Showing 101 - 110 of 257 Items
Identification and cardiotropic actions of sulfakinin peptides in the American lobster Homarus americanus
Date: 2007-07-01
Creator: Patsy S. Dickinson, Jake S. Stevens, Szymon Rus, Henry R. Brennan, Christopher C., Goiney, Christine M. Smith, Lingjun Li, David W. Towle, Andrew E. Christie
Access: Open access
- In arthropods, a group of peptides possessing a -Y(SO3H)GHM/ LRFamide carboxy-terminal motif have been collectively termed the sulfakinins. Sulfakinin isoforms have been identified from numerous insect species. In contrast, members of this peptide family have thus far been isolated from just two crustaceans, the penaeid shrimp Penaeus monodon and Litopenaeus vannamei. Here, we report the identification of a cDNA encoding prepro-sulfakinin from the American lobster Homarus americanus. Two sulfakinin-like sequences were identified within the open-reading frame of the cDNA. Based on modifications predicted by peptide modeling programs, and on homology to the known isoforms of sulfakinin, particularly those from shrimp, the mature H. americanus sulfakinins were hypothesized to be pEFDEY(SO3H)GHMRFamide (Hoa-SK I) and GGGEY(SO3H)DDY(SO3H)GHLRFamide (Hoa-SK II). Hoa-SK I is identical to one of the previously identified shrimp sulfakinins, while Hoa-SK II is a novel isoform. Exogenous application of either synthetic Hoa-SK I or Hoa-SK II to the isolated lobster heart increased both the frequency and amplitude of spontaneous heart contractions. In preparations in which spontaneous contractions were irregular, both peptides increased the regularity of the heartbeat. Our study provides the first molecular characterization of a sulfakinin-encoding cDNA from a crustacean, as well as the first demonstration of bioactivity for native sulfakinins in this group of arthropods.
Assessing parameters influencing interhomolog proximity of paired homologous chromosomes in Drosophila This record is embargoed.
- Embargo End Date: 2026-05-20
Date: 2021-01-01
Creator: Molly Margaret Moore
Access: Embargoed
Probing the mechanism of recognition of ssDNA by the Cdc13-DBD
Date: 2008-03-01
Creator: Aimee M. Eldridge, Deborah S. Wuttke
Access: Open access
- The Saccharomyces cerevisiae protein Cdc13 tightly and specifically binds the conserved G-rich single-stranded overhang at telomeres and plays an essential role in telomere end-protection and length regulation. The 200 residue DNA-binding domain of Cdc13 (Cdc13-DBD) binds an 11mer single-stranded representative of the yeast telomeric sequence [Tel11, d(GTGTGGGTGTG)] with a 3 pM affinity and specificity for three bases (underlined) at the 5′ end. The structure of the Cdc13-DBD bound to Tel11 revealed a large, predominantly aromatic protein interface with several unusual features. The DNA adopts an irregular, extended structure, and the binding interface includes a long (∼30 amino acids) structured loop between strands β2-β3 (L2-3) of an OB-fold. To investigate the mechanism of ssDNA binding, we studied the free and bound states of Cdc13-DBD using NMR spectroscopy. Chemical shift changes indicate that the basic topology of the domain, including L2-3, is essentially intact in the free state. Changes in slow and intermediate time scale dynamics, however, occur in L2-3, while conformational changes distant from the DNA interface suggest an induced fit mechanism for binding in the 'hot spot' for binding affinity and specificity. These data point to an overall binding mechanism well adapted to the heterogeneous nature of yeast telomeres. © 2008 The Author(s).
Mass Spectrometry Quantification, Localization, and Discovery of Feeding-Related Neuropeptides in Cancer borealis
Date: 2021-02-17
Creator: Kellen Delaney, Mengzhou Hu, Tessa Hellenbrand, Patsy S. Dickinson, Michael P., Nusbaum, Lingjun Li
Access: Open access
- The crab Cancer borealis nervous system is an important model for understanding neural circuit dynamics and modulation, but the identity of neuromodulatory substances and their influence on circuit dynamics in this system remains incomplete, particularly with respect to behavioral state-dependent modulation. Therefore, we used a multifaceted mass spectrometry (MS) method to identify neuropeptides that differentiate the unfed and fed states. Duplex stable isotope labeling revealed that the abundance of 80 of 278 identified neuropeptides was distinct in ganglia and/or neurohemal tissue from fed vs unfed animals. MS imaging revealed that an additional 7 and 11 neuropeptides exhibited altered spatial distributions in the brain and the neuroendocrine pericardial organs (POs), respectively, during these two feeding states. Furthermore, de novo sequencing yielded 69 newly identified putative neuropeptides that may influence feeding state-related neuromodulation. Two of these latter neuropeptides were determined to be upregulated in PO tissue from fed crabs, and one of these two peptides influenced heartbeat in ex vivo preparations. Overall, the results presented here identify a cohort of neuropeptides that are poised to influence feeding-related behaviors, providing valuable opportunities for future functional studies.
Conifer forest photosynthetic seasonality: exploring the effect of winter severity and the efficacy of different remote sensing methodologies This record is embargoed.
- Embargo End Date: 2026-05-20
Date: 2021-01-01
Creator: Anneka Florence Williams
Access: Embargoed
Sutural loosening and skeletal flexibility during growth: Determination of drop-like shapes in sea urchins
Date: 2002-02-07
Creator: Amy S. Johnson, Olaf Ellers, Jim Lemire, Melissa Minor, Holly A., Leddy
Access: Open access
- The shape of sea urchins may be determined mechanically by patterns of force analogous to those that determine the shape of a water droplet. This mechanical analogy implies skeletal flexibility at the time of growth. Although comprised of many rigid calcite plates, sutural collagenous ligaments could confer such flexibility if the sutures between plates loosened and acted as joints at the time of growth. We present experimental evidence of such flexibility associated with weight gain and growth. Over 13-, 4-, and 2-week periods, fed urchins (Strongylocentrotus droebachiensis) gained weight and developed looser sutures than unfed urchins that maintained or lost weight. Further, skeletons of fed urchins force-relaxed more than did those of unfed urchins and urchins with loose sutures force-relaxed more than those with tight sutures. Urchins (Strongylocentrotus franciscanus) fed for two and a half weeks, gained weight, also had looser skeletons and deposited calcite at sutural margins, whereas unfed ones did not. In field populations of S. droebachiensis the percentage having loose sutures varied with urchin diameter and reflected their size-specific growth rate. The association between feeding, weight gain, calcite deposition, force relaxation and sutural looseness supports the hypothesis that urchins deform flexibly while growing, thus determining their drop-like shapes.
A hydrophobic, carboxy-proximal region of a light-harvesting chlorophyll a/b protein is necessary for stable integration into thylakoid membranes.
Date: 1989-01-01
Creator: B. D. Kohorn, E. M. Tobin
Access: Open access
- Proteins synthesized as soluble precursors in the cytoplasm of eukaryotic cells often cross organellar membrane barriers and then insert into lipid bilayers. One such polypeptide, the light-harvesting chlorophyll a/b-binding protein (LHCP), must also associate with pigment molecules and be assembled into the photosystem II light-harvesting complex in the chloroplast thylakoid membrane. A study of the import of mutant LHCPs into isolated chloroplasts has shown that a putative alpha-helical membrane-spanning domain near the carboxy terminus (helix 3) is essential for the stable insertion of LHCP in the thylakoid. Protease digestion experiments are consistent with the carboxy terminus of the protein being in the lumen. This report also shows that helix 3, when fused to a soluble protein, can target it to the thylakoids of isolated, intact chloroplasts. Although helix 3 is required for the insertion of LHCP and mutant derivatives into the thylakoid, the full insertion of helix 3 itself requires additionally the presence of other regions of LHCP. Thus, LHCP targeting and integration into thylakoid membranes requires a complex interaction involving a number of different domains of the LHCP polypeptide.
A genome-wide screen identifies genes that affect somatic homolog pairing in drosophila
Date: 2012-07-01
Creator: Jack R. Bateman, Erica Larschan, Ryan D'Souza, Lauren S. Marshall, Kyle E., Dempsey, Justine E. Johnson, Barbara G. Mellone, Mitzi I. Kuroda
Access: Open access
- In Drosophila and other Dipterans, homologous chromosomes are in close contact in virtually all nuclei, a phenomenon known as somatic homolog pairing. Although homolog pairing has been recognized for over a century, relatively little is known about its regulation. We performed a genome-wide RNAibased screen that monitored the X-specific localization of the male-specific lethal (MSL) complex, and we identified 59 candidate genes whose knockdown via RNAi causes a change in the pattern of MSL staining that is consistent with a disruption of X-chromosomal homolog pairing. Using DNA fluorescent in situ hybridization (FISH), we confirmed that knockdown of 17 of these genes has a dramatic effect on pairing of the 359 bp repeat at the base of the X. Furthermore, dsRNAs targeting Pr-set7, which encodes an H4K20 methyltransferase, cause a modest disruption in somatic homolog pairing. Consistent with our results in cultured cells, a classical mutation in one of the strongest candidate genes, pebble (pbl), causes a decrease in somatic homolog pairing in developing embryos. Interestingly, many of the genes identified by our screen have known roles in diverse cell-cycle events, suggesting an important link between somatic homolog pairing and the choreography of chromosomes during the cell cycle. © 2012 Bowers et al.
Two modes of transvection at the eyes absent gene of Drosophila demonstrate plasticity in transcriptional regulatory interactions in cis and in trans
Date: 2019-01-01
Creator: Katherine Tian, Rachel E. Henderson, Reyna Parker, Alexia Brown, Justine E., Johnson, Jack R. Bateman
Access: Open access
- For many genes, proper gene expression requires coordinated and dynamic interactions between multiple regulatory elements, each of which can either promote or silence transcription. In Drosophila, the complexity of the regulatory landscape is further complicated by the tight physical pairing of homologous chromosomes, which can permit regulatory elements to interact in trans, a phenomenon known as transvection. To better understand how gene expression can be programmed through cis- and trans-regulatory interactions, we analyzed transvection effects for a collection of alleles of the eyes absent (eya) gene. We find that trans-activation of a promoter by the eya eye-specific enhancers is broadly supported in many allelic backgrounds, and that the availability of an enhancer to act in trans can be predicted based on the molecular lesion of an eya allele. Furthermore, by manipulating promoter availability in cis and in trans, we demonstrate that the eye-specific enhancers of eya show plasticity in their promoter preference between two different transcriptional start sites, which depends on promoter competition between the two potential targets. Finally, we show that certain alleles of eya demonstrate pairing-sensitive silencing resulting from trans-interactions between Polycomb Response Elements (PREs), and genetic and genomic data support a general role for PcG proteins in mediating transcriptional silencing at eya. Overall, our data highlight how eya gene regulation relies upon a complex but plastic interplay between multiple enhancers, promoters, and PREs.
Monteverde: ecología y conservación de un bosque nuboso tropical
Date: 2014-12-01
Creator: Nathaniel T Wheelwright, Nalini M Nadkarni
Access: Open access
- La Reserva Biológica Bosque Nuboso Monteverde ha capturado la atención mundial de biólogos, conservacionistas y ecólogos y allí se han hecho vastas investigaciones durante los últimos 40 años. Unos 40.000 ecoturistas visitan el Bosque Nuboso cada año y se considera el bosque lluvioso arquetípico de las altitudes altas. Este libro, una traducción actualizada de "Monteverde: Ecology and Conservation of a Tropical Cloud Forest", editado por Nalini Nadkarni y Nathaniel T. Wheelwright (Oxford University Press, 2000) presenta capítulos sintéticos y recuentos específicos escritos por más de 100 biólogos y residentes locales. En un solo volumen documenta todo lo que se sabe en 2014 de la diversidad biológica de Monteverde, Costa Rica, y cómo protegerla. The Monteverde Cloud Forest Reserve has captured the worldwide attention of biologists, conservationists, and ecologists and has been the setting for extensive investigation over the past 40 years. Roughly 40,000 ecotourists visit the Cloud Forest each year, and it is often considered the archetypal high-altitude rain forest. This book, an updated and expanded version of "Monteverde: Ecology and Conservation of a Tropical Cloud Forest", edited by Nalini Nadkarni and Nathaniel T. Wheelwright (Oxford University Press, 2000), features synthetic chapters and specific accounts written by more than 100 biologists and local residents. The 862-page book includes 12 new short chapters and documents in a single volume everything known in 2014 about the biological diversity of Monteverde, Costa Rica, and how to protect it. El texto del libro ha sido dividido en dos partes para leer en línea: Parte 1: Agradecimientos, Prólogos, Capítulos 1-7 Parte 2: Capítulos 8-12, Appéndices Para hacer zoom, haga clic en la página. Para encontrar en el libro referencias a cualquier tema, especie, etc., haga clic en el “Q,” espere hasta la pantalla nueva, haga clic en el “Q” otra vez, y entre la palabra clave.