Showing 141 - 150 of 257 Items
Examining the Ability of Remote Sensing to Characterize Turfgrass Stress Physiology
Date: 2022-01-01
Creator: Benjamin Ross
Access: Open access
- Remote sensing of solar induced chlorophyll fluorescence (SIF) is a valuable tool in understanding the global carbon cycle. While SIF is highly correlated with photosynthesis at the ecosystem scale, the role that remote sensing of SIF can play at smaller scales is still unclear. The goal of my research was to investigate the ability of SIF to detect changes in pigmentation, photosynthesis, and energy partitioning at the grass canopy and leaf level in response to water stress and abscisic acid (ABA) hormone treatments. Both treatments immediately inhibited photosynthesis by limiting gas exchange through stomatal closure, but SIF declined gradually. Recovery of photosynthesis after alleviation of water stress was not reflected in remote measurements of SIF. I found that senescence in the tips of grasses had been driving changes in remote measurements, which affected remote measurements even when measured leaf-level gas exchange in the lower living tissue recovered. This heterogeneous senescence pattern contextualizes the disconnect between SIF and photosynthesis in stressed turfgrass.
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.
Identifying a distinct developmental module in the zebrafish dentition
Date: 2018-01-01
Creator: Caleb Matthew Gordon
Access: Open access
- In the zebrafish pharynx, the first three teeth to form, 3V1, 4V1, and 5V1, have distinct adult and embryonic morphologies, suggesting that these teeth may form using different developmental pathways. Previous studies of gene expression profiles and mutant phenotypes in 3V1, 4V1, and 5V1 have identified four genes that might be involved in dissociating these tooth modules: pitx2b, eve1, pbx1a, and pbx1b. To determine how the developmental roles of these four genes differ across 3V1, 4V1, and 5V1, and obtain a better understanding of how these three teeth develop, I performed CRISPR/Cas9– mediated knockouts in each of these genes, or analyzed embryos from a stable transgenic mutant line where available, and observed the resulting tooth germs and mineralized tooth structures via fluorescence and confocal microscopy. Preliminary results implicate pitx2 as being required for tooth mineralization, offer a possible role for pbx1a, pbx1b, and eve1 in distinguishing the developmental pathway of 3V1, and suggest that 3V1 constitutes a distinct developmental module within the early ventral dentition.
Identification of SYWKQCAFNAVSCFamide: A broadly conserved crustacean C-type allatostatin-like peptide with both neuromodulatory and cardioactive properties
Date: 2009-04-15
Creator: Patsy S. Dickinson, Teerawat Wiwatpanit, Emily R. Gabranski, Rachel J. Ackerman, Jake S., Stevens, Christopher R. Cashman, Elizabeth A. Stemmler, Andrew E. Christie
Access: Open access
- The allatostatins comprise three structurally distinct peptide families that regulate juvenile hormone production by the insect corpora allata. A-type family members contain the C-terminal motif -YXFGLamide and have been found in species from numerous arthropod taxa. Members of the B-type family exhibit a -WX6Wamide C-terminus and, like the A-type peptides, appear to be broadly conserved within the Arthropoda. By contrast, members of the C-type family, typified by the unblocked C-terminus -PISCF, a pyroglutamine blocked N-terminus, and a disulfide bridge between two internal Cys residues, have only been found in holometabolous insects, i.e. lepidopterans and dipterans. Here, using transcriptomics, we have identified SYWKQCAFNAVSCFamide (disulfide bridging predicted between the two Cys residues), a known honeybee and water flea C-typelike peptide, from the American lobster Homarus americanus (infraorder Astacidea). Using matrix assisted laser desorption/ionization Fourier transform mass spectrometry (MALDI-FTMS), a mass corresponding to that of SYWKQCAFNAVSCFamide was detected in the H. americanus brain, supporting the existence of this peptide and its theorized structure. Furthermore, SYWKQCAFNAVSCFamide was detected by MALDI-FTMS in neural tissues from five additional astacideans as well as 19 members of four other decapod infraorders (i.e. Achelata, Anomura, Brachyura and Thalassinidea), suggesting that it is a broadly conserved decapod peptide. In H. americanus, SYWKQCAFNAVSCFamide is capable of modulating the output of both the pyloric circuit of the stomatogastric nervous system and the heart. This is the first demonstration of bioactivity for this peptide in any species.
Effects of Origin Environment and Temperature Acclimation on the Temperate Coral Astrangia poculata This record is embargoed.
- Embargo End Date: 2026-05-18
Date: 2023-01-01
Creator: Deva K Holliman
Access: Embargoed
Localizing Potential Messenger RNA Transport Protein Ips1 in Candida albicans Access to this record is restricted to members of the Bowdoin community. Log in here to view.
- Restriction End Date: 2027-06-01
Date: 2022-01-01
Creator: Yi Peng Wang
Access: Access restricted to the Bowdoin Community
RPCH modulation of a multi-oscillator network: Effects on the pyloric network of the spiny lobster
Date: 2001-01-01
Creator: Patsy S. Dickinson, Jane Hauptman, John Hetling, Anand Mahadevan
Access: Open access
- The neuropeptide red pigment concentrating hormone (RPCH), which we have previously shown to activate the cardiac sac motor pattern and lead to a conjoint gastric mill-cardiac sac pattern in the spiny lobster Panulirus, also activates and modulates the pyloric pattern. Like the activity of gastric mill neurons in RPCH, the pattern of activity in the pyloric neurons is considerably more complex than that seen in control saline. This reflects the influence of the cardiac sac motor pattern, and particularly the upstream inferior ventricular (IV) neurons, on many of the pyloric neurons. RPCH intensifies this interaction by increasing the strength of the synaptic connections between the IV neurons and their targets in the stomatogastric ganglion. At the same time, RPCH enhances postinhibitory rebound in the lateral pyloric (LP) neuron. Taken together, these factors largely explain the complex pyloric pattern recorded in RPCH in Panulirus.
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.
Distinct or shared actions of peptide family isoforms: I. Peptidespecific actions of pyrokinins in the lobster cardiac neuromuscular system
Date: 2015-09-01
Creator: Patsy S. Dickinson, Anirudh Sreekrishnan, Molly A. Kwiatkowski, Andrew E. Christie
Access: Open access
- Although the crustacean heart is modulated by a large number of peptides and amines, few of these molecules have been localized to the cardiac ganglion itself; most appear to reach the cardiac ganglion only by hormonal routes. Immunohistochemistry in the American lobster Homarus americanus indicates that pyrokinins are present not only in neuroendocrine organs ( pericardial organ and sinus gland), but also in the cardiac ganglion itself, where pyrokinin-positive terminals were found in the pacemaker cell region, as well as surrounding the motor neurons. Surprisingly, the single pyrokinin peptide identified from H. americanus, FSPRLamide, which consists solely of the conserved FXPRLamide residues that characterize pyrokinins, did not alter the activity of the cardiac neuromuscular system. However, a pyrokinin from the shrimp Litopenaeus vannamei [ADFAFNPRLamide, also known as Penaeus vannamei pyrokinin 2 (PevPK2)] increased both the frequency and amplitude of heart contractions when perfused through the isolated whole heart. None of the other crustacean pyrokinins tested (another from L. vannamei and two from the crab Cancer borealis) had any effect on the lobster heart. Similarly, altering the PevPK2 sequence either by truncation or by the substitution of single amino acids resulted in much lower or no activity in all cases; only the conservative substitution of serine for alanine at position 1 resulted in any activity on the heart. Thus, in contrast to other systems (cockroach and crab) in which all tested pyrokinins elicit similar bioactivities, activation of the pyrokinin receptor in the lobster heart appears to be highly isoform specific.