Hydrogen transfer between methanogens and fermentative heterotrophs in hyperthermophilic cocultures

Interactions involving hydrogen transfer were studied in a coculture of two hyperthermophilic microorganisms: Thermotoga maritima, an anaerobic heterotroph, and Methanococcus jannaschii, a hydrogenotrophic methanogen. Cell densities of T. maritima increased 10-fold when cocultured with M. jannaschii at 85 degrees C, and the methanogen was able to grow in the absence of externally supplied H(2) and CO(2). The coculture could not be established if the two organisms were physically separated by a dialysis membrane, suggesting the importance of spatial proximity. The significance of spatial proximity was also supported by cell cytometry, where the methanogen was only found in cell sorts at or above 4.5 mum in samples of the coculture in exponential phase. An unstructured mathematical model was used to compare the influence of hydrogen transport and metabolic properties on mesophilic and hyperthermophilic cocultures. Calculations suggest the increases in methanogenesis rates with temperature result from greater interactions between the methanogenic and fermentative organisms, as evidenced by the sharp decline in H(2) concentration in the proximity of a hyperthermophilic methanogen. The experimental and modeling results presented here illustrate the need to consider the interactions within hyperthermophilic consortia when choosing isolation strategies and evaluating biotransformations at elevated temperatures. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 268-278, 1997.     

Luminescence studies on RbI:Tb3+ crystals.

Optical absorption, photoluminescence, thermoluminescence (TL) and photostimulated luminescence (PSL) studies on RbI:Tb(3+) crystals irradiated with gamma-rays is reported. Photoluminescence of these crystals exhibits characteristic Tb(3+) emissions, due to transitions from the (5)D(3) and (5)D(4) levels to various levels of the (7)F septet. On F-bleaching the gamma-irradiated crystals, Z(3) centres are observed. The TL glow curve indicates a two-step thermal annihilation process for the radiatively created defects. The presence of the characteristic emissions due to terbium ions in the photostimulation at the F-band, and TL emissions under both glow peaks, confirm the participation of Tb ions in the defect production and recombination processes. Trap parameters for the TL process are calculated and presented. The low temperature glow peak is attributable to Z(3) centres.     

Cadherin Switching and Activation of ��-Catenin Signaling Underlie Proinvasive Actions of Calcitonin-Calcitonin Receptor Axis in Prostate Cancer

Calcitonin, a neuroendocrine peptide, and its receptor are localized in the basal epithelium of benign prostate but in the secretory epithelium of malignant prostates. The abundance of calcitonin and calcitonin receptor mRNA displays positive correlation with the Gleason grade of primary prostate cancers. Moreover, calcitonin increases tumorigenicity and invasiveness of multiple prostate cancer cell lines by cyclic AMP-dependent protein kinase-mediated actions. These actions include increased secretion of matrix metalloproteinases and urokinase-type plasminogen activator and an increase in prostate cancer cell invasion. Activation of calcitonin-calcitonin receptor autocrine loop in prostate cancer cell lines led to the loss of cell-cell adhesion, destabilization of tight and adherens junctions, and internalization of key integral membrane proteins. In addition, the activation of calcitonin-calcitonin receptor axis induced epithelial-mesenchymal transition of prostate cancer cells as characterized by cadherin switch and the expression of the mesenchymal marker, vimentin. The activated calcitonin receptor phosphorylated glycogen synthase kinase-3, a key regulator of cytosolic β-catenin degradation within the WNT signaling pathway. This resulted in the accumulation of intracellular β-catenin, its translocation in the nucleus, and transactivation of β-catenin-responsive genes. These results for the first time identify actions of calcitonin-calcitonin receptor axis on prostate cancer cells that lead to the destabilization of cell-cell junctions, epithelial-to-mesenchymal transition, and activation of WNT/β-catenin signaling. The results also suggest that cyclic AMP-dependent protein kinase plays a key role in calcitonin receptor-induced destabilization of cell-cell junctions and activation of WNT-β-catenin signaling.Prostate cancer (PC)² is the most commonly diagnosed cancer and the second leading cause of cancer deaths in men in the United States (1, 2). Although androgen ablation therapy is effective in men with advanced disease for some time, the disease subsequently progresses to the androgen-independent stage. The population of prostate cells expressing neuroendocrine factors such as calcitonin (CT) also increases during this progression (3–5). At this stage, the disease is metastatic and chemoresistant. Present evidence suggests that cancer metastasis is usually preceded by the disruption of normal cell-cell adhesion and the loss of integrity of the primary tumor site (6, 7). This process may include several genetic, molecular, and morphological changes characterized by epithelial-to-mesenchymal transition (EMT) (8–10). The EMT is characterized by the loss of cell polarity, altered cell-cell and cell-matrix adhesion, and acquisition of migratory, mesenchymal phenotype. Other reported changes include down-regulation of E-cadherin, induction of N-cadherin, release of β-catenin from junctional complexes, and its translocation to the nucleus (11–13). However, the precise molecular mechanisms associated with this process are obscure.Several growth factors, including hepatocyte growth factor, transforming growth factor-β, vascular endothelial growth factor, and epidermal growth factor, have been reported to induce EMT in tumor cell lines (14–16). We have shown that the expression of CT and its G protein-coupled receptor (CTR) is remarkably higher in advanced PCs, and the CT-CTR autocrine axis is a potent stimulator of PC cell tumorigenicity, invasion, and metastasis (4, 17–19). Although CT-stimulated increase in the motility and invasion of PC cells may be mediated by CT-stimulated secretion of matrix metalloproteinases and urokinase-type plasminogen activator, the precise molecular mechanisms preceding these CTR actions remain to be elucidated (18, 20). We tested the hypothesis that CT induces biochemical and morphological changes associated with EMT to increase the invasiveness of PC cells.Our results indicate that activation of the CT-CTR autocrine axis in prostate cancer cells induced several changes associated with EMT such as remodeling of tight and adherens junctions, cadherin switching, and activation of WNT/β-catenin signaling. In contrast, the silencing of the CT-CTR axis reversed this process. Moreover, cyclic AMP-dependent protein kinase (PKA) plays a key role in this CT-CTR-mediated process. This is the first study demonstrating the action of prostate CTR on junctional complexes and WNT/β-catenin signaling of PC cell lines.     

Ion chromatographic determination of thyroxine in urine

Thyroxine (3,5,3',5'-tetraiodo thyronine) is administered to patients suffering from endemic goiter as also in cases of non-iodine deficient ethiology and hypothyroidism. It is suggested that the uptake of thyroxine can be monitored by assessing the levels of the same in the urine of patients under treatment. For the purpose, a highly sensitive and selective ion chromatographic procedure is developed. The sample of urine is treated with sodium hydroxide and UV irradiated to convert iodine in thyroxine to iodide. Subsequently, iodide is separated on an anion exchanger AS 4A column using 50 mM NaOH as the eluent and determined spectrophotometrically at 226 nm.