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Biomedical subjects

F S Fay

Publications and source records attributed to F S Fay.

106 records · Page 6Linked to original sources
PubMed1977

Detection of contraction of isolated smooth muscle cells in suspension.

A Coulter counter has been utilized to assess the contractile state of suspensions of isolated smooth muscle cells prepared by enzymatic digestion of stomach muscularis of Bufo marinus. Pulse-duration and pulse-hieght histograms were constructed from the pulses that occur as cells pass through the Coulter counter orifice. Contraction of cells in suspension causes shifts in these pulse histograms to a greater percent of shorter duration pulses and of larger pulse heights. These shifts are consistent with teh assumption made in out studies that the duration and amplitude of the pulses generated are related to the length and cross-sectional area (or square of the diameter), respectively, of the cell. Shifts in the pulse-height histogram were found to be more reliable. The results of a calibration experiment in which shifts in the histograms of pulse heights were linerrly related to shifts in the histograms of all lengths measured from photomicrographs suggested that the shifts in the pulse-height histogram could be used as a continuous index of changes in the contractile state of a population of cells in suspension.

Animals↗
PubMed1977

Characteristics of response of isolated smooth muscle cells to cholinergic drugs.

The contractile responses of suspensions of isolated smooth muscle cells from the stomach muscularis of Bufo marinus were assessed with a Coulter counter. Contractile responses of strips from the same tissue were recorded isotonically. Suspensions of isolated smooth muscle cells exhibit a dose-dependent graded response to cholinergic agonists. The intact tissue has a lower sensitivity than the isolated cells to acetycholine but a higher sensitivity to carbachol. The higher sensitivity of isolated cells to acetycholine probably reflected decreased efficiency of cholinesterases upon removal of diffusion barriers. Because the isolated smooth muscle cells have affinity constants for atropine (K1 equals 0.07 +/- 0.02NM) and carbachol (9.5 +/- 3.7 muM) similar to that in this and other intact tissues, the affinity of the cholinergic receptor appears unaffected by cell isolation. The rate constant for dissociation (k2) of atropine was estimated from the slowing of response to carbachol by atropine; k2 in the isolated cells is 100 times larger than seen in intact tissues. Further insight into the interaction of cholinergic substances with their smooth muscle receptors might by obtained using this system. The isolated cells contain intact receptors, and diffusion limitations inherent to intact tissue have been removed.

Acetylcholine↗
PubMed1976

An ultrasensitive isometric force transducer for single smooth muscle cell mechanics.

The principles of operation, design, and performance of a differential photooptical transducer of very high sensitivity are described. Useful range is 10-2,000 mugf with sufficiently low drift to allow recordings of contractile responses of isolated single smooth muscle cells. Comparison with several previous designs is presented.

Muscle Contraction↗
PubMed1975

Contraction of isolated smooth muscle cells by inophore A23187.

Ionophore A23187 causes contraction of smooth muscle cells isolated from the stomach muscularis of Bufo marinus. The peak response is reached within 10 sec of inophore addition and then decays to a lesser, sustained contraction. The initial phase of contraction is maximal at A23187 concentrations greater than 5 X 10(-6) M and half maximal at 5 X 10(-7) M. Chelation of extracellular calcium by ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid (EGTA) does not affect the initial contraction produced by A23187, whereas it inhibits completely the sustained, secondary phase. Addition of calcium in excess of EGTA restores this phase rapidly and fully to control levels of contraction. A23187 produces a maximal, rapid contraction of muscle cells previously depolarized by incubation in high potassium medium. The ionophore also contracts isolated strips of stomach smooth muscle. A23187 appears to produce contraction of the isolated smooth muscle cells by transmembrane transport of calcium into the cytoplasm from both intracellular and extracellular sources.

Animals↗
PubMed1973

Contraction of isolated smooth-muscle cells--structural changes.

The contraction of isolated smooth-muscle cells has been correlated with evagination of the cell membrane, a marked change in myofilament orientation, and a decrease in cellular volume. Both localized and full contractions have been elicited in the same cell by varying the intensity of electrical stimulation. These results may be explained by a model of the smooth-muscle cell in which the contractile apparatus extends between attachment sites on the cell membrane that are relatively closely spaced.

Animals↗
PubMed1973

Reversible disaggregation of myofilaments in vertebrate smooth muscle.

Strips of taenia coli from guinea pigs were incubated under isometric conditions in Krebs-Ringer bicarbonate saline (MKR) containing various concentrations of Ca(+2) and/or Mg(+2). Spontaneous or chemically induced contractile activity was abolished within 15 min of exposure to MKR containing Ca(+2) at concentrations below 10(-6) M; contractile activity was restored by reincubation in normal MKR after 1-2 h. Exposure of taenia coli to MKR containing Ca(+2) at concentrations below 10(-6) M for 1 h or more led to loss of thick and thin myofilaments from the sarcoplasm as observed with the electron microscope. Except for the loss of these two filament types, the cells contained all other structural features observed in preparations incubated in MKR containing Ca(+2) at its normal level (1.3 x 10(-3) M). The loss of thick and thin myofilaments in strips exposed to a Ca(+2) concentration below 10(-6) M was reversed by reincubation for 30 min in MKR containing normal Ca(+2) levels. The observed loss of thick and thin myofilaments in response to low Ca(+2) is interpreted as resulting from the disaggregation of some or all of the molecular components of these two filament types.

Animals↗
PubMed1972

Correlation between fiber length, ultrastructure, and the length-tension relationship of mammalian smooth muscle.

The length-tension relationship was determined for strips of guinea pig taenia coli and correlated with the length and ultrastructural organization of the component fibers. The mean fiber length in "stretched" strips (passive >/= active tension) was 30% greater than that for fibers in "unstretched" strips (active >> passive tension). In stretched fibers the dense bodies and 100 A diameter myofilaments were consolidated into a mass near the center of fibers in cross-sectional profile. The thick myofilaments were segregated into the periphery of the fiber profiles. In unstretched fibers the dense bodies-100 A diameter filaments and the thick myofilaments were uniformly distributed throughout cross-sectional profiles. A tentative model is proposed to account for the change in fiber length and ultrastructural organization that accompanies stretch. The basic features of the model require the dense bodies to be linked together into a network by the 100 A diameter filaments. The functional consequences of stretching the fibers are discussed in relation to the model proposed for this network.

Animals↗
PubMedDate not supplied

Intracellular calibration of the fluorescent calcium indicator Fura-2.

We present the techniques we have used and the problems we have encountered in our laboratories in the in vivo calibration of the fluorescent Ca2(+)-indicator Fura-2. These techniques include the use of potentiometric methods for the precise control and determination of Ca2+ levels in bathing solutions, in association with methods for the equilibration of internal and external solutions with ionophores (Br-A23187, ionomycin, monensin and nigericin). A by-product of these techniques has been the development of a simple procedure that utilizes Fura-2 as a general indicator of ionized Ca2+ concentrations within the physiological range (pCa 7.5 to 5.5), in other experimental solutions. The major advantages of this relatively simple procedure are that it is (i) rapidly performed, (ii) independent of the total EGTA concentration within each experimental solution, (iii) independent of the absolute EGTA purity, and (iv) unaffected by a large number of potentially interfering cations (i.e. Mg2+, H+, K+, Na+) within the test solutions.

Benzofurans↗
PubMedDate not supplied

Ca2+ imaging in single living cells: theoretical and practical issues.

The measurement of intracellular calcium ion concentrations [( Ca2+]i) in single living cells using quantitative fluorescence microscopy draws from a diverse set of disciplines, including cellular biology, optical physics, statistics and computer science. Over the last few years, we have devised and built a number of systems for measuring [Ca2+]i with Fura-2, and have applied them in the exploration of a wide range of biological processes controlled by Ca2+. In this report we discuss these systems and their advantages and limitations. We also describe the theoretical and practical problems associated with using Fura-2 to measure [Ca2+]i, and the solutions that we, and others, have developed to overcome them. The approaches described should provide useful guidance for others interested in imaging [Ca2+] distribution in living cells. The factors that limit current methods are discussed, and areas for future development are highlighted.

Animals↗
PubMedDate not supplied

Calcium gradients in single smooth muscle cells revealed by the digital imaging microscope using Fura-2.

Calcium is believed to control a variety of cellular processes, often with a high degree of spatial and temporal precision. For a cell to use Ca2+ in this manner, mechanisms must exist for controlling the ion in a localized fashion. We have now gained insight into such mechanisms from studies which measured Ca2+ in single living cells with high resolution using a digital imaging microscope and the highly fluorescent Ca2+-sensitive dye, Fura-2. Levels of Ca2+ in the cytoplasm, nucleus and sarcoplasmic reticulum (SR) are clearly different. Free [Ca2+] in the nucleus and SR was greater than in the cytoplasm and these gradients were abolished by Ca2+ ionophores. When external Ca2+ was raised above normal in the absence of ionophores, free cytoplasmic Ca2+ increased but nuclear Ca2+ did not. Thus, nuclear [Ca2+] appears to be regulated independently of cytoplasmic [Ca2+] by gating mechanisms in the nuclear envelope. The observed regulation of intranuclear Ca2+ in these contractile cells may thus be seen as a way to prevent fluctuation in Ca2+-linked nuclear processes during the rise in cytoplasmic [Ca2+] which triggers contraction. The approach described here offers the opportunity of following changes in Ca2+ in cellular compartments in response to a wide range of stimuli, allowing new insights into the role of local changes in Ca2+ in the regulation of cell function.

Animals↗