Differential Selenium Uptake by Periphyton in Boreal Lake Ecosystems

Selenium (Se) is a naturally occurring trace element with a narrow margin between essentiality and toxicity in many organisms. Selenium is a contaminant of concern in the boreal forest region of North America because certain anthropogenic activities increase the loading of Se into cold-water aquatic ecosystems, which can have adverse effects on higher trophic levels such as fish, amphibians, and birds. Selenium is rapidly and efficiently assimilated from the water column into organisms at the base of the food web and transferred to higher trophic levels through dietary pathways. This initial step of aqueous Se uptake by organisms at the base of the food web is the greatest step in Se assimilation into aquatic food webs and has much uncertainty surrounding it. Complex assemblages of algae, bacteria, fungi, and detritus that exist at the sediment-water interface, also known as periphyton, play a key role in Se incorporation and biotransformation to more harmful organic forms and in energy cycling in aquatic systems. There are significant site-specific differences that exist in Se enrichment into aquatic food webs by organisms at the base of the food web, which makes predicting the ecotoxicological effects of elevated Se loading uncertain, varying 102 to 106-fold among different systems. Most field studies focused on the ecological risk assessment of Se have been conducted in warm-water systems and more research is needed regarding the effects of increased Se loading in cold freshwater ecosystems, including how certain water quality variables influence the incorporation of Se into food webs by organisms like periphyton. Additionally, boreal lakes specifically can be at a greater risk to Se toxicity at elevated levels due to the generally low presence of buffering ions like sulfate and phosphate which are known to interfere with Se uptake by various organisms. The goals of my research were to further address these research gaps to better understand the biodynamics of Se assimilation by organisms at the base of cold freshwater food webs. Specifically, an experiment was performed examining the bioaccumulation of low environmentally relevant concentrations of Se as selenite reflecting the current Se guidelines in naturally grown periphyton from multiple boreal lakes. The Se exposure concentrations used were 0.5, 1, 2, 4 μg/L, corresponding to the current freshwater lentic Se guidelines of 1 μg/L in Canada, 1.5 μg/L in the United States, and 2 μg/L in British Columbia. The results of the research revealed that periphyton rapidly and variably accumulated Se at low aqueous Se concentrations in a concentration-dependent manner. A range of periphyton tissue Se concentrations of 8.0 – 24.9 μg/g dm was seen in the 1 – 2 μg/L treatments surrounding the current freshwater Se guidelines, reaching 30.9 – 50.2 μg/g dm in the highest treatments in certain boreal lake systems. Previous studies have reported adverse effects in invertebrates fed periphyton at similar Se concentrations, suggesting that systems exposed to low levels of Se could experience adverse effects in certain higher trophic level populations. Differential uptake of Se into periphyton among the five studied lakes was also observed, where periphyton from mesotrophic lakes generally accumulated more Se than periphyton from oligotrophic lakes. The differences in Se uptake were likely explained by periphyton community composition and water chemistry differences, however significant correlations between these variables were observed. Higher proportions of the specific algal phylum known as the charophytes in periphyton grown in more oligotrophic lakes corresponded to decreased periphyton Se uptake, as well as in the presence of water with higher dissolved inorganic carbon content. Increased proportions of another algal phyla known as the bacillariophytes or diatoms in periphyton from more mesotrophic lakes corresponded to increased periphyton Se uptake, as well as in the presence of higher total dissolved phosphorus content. The trends demonstrated by different water chemistry and periphyton community variables in this experiment among multiple boreal lakes could serve as representative factors to consider when assessing potential risks of Se toxicity in different lentic systems. The results of this research provide further insight on the biodynamics of Se assimilation at the base of boreal lake food webs at environmentally relevant concentrations, which can potentially inform Se ecological risk assessments in cold, freshwater ecosystems in North America

Echocardiographic evaluation of velocity ratio, velocity time integral ratio, and pulmonary valve area in dogs with pulmonary valve stenosis.

BackgroundVelocity ratio, velocity time integral (VTI) ratio, and pulmonary valve area indexed to body surface area (iPVA) are methods of assessment of pulmonary valve stenosis (PS) severity that are less dependent on blood flow. Studies evaluating these methods are limited.ObjectivesTo determine the effects of butorphanol, atenolol, and balloon valvuloplasty (BV) on velocity ratio, VTI ratio, iPVA, mean PG, and max PG.AnimalsTwenty-seven dogs with PS (max PG >50 mm Hg).MethodsProspective study. All dogs underwent an echocardiogram at baseline, 5-minutes after administration of butorphanol (0.2-0.25 mg/kg IV), and 2-to-4 weeks after atenolol (1-1.5 mg/kg q12h). Twenty-one of these were evaluated 24-hours after BV.ResultsThere were no significant differences (P > .05) amongst any of the methods of assessment of PS severity after butorphanol. After atenolol, mean (SD) of mean (57.0 [21.0] mm Hg) and max PG (93.1 [33.8] mm Hg) were significantly decreased (P ≤ .047) compared with baseline (65.2 [26.2] mm Hg and 108 [44.4] mm Hg, respectively). After atenolol, there were no significant (P ≥ .12) differences in velocity ratio (0.29 [0.09]), VTI ratio (0.18 [0.05]), or iPVA (0.43 [0.16] cm2 /m2 ) compared with baseline (0.30 [0.09], 0.19 [0.09], 0.44 [0.17] cm2 /m2 , respectively).Conclusions and clinical importanceAtenolol might reduce mean and max PG but does not alter less flow-dependent methods of assessment of PS severity (velocity ratio, VTI ratio, and iPVA) in dogs with PS. Results support an integrative approach to assessment of PS severity that includes less flow-dependent methods, particularly in states of altered flow or right ventricular function

Dynamic visualization of protein interactions: Mapping and FRET biosensor development

Intracellular levels of the RNA-binding protein and pluripotency factor, Lin28a, are tightly controlled to govern cellular and organismal growth. Lin28a is extensively regulated at the post-transcriptional level, and can undergo mitogen-activated protein kinase (MAPK)-mediated elevation from low basal levels in differentiated cells by phosphorylation-dependent stabilizing interaction with the RNA-silencing factor HIV TAR-RNA-binding protein (TRBP). However, molecular and spatio-temporal details of this critical control mechanism remained unknown. In the second chapter of this work, we dissect the interacting regions of Lin28a and TRBP proteins and develop a sensor to visualize this interaction. We identify truncated domains of Lin28a and of TRBP that are sufficient to support co-association and mutual elevation of protein levels, and a requirement for MAPK-dependent phosphorylation of TRBP at putative ERK-target serine 152 in mediating increase of Lin28a protein by TRBP. The phosphorylation-dependent association of Lin28a and TRBP truncated constructs is leveraged to develop a FRET-based sensor for dynamic monitoring of Lin28a and TRBP interaction. We demonstrate response of this FRET sensor to growth factor stimulation in living cells, with coimaging of Erk activation to achieve further understanding of the role of MAPK signaling in Lin28a regulation. The IκB kinase (IKK) is a key mediator of NFκB activation, which affects inflammatory signaling. In the third chapter of this work, we expand our focus from Lin28a to review the process of biosensor development for kinase activity, taking as a case study our efforts to develop a FRET-based biosensor for IKK. We successfully identified an IKK substrate peptide that could be inducibly phosphorylated, and had some success in visualizing this substrate’s phosphorylation. However, further optimization will be required to engineer a sensor that reliably diffuses throughout the cell and does not perturb the NFκB signaling status of the cell

Aberrant migration and surgical removal of a heartworm (Dirofilaria immitis) from the femoral artery of a cat.

A cat was evaluated for an acute-onset of right pelvic limb paresis. Thoracic radiographs revealed normal cardiac size and tortuous pulmonary arteries. Abdominal ultrasound identified a heartworm (HW) extending from the caudal abdominal aorta into the right external iliac artery and right femoral artery. The cat was HW-antigen positive. Echocardiography revealed a HW within the right branch of the main pulmonary artery and evidence of pulmonary hypertension. An agitated-saline contrast echocardiogram revealed a small right to left intracardiac shunt at the level of the atria. Surgical removal of the HW was performed with no substantial postoperative complications. There was return of blood flow and improved motor function to the limb. The cat remains mildly paretic on the affected limb with no other clinical signs

A comparative gene analysis with rice identified orthologous group II HKT genes and their association with Na+ concentration in bread wheat

Background Although the HKT transporter genes ascertain some of the key determinants of crop salt tolerance mechanisms, the diversity and functional role of group II HKT genes are not clearly understood in bread wheat. The advanced knowledge on rice HKT and whole genome sequence was, therefore, used in comparative gene analysis to identify orthologous wheat group II HKT genes and their role in trait variation under different saline environments. Results The four group II HKTs in rice identified two orthologous gene families from bread wheat, including the known TaHKT2;1 gene family and a new distinctly different gene family designated as TaHKT2;2. A single copy of TaHKT2;2 was found on each homeologous chromosome arm 7AL, 7BL and 7DL and each gene was expressed in leaf blade, sheath and root tissues under non-stressed and at 200 mM salt stressed conditions. The proteins encoded by genes of the TaHKT2;2 family revealed more than 93 % amino acid sequence identity but ≤52 % amino acid identity compared to the proteins encoded by TaHKT2;1 family. Specifically, variations in known critical domains predicted functional differences between the two protein families. Similar to orthologous rice genes on chromosome 6L, TaHKT2;1 and TaHKT2;2 genes were located approximately 3 kb apart on wheat chromosomes 7AL, 7BL and 7DL, forming a static syntenic block in the two species. The chromosomal region on 7AL containing TaHKT2;1 7AL-1 co-located with QTL for shoot Na+ concentration and yield in some saline environments. Conclusion The differences in copy number, genes sequences and encoded proteins between TaHKT2;2 homeologous genes and other group II HKT gene families within and across species likely reflect functional diversity for ion selectivity and transport in plants. Evidence indicated that neither TaHKT2;2 nor TaHKT2;1 were associated with primary root Na+ uptake but TaHKT2;1 may be associated with trait variation for Na+ exclusion and yield in some but not all saline environments

PCR and FISH Detection Extends the Range of Pfiesteria piscicida in Estuarine Waters

PCR and fluorescent in situ hybridization probes were used to assay for the presence of the dinoflagellate Pfiesteria piscicida in 170 estuarine water samples collected from New York to northern Florida. 20% of samples tested positive for the presence of P. piscicida, including sites where fish kills due to Pfiesteria have occurred and sites where there was no historical evidence of such events. The results extend the known range of P. piscicida northward to Long Island, New York. The results also suggest that P. piscicida is common, and normally benign, inhabitatant of estuarine waters of the eastern US

A comparative gene analysis with rice identified orthologous group II HKT genes and their association with Na+ concentration in bread wheat

Background Although the HKT transporter genes ascertain some of the key determinants of crop salt tolerance mechanisms, the diversity and functional role of group II HKT genes are not clearly understood in bread wheat. The advanced knowledge on rice HKT and whole genome sequence was, therefore, used in comparative gene analysis to identify orthologous wheat group II HKT genes and their role in trait variation under different saline environments. Results The four group II HKTs in rice identified two orthologous gene families from bread wheat, including the known TaHKT2;1 gene family and a new distinctly different gene family designated as TaHKT2;2. A single copy of TaHKT2;2 was found on each homeologous chromosome arm 7AL, 7BL and 7DL and each gene was expressed in leaf blade, sheath and root tissues under non-stressed and at 200 mM salt stressed conditions. The proteins encoded by genes of the TaHKT2;2 family revealed more than 93 % amino acid sequence identity but ≤52 % amino acid identity compared to the proteins encoded by TaHKT2;1 family. Specifically, variations in known critical domains predicted functional differences between the two protein families. Similar to orthologous rice genes on chromosome 6L, TaHKT2;1 and TaHKT2;2 genes were located approximately 3 kb apart on wheat chromosomes 7AL, 7BL and 7DL, forming a static syntenic block in the two species. The chromosomal region on 7AL containing TaHKT2;1 7AL-1 co-located with QTL for shoot Na+ concentration and yield in some saline environments. Conclusion The differences in copy number, genes sequences and encoded proteins between TaHKT2;2 homeologous genes and other group II HKT gene families within and across species likely reflect functional diversity for ion selectivity and transport in plants. Evidence indicated that neither TaHKT2;2 nor TaHKT2;1 were associated with primary root Na+ uptake but TaHKT2;1 may be associated with trait variation for Na+ exclusion and yield in some but not all saline environments

Cardiac Effects of a Single Dose of Pimobendan in Cats With Hypertrophic Cardiomyopathy; A Randomized, Placebo-Controlled, Crossover Study

Background: Pimobendan has been shown to impart a significant survival benefit in cardiomyopathic cats who receive it as part of heart failure therapy. However, use of pimobendan remains controversial in cats with hypertrophic cardiomyopathy (HCM) due to lack of pharmacodynamic data for pimobendan in cats with HCM and due to theoretical concerns for exacerbating left ventricular outflow tract obstructions. Hypothesis/Objectives: Our objective was to investigate the cardiac effects of pimobendan in cats with HCM. We hypothesized that pimobendan would not exacerbate left ventricular outflow tract obstructions and that it would improve echocardiographic measures of diastolic function. Animals: Thirteen purpose-bred cats were studied from a research colony with naturally-occurring HCM due to a variant in myosin binding protein C. Methods: Cats underwent two examinations 24 h apart with complete standard echocardiography. On their first day of evaluation, they were randomized to receive oral placebo or 1.25 mg pimobendan 1 h prior to exam. On their second examination, they were crossed over and received the remaining treatment. Investigators were blinded to all treatments. Results: The pimobendan group had a significant increase in left atrial fractional shortening (pimobendan group 41.7% ± 5.9; placebo group 36.1% ± 6.0; p = 0.04). There was no significant difference in left ventricular outflow tract (LVOT) velocities between the groups (pimobendan group 2.8 m/s ± 0.8; placebo group 2.6 m/s ± 1.0). There were no significant differences between the number of cats with LVOT obstructions between groups (12 in pimobendan group; 11 in placebo group; p = 1.00). There were no detectable differences in any systolic measures, including left ventricular fractional shortening, mitral annular plane systolic excursion, and tricuspid annular plane systolic excursion. Doppler-based diastolic function assessment was precluded by persistent tachycardia. Conclusions: Improved left atrial function in the pimobendan group could explain some of the reported survival benefit for HCM cats in CHF. Pimobendan did not exacerbate LVOT obstructions and thus may not be contraindicated in HCM cats with LVOT obstructions. Future studies are needed to better characterize other physiologic effects, particularly regarding diastolic function assessment, and to better assess safety of pimobendan over a longer time-course.Center for Companion Animal Health at the University of California Davis, School of Veterinary Medicine [2016-15-F]Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]