Perturbation of membrane fluidity

Lenaz, Giorgio; Curatola, G; Masotti, Lanfranco

doi:10.1007/bf01558409

Cited by 70 publications

(8 citation statements)

References 293 publications

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“…Lysozyme adsorption to S. sanguis 903, however, may be considerably more complex than HEWL-dye binding. Since temperature is known to affect membrane fluidity (20), the temperature dependence of lysozyme adsorption could indicate an interaction with the bacterial membrane or membranebound structure. A lysozyme interaction with the membrane cannot fully explain the temperature dependence of adsorption, however, because adsorption in ammonium acetate was virtually identical in ice and at 37°C at a low ionic strength (Fig.…”

Section: Discussionmentioning

confidence: 99%

Adsorption of Lysozyme from Human Whole Saliva by Streptococcus sanguis 903 and Other Oral Microorganisms

Laible

Germaine

1982

Infect Immun

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Several strains of Streptococcus sanguis, Streptococcus mutans, Streptococcus mitis, Actinomyces viscosus, and Actinomyces naeslundii plus fresh isolates of Streptococcus salivarius were surveyed for their abilities to deplete lysozyme from human-whole-saliva supematant. Bacteria were incubated in saliva for 60 min at 37°C and then removed by centrifugation, and the recovered supernatant solutions were assayed for lysozyme activity by using whole cells of Micrococcus lysodeikticus as the substrate. Mean lysozyme depletions by bacterial strains varied over a wide (eightfold) range. The greatest mean depletion of lysozyme (60 to 70%) was observed with S. sanguis (biotype I), serotype b of S. mutans, and the fresh S. salivarius isolates. The lowest mean depletion was noted with S. mitis (15%) and biotype II S. sanguis (ca. 30%). The remaining species and strains exhibited an intermediate degree of depletion. In studies with S. sanguis 903, lysozyme was depleted by normal or heated (90°C, 30 min) bacteria and could be recovered from the organism. Furthermore, under appropriate conditions, lysozyme depletion by cells at 0 and 37°C was very similar. On the basis of these observations, we concluded that depletion was due to the adsorption of lysozyme by the organism. With S. sanguis 903, lysozyme adsorption depended on the concentration of bacteria, time of incubation, and the ionic strength of the medium. The extent of adsorption, however, was independent of pH's of 3.9 to 8.3. When a low concentration of S. sanguis 903 was used, lysozyme adsorption reached saturation (4 pLg of adsorbed lysozyme per 107 cells) at 20 jig of lysozyme

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Section: Discussionmentioning

confidence: 99%

Adsorption of Lysozyme from Human Whole Saliva by Streptococcus sanguis 903 and Other Oral Microorganisms

Laible

Germaine

1982

Infect Immun

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“…Polyunsaturated fatty acids (PUFA) are essential for heterothermic mammals preparing for winter. PUFA have lower melting points and can retain fluidity of cell membranes at low temperature (Lenaz et al, ; Brown and London, ). Animals that hibernate during winter and use torpor (i.e., controlled reductions in body temperature and metabolic rate) require enough PUFA in their pre‐hibernation diet to enable cell functioning at low body temperatures ( T b ).…”

mentioning

confidence: 99%

Effect of dietary fatty acids on metabolic rate and nonshivering thermogenesis in golden hamsters

Jefimow

Wojciechowski

2013

J. Exp. Zool.

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Hibernating rodents prior to winter tend to select food rich in polyunsaturated fatty acids (PUFA). Several studies found that such diet may positively affect their winter energy budget by enhancing torpor episodes. However, the effect of composition of dietary fatty acids (FA) on metabolism of normothermic heterotherms is poorly understood. Thus we tested whether diets different in FA composition affect metabolic rate (MR) and the capacity for nonshivering thermogenesis (NST) in normothermic golden hamsters (Mesocricetus auratus). Animals were housed in outdoor enclosures from May 2010 to April 2011 and fed a diet enriched with PUFA (i.e., standard food supplemented weekly with sunflower and flax seeds) or with saturated and monounsaturated fatty acids (SFA/MUFA, standard food supplemented with mealworms). Since diet rich in PUFA results in lower MR in hibernating animals, we predicted that PUFA-rich diet would have similar effect on MR of normothermic hamsters, that is, normothermic hamsters on the PUFA diet would have lower metabolic rate in cold and higher NST capacity than hamsters supplemented with SFA/MUFA. Indeed, in winter resting metabolic rate (RMR) below the lower critical temperature was higher and NST capacity was lower in SFA/MUFA-supplemented animals than in PUFA-supplemented ones. These results suggest that the increased capacity for NST in PUFA-supplemented hamsters enables them lower RMR below the lower critical temperature of the thermoneural zone.

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“…Support for this contention has been drawn from studies that demonstrate that ethanol and other alcohols disrupt or "fluidize" the lipid structure of membranes (Seeman, 1972;Chin and Goldstein, 1977~;Harris and Schroeder, 1981). The biological function of the membrane-bound proteins are, in most instances, dependent on their lipid surroundings (Kimelberg, 1975;Lenaz et al, 1975) and thus both the structural and functional components of neuronal membranes could be affected by ethanol. The response of membrane-bound enzyme systems to membrane perturbations cannot, however, be predicted with certainty.…”

mentioning

confidence: 99%

Ethanol's Effects on Cortical Adenylate Cyclase Activity

Saito

Lee

Tabakoff

1985

Journal of Neurochemistry

111

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The effects of ethanol on beta-adrenergic receptor-coupled adenylate cyclase (AC) of mouse cerebral cortex were examined. The addition of ethanol (20-500 mM) to incubation mixtures containing cortical membranes demonstrated that ethanol could increase AC activity and potentiate the stimulatory effects of guanylyl-imidodiphosphate [Gpp(NH)p] on AC activity. Ethanol increased the rate of activation of AC by guanine nucleotides and concomitantly decreased the EC50 for magnesium required to achieve maximal stimulation of cortical AC. The EC50 values for Gpp(NH)p and isoproterenol stimulation of AC activity were also altered by ethanol. Ethanol was capable of stimulating AC extracted by use of digitonin. The AC activity in the digitonin extract was no longer sensitive to the addition of Gpp(NH)p or NaF, but was still stimulated by ethanol. We propose multiple sites of action for ethanol in stimulating cortical AC activity. These sites include actions at the beta-adrenergic receptor, at the G/F coupling proteins, and at the catalytic unit of cortical AC. Comparison of ethanol's actions on cortical beta receptor coupled AC activity with prior reported actions of ethanol on striatal dopamine (DA)-sensitive AC indicated differential sensitivities of these two AC systems to ethanol. These differences may be determined by specific coupling characteristics of the striatal and cortical AC systems or by differences in the plasma membranes in which striatal and cortical AC systems are located.

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Perturbation of membrane fluidity

Cited by 70 publications

References 293 publications

Adsorption of Lysozyme from Human Whole Saliva by Streptococcus sanguis 903 and Other Oral Microorganisms

Adsorption of Lysozyme from Human Whole Saliva by Streptococcus sanguis 903 and Other Oral Microorganisms

Effect of dietary fatty acids on metabolic rate and nonshivering thermogenesis in golden hamsters

Ethanol's Effects on Cortical Adenylate Cyclase Activity

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