Monodeiodination of thyroxine to 3, 5, 3'-triiodothyronine and to 3, 3', 5'-triiodothyronine in isolated dog renal cortical tubuli

Monodeiodination of T4 to T3 and rT3 in the intact cells of dog renal tubuli and glomeruli was investigated. The tubuli and glomeruli were obtained by a sieve method. T4 (2 micrograms/ml) was incubated in Tris-HCl buffer, pH 7.5, with renal cells (180 micrograms protein/ml) and 5 mM DTT for 1 h at 37 degrees C and the T3 and rT3 generated during incubation were measured by specific radioimmunoassays. In order of decreasing activity, dog renal cortical tubuli, cortical homogenate, glomeruli and medullary tubuli were capable of converting T4 to T3. Net rT3 production from T4 in cortical tubuli was also greater than that in cortical homogenate. The conversion of T4 to T3 and also to rT3 in cortical tubuli was enzymatic in nature, since the reactions showed dependence on time and protein concentration; instability to heating; temperature and pH optimum. The production of T3 and rT3 from T4 was maximum at pH 6.5 and at pH 9.5, respectively, indicating that two different enzymic systems, a 5- and a 5'-monodeiodinase, might be involved in the deiodination of the tyrosyl and the phenolic ring of T4 in dog kidney.     

Mouse and human CD14 (myeloid cell-specific leucine-rich glycoprotein) primary structure deduced from cDNA clones

cDNA clones complementary to MS7-4 (Setoguchi et al. (1988) Somat. Cell Mol. Genet. 14, 427-438) from a mouse macrophage cDNA library were separated. Sequence analysis of these clones demonstrated that the longest cDNA clone, MS7X, had a 1366 bp insert and high homology with that of the human CD14 gene (Ferrero and Goyert (1988) Nucleic Acids Res. 16, 4173). Using the MS7X cDNA probe, cDNA clones were separated from cDNA libraries constructed from a human macrophage cell line and macrophages. The total cDNA sequence was 1364 bp in length, with an open reading frame of 1125 nucleotides matching that of the human CD14 gene except for one nucleotide difference. The amino-acid sequence (mouse CD14), deduced from the nucleotide sequence of the MS7X insert consisted of 351 amino-acid residues with a high leucine content (17.66%) and five putative N-glycosylation sites, and in vitro translation predicted a protein of molecular mass of 37.5 kDa. Human CD14 had 356 amino-acid residues, with high leucine content (15.5%), and contained four putative N-glycosylation sites. Mouse CD14 showed 13 building blocks, of which internal nine blocks have a conserved leucine motif and significant homology with human leucine-rich alpha 2-glycoprotein.     

Crucial Role of Extracellular Polysaccharides in Desiccation and Freezing Tolerance in the Terrestrial Cyanobacterium Nostoc commune

The cyanobacterium Nostoc commune is adapted to the terrestrial environment and has a cosmopolitan distribution. In this study, the role of extracellular polysaccharides (EPS) in the desiccation tolerance of photosynthesis in N. commune was examined. Although photosynthetic O₂ evolution was not detected in desiccated colonies, the ability of the cells to evolve O₂ rapidly recovered after rehydration. The air-dried colonies contained approximately 10% (wt/wt) water, and field-isolated, natural colonies with EPS were highly water absorbent and were rapidly hydrated by atmospheric moisture. The cells embedded in EPS in Nostoc colonies were highly desiccation tolerant, and O₂ evolution was not damaged by air drying. Although N. commune was determined to be a mesophilic cyanobacterium, the cells with EPS were heat tolerant in a desiccated state. EPS could be removed from cells by homogenizing colonies with a blender and filtering with coarse filter paper. This treatment to remove EPS did not damage Nostoc cells or their ability to evolve O₂, but O₂ evolution was significantly damaged by desiccation treatment of the EPS-depleted cells. Similar to the EPS-depleted cells, the laboratory culture strain KU002 had only small amount of EPS and was highly sensitive to desiccation. In the EPS-depleted cells, O₂ evolution was also sensitive to freeze-thaw treatment. These results strongly suggest that EPS of N. commune is crucial for the stress tolerance of photosynthesis during desiccation and during freezing and thawing.     

Characterization of the bovine ampkγ1 gene

AMP-activated protein kinase (AMPK) represents the mammalian form of the core component of a kinase cascade that is conserved between fungi, plants, and animals. AMPK plays a major role in protecting mammalian cells from metabolic stress by switching off biosynthetic pathways that require ATP and switching on ATP-regenerating pathways. In this report, we describe the isolation and characterization of the gene for the noncatalytic bovine gamma1 subunit of AMPK. The bovine ampkgamma1 (PRKAG1) gene spans in excess of 14 kb and is located at BTA 5q21-q22. It consists of 12 exons ranging in size from 38 b to 166 b, interspersed with 11 introns that range between 97 b and 6753 b in length. The coding region of the bovine gene shares 93% and 90% nucleotide sequence similarity with its human and rat counterparts, and the bovine AMPKgamma1 protein is 98% and 95% identical to its human and rat homologs, respectively, in amino acid sequence. SNP discovery using a cattle DNA panel revealed a number of polymorphisms that may be useful for the evaluation of ampkgamma1 as a candidate gene for energy metabolism-related production traits.     

Rapid evolution and the convergence of ecological and evolutionary time

Recent studies have documented rates of evolution of ecologically important phenotypes sufficiently fast that they have the potential to impact the outcome of ecological interactions while they are underway. Observations of this type go against accepted wisdom that ecological and evolutionary dynamics occur at very different time scales. While some authors have evaluated the rapidity of a measured evolutionary rate by comparing it to the overall distribution of measured evolutionary rates, we believe that ecologists are mainly interested in rapid evolution because of its potential to impinge on ecological processes. We therefore propose that rapid evolution be defined as a genetic change occurring rapidly enough to have a measurable impact on simultaneous ecological change. Using this definition we propose a framework for decomposing rates of ecological change into components driven by simultaneous evolutionary change and by change in a non‐evolutionary factor (e.g. density dependent population dynamics, abiotic environmental change). Evolution is judged to be rapid in this ecological context if its contribution to ecological change is large relative to the contribution of other factors. We provide a worked example of this approach based on a theoretical predator–prey interaction [ Abrams, P. & Matsuda, H. (1997) . Evolution, 51, 1740], and find that in this system the impact of prey evolution on predator per capita growth rate is 63% that of internal ecological dynamics. We then propose analytical methods for measuring these contributions in field situations, and apply them to two long‐term data sets for which suitable ecological and evolutionary data exist. For both data sets relatively high rates of evolutionary change have been found when measured as character change in standard deviations per generation (haldanes). For Darwin's finches evolving in response to fluctuating rainfall [ Grant, P.R. & Grant, B.R. (2002) . Science, 296, 707], we estimate that evolutionary change has been more rapid than ecological change by a factor of 2.2. For a population of freshwater copepods whose life history evolves in response to fluctuating fish predation [ Hairston, N.G. Jr & Dillon, T.A. (1990) . Evolution, 44, 1796], we find that evolutionary change has been about one quarter the rate of ecological change – less than in the finch example, but nevertheless substantial. These analyses support the view that in order to understand temporal dynamics in ecological processes it is critical to consider the extent to which the attributes of the system under investigation are simultaneously changing as a result of rapid evolution.