Acute and Chronic Effects of Ethanol on Transbilayer Membrane Domains

Alcohols, including ethanol, have a specific effect on transbilayer and lateral membrane domains. Recent evidence has shown that alcohols in vitro have a greater effect on fluidity of one leaflet as compared to the other. The present study examined effects of chronic ethanol consumption on fluidity of synaptic plasma membrane (SPM) exofacial and cytofacial leaflets using trinitrobenzenesulfonic acid (TNBS) labeling and differential polarized fluorometry of 1,6-diphenyl-1,3,5-hexatriene (DPH). Mice were administered ethanol or a control liquid diet for 3 weeks. Animals were killed and SPM prepared. The exofacial leaflet of SPM was significantly more fluid than the cytofacial leaflet in both groups, as indicated by limiting anisotropy of DPH. However, differences between the two leaflets were much smaller in the ethanol-treated group. Ethanol at concentrations seen clinically had a greater effect in vitro on the more fluid exofacial leaflet. This asymmetric effect of ethanol was significantly diminished in the exofacial leaflet of the ethanol-treated mice. Chronic ethanol consumption has a specific effect on membranes. Membrane functions that may be regulated by asymmetry of fluidity and lipid distribution may be altered by chronic ethanol consumption.     

Molecular Regulation of Renal Phosphate Transport

Received: 18 April 1996/Revised: 26 June 1996     

DEVELOPMENTAL STABILITY IN LEAVES OF CLARKIA TEMBLORIENSIS (ONAGRACEAE) AS RELATED TO POPULATION OUTCROSSING RATES AND HETEROZYGOSITY

Four natural populations of Clarkia tembloriensis, whose levels of heterozygosity and rates of outcrossing were previously found to be correlated, are examined for developmental instability in their leaves. From the northern end of the species range, we compare a predominantly selfing population (t? = 0.26) with a more outcrossed population (t? = 0.84), which is genetically similar. From the southern end of the range, we compare a highly selfing population (t? = 0.03) with a more outcrossed population (t? = 0.58). We measured developmental stability in the populations using two measures of within-plant variation in leaf length as well as calculations of fluctuating asymmetry (FA) for several leaf traits. Growth-chamber experiments show that selfing populations are significantly more variable in leaf length than more outcrossed populations. Developmental instability can contribute to this difference in population-level variance. Plants from more homozygous populations tend to have greater within-plant variance over developmentally comparable nodes than plants from more heterozygous populations, but the difference is not significant. At the upper nodes of the plant, mature leaf length declines steadily with plant age, allowing for a regression of leaf length on node. On average, the plants from more homozygous populations showed higher variance about the regression (MSE) and lower R² values, suggesting that the decline in leaf length with plant age is less stable in plants from selfing populations than in plants from outcrossing populations. Fluctuating asymmetry (FA) was calculated for four traits within single leaves at up to five nodes per plant. At the early nodes of the plant where leaf arrangement is opposite, FA was also calculated for the same traits between opposite leaves at a node. Fluctuating asymmetry is significantly greater in the southern selfing population than in the neighboring outcrossed population. Northern populations do not differ in FA. Fluctuating asymmetry can vary significantly between nodes. The FA values of different leaf traits were not correlated. We show that developmental stability can be measured in plants using FA and within-plant variance. Our data suggest that large differences in breeding system are associated with differences in stability, with more inbred populations being the least stable.     

A karyological study of Asphodelus L. (Asphodelaceae) from the Western Mediterranean

The following aspects of Asphodelus karyology are analysed: base number, polyploidy, chromosome size, chromosome morphology, satellited chromosomes, structural heteromorphism, karyotype asymmetry and karyotype evolution. The base number 0 ×= 14 is common to all species except for A. refractus , which has the derived ×= 13. Three ploidy levels occur, often in the same species; diploid, tetraploid and hexaploid, with 2n = 28, 56 and 84. Chromosomes are generally small to medium-small, with the occasional presence of medium-large chromosomes. The most frequent chromosome types are metacentric of type m and submetacentric. Metacentric chromosomes of type M occur only in sections. Verineopsis, Verinea and Plagiasphodelus ; subtelocentric chromosomes occur only in sections Asphodelus and Plagiasphodelus. There is a wide variability in relation to the number of satellited chromosomes, relative to ploidy level. There are usually two to four in diploids, four to eight in tetraploids and usually six, exceptionally up to 12, in the hexaploid. Satellites are present on the shortest arm, exceptionally on the longest arm. There is a high degree of structural heteromorphism in practically all the species which affects satellited and non satellited chromosomes. Karyotype asymmetry is generally of type 2B. Inter-and intra-chromosomal differences are estimated by the A1 and A2 indexes. Both indices vary in the karyotype evolution of the genus, with a decrease of A1 and an increase of A2. The role of polyploidy, hybridization, asymmetry and decrease of chromosome size in the evolution of Asphodelus is discussed.     

Catabolism of caffeine and related purine alkaloids in leaves ofCoffea arabica L.

In a study of purine alkaloid catabolism pathways in coffee,¹⁴C-labelled theobromine, caffeine, theophylline and xanthine were incubated with leaves ofCoffea arabica. Incorporation of label into¹⁴CO₂ was determined and methanol-soluble metabolites were analysed by high-performance liquid chromatography-radiocounting. The data obtained demonstrate catabolism of caffeine theophylline 3-methylxanthine xanthine. Xanthine is degraded further by the conventional purine catabolism pathway to CO₂ and NH₃ via uric acid, allantoin and allantoic acid. The conversion of caffeine to theophylline is the rate-limiting step in purine alkaloid catabolism and provides a ready explanation for the high concentration of endogenous caffeine found inC. arabica leaves. Although theobromine is converted primarily to caffeine, a small portion of the theobromine pool appears to be degraded to xanthine by a caffeine-independent pathway. In addition to being broken down to CO₂, via the purine catabolism pathway, xanthine is metabolised to 7-methylxanthine. Metabolism of [2-¹⁴C]xanthine byC. arabica leaves in the presence of 5 mM allopurinol results in very large increases in incorporation of radioactivity into 7-methylxanthine as degradation of the substrate via the purine catabolism pathway is blocked. The identity of 7-methylxanthine in these studies was confirmed by gas chromatography-mass spectrometry analysis.Abbreviations HPLC-RC high-performance liquid chromatography-radiocounting This work was supported by the British Council which provided H.A. with Japan-UK travel grants. F.M.G. was supported by a Biotechnology and Biological Sciences Research Council grant to A.C.     

Hand dominance and bilateral asymmetry in the structure of the second metacarpal

Bilateral asymmetry in the structure of the second metacarpal was examined in relation to functional hand dominance in a large, clinically nonselected, healthy population sample from the Baltimore Longitudinal Study of Aging. Bilateral bone measurements were made from anteroposterior hand radiographs of a total of 992 individuals, 609 males and 383 females, with an age range of 19–94 years. Hand dominance was determined on the basis of personal impression. Total width and medullary width at the midshaft of the second metacarpal were measured to 0.05 mm using a Helios caliper. These two measurements were used to derive cortical thickness, cortical bone area, periosteal (total) area, medullary area, percent cortical area, and the second moment of area in the mediolateral plane. In both right and left-handed individuals, statistically significant side differences were found in the calculated bone areas and the second moment of area, with the dominant hand being larger. Cortical thickness did not show significant side-related differences for either handedness. These results show that functional handedness leads to periosteal and endosteal expansion of the second metacarpal cortex on the dominant side, increasing bone strength without increasing cortical thickness. This is the first time this pattern of asymmetry has been reported in left-handers as well as right-handers. Our results argue for the primacy of environmental (mechanical) effects in determining bilateral asymmetry of limb bone structural properties. © 1994 Wiley-Liss, Inc.     

The effect of ethanol on lateral and rotational mobility of plasma membrane vesicles isolated from cultured mar 18.5 hybridoma cells

Intramolecular excimer formation of 1,3-di(1-pyrenyl)propane (Py-3-Py) and fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) were used to evaluate the effect of ethanol on the rate and range of the lateral mobility and the range of the rotational mobility of bulk bilayer structures of the plasma membrane vesicles (ATCC-PMV) isolated from cultured hybridoma cells (ATCC TIB 216). In a concentration-dependent manner, ethanol increased the excimer to monomer fluorescence intensity ratio (I/I) of Py-3-Py in the ATCC-PMV and decreased the anisotropy (r), limiting anisotropy (r) and order parameter (S) of DPH in the ATCC-PMV. This indicates that ethanol increased both the lateral and rotational mobility of the probes in the ATCC-PMV. Selective quenching of DPH by trinitrophenyl groups was utilized to examine the range of transbilayer asymmetric rotational diffusion of the ATCC-PMV. The anisotropy (r), limiting anisotropy (r ) and order parameter (S) of DPH in the inner monolayer were 0.024, 0.032, and 0.069, respectively, greater than calculated for the outer monolayer of the ATCC-PMV. Selective quenching of DPH by trinitrophenyl groups was also used to examine the transbilayer asymmetric effects of ethanol on the range of the rotational mobility of the ATCC-PMV. Ethanol had a greater increasing effect on the range of the rotational mobility of the outer monolayer as compared to the inner monolayer of the ATCC-PMV. It has been proven that ethanol exhibits a selective rather than nonselective fluidizing effect within the transbilayer domains of the ATCC-PMV.This paper was supported in part by a research grant from the Korea Science and Engineering Foundation (KOSEF 88-1013-01) and from the Korea Research Foundation (1991–1993).     

Skeletal asymmetry and hand preference during termite fishing by gombe chimpanzees

Skeletons of chimpanzees with recorded life stories allow assessment of the potential relationships among hard tissue features and expressed behaviors. We analyze bone size, weight, and mineralization to assess osteological characters for identification of laterality of expressed behaviors involving the upper body. Results show that associations are not yet clearly defined.     

Unambiguous through-bond sugar-to-base correlations for purines in 13C, 15N-labeled nucleic acids: The HsCsNb,HsCs(N)bCb,and HbNbCb experiments

Summary A set of three 3D (¹H, ¹³C, ¹⁵N) triple-resonance correlation experiments has been designed to provide H1-H8 intraresidue sugar-to-base correlations in purines in an unambiguous and efficient manner. Together, the H_sC_sN_b, H_sC_s(N)_bC_b, and H_bN_bC_b experiments correlate the H1 sugar proton to the H8 proton of the attached base by means of the {H1, C1, N9, C8, H8} heteronuclear scalar coupling network. The assignment strategy presented here allows for unambiguous H1-H8 intraresidue correlations, provided that no two purines have both the same H1 and C1 chemical shifts and the same C8 and N9 chemical shifts. These experiments have yielded H1-H8 intraresidue sugar-to-base correlations for all five guanosines in the [¹³C, ¹⁵N] isotopically labeled RNA duplex r(GGCGCUUGCGUC)₂.     

Brain Purines in a Genetic Mouse Model of Lesch-Nyhan Disease

Abstract: Mice carrying a mutation in the gene encoding the purine salvage enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT) have recently been produced to provide an animal model for Lesch-Nyhan disease. The current-studies were conducted to characterize the consequences of the mutation on the expression of HPRT and to characterize potential changes in brain purine content in these mutants. Our results indicate that the mutant animals have no detectable HPRT-immunoreactive material on western blots and no detectable HPRT enzyme activity in brain tissue homogenates, confirming that they are completely HPRT deficient (HPRT^-). Despite the absence of HPRT-mediated purine salvage, the animals have apparently normal brain purine content. However, de novo purine synthesis, as measured by [¹⁴C]formate incorporation into brain purines, is accelerated four- to fivefold in the mutant animals. This increase in the synthesis of purines may protect the HPRT^- mice from potential depletion of brain purines despite complete impairment of HPRT-mediated purine salvage.