Fluorescence anisotropy--a parameter for characterizing membrane fluidity

The lipophilic fluorescent probe diphenylhexatriene (DPH) has been shown previously to behave as a marker of plasma membrane in living cell systems, and it is therefore been widely used in membrane fluidity studies via fluorescence anisotropy measurements. The anisotropic coefficient, which is inversely related to the rotational motion of the probe in membrane phospholipids, was significantly higher at 37 degrees C than at 23 degrees C for 9 series of red blood cells ghosts obtained from three healthy subjects. We also have studied the importance of the nature of two different polaroid films which permits the observation of fluorescence polarization.     

To predict some of the people some of the time: A reexamination of the moderator variable approach in personality theory.

Bem and Allen (1974) proposed but did not test the notion that trait relevance moderates cross-situational behavior consistency, but did obtain support, albeit weaker than is generally recognized, for a moderator effect of self-reported consistency. Kenrick and Stringfield (1980) showed that self-reported observability of behavior may also moderate self–peer consistency, but replication attempts were not entirely successful. Our investigation produced significant moderator effects on self–peer correlations for trait relevance, consistency, and observability when each of these variables was analyzed alone; we also obtained significant moderator effects for trait relevance and self-reported consistency (but not for observability) when all the variables were included in the same regression analysis. There was significant support for the prediction that the moderators combine additively: Self–peer correlations increased linearly as a function of the number of contributing moderator effects. There was even stronger support for the prediction that the moderators combined in an all-or-nothing manner: Self–peer correlations were high when the level of all three moderators was high, and low when the level of one or more of the three moderators was low. Our future research recommendation? Identify the optimal moderators and the manner in which they can be combined. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Probability and fuzziness

We discuss some relationships between probability theory and statistics on one hand, and the theory of fuzzy sets on the other hand. We develop various statistical techniques for the analysis of imprecise data and for inference based on imprecise data. We study the estimation of fuzzy parameters, testing problems with fuzzy probabilities, and confidence estimation under uncertainty. Finally, we indicate some possible applications to the assessment of credibility in expert systems.     

Effect of lysoplatelet-activating factor on human sperm fertilizing ability

OBJECTIVE: To evaluate the penetration rates in the hamster zona-free oocyte sperm penetration assay (SPA) after exposure of spermatozoa to lysoplatelet-activating factor (LPAF) and lysophosphatidyl choline (LPC). DESIGN: Washed human spermatozoa were exposed to 100 microM of LPAF or LPC, followed by the assessment of their fertilizing ability using the SPA. The percentage of penetration, the sperm binding in the SPA, the percentage of motile spermatozoa, and the acrosome reaction rates were quantified. SETTING: Private research and university laboratories. PATIENTS, PARTICIPANTS: Fresh and frozen semen samples from fertile donors with proven fertility were used as well as fresh semen from infertile patients attending a fertility clinic. All the infertile patients had abnormal semen analysis. INTERVENTIONS: Human spermatozoa were incubated for 90 minutes in the presence or absence of LPAF or LPC at 100 microM with 0.3% albumin in Ham's F-10 (GIBCO, Dorval, Quebec, Canada), and their fertilizing ability was evaluated using the SPA. The effect of these lysophospholipids on the percentage of acrosome reaction was evaluated with a fluorescent microscopy technique. RESULTS: The penetration rates of the SPA in male factor increased significantly from 3% +/- 6% with controls to 19% +/- 9% and 34% +/- 22% after incubation with LPC and LPAF, respectively. Sperm-oocyte binding was not significantly increased in this group. Sperm penetration assay penetration rates were also increased in fertile cryopreserved spermatozoa with LPC and LPAF. In this group, the acrosome reaction was significantly increased from 2% +/- 1% in controls to 10% +/- 6% and 8% +/- 3% after incubation with LPC and LPAF, respectively. CONCLUSION: Lysoplatelet-activating factor and LPC independently increased the penetration rate of spermatozoa and the percentage of acrosome reaction. Lysophosphatidylcholine and LPAF may be beneficial in the treatment of spermatozoa with male factor infertility and may increase fertilization rates in IVF.     

Formation of octadecadienoate dimers by soybean lipoxygenases

The aim of this investigation was to determine whether the regioselectivity found for lipoxygenases in the formation of fatty acid hydroperoxides from linoleic acid is reflected in the formation of dimeric products in secondary reactions involving linoleic acid, product hydroperoxide and lipoxygenase. A method was therefore developed for the separation and identification of dimers formed by fusion of two linoleic acid radicals or a linoleic acid radical and linoleate. The method includes solid-phase extraction, preparative separation of products by thin-layer chromatography, derivatization to the corresponding fully hydrogenated methyl esters and capillary gas chromatography (GC) coupled with electron impact mass spectrometry. We present evidence that the formation of octadecadienoate dimers, during the secondary reaction of soybean lipoxygenase-1 or lipoxygenase-3, is a nonenzymic process that can be envisaged by nonspecific association of intermediate fatty acid radicals (L^*) that have dissociated from the enzyme. We could show that the relative amounts of different octadecadienoate dimers formed remain unaltered, regard-less of pH and type of soybean isoenzyme used. Quantitative analysis by GC showed that under the reaction conditions used, the formation of dimers branching at the 13-position is preferred.     

To dispel fantasies about the fantasy-based measure of fear of success.

A review of M. Horner's (1968) study and subsequent research using the fantasy-based measure of fear of success suggested the following conclusions: Horner's results do not support the hypothesis that high-fear-of-success females perform poorly under competitive conditions; there are no reliable age or sex differences in motivation to avoid success; fear of success and sex role orientation appear to be unrelated; it is not clear whether the fear-of-success measure taps a motive or taps cultural stereotypes; there are no consistent relationships between fear of success and achievement-related variables; the reliability of the fear-of-success measure is low (probably in the .30-.40 range); and there are no consistent relationships between fear of success and any behavioral measures. It is suggested that future research will have to use new measures of fear of success. 3 such measures and preliminary findings are presented. (43 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Determinants of consensus estimates: Attribution, salience, and representativeness.

Five experiments examined the effects of attribution, salience, and representativeness of a target person's behavior on consensus bias—the tendency to generalize from the target's behavior to the behavior of the group. Ss were 762 undergraduates. Exp I showed that actors and observers induced to make a situational attribution for a behavior perceived this behavior as more common than did those induced to make a dispositional attribution. Exps II and III showed that observers perceived salient behavior as more common in the group than nonsalient behavior. Exps IV and V showed that observers were more likely to generalize from the behavior of a representative target than from the behavior of a nonrepresentative target. It is concluded that attributes of the target's behavior exercise strong influence on consensus estimates. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stability of fatty acyl-coenzyme a thioester ligands of hepatocyte nuclear factor-4α and peroxisome proliferator-activated receptor-α

Although long-chain fatty acyl-coenzyme A (LCFA-CoA) thioesters are specific high-affinity ligands for hepatocyte nuclear factor-4α (HNF-4α) and peroxisome proliferator-activated receptor-α (PPARα), X-ray crystals of the respective purified recombinant ligand-binding domains (LBD) do not contain LCFA-CoA, but instead exhibit bound LCFA or have lost all ligands during the purification process, respectively. As shown herein: (i) The acyl chain composition of LCFA bound to recombinant HNF-4α reflected that of the bacterial LCFA-CoA pool, rather than the bacterial LCFA pool. (ii) Bacteria used to produce the respective HNF-4α and PPARα contained nearly 100-fold less LCFA-CoA than LCFA. (iii) Under conditions used to crystallize LBD (at least 3 wk at room temperature in aqueous buffer), 16∶1-CoA was very unstable in buffer alone. (iv) In the presence of the respective nuclear receptor (i.e., HNF-4α and PPARα), LBD 70–75% of 16∶1-CoA was degraded after 1 d at room temperature in the crystallization buffer, whereas as much as 94–97% of 16∶1-CoA was degraded by 3 wk. (v) Cytoplasmic LCFA-CoA binding proteins such as acyl-CoA binding protein, sterol carrier protein-2, and liver-FA binding protein slowed the process of 16∶1-CoA degradation proportional to their respective affinities for this ligand. Taken together, these data for the first time indicated that the absence of LCFA-CoA in the crystallized HNF-4α and PPARα was due to the paucity of LCFA-CoA in bacteria as well as to the instability of LCFA-CoA in aqueous buffers and the conditions used for LBD crystallization. Furthermore, instead of protecting bound LCFA-CoA from autohydrolysis like several cytoplasmic LCFA-CoA binding proteins, these nuclear receptors facilitated LCFA-CoA degradation.