Thyroid hormone stimulates protein synthesis in the cardiomyocyte by activating the Akt-mTOR and p70S6K pathways

Thyroid hormones affect cardiac growth and phenotype; however, the mechanisms by which the hormones induce cardiomyocyte hypertrophy remain uncharacterized. Tri-iodo-L-thyronine (T3) treatment of cultured cardiomyocytes for 24 h resulted in a 41 +/- 5% (p < 0.001) increase in [(3)H]leucine incorporation into total cellular protein. This response was abrogated by the phosphatidylinositol 3-kinase (PI3K) inhibitor, wortmannin. Co-immunoprecipitation studies showed a direct interaction of cytosol-localized thyroid hormone receptor TRalpha1 and the p85alpha subunit of PI3K. T3 treatment rapidly increased PI3K activity by 52 +/- 3% (p < 0.005), which resulted in increased phosphorylation of downstream kinases Akt and mammalian target of rapamycin (mTOR). This effect was abrogated by pretreatment with wortmannin or LY294002. Phosphorylation of p70(S6K), a known target of mTOR, occurred rapidly following T3 treatment and was inhibited by rapamycin and wortmannin. In contrast, phosphorylation of the p85 variant of S6K in response to T3 was not blocked by LY294002, wortmannin, or rapamycin, thus supporting a T3-activated pathway independent of PI3K and mTOR. 40 S ribosomal protein S6, a target of p70(S6K), and 4E-BP1, a target of mTOR, were both phosphorylated within 15-25 min of T3 treatment and could be inhibited by wortmannin and rapamycin. Thus, rapid T3-mediated activation of PI3K by cytosolic TRalpha1 and subsequent activation of the Akt-mTOR-S6K signaling pathway may underlie one of the mechanisms by which thyroid hormone regulates physiological cardiac growth.     

Fibronectin quantification without antibodies: a bioassay for the detection of the gelatin-captured macromolecule

We have developed a new cell-adhesion-bioassay (CAA) for the quantitative determination of fibronectin in biological fluids. The assay is based on two particular properties of fibronectin: it specifically binds to gelatin with high affinity and simultaneously it can anchor to different surface molecules of a cell. First fibronectin, derived from very different biological fluids, is purified in situ, within the wells of the microtiter plates applied for the assay, using solid surface bound gelatin. After capturing the macromolecule, it is quantified based on its cell adhesive properties. In contrast to ELISA the CAA does not require specific antibodies, and as the Jurkat cells used as indicator cells, seem to recognize fibronectin from different species equally; species specificity of the reagent plays smaller, perhaps negligible, role in the determination of the amount of the macromolecule. The CAA method may not replace fibronectin specific ELISA-s, but using its principle, improved applications, for example a capture EIA for determining fibronectin can easily be envisioned and CAA may serve as a viable alternative for EIA-s when specific antibodies are not available or when relative measurement of not only the soluble but cell surface associated fibronectin is necessary.     

Changes in chlorophyll fluorescence parameters and oxidative stress responses of bush bean genotypes for selecting contrasting acclimation strategies under water stress

Drought resistance of bean landraces was compared in order to select genotypes with either high morphological or high biochemical-physiological plasticity. The lines in the former group exhibited fast reduction in fresh and dry mass, decreased the water potential in primary leaves after irrigation withdrawal and the biomass mobilized from the senescent primary leaves was allocated into the roots. These genotypes had high frequency of primary leaf abscission under water stress. The genotypes with plasticity at the biochemical level maintained high water potential and photochemical efficiency, i.e. effective quantum yield, high photochemical (qP) and low non-photochemical (NPQ) quenching in primary leaves under drought stress. While superoxide dismutase activity was not influenced by the drought and the genotype, catalase activity increased significantly in the primary leaves of the genotypes with efficient biochemical adaptation. Lines with high morphological plasticity exhibited higher quaiacol peroxidase activity under drought. Proline may accumulate in both cases, thus it may be a symptom of protein degradation or a successful osmotic adaptation. On the basis of contrasting responses, the genetic material cannot be screened for a large-scale breeding program by a single physiological parameter but by a set of the methods presented in this work.     

Activity-related changes of body fat and motor performance in obese seven-year-old boys

The effects of 35 weeks of extra-curricular, mainly aerobic, dynamic physical activity were analysed in overweight and obese 7-year-old boys contrasted with control groups. Body composition was estimated by using the body mass index (BMI) and skinfold thicknesses. Overweight or obesity was defined according to the suggestions of Cole and associates (2000). The activity program consisted of swimming and water games, folk dance, and soccer. Data were collected four times between September 2003 and October 2004. Thirty-one overnight or obese boys volunteered to participate in the activity program (weekly, to physical classes of 45 min. plus three extra-curricular activity sessions of 60 min. duration). The control subjects were 43 overweight or obese boys, and 75 non-overweight and non-obese ones. The controls had only two curricular physical education classes every week. Physical performance capacity was tested by 30 m dash, 400 m run, standing long jump, and fist-ball throw. Body fat content estimated by taking the sum of five skinfolds decreased significantly during the 35-week training program. However, body weight as well as skinfold thicknesses increased significantly during the four month non-active period that followed. Physical performance improved during the test period, but deteriorated between the third and fourth data collections. BMI, as well as the sum of five skinfolds increased in both control groups.Physical performance decreased in the overweight control subjects and increased moderately in the non obese ones. We inferred that more vigorous habitual exercise alone, i.e., without a program of dietary control, though effective, could not efficiently stabilise body fat, still less achieve a lasting reduction of it. Obese, but also overweight subjects need long term exercise programs of sufficient intensity, duration and frequency, plus dietary measures, to get rid of excess body fat.     

Protein synthesis and transport by the rat choroid plexus and ependyma

Summary Light (LM-ARG) and electron microscope (EM-ARG) autoradiographs were prepared from immature rat choroid plexus and ependyma at 5, 10, 30, and 60 min and 16 h following intraperitoneal administration of [³H]- labeled amino acid mixtures. Intracellular protein synthesis and transport were ascertained in lateral and fourth ventricle choroid plexus epithelium by quantitative EM-ARG at the several post-injection intervals. ARG were also prepared from choroid plexuses cultured for one day, pulse labeled for one hour and reincubated for various periods in nonradioactive media. Significant labeling of both attached and free apical protrusions (blebs) was observed in both choroid plexus and ependyma in vivo and in choroid plexus in vitro. This phenomenon was interpreted as a physiologically significant mechanism for protein transport (apocrine secretion) by epithelia into the cerebrospinal fluid (CSF).This study was supported in part by N.I.H. Research Grant NS 12906     

Lactobacilli in the intestinal microbiota of Swedish infants

Lactobacillus colonisation was examined in 112 Swedish infants. Faecal samples obtained at 1, 2, 4 and 8 weeks and at 6, 12 and 18 months of age were cultivated quantitatively on Rogosa agar. Lactobacilli were speciated by PCR and typed to the strain level by randomly amplified polymorphic DNA (RAPD). Lactobacilli reached a peak at 6 months when 45% of the infants were colonised. L. rhamnosus and L. gasseri were the most common species in this period. Colonisation by lactobacilli in general (P < 0.01) and L. rhamnosus in particular (P < 0.05) was more common in breast-fed than in weaned infants at 6 months of age. Lactobacillus isolation reached a nadir of 17% by 12 months (P < 0.0001), but increased to 31% by 18 months of age P < 0.05). The food-related species L. paracasei, L. plantarum, L. acidophilus and L. delbrueckii dominated in this second phase. A single strain persisted for at least 3 weeks in 17% of the infants during the first 6 months, most commonly L. rhamnosus. Lactobacillus population counts in colonised infants increased from 10(6.4) cfu/g at 1 week to 10(8.8) cfu/g at 6 months, and then dropped to 10(5.4) cfu/g faeces at 12 months of age. Lactobacillus colonisation was not significantly related to delivery mode, or to presence of siblings or pets in the household. Our results suggest that certain Lactobacillus species, especially L. rhamnosus, thrive in the intestinal flora of breast-fed infants. After weaning they are replaced by other Lactobacillus species of types found in food.     

The effects of windthrow on plant species richness in a Central European beech forest

The effects of soil disturbance caused by the uprooting of a single or a few canopy trees on species richness and composition of vascular plant species and bryophytes were examined in a temperate beech forest (Fagus sylvatica) in northern Germany. We recorded the vegetation in 57 pairs of disturbed and adjacent undisturbed plots and established a chronosequence of mound ages to study the effect of time since microsite formation on plant species richness and composition. We found significant differences in plant species richness and composition between disturbed and adjacent undisturbed plots. Species richness of both vascular plants and bryophytes was higher in the disturbed than in the undisturbed plots, but these differences were more pronounced for bryophytes. We suggest that three main factors are responsible for this differential response. The availability of microsites on the forest floor that are suitable for the recruitment of bryophytes is lower than for vascular plants. Establishment of bryophytes in disturbed microsites is favoured by a greater abundance of propagules in the close vicinity and in the soil of the disturbed microsites, as well as by a greater variety of regeneration strategies in bryophytes than in vascular plants. Time since mound formation was a major factor determining plant species richness and composition. A significant decrease in the mean number of species was found from young mounds to intermediate and old mounds. However, differences were observed between vascular plants and bryophytes in the course of changes through time in species richness and composition. A large number of exclusive and infrequent vascular plant species was observed on young mounds, among them several disturbance specialists. We suggest that the establishment of many vascular plant species was infrequent and short-lived due to unfavourable light conditions and a low abundance of propagules. By contrast, the development of a litter layer was the main reason for the decreased mean number of bryophytes on old mounds. Our study supports the view that groups of species differing in important life history traits exhibit different responses to soil disturbance.     

Expression of NADPH oxidase homologues and accessory genes in human cancer cell lines,tumours and adjacent normal tissues

The family of NADPH oxidase (NOX) genes produces reactive oxygen species (ROS) pivotal for both cell signalling and host defense. To investigate whether NOX and NOX accessory gene expression might be a factor common to specific human tumour types, this study measured the expression levels of NOX genes 1–5, dual oxidase 1 and 2, as well as those of NOX accessory genes NoxO1, NoxA1, p47^phox, p67^phox and p22^phox in human cancer cell lines and in tumour and adjacent normal tissue pairs by quantitative, real-time RT-PCR. The results demonstrate tumour-specific patterns of NOX gene expression that will inform further studies of the role of NOX activity in tumour cell invasion, growth factor response and proliferative potential.