Department of Biological Sciences

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Archvillin, a muscle-specific isoform of supervillin, is an early expressed component of the costameric membrane skeleton
(The Company of Biologists, 2003-02) Oh, Sang W.; Pope, Robert K.; Smith, Kelly P.; Crowley, Jessica L.; Nebl, Thomas; Lawrence, Jeanne B.; Luna, Elizabeth J.
The membrane skeleton protein supervillin binds tightly to both F-actin and membranes and can potentiate androgen receptor activity in non-muscle cells. We report that muscle, which constitutes the principal tissue source for supervillin sequences, contains a ~250 kDa isoform of supervillin that localizes within nuclei and with dystrophin at costameres, regions of F-actin membrane attachment in skeletal muscle. The gene encoding this protein, ‘archvillin’ (Latin, archi; Greek, árchos; ‘principal’ or ‘chief’), contains an evolutionarily conserved, muscle-specific 5¢ leader sequence. Archvillin cDNAs also contain four exons that encode ~47 kDa of additional muscle-specific protein sequence in the form of two inserts within the function-rich N-terminus of supervillin. The first of these muscle-specific inserts contains two conserved nuclear targeting signals in addition to those found in sequences shared with supervillin. Archvillin, like supervillin, binds directly to radiolabeled F-actin and co-fractionates with plasma membranes. Colocalization of archvillin with membraneassociated actin filaments, non-muscle myosin II, and – to a lesser extent – vinculin was observed in myoblasts. Striking localizations of archvillin protein and mRNA were observed at the tips of differentiating myotubes. Transfected protein chimeras containing archvillin insert sequences inhibited myotube formation, consistent with a dominant-negative effect during early myogenesis. These data suggest that archvillin is among the first costameric proteins to assemble during myogenesis and that it contributes to myogenic membrane structure and differentiation. Keywords: Costamere, Sarcolemma, Membrane skeleton, C2C12 cells, 50MB-1 cells
Blood Pressure in the Greenland Shark as Estimated from Ventral Aortic Elasticity
(Journal of Experimental Biology, 2018) Shadwick, Robert E.; Bernal, Diego; Bushnell, Peter G. (Peter Gerald); Steffensen, John F.
We conducted in vitro inflations of freshly excised ventral aortas of the Greenland shark, Somniosus microcephalus, and used pressure– diameter data to estimate the point of transition from high to low compliance, which has been shown to occur at the mean blood pressure in other vertebrates including fishes. We also determined the pressure at which the modulus of elasticity of the aorta reached 0.4 MPa, as occurs at the compliance transition in other species. From these analyses, we predict the average ventral aortic blood pressure in S. microcephalus to be about 2.3–2.8 kPa, much lower than reported for other sharks. Our results support the idea that this species is slow moving and has a relatively low aerobic metabolism. Histological investigation of the ventral aorta showsthat elastic fibres are present in relatively low abundance and loosely connected, consistent with this aorta having high compliance at a relatively low blood pressure.
Cannabis use is associated with a substantial reduction in premature deaths in the United States.
(Indiana University South Bend, 2017-08-11) Clark, Thomas M.
Adverse effects of moderate Cannabis use on physical health are subtle and rarely fatal, while Cannabis use is associated with decreased rates of obesity, diabetes mellitus, mortality from traumatic brain injury, use of alcohol and prescription drugs, driving fatalities, and opioid overdose deaths. These data suggest that Cannabis use may decrease premature deaths. To date, no studies have attempted to estimate impacts of Cannabis use on premature death that include both adverse and beneficial effects on physical health. Marijuana use is estimated to reduce premature deaths from diabetes mellitus, cancer, and traumatic brain injury by 989 to 2,511 deaths for each 1% of the population using Cannabis. The analysis predicts an estimated 23,500 to 47,500 deaths prevented annually if medical marijuana were legal nationwide. A number of other potential causes of reduced mortality due to Cannabis use were revealed, but were excluded from the analysis because quantitative data were lacking. These estimates thus substantially underestimate the actual impact of Cannabis use on premature death. Overall, prohibition is estimated to lead to similar numbers of premature deaths as drunk driving, homicide, or fatal opioid overdose. Cannabis use prevents thousands of premature deaths each year, and Cannabis prohibition is revealed as a major cause of premature death in the U.S. Keywords: Cannabis, marijuana, medical marijuana, mortality rate, prohibition, public health, cancer, cardiovascular disease, diabetes mellitus, liver disease, lung disease, suicide, TBI, opioid overdose, driving fatalities, systematic review, meta-analysis.
Coexistence of Mutualists and Antagonists: Exploring the Impact of Cheaters on the Yucca - Yucca Moth Mutualism
(Oecologia, 2001) Marr, Deborah L.; Brock, Marcus T.; Pellmyr, Olle
Abstract Mutualists and non-mutualistic cheaters commonly coexist, but the effect of mutualist-cheater interactions on the evolution and stability of mutualisms or persistence of cheater populations is not well understood. Yuccas and yucca moths are an example of an obligate mutualism in which cheaters are frequently present. Larvae of both pollinators and cheaters eat developing yucca seeds, but cheaters no longer pollinate and rely on the mutualist species for seed availability. In this study we focus on interactions between the cheater Tegeticula intermedia and the pollinator T. yuccasella in fruits of the host Yucca filamentosa. We examined the effect of pollinator and cheater density on larval mass and larval mortality, the effect of fruit mass on larval interactions, and the degree of variability in pollinator-cheater interactions across 3 years. This study was done in a natural population to determine whether these two larval species affect each other under natural conditions. Genetic markers (both protein electrophoresis and DNA sequencing) were used to identify the larvae to species. We found no correlation between larval number and mortality for either pollinators or cheaters. Furthermore, pollinator mass was not correlated with number of cheater larvae per fruit in any year. Mass of cheater larvae was not correlated with number of pollinator larvae per fruit in two of three years; in one year, there was a negative correlation between number of pollinator larvae on mass of cheater larvae only in small fruits. Our results suggest that larval competition between species is weak and asymmetric; when it occurs, cheater larvae incur the cost. The number of cheaters and pollinators per fruit was negatively correlated in two of three years. The lack of a positive correlation in number of cheater and pollinator larvae per fruit may contribute to lowering the potential for seed competition among larvae. In addition, larval density per fruit differed across years by as much as 30%. However, this degree of difference was apparently not enough to cause seed limitation because no effect of pollinator larvae on either mass or mortality of cheater larvae was detected in years with the highest larval densities per fruit. In contrast to the weak effects of pollinator-cheater interactions, fruit mass accounted for much of the variation in number and mass of both pollinator and cheater larvae within and across years. Larger fruits generally had heavier and higher numbers of larvae compared to smaller fruits. Overall, in this population at least within the time period studied, pollinators and cheaters coexisted with little conflict in fruit. This result is consistent with the hypothesis that the recent rapid radiation of species in the T. yuccasella complex may be explained in part by the ability of multiple pollinator species (some of whom have become cheaters) to use fruits without severe competition. Keywords: Mutualism, Antagonism, Species coexistence, Stability of cheaters, Plant-pollinator interactions
Comparative genomics of the pathogenic ciliate Ichthyophthirius multifiliis, its free-living relatives and a host species provide insights into adoption of a parasitic lifestyle and prospects for disease control
(BMC, 2011) Coyne, Robert S.; Wilkes, David E.; Rajagopalan, Vidyalakshmi
Background: Ichthyophthirius multifiliis, commonly known as Ich, is a highly pathogenic ciliate responsible for ‘white spot’, a disease causing significant economic losses to the global aquaculture industry. Options for disease control are extremely limited, and Ich’s obligate parasitic lifestyle makes experimental studies challenging. Unlike most well-studied protozoan parasites, Ich belongs to a phylum composed primarily of free-living members. Indeed, it is closely related to the model organism Tetrahymena thermophila. Genomic studies represent a promising strategy to reduce the impact of this disease and to understand the evolutionary transition to parasitism. Results: We report the sequencing, assembly and annotation of the Ich macronuclear genome. Compared with its free-living relative T. thermophila, the Ich genome is reduced approximately two-fold in length and gene density and three-fold in gene content. We analyzed in detail several gene classes with diverse functions in behavior, cellular function and host immunogenicity, including protein kinases, membrane transporters, proteases, surface antigens and cytoskeletal components and regulators. We also mapped by orthology Ich’s metabolic pathways in comparison with other ciliates and a potential host organism, the zebrafish Danio rerio. Conclusions: Knowledge of the complete protein-coding and metabolic potential of Ich opens avenues for rational testing of therapeutic drugs that target functions essential to this parasite but not to its fish hosts. Also, a catalog of surface protein-encoding genes will facilitate development of more effective vaccines. The potential to use T. thermophila as a surrogate model offers promise toward controlling ‘white spot’ disease and understanding the adaptation to a parasitic lifestyle.
Differences in Pollination Syndromes and the Frequency of Autonomous Delayed Selfing Between Co-flowering Hibiscus poneurus (Sprague and Hutch) and H. flavifolius (Ulbr) from Kenya
(Journal of Pollination Ecology, 2018-02) Ruiz-Guajardo, Juan Carlos; Schnabel, Andrew; McCallum, Britnie; Otero Arnaiz, Adriana; Baldock, Katherine; Stone, Graham
Delayed autonomous selfing offers a mechanism for seed production when pollination levels are low or unpredictable. At Mpala Research Centre (MRC) in Kenya, we examined the relationships between floral attraction, insect visitation, and delayed autonomous selfing through backwards stylar curvature in the co-flowering Hibiscus aponeuru s and H. flavifolius . Despite producing similar pollen and nectar rewards, visitation rates and the composition of floral visitor guilds varied significantly between these species. Across four years of observations, floral visitation in H. flavifolius was dominated by bees , and in H. aponeurus by a mixture of bees, butterflies and beetles. Visitation rates to H. flavifolius flowers (range 0.17 - 2.1 visits flr-1hr-1) were two times greater than to H. aponeurus flowers (range 0 - 2.7 visits flr-1hr-1), which resulted in significantly higher pollen deposition and removal rates in H. flavifolius than in H. aponeurus. Field crosses demonstrated little pollen limitation in either species. In open-pollinated flowers, H. aponeurus displayed significantly greater stylar curvature and apparent self-pollination than did H. flavifolius . Floral attributes in H. aponeurus , such as a smaller corolla size and a downwards orientation of the stylar column, also suggest that delayed selfing is a more important mechanism of reproductive assurance in this species than in H. flavifolius . Determining whether these differences in insect visitation and stylar curvature are characteristic for these species or are unique to MRC will require comparison with populations located in other parts of the ranges, genetic tests of selfing rates, and chemical analyses of nectar, pollen, and floral volatiles. Keywords: Delayed autonomous selfing, Hibiscus, pollination, stylar curvature, Mpala Research Centre
Differences in the Effects of Salinity on Larval Growth and Developmental Programs of a Freshwater and a Euryhaline Mosquito Species (Insecta: Diptera, Culicidae)
(The Journal of Experimental Biology, 2004) Clark, Thomas M.; Flis, Benjamin J.; Remold, Susanna K.
The effects of salinity on growth and development of the euryhaline Ochlerotatus taeniorhynchus and the freshwater Aedes aegypti are compared. O. taeniorhynchus grow larger, and have greater intrinsic growth rates, than A. aegypti. Females of each species attain greater mass, take longer to develop, and have greater growth rates than do males. In O. taeniorhynchus, pupal mass, larval stage duration and growth rates (dry mass) increase with salinity, whereas growth rates (wet mass) remain constant across salinities, reflecting a decrease in percent body water. The pupal mass (wet or dry) of O. taeniorhynchus is determined primarily by effects of salinity on the rate of assimilation of dry mass, because the latter contributes very strongly to final pupal mass in both species. In contrast, the duration of A. aegypti larval stage follows a U-shaped curve, with most rapid development at intermediate salinities. Growth rates of A. aegypti decrease with increasing salinity, and percent body water is constant across salinities. As for O. taeniorhynchus, duration of A. aegypti larval stage increases at high salinity. However, this increase in larval stage duration cannot compensate for the decrease in growth rate at high salinity, resulting in an overall decrease in both wet and dry pupal mass at high salinity. Thus, salinity has fundamentally different effects on developmental programs and phenotypic plasticity in the two species investigated. Key words: mosquito larvae, salinity, life history, growth rate, developmental rate, Aedes aegypti, Ochlerotatus taeniorhynchus, insect.
Discordant Responses to MAPK Pathway Stimulation Include Axonal Growths in Adult Drosophila Photoreceptors
(Frontiers Media, 2018) Mecklenburg, Kirk L.; Weghorst, Forrest P.; Freed, Stephanie A.; O’Tousa, Joseph E.
Wallenda (WND) is the Drosophila member of a conserved family of dual leucine-zipper kinases (DLK) active in both neuronal regeneration and degeneration. We examined the role of WND over-expression on sensory neuron morphology by driving WND in multiple subtypes of Drosophila photoreceptors. WND overexpression under control of the pan-retinal GAL4 driver GMR causes multiple photoreceptor defects including cell death, rhabdomere degeneration, and axonal sprouting. Individual photoreceptor subtypes were assayed using GAL4 drivers specific for each photoreceptor class. Many R7 and R8 cells exhibit axonal sprouting while some show cell degeneration. Delaying the onset of WND overexpression until 20 days of age showed that older adult R7 cells retain the ability to initiate new axon growth. R1–6 photoreceptor cells degenerate in response to WND expression and exhibit rhodopsin loss and rhabdomere degeneration. RNAi knockdown of the MAPK signaling components Kayak (KAY) and Hemipterous (HEP) attenuates the WND-induced loss of Rh1 rhodopsin. UAS-induced HEP expression is similar to WND expression, causing degeneration in R1–6 photoreceptors and axonal sprouting in R7 photoreceptors. These results demonstrate that WND in adult Drosophila photoreceptor cells acts through MAPK signaling activity with both regenerative and degenerative responses. These photoreceptors provide a tractable experimental model to reveal cellular mechanisms driving contradictory WND signaling responses.
Effects of Consumption of Juniper (Juniperus monosperma) on Cost of Thermoregulation in the Woodrats Neotoma albigula and Neotoma stephensi at Different Acclimation Temperatures
(University of Chicago Press, 2003-06) McLister, James D.; Sorensen, Jenifer S.; Dearing, M. Denise
A study was done to test whether toxic plants that occur naturally in the diet affect thermoregulation in mammalian herbivores. The woodrats Neotoma albigula and Neotoma stephensi both consume juniper (Juniperus monosperma), a plant with high levels of toxic compounds. Body temperature (Tb), basal metabolic rate (BMR), and the minimum cost of thermogenesis (Cmin) were measured for both species on control and juniper diets following warm (25°C) and cold (18°C) acclimation. In N. albigula, diet had no uniform effect on Tb, BMR, or Cmin, but -temperature interaction effects on Tb diet x acclimation and Cmin were highly significant (P ! 0.005). For thermoregulation at 15°C, juniper consumption increased the metabolic cost for warm-acclimated N. albigula by 50% but decreased the metabolic cost in cold-acclimated N. albigula by 24%. In N. stephensi, diet significantly affected Tb and Cmin (P ! 0.05), but there were no significant diet x acclimation-temperature interaction effects. For thermoregulation at 15°C, juniper consumption increased the metabolic cost for warm-acclimated N. stephensi by 33% but had no significant effect on metabolic cost in cold-acclimated N. stephensi. Keywords: Body temperature -- Regulation; One-seed juniper; White-throated wood rat; Neotoma
The Electrical Properties of the Anterior Stomach of the Larval Mosquito (Aedes Aegypti)
(The Company of Biologists, 2000) Clark, Thomas M.; Koch, Alan; Moffett, David F.
The electrical properties of the anterior stomach of the larval mosquito (Aedes aegypti) were determined. At late times after cannulation, the intraluminal space constant was 936 mm, which is almost as long as the isolated tissue itself. At this time, the resistance of the apical cell membranes dominates the transcellular resistance; it is approximately 14 times the resistance of the basal cell membrane. Two physiologically distinct epithelial cell types were identified. One type has a stable basal potential of approximately 65 mV and responds to 5-hydroxytryptamine with hyperpolarization. The second cell type initially shows a basal potential of 100mV. However, this basal potential decays in the first few minutes in parallel with the decay of the transintestinal potential. This latter cell type does not respond to 5-hydroxytryptamine. Key words: mosquito, Aedes aegypti, midgut, larva, intracellular potential, 5-hydroxytryptamine.
Engineering synthetic antibody binders for allosteric inhibition of prolactin receptor signaling
(BMC, 2015) Rizk, Shahir S.; Kouadio, Jean-Louis K.; Szymborska, Anna; Duguid, Erica M.; Mukherjee, Somnath S.; Zheng, Jiamao; Clevenger, Charles V.; Kossiakoff, Anthony A.
Background: Many receptors function by binding to multiple ligands, each eliciting a distinct biological output. The extracellular domain of the human prolactin receptor (hPRL-R) uses an identical epitope to bind to both prolactin (hPRL) and growth hormone (hGH), yet little is known about how each hormone binding event triggers the appropriate response. Findings: Here, we utilized a phage display library to generate synthetic antibodies (sABs) that preferentially modulate hPRL-R function in a hormone-dependent fashion. We determined the crystal structure of a sAB-hPRL-R complex, which revealed a novel allosteric mechanism of antagonism, whereby the sAB traps the receptor in a conformation more suitable for hGH binding than hPRL. This was validated by examining the effect of the sABs on hormone internalization via the hPRL-R and its downstream signaling pathway. Conclusions: The findings suggest that subtle structural changes in the extracellular domain of hPRL-R induced by each hormone determine the biological output triggered by hormone binding. We conclude that sABs generated by phage display selection can detect these subtle structural differences, and therefore can be used to dissect the structural basis of receptor-ligand specificity. Keywords: Prolactin signaling, Synthetic antibody, Phage display, Allostery
Estimating Consumption Rates of Juvenile Sandbar Sharks (Carcharhinus plumbeus) in Chesapeake Bay, Virginia, Using a Bioenergetic Model
(Fishery Bulletin, 2006) Dowd, W. Wesley; Brill, Richard W.; Bushnell, Peter G. (Peter Gerald); Musick, John A.
Using a bioenergetics model, we estimated daily ration and seasonal prey consumption rates for six age classes of juvenile sandbar sharks (Carcharhinus plumbeus) in the lower Chesapeake Bay summer nursery area. The model, incorporating habitat and species-specific data on growth rates, metabolic rate, diet composition, water temperature (range 16.8−27.9°C), and population structure, predicted mean daily rations between 2.17 ±0.03 (age-0) and 1.30 ±0.02 (age-5) % body mass/day. These daily rations are higher than earlier predictions for sandbar sharks but are comparable to those for ecologically similar shark species. The total nursery population of sandbar sharks was predicted to consume ~124,000 kg of prey during their 4.5 month stay in the Chesapeake Bay nursery. The predicted consumption rates support the conclusion that juvenile sandbar sharks exert a lesser top-down effect on the Chesapeake Bay ecosystem than do teleost piscivores and humans.
Eye lens radiocarbon reveals centuries of longevity in the Greenland shark (Somniosus microcephalus)
(American Association for the Advancement of Science, 2016-08) Nielsen, Julius; Hedelholm, Rasmus B.; Heinemeier, Jan; Bushnell, Peter G. (Peter Gerald); Christiansen, Jørgen S.; Olsen, Jesper; Bronk Ramsey, Christopher; Brill, Richard Walter; Simon, Malene Juul, 1973-; Steffensen, John F.; Steffensen, Kirstine F.
Greenland shark (Somniosus microcephalus), a species iconic to the Arctic Seas, grows slowly and reach >500 cm total length suggesting a lifespan well beyond those of other vertebrates. Radiocarbon dating of eye lens nuclei from 28 female Greenland shark (81-502 cm in total length) revealed a lifespan of at least 272 years. Only the smallest sharks (≤ 220 cm) showed sign of the radiocarbon bomb pulse, a time marker of the early 1960s. Age ranges of pre-bomb sharks (reported as mid-point ± 1/2 range at 95.4 % probability) revealed the age at sexual maturity to be at least 156 ± 22 years, and the largest animal (502 cm) to be 392 ± 120 years old. Our results show that Greenland shark is the longest-lived vertebrates known and raise concerns for species conservation.
Horizontal and Vertical Movements of Juvenile Bluefin Tuna (Thunnus thynnus), in Relation to Oceanographic Conditions of the Western North Atlantic, Determined with Ultrasonic Telemetry
(National Marine Fisheries Service, 2001-07) Brill, Richard Walter; Lutcavage, Molly; Metzger, Greg; Bushnell, Peter G. (Peter Gerald); Arendt, Michael D., 1974-; Lucy, Jon; Watson, Cheryl Lynn; Foley, David G.
We employed ultrasonic transmitters to follow (for up to 48 h) the horizontal and vertical movements of five juvenile (6.8–18.7 kg estimated body mass) bluefin tuna (Thunnus thynnus) in the western North Atlantic (off the eastern shore of Virginia). Our objective was to document the fishes’ behavior and distribution in relation to oceanographic conditions and thus begin to address issues that currently limit population assessments based on aerial surveys. Estimation of the trends in adult and juvenile Atlantic bluefin tuna abundance by aerial surveys, and other fishery-independent measures, is considered a priority. Juvenile bluefin tuna spent the majority of their time over the continental shelf in relatively shallow water (generally less then 40 m deep). Fish used the entire water column in spite of relatively steep vertical thermal gradients (≈24°C at the surface and ≈12°C at 40 m depth), but spent the majority of their time (≈90%) above 15 m and in water warmer then 20°C. Mean swimming speeds ranged from 2.8 to 3.3 knots, and total distance covered from 152 to 289 km (82–156 nmi). Because fish generally remained within relatively con-fined areas, net displacement was only 7.7–52.7 km (4.1–28.4 nmi). Horizontal movements were not correlated with sea surface temperature. We propose that it is unlikely that juvenile bluefin tuna in this area can detect minor horizontal temperature gradients (generally less then 0.5°C/km) because of the steep vertical temperature gradients (up to ≈0.6°C/m) they experience during their regular vertical movements. In contrast, water clarity did appear to influence behavior because the fish remained in the intermediate water mass between the turbid and phytoplankton-rich plume exiting Chesapeake Bay (and similar coastal waters) and the clear oligotrophic water east of the continental shelf.
How Does Cannabis Reduce Obesity Rates?
(Indiana University South Bend, 2018) Clark, Thomas M.
Professor Clark provides evidence for a weight loss therapy based on weekly Cannabis use combined with daily omega-3 supplements.
Modulation of Appetite and Feeding Behavior of the Larval Mosquito Aedes aegypti by the Serotonin-selective Reuptake Inhibitor Paroxetine: Shifts Between Distinct Feeding Modes and the Influence of Feeding Status
(The Company of Biologists, 2014) Kinney, Michael P.; Panting, Nicholas D.; Clark, Thomas M.
The effects of the serotonin-selective reuptake inhibitor paroxetine (2×10–5 mol l–1) on behavior of the larval mosquito Aedes aegypti are described. Four discrete behavioral states dominate larval behavior: wriggling, two distinct types of feeding, and quiescence. Feeding behaviors consist of foraging along the bottom of the container (substrate browsing), and stationary filter feeding while suspended from the surface film. Fed larvae respond to paroxetine with increased wriggling, and reductions in both feeding behaviors. In contrast, food-deprived larvae treated with paroxetine show no change in the proportion of time spent wriggling or feeding, but shift from stationary filter feeding to substrate browsing. Thus, actions of paroxetine in fed larvae are consistent with suppression of appetite and stimulation of wriggling, whereas paroxetine causes food deprived larvae to switch from one feeding behavior to another. Further analysis of unfed larvae revealed that paroxetine decreased the power stroke frequency during wriggling locomotion, but had no effect on the swimming velocity during either wriggling or substrate browsing. These data suggest that: (1) serotonergic pathways may trigger shifts between distinct behaviors by actions on higher level (brain) integrating centers where behaviors such as feeding and locomotion are coordinated; (2) these centers in fed and food deprived larvae respond differently to serotonergic stimulation suggesting sensory feedback from feeding status; and (3) serotonergic pathways also modulate central pattern generators of the nerve cord where the bursts of action potentials originate that drive the rhythmic muscle contractions of wriggling. KEY WORDS: Aedes aegypti, Mosquito, Behavior, Paroxetine, Serotonin, Feeding, SSRI, Appetite, Wriggling, Substrate browsing, Stationary filter feeding
Neonatal Thyroxine Activation Modifies Epigenetic Programming of the Liver
(Nature Research, 2021) Nair, T. Murlidharan; Fonseca, Tatiana L.; Garcia, Tzintzuni; Fernandes, Gustavo W.; Bianco, Antonio C.
The type 2 deiodinase (D2) in the neonatal liver accelerates local thyroid hormone triio- dothyronine (T3) production and expression of T3-responsive genes. Here we show that this surge in T3 permanently modiﬁes hepatic gene expression. Liver-speciﬁc Dio2 inactivation (Alb-D2KO) transiently increases H3K9me3 levels during post-natal days 1–5 (P1–P5), and results in methylation of 1,508 DNA sites (H-sites) in the adult mouse liver. These sites are associated with 1,551 areas of reduced chromatin accessibility (RCA) within core promoters and 2,426 within intergenic regions, with reduction in the expression of 1,363 genes. There is strong spatial correlation between density of H-sites and RCA sites. Chromosome con- formation capture (Hi-C) data reveals a set of 81 repressed genes with a promoter RCA in contact with an intergenic RCA ~300 Kbp apart, within the same topologically associating domain (χ2 = 777; p < 0.00001). These data explain how the systemic hormone T3 acts locally during development to deﬁne future expression of hepatic genes.
Novel Plant Secondary Metabolites Impact Dietary Specialists More Than Generalists (Neotoma spp.)
(Ecology, 2005) Sorensen, Jennifer S.; McLister, James D.; Dearing, M. Denise (Maria-Denise)
Theory predicts that dietary specialization is limited in part because of physiological trade-offs associated with specialization. Specifically, dietary specialists are predicted to evolve mechanisms that reduce costs and enhance excretion of plant secondary metabolites (PSMs) that they frequently consume, but are less energetically and/or mechanistically efficient at eliminating novel PSMs. Although examples of trade-offs associated with dietary specialization have been documented among insects, trade-offs have not been investigated in mammalian herbivores. To initially investigate the physiological trade-offs associated with specialization in mammalian herbivores, we determined the impact of ingesting novel PSMs on the energy budgets of a juniper specialist (Neotoma stephensi) and generalist (N. albigula) woodrat. These results were then compared to the impact of juniper intake, the plant species preferred by the specialist, on energy budgets in these same species. Energy budgets were evaluated by measuring apparent metabolizable energy intake (AMEI, energy consumed 2 energy excreted) and energy expended on basal metabolic rate (BMR) and voluntary wheel running in specialist and generalist woodrats fed a formulated diet with and without PSMs from the novel plant creosote (Larrea tridentata). Both specialists and generalists were energetically impacted by the intake of a diet containing novel PSMs, primarily through decreased intake of creosote diet and increased excretion of energy in the urine. However, specialists were impacted to a greater extent than generalists. Specialists decreased body mass, whereas generalists maintained body mass. Specialists also reduced intake and AMEI when consuming creosote diet compared to control to a greater extent than generalists. In turn, specialists had one-sixth the energy available for energy dependent activities than generalists on a diet containing novel PSMs. These results are in stark contrast to the comparisons between specialists and generalists consuming PSMs from their natural diet. Specialists consumed more juniper, had higher AMEI and available energy than generalists when fed diets containing juniper foliage. These data provide the first support that physiological trade-offs associated with dietary specialization may exist in mammalian herbivores. Key words: generalist; mammalian herbivore; Neotoma albigula; Neotoma stephensi; novel PSM; specialist; trade-off.
The Novel Signal Peptides, Pedibin and Hym-346, Lower Positional Value Thereby Enhancing Foot Formation in Hydra
(The Company of Biologists, 1999-01) Grens, Ann; Shimizu, Hiroshi; Hoffmeister, Sabine A. H.; Bode, Hans R.; Fujisawa, Toshitaka
Signaling molecules affecting patterning processes are usually proteins and rarely peptides. Two novel peptides, pedibin and Hym-346, that are closely related to one another have been isolated from Hydra vulgaris and Hydramagnipapillata. Several experiments indicate that both cause a reduction in the positional value gradient, the principle patterning process governing the maintenance of form in the adult hydra. The peptides cause an increase in the rate of foot regeneration following bisection of the body column. Treatment of animals with either peptide for an extended period of time resulted in an apical extension of the range of expression of CnNk-2 along the body column. Such an extension is correlated with a decrease in positional value. Transplantation of tissue treated with Hym-346 results in an increase in the fraction forming feet, and aggregates derived from Hym-346 tissue form more feet and fewer heads. The latter two experiments provide a direct measure of the lowering of positional value in the treated tissue. These results suggest that peptides play signaling roles in patterning processes in cnidaria and, plausibly, in more complex metazoans as well. Key words: Hydra, Pedibin/Hym-346, Foot formation
pH tolerances and regulatory abilities of freshwater and euryhaline Aedine mosquito larvae
(The Company of Biologists, 2004) Clark, Thomas M.; Flis, Benjamin J.; Remold, Susanna Klara
The pH regulatory abilities of two members of the mosquito tribe Aedini, known to have dramatically different saline tolerances, are investigated. The freshwater mosquito Aedes aegypti and the euryhaline Ochlerotatus taeniorhynchus tolerate very similar pH ranges. Both species complete larval development in waters ranging from pH·4 to pH·11, but naïve larvae always die in water of pH·3 or 12. Across the pH range 4–11, the hemolymph pH of O. taeniorhynchus is maintained constant while that of A. aegypti varies by 0.1 pH units. The salt composition of the water (3.5·g·l–1 sea salt, 3.5·g·l–1 NaCl, or nominally salt-free) has no effect on the range of pH tolerated by A. aegypti. In both speies, the effects of pH on larval growth and development are minor in comparison with the influence of species and sex. Acclimation of A. aegypti to pH·4 or 11 increases survival times in pH·3 or 12, respectively, and allows a small percentage of larvae to pupate successfully at these extreme pH values. Such acclimation does not compromise survival at the other pH extreme. Key words: mosquito larvae, pH regulation, pH acclimation, life history, Aedes aegypti, Ochlerotatus taeniorhynchus

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