The Behavior of Low Molecular Weight Organic Carbon-14 Containing Compounds in Contaminated Groundwater During Denitrification and Iron-Reduction

Abstract

Aqueous low molecular weight organic carbon-14 (¹⁴C) substances can be formed by the oxidation of carbide and impurities within nuclear fuel cladding. During reprocessing and interim storage ¹⁴C-labeled organic compounds may leak to the shallow subsurface environments at nuclear facilities where denitrifying and iron reducing zones can exist. ¹⁴C-labeled organic compounds (acetate, formate, formaldehyde and methanol) were used as electron donors in microcosm experiments, under both denitrification and iron reduction, using glacial outwash sediments and groundwater composition representative of the Sellafield nuclear reprocessing site, UK. In denitrifying microcosms, <6% of the initial ¹⁴C-DOC remained 15?days after injection into the microcosm irrespective of the electron donor; with concurrent ¹⁴CO2 (g) production. Lack of removal in sterile controls suggests that ¹⁴C-organics were metabolized by microorganisms. Under iron-reducing conditions both ¹⁴C-carboxylates were removed from solution rapidly, but some formaldehyde and methanol remained in solution 32?days after injection into the microcosm so there is potential that a proportion of ¹⁴C-formaldehyde and ¹⁴C-methanol may persist for longer in subsurface environments.     

The proinflammatory phenotype of PECAM-1-deficient mice results in atherogenic diet-induced steatohepatitis

The severity of nonalcoholic steatohepatitis (NASH) is determined by environmental and genetic factors, the latter of which are incompletely characterized. Platelet endothelial cell adhesion molecule-1 (PECAM-1) is a 130-kDa transmembrane glycoprotein expressed on blood and vascular cells. In the present study, we provide data for the novel finding that genetic deficiency of PECAM-1 potentiates the development and progression of NASH. We found that the rate of development and severity of diet-induced NASH are markedly enhanced in PECAM-1-deficient [knockout (KO)] mice relative to wild-type (WT) mice, as measured by histological and biochemical evaluation. Livers from KO mice exhibited typical histological features of NASH, including macrovesicular fat accumulation, hepatocyte injury with infiltration of inflammatory cells, fibrosis, and heightened oxidative stress. Alanine aminotransferase, a marker for liver injury, was also significantly higher in KO compared with WT mice. Consistent with a role for PECAM-1 as a suppressor of proinflammatory cytokines, plasma levels of inflammatory cytokines, including TNF-alpha and monocyte chemoattractant protein-1 (MCP-1), were also significantly higher in KO compared with WT mice. These findings are the first to show that the PECAM-1-deficient mouse develops progressive nonalcoholic fatty liver disease (NAFLD), supporting a role for PECAM-1 as a negative regulator of NAFLD progression. Future examination of recently identified PECAM-1 allelic isoforms in humans as potential risk factors for developing NASH may be warranted.     

Progressive enzyme changes within anatomically defined segments of rabbit nephron: demonstration with a new technique

The kidney is an extremely heterogeneous organ, with morphological, physiological, and metabolic changes occurring from segment to segment along each nephron. To determine the heterogeneity that might exist within discrete anatomical segments of rabbit nephron, we developed a technique for making quantitative enzyme assays in serial samples, about 100 micron long, along identified segments of the nephron. Results for three enzymes in proximal convoluted and straight tubules show that adenylate kinase, an enzyme of high-energy phosphate metabolism, gradually decreases along the S1 and S2 segments of the proximal tubule, with no abrupt changes. Fructose bisphosphatase, a gluconeogenic enzyme, is high along the major portion of the proximal tubule but plummets along the final millimeter of S3. Conversely, phosphofructokinase, a glycolytic enzyme, is very low along the proximal tubule but increases sharply within the final millimeter. These data underscore the biochemical heterogeneity of the nephron, illustrating the enzyme levels may change markedly even within anatomically defined regions. They also suggest the importance of further studies of this type and demonstrate a practical means for such studies.     

Cytoplasmic Dynein Function Is Essential in Drosophila Melanogaster

The microtubule motor cytoplasmic dynein has been implicated in a variety of intracellular transport processes. We previously identified and characterized the Drosophila gene Dhc64C, which encodes a cytoplasmic dynein heavy chain. To investigate the function of the cytoplasmic dynein motor, we initiated a mutational analysis of the Dhc64C dynein gene. A small deletion that removes the chromosomal region containing the heavy chain gene was used to isolate EMS-induced lethal mutations that define at least eight essential genes in the region. Germline transformation with a Dhc64C transgene rescued 16 mutant alleles in the single complementation group that identifies the dynein heavy chain gene. All 16 alleles were hemizygous lethal, which demonstrates that the cytoplasmic dynein heavy chain gene Dhc64C is essential for Drosophila development. Furthermore, our failure to recover somatic clones of cells homozygous for a Dhc64C mutation indicates that cytoplasmic dynein function is required for cell viability in several Drosophila tissues. The intragenic complementation of dynein alleles reveals multiple mutant phenotypes including male and/or female sterility, bristle defects, and defects in eye development.     

Analysis of site-specific phosphorylation of the retinoblastoma protein during cell cycle progression

Differential phosphorylation of the retinoblastoma protein plays a pivotal role in cell cycle regulation. The retinoblastoma protein is specifically phosphorylated during the cell cycle by cyclin-dependent kinase complexes which intersect with many cellular signaling networks. Since the loss of the retinoblastoma signaling pathways occurs in a wide variety of human tumors, understanding the significance of site-specific phosphorylation can clarify the role of selected cyclin-dependent kinase complexes during cell cycle progression. Here we describe the phosphospecificity and cellular characterization of a panel of polyclonal antibodies that recognize unique phosphorylation sites within the retinoblastoma protein. These reagents were used to validate authentic cellular retinoblastoma phosphorylation sites at amino acids 780, 795, and 807/811 correlating with the G1-S transition.     

Purification of an endopeptidase involved with storage-protein degradation in Phaseolus vulgaris L. cotyledons

Phaseolin, the major seed storage protein of Phaseolus vulgaris L., is degraded in the cotyledons in the first 7–10 d following seed germination. We assayed cotyledon extracts for protease activity by using [³H]phaseolin as a substrate and then fractionated the digestion mixtures by sodium dodecyl sulfate-polyacrylamide gel electrophoresis in order to identify the cleavage products. The cotyledons of 4-d-old seedlings contain an endopeptidase which cleaves the polypeptides of [³H]phaseolin (apparent molecular weights=51 000, 48 000, 46 000 and 43 000) into three discrete clusters of proteolytic fragments (M _rs=27 000, 25 000 and 23 000). Endopeptidase activity is not detected in the cotyledons until the protein content of these organs starts to decline, shortly after the first day of seedling growth. Endopeptidase activity increases to a maximum level in the cotyledons of 5-d-old seedlings and then declines to a minimum value by day 10. The enzyme was purified 335-fold by ammonium-sulfate precipitation, organomercurial-agarose chromatography, gel filtration and ion-exchange chromatography. The endopeptidase constitutes 0.3% of the protein content in the cotyledons of 4-d-old seedlings. It is a cysteine protease with a single polypeptide chain (M _r=30 000). Optimum hydrolysis of [³H]phaseolin occurs at pH 5. The enzyme is irreversibly inactivated at pH values above 7 and at temperatures above 45° C. The endopeptidase attacks only a limited number of peptide bonds in [³H]phaseolin, without causing any appreciable change in the native molecular weight of the storage protein. The endopeptidase is also able to hydrolyze the bean-seed lectin, phytohemagglutinin. Thus, this enzyme may play a general role in degrading cotyledon proteins of P. vulgaris following seed germination.Abbreviations Da dalton - DTT dithiothreitol - M _r apparent molecular weight - PAGE polyacrylamide gel electrophoresis - PHA phytohemagglutinin - SDS sodium dodecyl sulfate     

The galenic and hippocratic challenges to Aristotle's conception theory

Conclusion As a result of this case study, additional questions arise. These can be cast into at least three groups. The first concerns the development of critical empiricism in the ancient world: a topic of much interest in our own century, expecially with regard to the work of the logical empiricists. Many of the same arguments are present in the ancient world and were hotly debated from the Hippocratic writers through and beyond Galen. Some of the ways in which Galen reacts to Hippocratic and Aristotelian influences may, in part, be explained by Galen's own posture as a so-called Dogmatist. Both the Empirics and the Methodists offered alternative viewpoints on the place, role, and limits of observation in biomedical research. Though I have written on this relationship in the Hippocratic writers and Aristotle,⁴⁴ it remains to be discussed in detailed fashion just how critical empiricism acted in Galen's evaluation of biomedical problems (aporiai). Contrasts between Galen and his predecessors might further clarify this issue both as a historical question and as it affects the construction of biological theory.The second area explores the question of how one develops comprehensive theories. In this respect Galen follows Aristotle's methodology rather closely. Both look at what theories are available to them and then systematically review the problems raised, at the same time refuting what they find inadequate. This is an effective strategy, for it permits utilizing the best features of earlier work to fashion a new whole. Indeed, Galen himself seems to attribute his use of such a methodology to his ecletic medical and philosophical training. Both Aristotle and Galen endeavor to employ techniques of theory integration. That is, they use aspects of theories they have already espoused to deal with new problems. This suggests the emergence of formal, logical coherence as an element in theory evaluation. The obvious drawback is that it can cause mistakes in one area to be repeated and ingrained in other areas. Such errors, because they are at the very core of an explanatory framework, may take centuries to correct. Future studies may shed light on how theory integration acts both in a positive and in a negative way.Finally, this case study offers a glimpse of how science progresses. Even though the advances in medical technology were comparatively minor, there is a great deal more sophistication in the conception theoreis of Aristotle and Galen than was present in the Hippocratic writers. Some of this (in Galen's case) had to do with increased anatomic and physiological knowledge, but most, I believe, is due to the evolution of scientific knowledge. If further work were done specifically on this question, it might document more completely how scientific knowledge on a specific topic evolves. The mode of advancement is primarily through gradual refinement of the types of questions being asked by these ancient authors, and the ramifications of their answers.Ancient theories of conception offer a fine case study in the history and philosophy of how a theory begins the develops. I have tried to suggest some interrelationships among the more important theories, as they focused upon Aristotle's own conception theory. There has been renewed interest in such cases in recent years. It is my hope that future specialized studies will increase our knowledge of method and practice in these important case studies and thereby augment our understanding of the genesis and application of biological theories.     

A study of variance in measurements of tank-treading frequency in populations of normal human red cells

The statistical variance in rheoscopic measurements of tank-treading frequency ( TTF ) of normal human red cells has been investigated and the sources of this variance analyzed. Experiments were designed to expose the influence of donor, the stability of a donor's cells over a 2-month period, storage time from venipuncture to testing, cell age, applied shear rate and variations in the rheoscope gap due to trial-to-trial manipulation. The results show that the TTF varies linearly with applied shear rate within the range 20 to 180 s-1 and is strongly dependent on cell age. The slope of the TTF characteristic is not significantly different in cells taken from different, but hematologically normal adults nor does it change significantly over time in a particular donor. TTF measurements may be useful in distinguishing rheologically abnormal cell populations which differ from normal cells by at least 10%.