Showing 2011 - 2020 of 2039 Items
Injecting gryllus bimaculatus eggs
Date: 2019-08-01
Creator: Samantha K. Barry
Taro Nakamura
Yuji Matsuoka
Christoph Straub
Hadley W., Horch
Cassandra G. Extavour
Access: Open access
- Altering gene function in a developing organism is central to different kinds of experiments. While tremendously powerful genetic tools have been developed in traditional model systems, it is difficult to manipulate genes or messenger RNA (mRNA) in most other organisms. At the same time, evolutionary and comparative approaches rely on an exploration of gene function in many different species, necessitating the development and adaptation of techniques for manipulating expression outside currently genetically tractable species. This protocol describes a method for injecting reagents into cricket eggs to assay the effects of a given manipulation on embryonic or larval development. Instructions for how to collect and inject eggs with beveled needles are described. This relatively straightforward technique is flexible and potentially adaptable to other insects. One can gather and inject dozens of eggs in a single experiment, and survival rates for buffer-only injections improve with practice and can be as high as 80%. This technique will support several types of experimental approaches including injection of pharmacological agents, in vitro capped mRNA to express genes of interest, double-stranded RNA (dsRNA) to achieve RNA interference, use of clustered regularly interspaced short palindromic repeats (CRISPR) in concert with CRISPR-associated protein 9 (Cas9) reagents for genomic modification, and transposable elements to generate transient or stable transgenic lines.
De novo assembly of a transcriptome for the cricket Gryllus bimaculatus prothoracic ganglion: An invertebrate model for investigating adult central nervous system compensatory plasticity
Date: 2018-07-01
Creator: Harrison P. Fisher
Micah G. Pascual
Sylvia I. Jimenez
David A. Michaelson
Colby T., Joncas
Eleanor D. Quenzer
Andrew E. Christie
Hadley W. Horch
Access: Open access
- The auditory system of the cricket, Gryllus bimaculatus, demonstrates an unusual amount of anatomical plasticity in response to injury, even in adults. Unilateral removal of the ear causes deafferented auditory neurons in the prothoracic ganglion to sprout dendrites across the midline, a boundary they typically respect, and become synaptically connected to the auditory afferents of the contralateral ear. The molecular basis of this sprouting and novel synaptogenesis in the adult is not understood. We hypothesize that well-conserved developmental guidance cues may recapitulate their guidance functions in the adult in order to facilitate this compensatory growth. As a first step in testing this hypothesis, we have generated a de novo assembly of a prothoracic ganglion transcriptome derived from control and deafferented adult individuals. We have mined this transcriptome for orthologues of guidance molecules from four well-conserved signaling families: Slit, Netrin, Ephrin, and Semaphorin. Here we report that transcripts encoding putative orthologues of most of the candidate developmental ligands and receptors from these signaling families were present in the assembly, indicating expression in the adult G. bimaculatus prothoracic ganglion.
Interaction of stretch feedback and beat regularity in response to AMGSEFLamide in the heart of Homarus americanus
Date: 2020-01-01
Creator: William Allen
Access: Open access
- Central pattern generators (CPGs) are neural circuits whose component neurons possess intrinsic properties and synaptic connections that allow them to generate rhythmic motor outputs in the absence of descending inputs. The cardiac ganglion (CG) is a nine-cell CPG located in the American lobster, Homarus americanus. Stretch of the myocardium feeds back to the CG through mechano-sensitive dendrites and is thought to play a role in maintaining regularity in the beating pattern of the heart. The novel peptide AMGSEFLamide has been observed to induce irregular beating patterns when applied at high concentrations. This study investigated the interaction between stretch-related feedback and AMGSEFLamide modulation in generating irregular beating patterns in the whole heart of Homarus americanus. It was hypothesized that greater longitudinal stretch of the heart would result in greater regularity in the instantaneous beat frequency, based on previous findings that stretch-sensitive dendrites play a role in the regulation of the heartbeat. Furthermore, it was predicted that the elimination of stretch feedback via deafferentation of the heart would augment the irregularity induced by AMGSEFLamide. Data showed significantly increased irregularity in beating in response to 10-6 M AMGSEFLamide application. Longitudinal stretch did not reliably alter baseline variability in frequency, nor did it influence the modulatory effect of AMGSEFLamide. Deafferentation did not significantly alter baseline irregularity. Deafferented preparations did exhibit a trend of responding to AMGSEFLamide with a greater percent increase in irregularity compared to when afferents were intact, suggesting a potential role of stretch-stabilization in response to modulatory perturbations in the Homarus heart.
Demography of a Collapsing Aerial Insectivore Population
Date: 2017-05-01
Creator: Liam Taylor
Access: Open access
- Aerial insectivores have been declining across northeastern North America since the end of the 20th century. The mechanisms and demographic patterns of this decline are unclear. On Kent Island, New Brunswick, Canada, an isolated population of Tree Swallows (Tachycineta bicolor) collapsed between 1987 and 2010. To explore how demographic rates (i.e., survival, reproduction, and immigration) drove the population dynamics of these northeastern aerial insectivores, we combined productivity, population survey, and capture-recapture data in an integrated population model analysis. Neither consistently low juvenile survival rates, adult survival rates, nor clutch size were correlated with population growth rate across years. Alternatively, male and female immigration, hatching success, and fledging success rates were correlated with population growth rate. Because local hatching and fledging success rates cannot influence a population without local recruitment, we argue that the demography of these Tree Swallows is mainly structured by immigration. Parameter-substitution simulations revealed that overall decline was likely even if the population had avoided the worst years of demographic collapse. Breeding Bird Survey comparisons demonstrated how the Kent Island population represents both a demographic and geographical extreme at the edge of a declining region. These demographic patterns highlight the sensitivity, even to the point of local extinction, of some isolated populations to region-scale patterns in the production of potential immigrants.
In situ HCR in non-traditional arthropods
Date: 2024-01-25
Creator: Heather Bruce
Hadley Wilson Horch
Access: Open access
- Visualizing the expression of genes is a fundamental tool in molecular biology. Traditional colorimetric in situ hybridization using long RNA probes has been a staple for visualizing gene expression but has many drawbacks. In situ HCR v3.0, developed by Choi et. al. 2018, offers improvements over traditional in situs in nearly every aspect: probes can simply be ordered rather than painstakingly cloned and transcribed, which also makes them cost-effective; an HCR takes just three days to complete rather than five or more days; HCR is robust and works well for first-time users; and HCR probes can be multiplexed, allowing four to eight genes to be visualized in a single sample. HCR has been used successfully in many arthropods, including insects (Drosophila, Tribolium), crustaceans (Parhyale, Daphnia, Artemia), and chelicerates (Limulus horseshoe crab, Acanthoscurria tarantula). In this demo, you will learn how to design and order HCR probes as well as best practices for experimental design.
Interview with David Ray by Andrea L’Hommedieu
Date: 2008-03-24
Creator: David P Ray
Access: Open access
- Biographical NoteDavid Paul Ray was born on July 21, 1952, in Eastport, Maine. He was the third of six children and second-generation Lebanese on his father’s side. He attended the University of Maine, Orono and was graduated in 1974 with a degree in political science; he then attended Cornell Law School. He began his law career with the firm Jensen, Baird with George Mitchell and later became a clerk for Mitchell during his federal judgeship. When Mitchell was appointed to fill Senator Muskie’s vacated Senate seat, Ray accompanied him to Washington D.C., working on his staff as a legislative assistant for the next two years. Ray returned to Maine to continue his law career after the transition period. SummaryInterview includes discussion of: family and educational background; growing up in Eastport, Maine; political professors at the University of Maine; Mitchell’s legal career and federal judgeship; interning for Bill Cohen; Mitchell’s Senate office in Washington D.C.; and notable staff members in Mitchell’s Senate office.
Interview with Heather Mitchell (1) by Brien Williams
Date: 2010-02-05
Creator: Heather M Mitchell
Access: Open access
- Biographical NoteHeather McLachlan Mitchell was born and raised in Montreal, Canada, and lived in Paris, France, for fifteen years. She was assistant to the executive director of the Association of Tennis Professionals and subsequently represented professional male tennis players. She relocated from Paris to New York and in 1993 met George Mitchell at the U.S. Open. The two were married in 1994. She later worked independently coordinating tennis events. Once their children started school, she began working as a literary agent at Gelfman Schneider. SummaryInterview includes discussion of: Heather Mitchell’s career representing professional tennis players; meeting George Mitchell at the U.S. Open in 1993; her transition from sports to politics; George Mitchell’s tennis playing; dating Mitchell; the decision to get married and not run for reelection; Heather’s career as a literary agent after their children entered school; Northern Ireland; security issues in Northern Ireland; Mitchell’s contact with Verner Liipfert, the State Department, and the White House during his time in Northern Ireland; Mitchell’s becoming chairman of the Walt Disney Co.; Mitchell’s transition from Verner Liipfert to DLA Piper; becoming special envoy to the Middle East; Heather’s role in supporting Mitchell; the balance between public and private life; and Mitchell’s sense of humor.
Interview with George Mitchell (2) by Andrea L’Hommedieu and Mike Hastings
Date: 2008-09-11
Creator: George J Mitchell
Access: Open access
- Biographical NoteGeorge J. Mitchell was born on August 20, 1933, in Waterville, Maine, to Mary Saad, a factory worker, and George Mitchell, a laborer. Senator Mitchell spent his youth in Waterville. After receiving his bachelor's degree from Bowdoin College in 1954, he served as an officer in the U.S. Army Counter Intelligence Corps until 1956. In 1960 he earned a law degree from Georgetown University. Mitchell worked for Senator Edmund S. Muskie as executive assistant and as deputy campaign manager during Muskie's 1972 presidential campaign. He later became U.S. senator (D-Maine) 1980-1995, Senate majority leader 1989-1995, and, upon his retirement from the Senate, special advisor on Northern Ireland 1995-1998. Since 1998, Senator Mitchell has served on many boards and committees and has received high profile appointments including: chairman of the Sharm el-Sheikh International Fact-Finding Committee on the crisis between Israel and the Palestinian Authority (2000); overseer of the Red Cross Liberty Fund (2001); lead investigator into the illegal use of performance enhancing substances in Major League Baseball (2006); and special envoy for Palestinian-Israeli affairs (2009-2011). SummaryInterview includes discussion of: Maine Indian Land Claims case; Joseph Brennan; appointment to U.S. Senate; Acadia National Park; Finance Committee assignment story; becoming majority leader story; Bennett Johnston; John Glenn; deputy president pro tempore; John Stennis; 1982 election time ‘polls’ story; Howell Heflin and the Tennessee-Tombigbee Canal; foreign affairs interests; 1986 Gorbachev meeting; Berlin trip; Clarence Thomas confirmation hearing; bargaining as a tool in the Senate; John Major story; John Tower hearing story; filibusters and how the use of them has changed; Senate parliamentarians and their role; relationship with Robert Dole; Brady Bill; and striking a balance with Senate security.
Interview with Bill Mitchell by Andrea L’Hommedieu
Date: 2008-04-24
Creator: William 'Bill' E Mitchell
Access: Open access
- Biographical NoteWilliam “Bill” Mitchell was born in Waterville, Maine, on November 18, 1961, to Paul and Yvette Mitchell. He grew up in Waterville and attended Western New England College, then returned to Waterville and became involved with his father’s business, GHM Insurance Agency, where he continues to work. George J. Mitchell, Jr. is Bill’s uncle and Paul’s brother. SummaryInterview includes discussion of: Waterville, Maine, from the 1960s to present; Lebanese influence and other ethnic and religious backgrounds while growing up in Waterville; family involvement in politics; Atkin’s Printing Company; involvement in George Mitchell’s 1974 Maine gubernatorial campaign; family experiences with George Mitchell; cribbage; traditional Lebanese cooking; memories of his grandparents, George, Sr. and Mary (Saad); Waterville’s response to George Mitchell; and family values.
Interview with Susan Longley by Andrea L’Hommedieu
Date: 2010-03-23
Creator: Susan W Longley
Access: Open access
- Biographical NoteSusan Walsh Longley was born in December, 1955, in Lewiston, Maine, to James B. and Helen Longley. Her father, a successful insurance businessman, ran for governor in 1974 and won election during her senior year in high school. She attended Mt. Holyoke College, graduating in the class of 1978. In 1984-1985, she worked on Senator Mitchell’s Senate staff as a legislative correspondent. She established her own law practice in 1989 and later served as a Maine state senator representing Waldo County. SummaryInterview includes discussion of: family and educational background; her father, former Maine governor Jim Longley and his election as an independent; 1974 Maine gubernatorial campaign; anecdote about being hired by Senator Mitchell; U.S. Senate staff relationships: Gayle Cory, Mary McAleney, Anita Jensen; Topsham overpass issue; working on Mitchell’s Senate staff 1984-85; and environmental correspondence.