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• 31. [Article] Norepinephrine and temperature regulation in goldfish

  Cannulae were implanted into forebrain loci of goldfish (Carassius auratus; 45-90 g) to determine (i) the effects and site of action of intracranial norepinephrine (NE) injections on behavioral thermoregulation ...

  Citation × Citation Citation Abstract Copy Title: Norepinephrine and temperature regulation in goldfish Author: Wollmuth, Lonnie Paul Year: 1987 Cannulae were implanted into forebrain loci of goldfish (Carassius auratus; 45-90 g) to determine (i) the effects and site of action of intracranial norepinephrine (NE) injections on behavioral thermoregulation and (ii) the mechanism and the types of adrenoreceptors involved in the thermoregulatory effect of NE. After 30 min in a thermal gradient, implanted fish were injected with norepinephrinebitartrate salt (2.5-500 ng NE) in a total volume of 0.2 ul (carrier was 0.7% NaCl). Injections of 5, 10, 25, and 50 ng NE into the anterior aspect of the nucleus preopticus periventricularis (NPP1 Peter and Gill 1975) led to consistent, dose-dependent decreases in selected temperature. No effect on temperature selection was observed following injections of 2.5 ng NE or control injections of 100 ng tartaric acid. The effects of injections into other loci, including intraventricular injections, were dependent upon the dose and proximity to the anterior NPP1 at sites adjacent to the anterior NPP, larger doses were required, and the effects became inconsistent. At sites further removed, no effect on selected temperature was observed1 included in this category were more caudal sites within the NPP and the nucleus preopticus. Title: Norepinephrine and temperature regulation in goldfish Author: Wollmuth, Lonnie Paul Year: 1987 Cannulae were implanted into forebrain loci of goldfish (Carassius auratus; 45-90 g) to determine (i) the effects and site of action of intracranial norepinephrine (NE) injections on behavioral thermoregulation and (ii) the mechanism and the types of adrenoreceptors involved in the thermoregulatory effect of NE. After 30 min in a thermal gradient, implanted fish were injected with norepinephrinebitartrate salt (2.5-500 ng NE) in a total volume of 0.2 ul (carrier was 0.7% NaCl). Injections of 5, 10, 25, and 50 ng NE into the anterior aspect of the nucleus preopticus periventricularis (NPP1 Peter and Gill 1975) led to consistent, dose-dependent decreases in selected temperature. No effect on temperature selection was observed following injections of 2.5 ng NE or control injections of 100 ng tartaric acid. The effects of injections into other loci, including intraventricular injections, were dependent upon the dose and proximity to the anterior NPP1 at sites adjacent to the anterior NPP, larger doses were required, and the effects became inconsistent. At sites further removed, no effect on selected temperature was observed1 included in this category were more caudal sites within the NPP and the nucleus preopticus. Close

• 32. [Article] Anoxia Tolerance During Vertebrate Development - Insights from Studies on the Annual Killifish Austrofundulus limnaeus

  This is chapter 1 from Anoxia -- This book reviews how severe oxygen deprivation affects biological systems - from the molecular to the ecological level. The contributing authors come from diverse regions ...

  Citation × Citation Citation Abstract Copy Title: Anoxia Tolerance During Vertebrate Development - Insights from Studies on the Annual Killifish Austrofundulus limnaeus Author: Podrabsky, Jason E., Riggs, Claire L., Duerr, Jeffrey M. Year: 2012 This is chapter 1 from Anoxia -- This book reviews how severe oxygen deprivation affects biological systems - from the molecular to the ecological level. The contributing authors come from diverse regions of the world, which proves the interest in the academic analysis of oxygen deprivation. The diversity in the experimental approach scientists take, in order to understand the influence oxygen deprivation has on living systems, is apparent throughout this book. One of the presented ideas deals with the exploration and examination of the physiological, cellular and genetic characteristics of killifish embryos and nematodes exposed to anoxia. Furthermore, the book includes material on the mechanisms regulating hypoxia and anoxia tolerance and their implications of on human health issues. Finally, new methodologies to examine oxygen deprivation and the impact of human-related activities on oxygen level, within important ecological systems such as Lake Victoria, are presented. There is no doubt that the oxygen molecule is central to every stratum of biological systems. Title: Anoxia Tolerance During Vertebrate Development - Insights from Studies on the Annual Killifish Austrofundulus limnaeus Author: Podrabsky, Jason E., Riggs, Claire L., Duerr, Jeffrey M. Year: 2012 This is chapter 1 from Anoxia -- This book reviews how severe oxygen deprivation affects biological systems - from the molecular to the ecological level. The contributing authors come from diverse regions of the world, which proves the interest in the academic analysis of oxygen deprivation. The diversity in the experimental approach scientists take, in order to understand the influence oxygen deprivation has on living systems, is apparent throughout this book. One of the presented ideas deals with the exploration and examination of the physiological, cellular and genetic characteristics of killifish embryos and nematodes exposed to anoxia. Furthermore, the book includes material on the mechanisms regulating hypoxia and anoxia tolerance and their implications of on human health issues. Finally, new methodologies to examine oxygen deprivation and the impact of human-related activities on oxygen level, within important ecological systems such as Lake Victoria, are presented. There is no doubt that the oxygen molecule is central to every stratum of biological systems. Close

• 33. [Article] Nitrogen and iron interactions in filamentous cyanobacteria

  The investigations described in this paper are an attempt to further define and quantify the interrelationship of nitrogen fixation and iron nutritional physiology in these two species. Chapter II will ...

  Citation × Citation Citation Abstract Copy Title: Nitrogen and iron interactions in filamentous cyanobacteria Author: Hutchins, David Allen Year: 1989 The investigations described in this paper are an attempt to further define and quantify the interrelationship of nitrogen fixation and iron nutritional physiology in these two species. Chapter II will present and compare data on nutritional ratios of field collected Trichodesmium colonies and laboratory Anabaena cultures, with the intent of examining possible correlations between observed iron levels and protein nitrogen and chlorophyll concentrations, as well as nitrogen fixation rates. Chapter Ill is an examination of nitrogen fixation and siderophore production in Anabaena with emphasis on the possible implications of hypothesized synergistic effects of these two physiological capabilities on cyanobacterial dominance and bloom formation. Chapter IV will deal with the possibility of gratuitous manganese repression of Anabaena siderophore production in the manner described by Hantke (1987) for regulation of siderophore production in E. coli. The Conclusions chapter (Chapter V) will present a discussion of the results of these experiments in the context of current problems in cyanobacterial physiology, ecology and evolution. It is hoped that a significant contribution can be made to our understanding of the related problems of cyanobacterial dominance in freshwater ecosysytems and the scarcity of cyanobacterial nitrogen fixation in marine ecosystems. Title: Nitrogen and iron interactions in filamentous cyanobacteria Author: Hutchins, David Allen Year: 1989 The investigations described in this paper are an attempt to further define and quantify the interrelationship of nitrogen fixation and iron nutritional physiology in these two species. Chapter II will present and compare data on nutritional ratios of field collected Trichodesmium colonies and laboratory Anabaena cultures, with the intent of examining possible correlations between observed iron levels and protein nitrogen and chlorophyll concentrations, as well as nitrogen fixation rates. Chapter Ill is an examination of nitrogen fixation and siderophore production in Anabaena with emphasis on the possible implications of hypothesized synergistic effects of these two physiological capabilities on cyanobacterial dominance and bloom formation. Chapter IV will deal with the possibility of gratuitous manganese repression of Anabaena siderophore production in the manner described by Hantke (1987) for regulation of siderophore production in E. coli. The Conclusions chapter (Chapter V) will present a discussion of the results of these experiments in the context of current problems in cyanobacterial physiology, ecology and evolution. It is hoped that a significant contribution can be made to our understanding of the related problems of cyanobacterial dominance in freshwater ecosysytems and the scarcity of cyanobacterial nitrogen fixation in marine ecosystems. Close

• 34. [Article] Emergence of New sRNAs in Enteric Bacteria is Associated with Low Expression and Rapid Evolution

  Non-coding small RNAs (sRNAs) are critical to post-transcriptional gene regulation in bacteria. However, unlike for protein-coding genes, the evolutionary forces that shape sRNAs are not understood. We ...

  Citation × Citation Citation Abstract Copy Title: Emergence of New sRNAs in Enteric Bacteria is Associated with Low Expression and Rapid Evolution Author: Kacharia, Fenil R., Millar, Jess A., Raghavan, Rahul Year: 2017 Non-coding small RNAs (sRNAs) are critical to post-transcriptional gene regulation in bacteria. However, unlike for protein-coding genes, the evolutionary forces that shape sRNAs are not understood. We investigated sRNAs in enteric bacteria and discovered that recently emerged sRNAs evolve at significantly faster rates than older sRNAs. Concomitantly, younger sRNAs are expressed at significantly lower levels than older sRNAs. This process could potentially facilitate the integration of newly emerged sRNAs into bacterial regulatory networks. Furthermore, it has previously been difficult to trace the evolutionary histories of sRNAs because rapid evolution obscures their original sources. We overcame this challenge by identifying a recently evolved sRNA in Escherichia coli, which allowed us to determine that novel sRNAs could emerge from vestigial bacteriophage genes, the first known source for sRNA origination. Title: Emergence of New sRNAs in Enteric Bacteria is Associated with Low Expression and Rapid Evolution Author: Kacharia, Fenil R., Millar, Jess A., Raghavan, Rahul Year: 2017 Non-coding small RNAs (sRNAs) are critical to post-transcriptional gene regulation in bacteria. However, unlike for protein-coding genes, the evolutionary forces that shape sRNAs are not understood. We investigated sRNAs in enteric bacteria and discovered that recently emerged sRNAs evolve at significantly faster rates than older sRNAs. Concomitantly, younger sRNAs are expressed at significantly lower levels than older sRNAs. This process could potentially facilitate the integration of newly emerged sRNAs into bacterial regulatory networks. Furthermore, it has previously been difficult to trace the evolutionary histories of sRNAs because rapid evolution obscures their original sources. We overcame this challenge by identifying a recently evolved sRNA in Escherichia coli, which allowed us to determine that novel sRNAs could emerge from vestigial bacteriophage genes, the first known source for sRNA origination. Close

• 35. [Article] Analyzing Early Embryonic Cell Division Defects in Caenorhabditis Elegans

  36 pages. A thesis presented to the Department of Biology and the Clark Honors College of the University of Oregon in partial fulfillment of the requirements for degree of Bachelor of Science, Spring 2...

  Citation × Citation Citation Abstract Copy Title: Analyzing Early Embryonic Cell Division Defects in Caenorhabditis Elegans Author: Krishnakumar, Sheetal Year: 2014 36 pages. A thesis presented to the Department of Biology and the Clark Honors College of the University of Oregon in partial fulfillment of the requirements for degree of Bachelor of Science, Spring 2014. Title: Analyzing Early Embryonic Cell Division Defects in Caenorhabditis Elegans Author: Krishnakumar, Sheetal Year: 2014 36 pages. A thesis presented to the Department of Biology and the Clark Honors College of the University of Oregon in partial fulfillment of the requirements for degree of Bachelor of Science, Spring 2014. Close

• 36. [Article] The Response of Mice to Infection by the Parasitic Nematode Trichinella: A Comparison of Trichinella Spiralis and Trichinella Pseudospiralis

  The intracellular parasite Trichinella is a genus in phylum Nematoda that contains six named species including Trichinella spiralis and Trichinella pseudospiralis. These parasites infect a large variety ...

  Citation × Citation Citation Abstract Copy Title: The Response of Mice to Infection by the Parasitic Nematode Trichinella: A Comparison of Trichinella Spiralis and Trichinella Pseudospiralis Author: Anderson, Barry Clayton Year: 2002 The intracellular parasite Trichinella is a genus in phylum Nematoda that contains six named species including Trichinella spiralis and Trichinella pseudospiralis. These parasites infect a large variety of wild and domestic animals, human beings and a few species of birds. The parasitic strategies and the pathological effects on the host between trichinella spiralis and Trichinella pseudospiralis are quite different. The purpose of this study is to gain an understanding of the physiological, immunological and pathological differences between these two species of Trichinella using infections in the mouse as a model. In the course of this research I have attempted to answer the following questions: A) Is cortisol a factor in the differences of the host response to Trichinella spiralis or Trichinella pseudospiralis? B) Are there differences in leukocyte response in the peripheral blood of Trichinella infected mice? C) Are there differences in the up-regulation or down-regulation of cell surface molecules on leukocytes in the spleens of Trichinella infected mice? D) Is there a difference in the degree of muscle damage (as measured by creatine phosphokinase) when infections by the two species of Trichinella are compared? E) Are there differences in angiogenesis and collagen deposition in Trichinella infected mice and are these differences related to cortisol? F) Is nitric oxide a component in parasite killing and are there differences in nitric oxide production in host mice when the two species of Trichinella are compared? My research has shown that there are significant differences in the parasitic strategies and pathological consequences in mice infected with one or the other of the two species of Trichinella. The two species appear to generate different immune and inflammatory responses from the host. Trichinella pseudospiralis is much less damaging to the host, generates a very different peripheral blood response, stimulates the production of substantially greater levels of serum cortisol, generates a significantly different profile in cytokine production presents a very different cell surface antigen profile and does not produce a collagen nurse cell or generate an angiogenic response when compared to T spiralis. In addition, I have shown a role for nitric oxide in parasite killing and a role for serum cortisol in larval survival. I have also shown that cortisol has no role in either collagen deposition or the angiogenic response in Balb/c mice under the experimental conditions detailed here. Title: The Response of Mice to Infection by the Parasitic Nematode Trichinella: A Comparison of Trichinella Spiralis and Trichinella Pseudospiralis Author: Anderson, Barry Clayton Year: 2002 The intracellular parasite Trichinella is a genus in phylum Nematoda that contains six named species including Trichinella spiralis and Trichinella pseudospiralis. These parasites infect a large variety of wild and domestic animals, human beings and a few species of birds. The parasitic strategies and the pathological effects on the host between trichinella spiralis and Trichinella pseudospiralis are quite different. The purpose of this study is to gain an understanding of the physiological, immunological and pathological differences between these two species of Trichinella using infections in the mouse as a model. In the course of this research I have attempted to answer the following questions: A) Is cortisol a factor in the differences of the host response to Trichinella spiralis or Trichinella pseudospiralis? B) Are there differences in leukocyte response in the peripheral blood of Trichinella infected mice? C) Are there differences in the up-regulation or down-regulation of cell surface molecules on leukocytes in the spleens of Trichinella infected mice? D) Is there a difference in the degree of muscle damage (as measured by creatine phosphokinase) when infections by the two species of Trichinella are compared? E) Are there differences in angiogenesis and collagen deposition in Trichinella infected mice and are these differences related to cortisol? F) Is nitric oxide a component in parasite killing and are there differences in nitric oxide production in host mice when the two species of Trichinella are compared? My research has shown that there are significant differences in the parasitic strategies and pathological consequences in mice infected with one or the other of the two species of Trichinella. The two species appear to generate different immune and inflammatory responses from the host. Trichinella pseudospiralis is much less damaging to the host, generates a very different peripheral blood response, stimulates the production of substantially greater levels of serum cortisol, generates a significantly different profile in cytokine production presents a very different cell surface antigen profile and does not produce a collagen nurse cell or generate an angiogenic response when compared to T spiralis. In addition, I have shown a role for nitric oxide in parasite killing and a role for serum cortisol in larval survival. I have also shown that cortisol has no role in either collagen deposition or the angiogenic response in Balb/c mice under the experimental conditions detailed here. Close

• 37. [Article] Pcif1 modulates Pdx1 protein stability and pancreatic β cell function and survival in mice

  The homeodomain transcription factor pancreatic duodenal homeobox 1 (Pdx1) is a major mediator of insulin transcription and a key regulator of the β cell phenotype. Heterozygous mutations in PDX1 are associated ...

  Citation × Citation Citation Abstract Copy Title: Pcif1 modulates Pdx1 protein stability and pancreatic β cell function and survival in mice Author: Claiborn, Kathryn C., Sachdeva, Mira M., Cannon, Corey E., Groff, David N., Singer, Jeffrey D., Stoffers, Doris A. Year: 2010 The homeodomain transcription factor pancreatic duodenal homeobox 1 (Pdx1) is a major mediator of insulin transcription and a key regulator of the β cell phenotype. Heterozygous mutations in PDX1 are associated with the development of diabetes in humans. Understanding how Pdx1 expression levels are controlled is therefore of intense interest in the study and treatment of diabetes. Pdx1 C terminus–interacting factor-1 (Pcif1, also known as SPOP) is a nuclear protein that inhibits Pdx1 transactivation. Here, we show that Pcif1 targets Pdx1 for ubiquitination and proteasomal degradation. Silencing of Pcif1 increased Pdx1 protein levels in cultured mouse β cells, and Pcif1 heterozygosity normalized Pdx1 protein levels in Pdx1+/– mouse islets, thereby increasing expression of key Pdx1 transcriptional targets. Remarkably, Pcif1 heterozygosity improved glucose homeostasis and β cell function and normalized β cell mass in Pdx1+/– mice by modulating β cell survival. These findings indicate that in adult mouse β cells, Pcif1 limits Pdx1 protein accumulation and thus the expression of insulin and other gene targets important in the maintenance of β cell mass and function. They also provide evidence that targeting the turnover of a pancreatic transcription factor in vivo can improve glucose homeostasis. Title: Pcif1 modulates Pdx1 protein stability and pancreatic β cell function and survival in mice Author: Claiborn, Kathryn C., Sachdeva, Mira M., Cannon, Corey E., Groff, David N., Singer, Jeffrey D., Stoffers, Doris A. Year: 2010 The homeodomain transcription factor pancreatic duodenal homeobox 1 (Pdx1) is a major mediator of insulin transcription and a key regulator of the β cell phenotype. Heterozygous mutations in PDX1 are associated with the development of diabetes in humans. Understanding how Pdx1 expression levels are controlled is therefore of intense interest in the study and treatment of diabetes. Pdx1 C terminus–interacting factor-1 (Pcif1, also known as SPOP) is a nuclear protein that inhibits Pdx1 transactivation. Here, we show that Pcif1 targets Pdx1 for ubiquitination and proteasomal degradation. Silencing of Pcif1 increased Pdx1 protein levels in cultured mouse β cells, and Pcif1 heterozygosity normalized Pdx1 protein levels in Pdx1+/– mouse islets, thereby increasing expression of key Pdx1 transcriptional targets. Remarkably, Pcif1 heterozygosity improved glucose homeostasis and β cell function and normalized β cell mass in Pdx1+/– mice by modulating β cell survival. These findings indicate that in adult mouse β cells, Pcif1 limits Pdx1 protein accumulation and thus the expression of insulin and other gene targets important in the maintenance of β cell mass and function. They also provide evidence that targeting the turnover of a pancreatic transcription factor in vivo can improve glucose homeostasis. Close

• 38. [Article] The Hyperthermophilic Archaeon Sulfolobus : from Exploration to Exploitation

  In the early 1970s, Sulfolobus was first isolated by Thomas Brock and co-workers from sulfur-rich acidic hot springs in Yellowstone National Park. Sulfolobus became one of the model organisms of Archaea ...

  Citation × Citation Citation Abstract Copy Title: The Hyperthermophilic Archaeon Sulfolobus : from Exploration to Exploitation Author: Brouns, Stan J.J., Ettema, Thijs J.G., Stedman, Kenneth M., Walther, Jasper, Smith, Hauke, Snijders, Ambrosius P.L., Young, Mark, Bernander, Rolf, Wright, Phillip C., Siebers, Betina, Van der Oost, John Year: 2003 In the early 1970s, Sulfolobus was first isolated by Thomas Brock and co-workers from sulfur-rich acidic hot springs in Yellowstone National Park. Sulfolobus became one of the model organisms of Archaea in general, and of Crenarchaea in particular. Many of its unusual physiological characteristics have been investigated, and several of its thermostable enzymes have been studied in considerable detail. For fundamental reasons, and because of its potential for industrial applications, Sulfolobus has been selected for a genome sequence project. The recent completion of the Sulfolobus solfataricus genome has set the stage for a series of postgenome research lines that will be reviewed here. Comparative genomics aims to unravel the cell’s metabolic potential (enzymes, pathways, and regulation) and compare it to other organisms. This in silico analysis of Sulfolobus has revealed several unique metabolic features and confirmed that the major control processes (transcription, translation, and replication) resemble eukaryal much more than bacterial equivalents. Currently, several research groups use a functional genomics approach—a genomebased, high-throughput analysis of the complete Sulfolobus cell—at the level of RNA (transcriptomics), protein (proteomics), and metabolic intermediates and products (metabolomics). Apart from analyzing the cell’s response to different cultivation conditions, the comparison of different genotypes (wild type and mutants) would be very interesting for both basic science and applied reasons. Much effort has recently been put into the establishment of tools that allow genetic engineering of Sulfolobus. The future challenge is to integrate available knowledge in order to understand the relevant mechanisms that enable Sulfolobus to thrive in its extreme habitats. Moreover, such a Systems Biology approach is essential as a basis for the directed engineering and industrial exploitation of this unique microorganism. Title: The Hyperthermophilic Archaeon Sulfolobus : from Exploration to Exploitation Author: Brouns, Stan J.J., Ettema, Thijs J.G., Stedman, Kenneth M., Walther, Jasper, Smith, Hauke, Snijders, Ambrosius P.L., Young, Mark, Bernander, Rolf, Wright, Phillip C., Siebers, Betina, Van der Oost, John Year: 2003 In the early 1970s, Sulfolobus was first isolated by Thomas Brock and co-workers from sulfur-rich acidic hot springs in Yellowstone National Park. Sulfolobus became one of the model organisms of Archaea in general, and of Crenarchaea in particular. Many of its unusual physiological characteristics have been investigated, and several of its thermostable enzymes have been studied in considerable detail. For fundamental reasons, and because of its potential for industrial applications, Sulfolobus has been selected for a genome sequence project. The recent completion of the Sulfolobus solfataricus genome has set the stage for a series of postgenome research lines that will be reviewed here. Comparative genomics aims to unravel the cell’s metabolic potential (enzymes, pathways, and regulation) and compare it to other organisms. This in silico analysis of Sulfolobus has revealed several unique metabolic features and confirmed that the major control processes (transcription, translation, and replication) resemble eukaryal much more than bacterial equivalents. Currently, several research groups use a functional genomics approach—a genomebased, high-throughput analysis of the complete Sulfolobus cell—at the level of RNA (transcriptomics), protein (proteomics), and metabolic intermediates and products (metabolomics). Apart from analyzing the cell’s response to different cultivation conditions, the comparison of different genotypes (wild type and mutants) would be very interesting for both basic science and applied reasons. Much effort has recently been put into the establishment of tools that allow genetic engineering of Sulfolobus. The future challenge is to integrate available knowledge in order to understand the relevant mechanisms that enable Sulfolobus to thrive in its extreme habitats. Moreover, such a Systems Biology approach is essential as a basis for the directed engineering and industrial exploitation of this unique microorganism. Close

• 39. [Article] Cullin-3 Targets Cyclin E for Ubiquitination and Controls S Phase in Mammalian Cells

  Cyclin E is an unstable protein that is degraded in a ubiquitin- and proteasome- dependent pathway. Two factors stimulate cyclin E ubiquitination in vivo: when it is free of its CDK partner, and when it ...

  Citation × Citation Citation Abstract Copy Title: Cullin-3 Targets Cyclin E for Ubiquitination and Controls S Phase in Mammalian Cells Author: Singer, Jeffrey D., Gurian-West, Mark, Clurman, Bruce, Roberts, James M. Year: 1999 Cyclin E is an unstable protein that is degraded in a ubiquitin- and proteasome- dependent pathway. Two factors stimulate cyclin E ubiquitination in vivo: when it is free of its CDK partner, and when it is phosphorylated on threonine 380. We pursued the first of these pathways by using a two-hybrid screen to identify proteins that could bind only to free cyclin E. This resulted in the isolation of human Cul-3, a member of the cullin family of E3 ubiquitin–protein ligases. We found that Cul-3 was bound to cyclin E but not to cyclin E-Cdk2 complexes in mammalian cells, and that overexpression of Cul-3 increased ubiquitination of cyclin E but not other cyclins. Conversely, deletion of the Cul-3 gene in mice caused increased accumulation of cyclin E protein, and had cell-type-specific effects on S-phase regulation. In the extraembryonic ectoderm, in which cells undergo a standard mitotic cycle, there was a greatly increased number of cells in S phase. In the trophectoderm, in which cells go through endocycles, there was a block to entry into S phase. The SCF pathway, which targets cyclins for ubiquitination on the basis of their phosphorylation state, and the Cul-3 pathway, which selects cyclin E for ubiquitination on the basis of its assembly into CDK complexes, may be complementary ways to control cyclin abundance. Title: Cullin-3 Targets Cyclin E for Ubiquitination and Controls S Phase in Mammalian Cells Author: Singer, Jeffrey D., Gurian-West, Mark, Clurman, Bruce, Roberts, James M. Year: 1999 Cyclin E is an unstable protein that is degraded in a ubiquitin- and proteasome- dependent pathway. Two factors stimulate cyclin E ubiquitination in vivo: when it is free of its CDK partner, and when it is phosphorylated on threonine 380. We pursued the first of these pathways by using a two-hybrid screen to identify proteins that could bind only to free cyclin E. This resulted in the isolation of human Cul-3, a member of the cullin family of E3 ubiquitin–protein ligases. We found that Cul-3 was bound to cyclin E but not to cyclin E-Cdk2 complexes in mammalian cells, and that overexpression of Cul-3 increased ubiquitination of cyclin E but not other cyclins. Conversely, deletion of the Cul-3 gene in mice caused increased accumulation of cyclin E protein, and had cell-type-specific effects on S-phase regulation. In the extraembryonic ectoderm, in which cells undergo a standard mitotic cycle, there was a greatly increased number of cells in S phase. In the trophectoderm, in which cells go through endocycles, there was a block to entry into S phase. The SCF pathway, which targets cyclins for ubiquitination on the basis of their phosphorylation state, and the Cul-3 pathway, which selects cyclin E for ubiquitination on the basis of its assembly into CDK complexes, may be complementary ways to control cyclin abundance. Close

• 40. [Article] Microbial Biomineralization of Iron

  Iron is a common cation in biomineral sand; it is present for example in magnetite produced by magnetotactic bacteria and in iron sulfides produced by sulfate reducing microorganisms. The work presented ...

  Citation × Citation Citation Abstract Copy Title: Microbial Biomineralization of Iron Author: Fang, Wen Year: 2013 Iron is a common cation in biomineral sand; it is present for example in magnetite produced by magnetotactic bacteria and in iron sulfides produced by sulfate reducing microorganisms. The work presented in this thesis focused on two types of microorganisms capable of forming iron biominerals. In the first project I have studied the effect of O2 on the respiratory physiology and the formation of magnetosomes by Magnetospirillum magneticum AMB-1. In the second project I have studied the relationship between olivine and the activity of dissimilatory sulfate reducing (DSR) microorganisms. For the first project, I grew cells of AMB-1 in cultures with various concentrations of O2 and monitored growth and the formation of magnetic mineral particles (MMP). Results have shown that AMB-1 cells grew better at 100-225 uMO2(aq) than at lower [O2], yet the formation of MMP was repressed at ~45 uM O2(aq) and strongly inhibited at >100 uM O2(aq).These results have helped better understand the dissimilarity between the optimal growth conditions of magnetotactic bacteria and the conditions needed for the formation of MMPs. My results have also shown that the reaction between H2S produced by DSRs and olivine is abiotic, not catalyzed and exergonic. The pH did not vary significantly during this reaction and pH variation (in the 5-9 range) did not significantly influence this chemical reaction. Bicarbonate inhibited the reaction between H2S and olivine, but not the chemical equilibrium. Phosphate, a weak iron chelator, influenced the equilibrium of the reaction and it is assumed to help increase the rate of olivine weathering in the presence of DSRs. The activity of DSRs was positively influenced by the presence and abundance of olivine. Based on my results I propose that olivine help DSR obtain energy more efficiently, but does not represent a source of energy or nutrients for the cells. These results helped better understand the formation of iron biominerals and signatures of this activity. Title: Microbial Biomineralization of Iron Author: Fang, Wen Year: 2013 Iron is a common cation in biomineral sand; it is present for example in magnetite produced by magnetotactic bacteria and in iron sulfides produced by sulfate reducing microorganisms. The work presented in this thesis focused on two types of microorganisms capable of forming iron biominerals. In the first project I have studied the effect of O2 on the respiratory physiology and the formation of magnetosomes by Magnetospirillum magneticum AMB-1. In the second project I have studied the relationship between olivine and the activity of dissimilatory sulfate reducing (DSR) microorganisms. For the first project, I grew cells of AMB-1 in cultures with various concentrations of O2 and monitored growth and the formation of magnetic mineral particles (MMP). Results have shown that AMB-1 cells grew better at 100-225 uMO2(aq) than at lower [O2], yet the formation of MMP was repressed at ~45 uM O2(aq) and strongly inhibited at >100 uM O2(aq).These results have helped better understand the dissimilarity between the optimal growth conditions of magnetotactic bacteria and the conditions needed for the formation of MMPs. My results have also shown that the reaction between H2S produced by DSRs and olivine is abiotic, not catalyzed and exergonic. The pH did not vary significantly during this reaction and pH variation (in the 5-9 range) did not significantly influence this chemical reaction. Bicarbonate inhibited the reaction between H2S and olivine, but not the chemical equilibrium. Phosphate, a weak iron chelator, influenced the equilibrium of the reaction and it is assumed to help increase the rate of olivine weathering in the presence of DSRs. The activity of DSRs was positively influenced by the presence and abundance of olivine. Based on my results I propose that olivine help DSR obtain energy more efficiently, but does not represent a source of energy or nutrients for the cells. These results helped better understand the formation of iron biominerals and signatures of this activity. Close