 functions to elongate microvilli and maximize their numbers on the apical surface, which together serve to increase the functional capacity of enterocyte.

scholarly journals Effect Of Surface Area Of Dialyzer Membrane On The Adequacy Of Haemodialysis

2012 ◽  
Vol 7 (2) ◽  
pp. 9-11 ◽  
Author(s):  
NS Chowdhury ◽  
FMM Islam ◽  
F Zafreen ◽  
BA Begum ◽  
N Sultana ◽  
...  
Keyword(s):  
Renal Disease ◽  
Surface Area ◽  
End Stage Renal Disease ◽  
Membrane Surface ◽  
Reduction Ratio ◽  
Urea Clearance ◽  
Membrane Surface Area ◽  
Stage Renal Disease ◽  
End Stage ◽  
Urea Reduction Ratio

Introduction: Patients with end stage renal disease require 12 hours of haemodialysis per week in three equal sessions (4 hours/day for 3 days/week). But the duration and frequency of treatment can be reduced by increasing the surface area of the dialyzer membrane. Methods: In this prospective study 40 patients of end stage renal disease receiving haemodialysis for more than six months were included to observe the effects of increment in the surface area of the dialyzer membrane on the adequacy of haemodialysis. Result: It was observed that 20 patients receiving haemodialysis on a dialyzer with membrane surface area of 1.2 m² did not have satisfactory solute clearance index. Urea reduction ratio was 45.9 ± 3.03 and fractional urea clearance (Kt/V) was 0.76 ± 0.09. On the other hand patients (20 cases) receiving haemodialysis on a dialyzer with membrane surface area of 1.3 m² had a urea reduction ratio 50.76± 5.16 and fractional urea clearance (Kt/V) 0.91 ± 0.16. All the patients of both groups received dialysis for 8 hours/week in two equal sessions (4 hours/day for 2 days/week). Statistically the increment was significant (p<0.001). Conclusion: This study reveals, adequacy of dialysis can be increased by increasing the surface area of the dialyzer membrane. So, considering the poor socioeconomic condition of Bangladesh and patients' convenience, a short duration, low cost dialysis regime can be tried by increasing the surface area of dialyzer membrane. DOI: http://dx.doi.org/10.3329/jafmc.v7i2.10387 JAFMC 2011; 7(2): 9-11

Membrane Surface Area to Volume Ratio in Chronic Subdural Hematomas: Critical Size and Potential Postoperative Target

2017 ◽  
Vol 100 ◽  
pp. 256-260 ◽  
Author(s):  
Appukutty Manickam ◽  
Laurence A.G. Marshman ◽  
Ross Johnston
Keyword(s):  
Surface Area ◽  
Critical Size ◽  
Membrane Surface ◽  
Volume Ratio ◽  
Membrane Surface Area ◽  
Subdural Hematomas
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