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1

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Quercetin inhibits hexose transport in a human diploid fibroblast (1978)

Salter, Donald W. ; Custead-Jones, Susan ; Cook, John S.

Springer

The journal of membrane biology 40 (1978), S. 67-76

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ISSN: 1432-1424

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Summary The flavonol quercetin, a phloretin analog, inhibits transport of 2-deoxyglucose and 3-O-methylglucose in a cultured human diploid fibroblast. This inhibition is related to transport itself and not to the reported effects of flavonoids on membrane-bound ATPases. From concentration-inhibition curves at several pH's we conclude that uncharged (acid) quercetin (pK=7.65) is the inhibitory form of the molecule (K I =10μm). Quercetin, unlike phloretin, is rapidly degraded in 0.1n NaOH; the degradation products are weakly inhibitory to hexose transport.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01909739

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2

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A broadband pulsed radio frequency electron paramagnetic resonance spectrometer for biological applications (1998)

Murugesan, Ramachandran ; Afeworki, Mobae ; Cook, John A. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Review of Scientific Instruments 69 (1998), S. 1869-1876

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ISSN: 1089-7623

Source: AIP Digital Archive

Topics: Physics , Electrical Engineering, Measurement and Control Technology

Notes: A time-domain radio frequency (rf) electron paramagnetic resonance (EPR) spectrometer/imager (EPRI) capable of detecting and imaging free radicals in biological objects is described. The magnetic field was 10 mT which corresponds to a resonance frequency of 300 MHz for paramagnetic species. Short pulses of 20–70 ns from the signal generator, with rise times of less than 4 ns, were generated using high speed gates, which after amplification to 283 Vpp, were deposited into a resonator containing the object of interest. Cylindrical resonators containing parallel loops at uniform spacing were used for imaging experiments. The resonators were maintained at the resonant frequency by tuning and matching capacitors. A parallel resistor and overcoupled circuit was used to achieve Q values in the range 20–30. The transmit and receive arms were isolated using a transmit/receive diplexer. The dead time following the trailing edge of the pulse was about 450 ns. The first stage of the receive arm contained a low noise, high gain and fast recovery amplifier, suitable for detection of spin probes with spin-spin relaxation times (T2) in the order of μs. Detection of the induction signal was carried out by mixing the signals in the receiver arm centered around 300 MHz with a local oscillator at a frequency of 350 MHz. The amplified signals were digitized and summed using a 1 GHz digitizer/summer to recover the signals and enhance the signal-to-noise ratio (SNR). The time-domain signals were transformed into frequency-domain spectra, using Fourier transformation (FT). With the resonators used, objects of size up to 5 cm3 could be studied in imaging experiments. Spatial encoding of the spins was accomplished by volume excitation of the sample in the presence of static field gradients in the range of 1.0–1.5 G/cm. The spin densities were produced in the form of plane integrals and images were reconstructed using standard back-projection methods. The image resolution of the phantom objects containing the spin probe surrounded by lossy biologic medium was better than 0.2 mm with the gradients used. To examine larger objects at local sites, surface coils were used to detect and image spin probes successfully. The results from this study indicate the potential of rf FT EPR for in vivo applications. In particular, rf FT EPR may provide a means to obtain physiologic information such as tissue oxygenation and redox status. © 1998 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.1148857

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3

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Two procedures for estimating mean cell volume (1977)

Will, Peter C. ; Brake, Emily T. ; Cook, John S.

Springer

Methods in cell science 3 (1977), S. 601-605

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ISSN: 1573-0603

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00918393

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4

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Community food security: Practice in need of theory? (1999)

Anderson, Molly D. ; Cook, John T.

Springer

Agriculture and human values 16 (1999), S. 141-150

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ISSN: 1572-8366

Keywords: Community food security ; Hunger ; Food security ; Food systems ; Planning ; Theory

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract Practitioners and advocates of community food security (CFS) envision food systems that are decentralized, environmentally-sound over a long time-frame, supportive of collective rather than only individual needs, effective in assuring equitable food access, and created by democratic decision-making. These themes are loosely connected in literature about CFS, with no logical linkages among them. Clear articulation in a theoretical framework is needed for CFS to be effective as a guide for policy and action. CFS theory should delimit the level of analysis (i.e., what are the boundaries of “community”); show how CFS relates to individual, household, and national food security and explain emergent properties, which are important at the community level of analysis; point to the best indicators of CFS or its lack; clarify the determinants of CFS; and clarify the stages of movement toward CFS. This theoretical base would allow researchers to develop valid and reliable measures, and allow practitioners to weigh alternative options to create strategic plans. A theoretical base also would help establish common ground with potential partners by making the connections to anti-hunger work, sustainable agriculture, and community development clear.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1007580809588

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5

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Study of Dynamical Properties of Coronal Structures in the Polar Regions (1999)

Karovska, Margarita ; Wood, Brian E. ; Cook, John W. ; [et al.]

Springer

Space science reviews 87 (1999), S. 219-222

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ISSN: 1572-9672

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract We present the results from a study of the dynamical properties of polar jets in the Sun's polar regions using LASCO C2 coronagraph and EIT observations. In the simplest impulsive acceleration scenarios for jets, gravity is expected to be the dominant force on the jet following the initial acceleration, especially in the Sun's polar regions where the open magnetic fields should not significantly impede the jet's motion. Our analysis shows that although at low heights the kinematics of the jets could be consistent with a gravitational deceleration of the ejected plasma, at higher heights their motions may simply follow the ambient solar wind outflow. If so, the polar jets can be used as tracers of the solar wind in coronal holes.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1005100618288

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6

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Reversible independent alterations in glucose transport and metabolism in cultured human cells deprived of glucoseResearch supported jointly by the National Cancer Institute and by the U.S. Energy Research and Development Administration under contract with the Union Carbide Corporation. Donald W. Salter is a predoctoral fellow supported by Grant GM 1974 from NIGMS, NIH. (1976)

Salter, Donald W. ; Cook, John S.

New York, NY [u.a.] : Wiley-Blackwell

Journal of Cellular Physiology 89 (1976), S. 143-155

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ISSN: 0021-9541

Keywords: Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Medicine

Notes: We have measured uptake of 3H-hexoses into diploid human cells by exposing them to brief pulses of isotopic sugar during the log-growth, subconfluent-growth, and confluent-growth (contact inhibited) phases of the strain HSWP derived from human skin. 3H-deoxyglucose appears to be taken up three times faster than 3H-glucose. After exposure to 3H-glucose for longer than one minute, the cells excrete ∼70% of the isotope into the medium as lactate. If lactate production (and hence excretion) is abolished by treating the cells with iodoacetic acid or dinitrofluorobenzene, neither of which inhibits transport, the uptake of 3H-glucose is found to be in fact somewhat larger than that of 3H-deoxyglucose. If cells are deprived of glucose for 24 hours, apparent uptake of 3H-glucose is enhanced 10-fold or more. This latter increase is accounted for by 2- to 3-fold enhancement of true transport plus retention of 〉 90% of the radioactivity, since little lactate is formed or excreted in glucose-deprived cells. Deoxyglucose, galactose, or pyruvate when present during glucose deprivation each have quantitatively different effects on the cells' capacity to produce lactate from a short pulse of glucose, but none of them prevents the enhancement of hexose transport. After restoration of 5 mM glucose to starved cells, their metabolism returns to normal (in the sense that ∼70% of the glucose taken up in a pulse is again excreted as lactate), with a half-time of 0.5 hour; but the transport of hexoses returns to control levels much more slowly, with a half-time of ∼6 hours. The two processes appear to be independently regulated.

Additional Material: 7 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/jcp.1040890114

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7

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Interaction of two mechanisms regulating alkali cations in hela cellsResearch jointly sponsored by the National Cancer Institute and by the U.S. Atomic Energy Commission under contract with the Union Carbide Corporation. (1975)

Cook, John S. ; Vaughan, Gerald L. ; Proctor, William R. ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

Journal of Cellular Physiology 86 (1975), S. 59-70

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ISSN: 0021-9541

Keywords: Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Medicine

Notes: The alkali cation content of HeLa cells is independent of culture density and of whether the cells are grown in suspension or attached to the culture vessel. With a cell doubling time of 28 hours, the cell K content turns over approximately once per hour. Following partial blockade of the alkali-cation transport system with ouabain, two distinct but interrelated mechanisms operate in the cellular response: (a) an increase in intracellular Na stimulates the pump so that the short-term alteration in electrolyte composition is less than would be expected from the fraction of pump sites inhibited, and (b) there is a cyclo-heximide-sensitive recovery in transport capacity reflecting a restoration of functional transport sites to their normal density on the cell surface. Experimental manipulations that mimic the effect of ouabain lead to a stimulation of transport, but they do not result in an increase in the number of ouabain-binding sites on the surface. The data are consistent with a four-to-six-hour turnover of transport sites at the surface, but there is no evidence for a specific induction of the transport system within this short-term recovery period.

Additional Material: 7 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/jcp.1040860108

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8

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Role of the membrane potential in serum-stimulated uptake of amino acid in a diploid human fibroblast (1977)

Villereal, Mitchel L. ; Cook, John S.

New York, N.Y. : Wiley-Blackwell

Journal of Supramolecular Structure 6 (1977), S. 179-189

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ISSN: 0091-7419

Keywords: valinomycin ; human fibroblast ; amino acid transport ; serum stimulation ; membrane potential ; Life Sciences ; Molecular Cell Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Chemistry and Pharmacology , Medicine

Notes: The Na+-dependent accumulation of α-aminoisobutyric acid (AIB), measured in normal growing and quiescent (serum-deprived) HSWP cells (human diploid fibroblast), was found to be twofold higher (AIBin/AIBout = 20-25) under the normal growing conditions. Serum stimulation of quiescent cells increases their AIB concentrating capacity by approximately 70% within 1 hr. These observations suggest that the driving forces for AIB accumulation may be reversibly influenced by the serum concentration of the growth medium. Addition of valinomycin (Val) to cells preequilibrated with AIB causes an enhanced accumulation of AIB, suggesting that the membrane potential can serve as a driving force for AIB accumulation. After preequilibration with AIB in 6 mM K+, transfer to 94 mM K+ with Val results in a marked and rapid net loss of AIB. The effect of Val on the accumulation of AIB is greatest in quiescent cells, with the intracellular AIB concentrations reaching those seen both in Val-stimulated normal cells and in Val-stimulated serum-stimulated cells. By adjusting [K+]0, in the presence of Val, the membrane potential of growing cells can be matched to that of quiescent cells or vice versa. When this is done, the two accumulate AIB to the same extent. Hence the AIB accumulating capacity is characteristic of the membrane potential rather than of the growth state. In summary, these data suggest that the accumulation of AIB in HSWP cells is influenced by changes in membrane potential and that a serum-associated membrane hyperpolarization could be responsible for the increased capacity for AIB accumulation in serumstimulated cells.

Additional Material: 5 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/jss.400060204

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