Some Conditions Necessary for Pinocytosis

1968 ◽  
Vol 26 ◽  
pp. 142-143
Author(s):  
M. W. Brightman
Keyword(s):  
Smooth Muscle ◽  
Cell Membrane ◽  
Toxic Effects ◽  
Cytological Evidence ◽  
Cell Processes

The cytological evidence for pinocytosis is the focal infolding of the cell membrane to form surface pits that eventually pinch off and move into the cytoplasm. This activity, which can be inhibited by oxidative and glycolytic poisons, is performed only by cell processes that are at least 300A wide. However, the interpretation of such toxic effects becomes equivocal if the membrane invaginations do not normally lead to the formation of migratory vesicles, as in some endothelia and in smooth muscle. The present study is an attempt to set forth some conditions under which pinocytosis, as distinct from the mere inclusion of material in surface invaginations, can take place.

Pressure-induced smooth muscle cell depolarization in pulmonary arteries from control and chronically hypoxic rats does not cause myogenic vasoconstriction

2005 ◽  
Vol 98 (3) ◽  
pp. 1119-1124 ◽  
Author(s):  
Jay S. Naik ◽  
Scott Earley ◽  
Thomas C. Resta ◽  
Benjimen R. Walker
Keyword(s):  
Smooth Muscle ◽  
Membrane Potential ◽  
Cell Membrane ◽  
Pulmonary Vascular Resistance ◽  
Vascular Resistance ◽  
Pulmonary Arteries ◽  
Barometric Pressure ◽  
Cell Membrane Potential ◽  
Intraluminal Pressure ◽  
Dose Dependent

Chronic obstructive pulmonary diseases, as well as prolonged residence at high altitude, can result in generalized airway hypoxia, eliciting an increase in pulmonary vascular resistance. We hypothesized that a portion of the elevated pulmonary vascular resistance following chronic hypoxia (CH) is due to the development of myogenic tone. Isolated, pressurized small pulmonary arteries from control (barometric pressure ≅ 630 Torr) and CH (4 wk, barometric pressure = 380 Torr) rats were loaded with fura 2-AM and perfused with warm (37°C), aerated (21% O2-6% CO2-balance N2) physiological saline solution. Vascular smooth muscle (VSM) intracellular Ca2+ concentration ([Ca2+]i) and diameter responses to increasing intraluminal pressure were determined. Diameter and VSM cell [Ca2+]i responses to KCl were also determined. In a separate set of experiments, VSM cell membrane potential responses to increasing luminal pressure were determined in arteries from control and CH rats. VSM cell membrane potential in arteries from CH animals was depolarized relative to control at each pressure step. VSM cells from both groups exhibited a further depolarization in response to step increases in intraluminal pressure. However, arteries from both control and CH rats distended passively to increasing intraluminal pressure, and VSM cell [Ca2+]i was not affected. KCl elicited a dose-dependent vasoconstriction that was nearly identical between control and CH groups. Whereas KCl administration resulted in a dose-dependent increase in VSM cell [Ca2+]i in arteries taken from control animals, this stimulus elicited only a slight increase in VSM cell [Ca2+]i in arteries from CH animals. We conclude that the pulmonary circulation of the rat does not demonstrate pressure-induced vasoconstriction.

Abstract 46: The Effects of Membrane Cholesterol on Vascular Smooth Muscle Cell Stiffness and Adhesion to Fibronectin

2017 ◽  
Vol 37 (suppl_1) ◽  
Author(s):  
Josh Childs ◽  
Zhongkui Hong Hong
Keyword(s):  
Smooth Muscle ◽  
Cell Membrane ◽  
Vascular Smooth Muscle ◽  
Atherosclerotic Plaque ◽  
Adhesion Force ◽  
Foam Cells ◽  
Sensory Function ◽  
Cell Stiffness ◽  
Membrane Cholesterol ◽  
Cholesterol Depletion

Atherosclerosis remains a major cause of cardiovascular disease (CVD). Cholesterol has been identified as a major contributor to the cause of atherosclerosis. It is well known that the cholesterol accumulation in macrophage-derived foam cells is the major component of atherosclerotic plaque. However, growing evidences suggests that cholesterol loading into vascular smooth muscle cells (VSMC) in atherosclerosis is much larger than previously known, and about 40% of total foam cells in the atherosclerotic plaque are VSMC-derived. Cholesterol may not only contribute as the fatty deposition in the atherosclerotic lesion, but also play a critical role in the VSMC migration toward the intima of the blood vessel wall. In addition, the arterial wall becomes stiffer during atherosclerosis altering the micromechanical environment experienced by the VSMCs leading to changes in VSMC stiffens, adhesion, and phenotype. Migration of VSMCs is a complex process including proliferation and phenotypic switching of VSMCs, thus contributing too many changes in cell membrane adhesion molecules. We tested the hypothesis that membrane cholesterol in VSMCs may play an important role in α 5 β 1 -integrin mediated adhesion, and alter the sensory function of VSMCs to ECM mechanical properties. In this study cholesterol manipulation was achieved using methyl-β-cyclodextrin, and gel substrates with varying stiffness were used to mimic the changing environment in atherosclerosis. Atomic force microscopy (AFM) was used to determine integrin-fibronectin adhesion force and cell stiffness. A custom-written MATLAB program was used to interpret the elasticity of the VSMC cytoskeleton and adhesion force. Cellular adhesion was measured for 50%-70% confluent cells with a sample size of 50 cells on a fibronectin coated AFM stylus probe. Our results show that there is a significant decrease in α5β1-integrin adhesion of VSMCs on substrates above 9 kPa upon membrane cholesterol depletion. Additionally, mechanotransduction of VSMCs upon cholesterol depletion is less efficient. In conclusion, cell membrane cholesterol and extracellular mechanical signals may synergistically regulate cellular mechanical functions of VSMCs and their migration in the progression of atherosclerosis.

Voltage-gated K+ channels at an early stage of chronic hypoxia-induced pulmonary hypertension in newborn piglets

2006 ◽  
Vol 291 (6) ◽  
pp. L1169-L1176 ◽  
Author(s):  
Candice D. Fike ◽  
Mark R. Kaplowitz ◽  
Yongmei Zhang ◽  
Jane A. Madden
Keyword(s):  
Pulmonary Hypertension ◽  
Smooth Muscle ◽  
Cell Membrane ◽  
Smooth Muscle Cell ◽  
Muscle Cell ◽  
Chronic Hypoxia ◽  
Early Stage ◽  
Membrane Properties ◽  
Voltage Gated ◽  
Muscle Cell Membrane

Our purpose was to determine whether smooth muscle cell membrane properties are altered in small pulmonary arteries (SPA) of piglets at an early stage of pulmonary hypertension. Piglets were raised in either room air (control) or hypoxia for 3 days. A microelectrode technique was used to measure smooth muscle cell membrane potential ( Em) in cannulated, pressurized SPA (100- to 300-μm diameter). SPA responses to the voltage-gated K+ (KV) channel antagonist 4-aminopyridine (4-AP) and the KV1 family channel antagonist correolide were measured. Other SPA were used to assess amounts of KV1.2, KV1.5, and KV2.1 (immunoblot technique). Em was more positive in SPA of chronically hypoxic piglets than in SPA of comparable-age control piglets. The magnitude of constriction elicited by either 4-AP or correolide was diminished in SPA from hypoxic piglets. Abundances of KV1.2 were reduced, whereas abundances of both KV1.5 and KV2.1 were unaltered, in SPA from hypoxic piglets. At least partly because of reduced amounts of KV1.2, smooth muscle cell membrane properties are altered such that Em is depolarized and KV channel family function is impaired in SPA of piglets at an early stage of chronic hypoxia-induced pulmonary hypertension.

Controlling the Mechanical Myofibroblast via SRC: A Potential Drug Discovery Platform

2010 ◽  
Author(s):  
W. David Merryman ◽  
Joshua D. Hutcheson
Keyword(s):  
Smooth Muscle ◽  
Drug Discovery ◽  
Connective Tissue ◽  
Cell Membrane ◽  
Genetic Mutation ◽  
Fibroblast Cells ◽  
Potential Drug ◽  
Fibrotic Disease ◽  
Tissue Fibrosis ◽  
Myofibroblast Phenotype

Connective tissue makes up a large portion of our bodies, with collagen constituting ∼30% of the protein of connective tissue. Any tissue that undergoes fibrosis, either due to a genetic mutation or with age or use, typically falls into the ubiquitous category of ‘connective tissue fibrosis’. There are multiple potential contributors to connective tissue fibrosis; however, two dominate the literature — mechanical stress/strain and cytokines. Both stimuli lead to activation of fibroblast cells to a myofibroblast phenotype, the cellular hallmark of fibrotic disease. The myofibroblast phenotype is indicated by the expression of smooth muscle α-actin (αSMA), which associates with myosin to form actin-myosin contractile elements and generates intracellular force that is transduced to the ECM via cell membrane integrins.

Cytosolic Calcium Oscillations in Smooth Muscle Cells

Physiology ◽  
2000 ◽  
Vol 15 (1) ◽  
pp. 50-55 ◽  
Author(s):  
Jean-Pierre Savineau ◽  
Roger Marthan
Keyword(s):  
Smooth Muscle ◽  
Membrane Potential ◽  
Cell Membrane ◽  
Smooth Muscle Cells ◽  
Inositol Trisphosphate ◽  
Muscle Cells ◽  
Cytosolic Calcium ◽  
Calcium Oscillations ◽  
Membrane Receptors ◽  
Cell Membrane Potential

In a variety of smooth muscle cells, agonists activating membrane receptors induce oscillations in the cytoplasmic Ca2+ concentration via an inositol trisphosphate-activated mechanism. Ca2+ oscillations participate in the control of cell membrane potential and the tone of smooth muscle. There is evidence that alterations in Ca2+ oscillations modulate smooth muscle responsiveness.

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