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.     

Plant virus infection development as affected by heavy metal stress

The work was focused on the investigation of possible dependencies between the development of viral infection in plants and the presence of high heavy metal concentrations in soil. Field experiments have been conducted in order to study the development of systemic tobacco mosaic virus (TMV) infection in Lycopersicon esculentum L. cv. Miliana plants under effect of separate salts of heavy metals Cu, Zn and Pb deposited in soil. As it is shown, simultaneous effect of viral infection and heavy metals in tenfold maximum permissible concentration leads to decrease of total chlorophyll content in experiment plants mainly due to the degradation of chlorophyll a. The reduction of chlorophyll concentration under the combined influence of both stress factors was more serious comparing to the separate effect of every single factor. Plants' treatment with toxic concentrations of lead and zinc leaded to slight delay in the development of systemic TMV infection together with more than twofold increase of virus content in plants that may be an evidence of synergism between these heavy metal's and virus' effects. Contrary, copper although decreased total chlorophyll content but showed protective properties and significantly reduced amount of virus in plants.     

L1 (LINE-1) retrotransposable elements provide a "fossil" record of the phylogenetic history of murid rodents

The single most difficult problem in phylogenetic analysis is deciding whether a shared taxonomic character is due to common ancestry or one that appeared independently due to convergence, parallelism, or reversion to an ancestral state. Mammalian L1 retrotransposons undergo periodic amplifications in which multiple copies of the elements are interspersed in the genome. Because these elements apparently are transmitted only by inheritance and are retained in the genome, a shared L1 amplification event can only be an inherited ancestral character. We propose that L1 amplification events can be an excellent tool for analyzing mammalian evolution and demonstrate here how we addressed several refractory problems in rodent systematics using L1 DNA as a taxonomic character.      

DNA methylation-associated colonic mucosal immune and defense responses in treatment-na?ve pediatric ulcerative colitis

Inflammatory bowel diseases (IBD) are emerging globally, indicating that environmental factors may be important in their pathogenesis. Colonic mucosal epigenetic changes, such as DNA methylation, can occur in response to the environment and have been implicated in IBD pathology. However, mucosal DNA methylation has not been examined in treatment-naïve patients. We studied DNA methylation in untreated, left sided colonic biopsy specimens using the Infinium HumanMethylation450 BeadChip array. We analyzed 22 control (C) patients, 15 untreated Crohn’s disease (CD) patients, and 9 untreated ulcerative colitis (UC) patients from two cohorts. Samples obtained at the time of clinical remission from two of the treatment-naïve UC patients were also included into the analysis. UC-specific gene expression was interrogated in a subset of adjacent samples (5 C and 5 UC) using the Affymetrix GeneChip PrimeView Human Gene Expression Arrays. Only treatment-naïve UC separated from control. One-hundred-and-twenty genes with significant expression change in UC (> 2-fold, P < 0.05) were associated with differentially methylated regions (DMRs). Epigenetically associated gene expression changes (including gene expression changes in the IFITM1, ITGB2, S100A9, SLPI, SAA1, and STAT3 genes) were linked to colonic mucosal immune and defense responses. These findings underscore the relationship between epigenetic changes and inflammation in pediatric treatment-naïve UC and may have potential etiologic, diagnostic, and therapeutic relevance for IBD.     

Dehydrolutein: a metabolically derived carotenoid never observed in raptors

Carotenoids are fat-soluble pigments synthesised by photosynthetic organisms(Brush,1990).Conversely,animals are incapable of synthesizing carotenoids de novo,and they must obtain them through their diet.However,some animal species are able to make some alterations to the basic chemical structure,converting ingested carotenoids into more oxidized and differently coloured forms(Schiedt,1998).     

Species diversity and decomposition in laboratory aquatic systems: the role of species interactions

1. Interest in the effects of biodiversity on ecosystem processes is increasing, stimulated by the global species decline. Different hypotheses about the biodiversity‐ecosystem functioning (BEF) relationship have been put forward and various underlying mechanisms proposed for different ecosystems. 2. We investigated BEF relationships and the role of species interactions in laboratory experiments focussing on aquatic decomposition. Species richness at three different trophic levels (leaf detritus, detritus‐colonising fungi and invertebrate detritivores) was manipulated, and its effects on leaf mass loss and fungal growth were assessed in two experiments. In the first, monocultures and mixtures of reed (Phragmites australis), alder (Alnus glutinosa) and oak (Quercus cerris) leaf disks were incubated with zero, one or eight fungal species. Leaf mixtures were also incubated with combinations of three and five fungal species. In the second experiment, reed leaf disks were incubated with all eight fungal species and offered to combinations of one, two, three, four or five macroinvertebrate detritivores with different feeding modes. 3. Results from the first experiment showed that leaf mass loss was directly related to fungal mass and varied unimodally with the number of fungi, with a maximum rate attained at intermediate diversity in oak and reed and at maximum diversity in alder (the fastest decomposing leaf). 4. Mixing litter species stimulated fungal growth but interactions between species of fungi slowed down decomposition. In contrast, mixtures of macroinvertebrate detritivores reduced fungal mass and accelerated leaf decomposition. Possible explanations of the positive relationship between detritivore diversity and decomposition are a reduction in fungal dominance and a differentiation in the use of different resource patches promoted by higher fungal diversity. 5. In conclusion, the results show a general increase in decomposition rate with increasing biodiversity that is controlled by within‐ and between‐trophic level interactions, and support the hypothesis of both bottom‐up and top‐down effects of diversity on this process.