The influence of dolichols on fluidity of mouse synaptic plasma membranes

Dolichols are isoprenologues which constitute an important component of biological membranes. However, an understanding of the effects of dolichols on the organization and dynamics of biological membranes has not been forthcoming. The experiments reported here are aimed at understanding the effects of dolichols on the physical properties of mouse brain synaptic plasma membranes. The effect of dolichols incorporated into mouse brain synaptic plasma membranes on fluorescent and electron spin resonance probes sensing the hydrophobic core differed from that of probes reporting closer to the surface of membrane bilayers. Dolichols significantly (P less than 0.01) lowered the polarization, limiting anisotropy, and order parameter of diphenylhexatriene in synaptic plasma membranes and liposomes extracted from synaptic plasma membranes, without changing the rotational relaxation time. Similarly, dolichol increased the fluidity reported by 16-doxylstearic acid in synaptic plasma membranes or liposomes extracted from synaptic plasma membranes. In contrast, dolichols exerted no effect on those properties for trans-parinaric acid or 5-doxylstearic acid in synaptic plasma membranes or liposomes derived therefrom. Dolichols can dramatically alter the structure and dynamics of lipid motion in synaptic plasma membranes and these effects are dependent on the location of the probe in the membrane.     

The involvement of histone H1[0] in chromatin structure.

Micrococcal nuclease digestion and light scattering are used to compare native chromatins with various histone H1[0] contents. The experimental data show that the higher the H1[0] content, the greater the ability to form compact structures with increasing ionic strength, and the lower the DNA accessibility to micrococcal nuclease. On the contrary, reconstituted samples from H1-depleted chromatin and pure individual H1 fractions behave in such a way that samples reconstituted with pure H1 degree give rise to a looser structure, more accessible to nuclease than samples reconstituted with H1-1. This contradiction suggests that the effect of H1o on chromatin structure must originate from the interaction of this histone with other components in native chromatin among which other histone H1 subfractions are good candidates.     

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.     

Mitochondrial DNA sequence evolution in sharks: rates, patterns, and phylogenetic inferences

Abundant representation of sharks in the fossil record makes this group a superb system in which to investigate rates and patterns of molecular evolution and to explore the strengths and weaknesses of phylogenetic inferences from molecular data. In this report, the molecular evolution of the cytochrome b gene in sharks is described and the information related to results from phylogenetic analysis of the data evaluated in the light of a phylogeny derived independently of the molecular data. Across divergent lineages of sharks there is evidence for significant substitution rate variation, departure from compositional equilibrium, and substantial homoplasy; nevertheless, the signal of evolutionary history is evident in patterns of shared transversions and amino acid replacements.      

Metabolic rate and directional nucleotide substitution in animal mitochondrial DNA

There is marked heterogeneity of nucleotide composition in mitochondrial DNA across divergent animals. Differences in nucleotide composition presumably reflect differences in directional nucleotide substitution for A+T or G+C nucleotides. In mitochondrial DNA, there is A+T directional nucleotide substitution in most (if not all) animals surveyed, and the magnitude of directional A+T nucleotide substitution differs greatly within and among groups. Differences in directional nucleotide substitution among lineages of mammals can be explained by changes in metabolic physiology. This relationship is thought to be mediated by the effect of oxygen radicals because these toxic compounds are by-products of aerobic metabolism and are known mutagens. Association between metabolism and nucleotide composition provides additional evidence in favor of the hypothesis that rates and patterns of nucleotide substitution in mitochondrial DNA can be influenced by factors that impinge on rates of endogenous DNA damage.      

Elemental distribution in striated muscle and the effects of hypertonicity: Electron probe analysis of cryo sections

A method of rapid freezing in supercooled Freon 22 (monochlorodifluoromethane) followed by cryoultramicrotomy is described and shown to yield ultrathin sections in which both the cellular ultrastructure and the distribution of diffusible ions across the cell membrane are preserved and intracellular compartmentalization of diffusabler ions can be quantitated. Quantitative electron probe analysis (Shuman, H., A.V. Somlyo, and A.P. Somlyo. 1976. Ultramicros. 1:317-339.) of freeze-dried ultrathin cryto sections was found to provide a valid measure of the composition of cells and cellular organelles and was used to determine the ionic composition of the in situ terminal cisternae of the sarcoplasmic reticulum (SR), the distribution of CI in skeletal muscle, and the effects of hypertonic solutions on the subcellular composition if striated muscle. There was no evidence of sequestered CI in the terminal cisternae of resting muscles, although calcium (66mmol/kg dry wt +/- 4.6 SE) was detected. The values of [C1](i) determined with small (50-100 nm) diameter probes over cytoplasm excluding organelles over nuclei or terminal cisternae were not significantly different. Mitochondria partially excluded C1, with a cytoplasmic/ mitochondrial Ci ratio of 2.4 +/- 0.88 SD. The elemental concentrations (mmol/kg dry wt +/- SD) of muscle fibers measured with 0.5-9-μm diameter electron probes in normal frog striated muscle were: P, 302 +/- 4.3; S, 189 +/- 2.9;C1, 24 +/- 1.1;K, 404 +/- 4.3, and Mg, 39 +/- 2.1. It is concluded that: (a) in normal muscle the "excess CI" measured with previous bulk chemical analyses and flux studies is not compartmentalized in the SR or in other cellular organelles, and (b) the cytoplasmic C1 in low [K](0) solutions exceeds that predicted by a passive electrochemical distribution. Hypertonic 2.2 X NaCl, 2.5 X sucrose, or 2.2 X Na isethionate produced: (a) swollen vacuoles, frequently paired, adjacent to the Z lines and containing significantly higher than cytoplasmic concentrations of Na and Cl or S (isethionate), but no detectable Ca, and (b) granules of Ca, Mg, and P = approximately (6 Ca + 1 Mg)/6P in the longitudinal SR. It is concluded that hypertonicity produces compartmentalized domains of extracellular solutes within the muscle fibers and translocates Ca into the longitudinal tubules.     

The distribution of histone H1 subfractions in chromatin subunits.

Rat liver chromatin was digested with micrococcal nuclease to various extents and fractionated into nucleosomes, di and trimers of nucleosomes on an isokinetic sucrose gradient. In conditions under which degradation of linker DNA within the particles was limited, the electrophoretic analysis of the histone content showed that the overall content of H1 histone increased from nucleosomes to higher order oligomers. Moreover, the histone H1 subfractions were found unevenly distributed among the chromatin subunits, one of them, H1--3 showing most variation. A more regular distribution of these subfractions was found in subunits obtained from a more extended digestion level of chromatin. It is suggested that the H1 subfractions differ in the protection they confer upon DNA.     

Smokers with CT Detected Emphysema and No Airway Obstruction Have Decreased Plasma Levels of EGF,IL-15, IL-8 and IL-1ra

Rationale

Low-grade inflammation and emphysema have been shown to be associated with an increased risk of lung cancer. However, the systemic inflammatory response in patients with emphysema is still unknown.

Objective

To compare the plasma cytokine profiles in two groups of current or former smokers without airway obstruction: a control group of individuals without computed tomography (CT) detected emphysema vs. a study group of individuals with CT detected emphysema.

Methods

Subjects underwent a chest CT, spirometry, and determination of EGF, IL-15, IL-1ra, IL-8, MCP-1, MIP-1β, TGFα, TNFα, and VEGF levels in plasma. Cytokine levels in each group were compared adjusting for confounding factors.

Results

160 current smokers and former smokers without airway obstruction participated in the study: 80 without emphysema and 80 subjects with emphysema. Adjusted group comparisons revealed significant reductions in EGF (−0.317, p = 0.01), IL-15 (−0.21, p = 0.01), IL-8 (−0.180, p = 0.02) and IL-1ra (−0.220, p = 0.03) in subjects with emphysema and normal spirometry.

Conclusions

Current or former smokers expressing a well-defined disease characteristic such as emphysema, has a specific plasma cytokine profile. This includes a decrease of cytokines mainly implicated in activation of apoptosis or decrease of immunosurveillance. This information should be taken into account when evaluated patients with tobacco respiratory diseases.