Biology
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Item STUDIES ON THE GNRH/GTH SYSTEM OF FEMALE STRIPED BASS (Marone saxatilis): EFFECTS OF GNRH AGONJST THERAPY AND COMPARISON OF REPRODUCTIVE ENDOCRINE PARAMETERS BETWEEN WILD AND CAPTIVE FISH(1999) Steven, Colin R.; Zohar, Yonathan; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, MD)In the striped bass (Marone saxatilis), and many other commercially important fish species, captivity results in an inability to complete final oocyte maturation (FOM), ovu lation , and spawning. We hypothesize that this effect is mediated by a disruption of the hypothalamo-pituitary-gonadal (HPG) axis at the level of the gonadotropin -releasing hormones (GnRHs). To confirm this hypothesis research was conducted focused on three objectives: First, to complement the battery of assays previously developed for analysis of the GnRH/GtH system in striped bass, an RNAse protection assay was developed to measure specific expression of the three forms of GnRH in striped bass (salmon GnRH, chicken GnRH-If and seabream GnRH). Secondly, effects of GnRH agonist-induced ovulation on the HPG axis of captive striped bass was examined by comparison of several reproductive endocrine parameters between females sampled at four stages of oocyte development. Finally, differences were examined between the reproductive endocrine status of wild and captive female striped bass. We conclude that sbGnRH is the most important form for the preovulatory release of pituitary GtH-II in striped bass. We suggest that captive females synthesize levels of GnRH mRNA that are comparable to their wild counterparts, however fail to release adequate quantities of bioactive GnRH within the pituitary to stimulate completion of FOM. This data may indicate that regulation of sbGnRH in striped bass occurs via post-transcriptional/ translational mechanisms. Furthermore, the presence of salmon GnRH in the pituitaries of captive fema les may be indicative of a possible role for salmon GnRH in the regulation of FOM.Item Impaired Focal Adhesion Kinase-Grb2 Interaction during Elevated Activity in Hippocampal Neurons(MDPI, 2015-07-10) Murase, SachikoExcitatory/inhibitory imbalances are implicated in many neurological disorders. Previously, we showed that chronically elevated network activity induces vulnerability in neurons due to loss of signal transducer and activator of transcription 3 (STAT3) signaling in response to the impairment of the serine/threonine kinase, extracellular-signal-regulated kinases 1/2 (Erk1/2) activation. However, how phosphorylation of Erk1/2 decreases during elevated neuronal activity was unknown. Here I show the pErk1/2 decrease induced by 4-aminopyridine (4-AP), an A-type potassium channel inhibitor can be blocked by a broad-spectrum matrix-metalloproteinase (MMP) inhibitor, FN-439. Surface expression levels of integrin β1 dramatically decrease when neurons are challenged by chronically elevated activity, which is reversed by FN-439. Treatment with 4-AP induces degradation of focal adhesion kinase (FAK), the mediator of integrin signaling. As a result, interactions between FAK and growth factor receptor-bound protein 2 (Grb2), the adaptor protein that mediates Erk1/2 activation by integrin, are severely impaired. Together, these data suggest the loss of integrin signaling during elevated activity causes vulnerability in neurons.Item Membrane Affinity of Platensimycin and Its Dialkylamine Analogs(MDPI, 2015-08-04) Rowe, Ian; Guo, Min; Yasmann, Anthony; Cember, Abigail; Sintim, Herman O.; Sukharev, SergeiMembrane permeability is a desired property in drug design, but there have been difficulties in quantifying the direct drug partitioning into native membranes. Platensimycin (PL) is a new promising antibiotic whose biosynthetic production is costly. Six dialkylamine analogs of PL were synthesized with identical pharmacophores but different side chains; five of them were found inactive. To address the possibility that their activity is limited by the permeation step, we calculated polarity, measured surface activity and the ability to insert into the phospholipid monolayers. The partitioning of PL and the analogs into the cytoplasmic membrane of E. coli was assessed by activation curve shifts of a re-engineered mechanosensitive channel, MscS, in patch-clamp experiments. Despite predicted differences in polarity, the affinities to lipid monolayers and native membranes were comparable for most of the analogs. For PL and the di-myrtenyl analog QD-11, both carrying bulky sidechains, the affinity for the native membrane was lower than for monolayers (half-membranes), signifying that intercalation must overcome the lateral pressure of the bilayer. We conclude that the biological activity among the studied PL analogs is unlikely to be limited by their membrane permeability. We also discuss the capacity of endogenous tension-activated channels to detect asymmetric partitioning of exogenous substances into the native bacterial membrane and the different contributions to the thermodynamic force which drives permeation.Item Genomic Characterization of a B Chromosome in Lake Malawi Cichlid Fishes(MDPI, 2018-12-05) Clark, Frances E.; Conte, Matthew A.; Kocher, Thomas D.B chromosomes (Bs) were discovered a century ago, and since then, most studies have focused on describing their distribution and abundance using traditional cytogenetics. Only recently have attempts been made to understand their structure and evolution at the level of DNA sequence. Many questions regarding the origin, structure, function, and evolution of B chromosomes remain unanswered. Here, we identify B chromosome sequences from several species of cichlid fish from Lake Malawi by examining the ratios of DNA sequence coverage in individuals with or without B chromosomes. We examined the efficiency of this method, and compared results using both Illumina and PacBio sequence data. The B chromosome sequences detected in 13 individuals from 7 species were compared to assess the rates of sequence replacement. B-specific sequence common to at least 12 of the 13 datasets were identified as the “Core” B chromosome. The location of B sequence homologs throughout the genome provides further support for theories of B chromosome evolution. Finally, we identified genes and gene fragments located on the B chromosome, some of which may regulate the segregation and maintenance of the B chromosome.Item Distribution and Community Assembly of Trees Along an Andean Elevational Gradient(MDPI, 2019-09-05) Worthy, Samantha J.; Jiménez Paz, Rosa A.; Pérez, Álvaro J.; Reynolds, Alex; Cruse-Sanders, Jennifer; Valencia, Renato; Barone, John A.; Burgess, Kevin S.Highlighting patterns of distribution and assembly of plants involves the use of community phylogenetic analyses and complementary traditional taxonomic metrics. However, these patterns are often unknown or in dispute, particularly along elevational gradients, with studies finding different patterns based on elevation. We investigated how patterns of tree diversity and structure change along an elevation gradient using taxonomic and phylogenetic diversity metrics. We sampled 595 individuals (36 families; 53 genera; 88 species) across 15 plots along an elevational gradient (2440–3330 m) in Ecuador. Seventy species were sequenced for the rbcL and matK gene regions to generate a phylogeny. Species richness, Shannon–Weaver diversity, Simpson’s Dominance, Simpson’s Evenness, phylogenetic diversity (PD), mean pairwise distance (MPD), and mean nearest taxon distance (MNTD) were evaluated for each plot. Values were correlated with elevation and standardized effect sizes (SES) of MPD and MNTD were generated, including and excluding tree fern species, for comparisons across elevation. Taxonomic and phylogenetic metrics found that species diversity decreases with elevation. We also found that overall the community has a non-random phylogenetic structure, dependent on the presence of tree ferns, with stronger phylogenetic clustering at high elevations. Combined, this evidence supports the ideas that tree ferns have converged with angiosperms to occupy the same habitat and that an increased filtering of clades has led to more closely related angiosperm species at higher elevations.Item Cooperativity and Steep Voltage Dependence in a Bacterial Channel(MDPI, 2019-09-11) Lin, Shang H.; Chang, Kai-Ti; Cherian, Nuval; Wu, Benjamin; Phee, Hyo; Cho, Christy; Colombini, MarcoThis paper reports on the discovery of a novel three-membrane channel unit exhibiting very steep voltage dependence and strong cooperative behavior. It was reconstituted into planar phospholipid membranes formed by the monolayer method and studied under voltage-clamp conditions. The behavior of the novel channel-former, isolated from Escherichia coli, is consistent with a linearly organized three-channel unit displaying steep voltage-gating (a minimum of 14 charges in the voltage sensor) that rivals that of channels in mammalian excitable membranes. The channels also display strong cooperativity in that closure of the first channel permits the second to close and closure of the second channel permits closure of the third. All three have virtually the same conductance and selectivity, and yet the first and third close at positive potentials whereas the second closes at negative potentials. Thus, is it likely that the second channel-former is oriented in the membrane in a direction opposite to that of the other two. This novel structure is named “triplin.” The extraordinary behavior of triplin indicates that it must have important and as yet undefined physiological roles.Item Adenyl Cyclase and Its Relationship to Insect Diapause in the European Corn Borer, Ostrinia Nubilalis (Hubner)(1978) Gelman, Dale Berkman; Lockard, J. David; Hayes, Dora K.; Botany and Science Teaching; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)The purpose of this study was to determine if there is a link between adenyl cyclase activity and the diapause condition in the European corn borer, Ostrinia nubilalis. Insects inhabiting those latitudes where cold and warm seasons alternate with one another have evolved mechanisms which allow them to remain dormant (in a state of diapause) during the winter months of the year. Photoperiod, as well as temperature and humidity, has been shown to control the onset, maintenance and termination of insect diapause. In recent years, evidence supporting a role for the cyclic AMP system, including adenyl cyclase, as well as a role for one or more biogenic amines in the pathway between light reception and the neuroendocrine regulation of the insect life cycle and in the multitude of neuroendocrine pathways controlling insect growth and metamorphosis has been accumulating. In light of this evidence, it was decided to investigate the effects of two light regimens, short day (diapausing-inducing) and long day (pupation-inducing), on adenyl cyclase activity of various stages of fifth instar European corn borer larval heads, and to determine the effects of the biogenic amine neurotransmitters, norepinephrine, octopamine, and dopamine on this activity. Adenyl cyclase activity was measured by a modification of the method of Krishna, et al., (1968). A summary of the results follows. In head extracts of fifth instar European corn borer larvae reared under both long day and short day photoperiodic regimens, adenyl cyclase activity in the presence of sodium fluoride increased as the larvae progressed through early, middle and mature stages. In long day larval heads, activity decreased in late prepupae and reached a low in pharate pupae. In contrast, adenyl cyclase activity in short day larval heads peaked in early diapause and then returned to prediapause levels during late diapause. Norepinephrine significantly enhanced adenyl cyclase activity only in early diapause larval head extracts, while octopamine significantly enhanced adenyl cyclase activity in head extracts of late short day mature and early diapause larvae. Dopamine was ineffective as an activator. An analysis of the combined effect of neurotransmitter and developmental stage revealed that in general, a given neurotransmitter in combination with short day larval head extracts resulted in higher adenyl cyclase levels than that neurotransmitter in combination with long day head extracts.Item Interannual and Regional Patterns of Abundance, Growth, and Feeding Ecology of Larval Bay Anchovy (Anchoa Mitchilli) in Chesapeake Bay(2003) Auth, Toby D.; Houde, Edward D.; Marine Estaurine and Environmental Science Program; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)Patterns in abundance, growth , and feeding by larval bay anchovy were examined in Chesapeake Bay from 1995-1999 to evaluate factors that contribute to variable recruitments of this abundant fish. The patterns were examined in relation to environmental factors, including hydrography and distributions of prey (zooplankton) and a probable predator (ctenophore). Larval abundances, sizes, feeding incidences, and growth rates varied annually and regionally. Averaged over five years, mean abundances in July decreased by almost two orders of magnitude from the mouth (38.l/m2) to the head (0.6/m) of the Bay, a long a declining salinity gradient. Yearly survey, bay-wide mean abundance varied nearly 10-fold; it was highest in 1998 (42. 7 /m2) and lowest in 1996 (4.6/m2). Feeding incidence was highest in 1998 (23%) and lowest in 1996 (9%), and varied regionally from 27% in the upper Bay to 13% in the mid Bay. Larvae fed predominantly during daylight. The most common prey ingested were copepod eggs and various life stages of calanoid copepods (primarily Acarlia Lonsa). Growth rates of larvae also differed annually and regionally. Mean growth rate was highest in 1998 (0.81 mm/d) and lowest in 1999 (0.68 mm/d), and varied regionally from 0.83 mm/d in the upper Bay to 0.71 mm/din the mid Bay. Zooplankton concentration was positively correlated with larval feeding incidence (r = +0.66) and growth rate (r = +0. 72). Larval feeding incidence was strongly correlated (r = +0.93) and summer larval abundance significantly correlated (r = +0.86) with fall recruitment of young-of-the-year bay anchovy.Item Ascidian gene-expression profiles(Springer Nature, 2002-09-25) Jeffery, William RWith the advent of gene-expression profiling, a large number of genes can now be investigated simultaneously during critical stages of development. This approach will be particularly informative in studies of ascidians, basal chordates whose genomes and embryology are uniquely suited for mapping developmental gene networks.Item Visualization and analysis of microarray and gene ontology data with treemaps(Springer Nature, 2004-06-28) Baehrecke, Eric H; Dang, Niem; Babaria, Ketan; Shneiderman, BenThe increasing complexity of genomic data presents several challenges for biologists. Limited computer monitor views of data complexity and the dynamic nature of data in the midst of discovery increase the challenge of integrating experimental results with information resources. The use of Gene Ontology enables researchers to summarize results of quantitative analyses in this framework, but the limitations of typical browser presentation restrict data access. Here we describe extensions to the treemap design to visualize and query genome data. Treemaps are a space-filling visualization technique for hierarchical structures that show attributes of leaf nodes by size and color-coding. Treemaps enable users to rapidly compare sizes of nodes and sub-trees, and we use Gene Ontology categories, levels of RNA, and other quantitative attributes of DNA microarray experiments as examples. Our implementation of treemaps, Treemap 4.0, allows user-defined filtering to focus on the data of greatest interest, and these queried files can be exported for secondary analyses. Links to model system web pages from Treemap 4.0 enable users access to details about specific genes without leaving the query platform. Treemaps allow users to view and query the data from an experiment on a single computer monitor screen. Treemap 4.0 can be used to visualize various genome data, and is particularly useful for revealing patterns and details within complex data sets.